1. General Inspection and Disassembly
2. Guide Shoe and Braids
3. Motor Procedures
4. Axles and Bearings
5. Wheels and Tires
6. Aligning the Drive Train
1. De-slotting: How does the car come off the track?
2. Power: Does the car appear to be getting proper power?
3. Car slows noticeably through tight turns
4. Car slows on the straights
5. Excessive noise
1. Setting the Vertical Center of Gravity
2. Magnet Tuning
a. Maximum Lap Speed Tuning
b. Performance Matched Tuning
c. Measuring Magnet Downforce
3. Weight Tuning
4. Selecting Gear Ratios
5. Motor Selection
6. Tire Selection
7. Chassis Weight Reduction, Guide Shoe Modification and Chassis Strengthening
8. Putting It All Together
1. Hot Motor on Weak Power
2. Removing the Brake Function.
3. Helping Your Weak Power
5. Basic Motor Repairs
6. Motor Modifications
When you first
get a new plastic chassis slot car, no matter what the manufacturer, there are a
few things that can be done to improve its performance. What we have tried to do
in this article is provide a good basic reference checklist that can be used to
prepare these cars. There are also sections on race tuning, repair and a couple
of other items that may be of interest. If you plan on race tuning your car you
should do these steps where applicable during the basic checklist part of the
article. The tips we have provided don't comply with any particular set of
racing rules so you, the reader, should make sure that any changes you make to
your car meets the standards set by your particular club or commercial track.
The things we suggest are only items that we have personally tried and that work
for us. Throughout the article you may notice the names of stores, Internet
sites and manufacturers. These are mentioned only as examples of where you can
obtain certain items; they are not recommendations or advertisements. As a final
note before we get down to it, we would like to apologize in advance for the
lack of pictures. At the time this article was written we didn't have a digital
camera. Perhaps we will add these items in the future.
1. General Inspection and Disassembly
a. First prior to removing the body from the chassis, check to see if there is any rubbing between the tires and the body. This can occur for a number of reasons on certain cars but for now look for out of round wheels / tires, unseated axle bushings loose wheels and make note for later repair.
b. Check the guide for unimpeded movement throughout its turning radius. Binding could indicate improper installation / seating, plastic mold " flash " causing interference or lubrication requirement, which will be accomplished after chassis removal. Make notes for repair at the applicable time.
c. Look for obvious defects such as improperly installed / stripped screws (cross threaded) or a warped chassis/ body. Stripped screws can be repaired by re-bushing the stripped post with glue and re-taping the screw. Warped chassis and bodies can usually be fixed by running hot water over the warped component and gently bending into shape. A hair dryer on a low setting can also be used. Check that the car sits properly and that all wheels appear to touch the track correctly. Sometimes, on some cars such as some FLY sidewinders, the top of the motor brush assembly will prevent the chassis from seating properly into the body. The result is a car sitting on 3 wheels with one wheel slightly off the track surface. This needs to be identified and corrected to insure proper handling.
d. Now remove the chassis assembly from the body, watching to see if any parts fall out when the chassis and body are separated. This may sound amusing but, believe me, several of the cars I've purchased have had various parts come bouncing out the first time I opened the car up. So be observant and watch for this so that you won't have to spend time trying to figuring out where some doodad or such came from.
e. Now that you have the car separated, put the body aside and let's begin with the chassis assembly.
f. Remove all components from the chassis including the wheels, axles, guide, motor, and bushings. This is where you make sure the chassis is not warped or damaged. As we mentioned earlier, warped chassis can usually be fixed by putting it under hot water and gently straightening it. It is usually helpful to check the chassis with the wheels/ axles installed and with the guide removed to make sure all four wheels touch the track or flat surface correctly and that one is not lifted; this is characteristic of a warped chassis.
2. Guide Shoe and Braids Back To Index
a. Check guide hole and axle/bearing holes for molding "flash" and remove as necessary. Reinstall the guide shoe. I use a small dab of silicone grease (DC-11) here to help freedom of movement. If you will be doing any trimming on shortening of the guide, I recommend that you wait until the wheels are installed so that all the references for this task are in place.
b. Make sure that the guide turns freely with the motor wires connected (step 3e.) and that the wires are routed such that they provide self centering for the guide shoe. This can usually be accomplished by "x" crossing the cables at the guide and/or by taping them to the chassis so that they provide spring flexing to the guide shoe. Older Scalextric cars have spring loaded contact between the braid and the motor leads. It is not self-centering and some people replace this system with an SCX/Ninco guide that can be wired like these types of cars with new motor wires and eyelets. We generally leave the newer SCX "suspension” guides alone since we haven’t figured out a good way to make them self entering. On these guides make sure that the springs are making proper contact with the guide. You may want to add a very small piece of plastic tubing between the guide holder and the guide on the SCX cars so that the guide bounce is reduced slightly. This will help to prevent deslots in the corners. To see if you need to add a spacer here take the car and put it on a piece of track. Bring it to the edge so that the guide is at the end of the slot. Take a small screw driver and put it under the guide in the slot and see if you can depress the guide any up into the chassis. If you can then you need to add some spacers between the guide and chassis so that you cannot push the guide up at all. You can then add a very thin additional spacer to unload weight off the front wheels. This will insure that your guide will have the maximum penetration in the slot at all times. After you add these spacers you may need to increase the spring tension of the spring contacts in the chassis. Also a small dab of super glue under each braid on top of the guide will keep them from coming loose from the guide at an inopportune time. If the car is not new, check for arcing between the spring contacts and the braid. This will show up as black carbon deposits on the tops of the braid. Arcing could indicate improper contact pressure between the spring contacts and the guide braid. Adjust the springs for more down pressure if you suspect this problem and clean or replace the contact braid.
c. Consideration should be given to replacing guide braids with the soft thin type made by companies such as PinkKar and Slotit. They make the front end of the car lower to the track. Braids should be cut to the same length as the guide and "combed" to provide a spread out configuration, slightly bend down at the end. Combing can be done using a soft wire brush and gently separating the braid at the track contact end. By using the capacitor mod in the Electrical Mods Section of this article you can reduce the effect of improper guide braid to rail contact.
d. One problem which all plastic chassis cars have to some extent is guide pin slop. There are several ways to improve the situation. One way is to thread a nut and washer to the guide pin and run it down to take up the excess movement. Another more detailed method is to fit the guide with a piece of brass tubing and glue it to the pin. Next, drill out the guide hole to get an exact fit. You may want to reinforce the outside of the guide holder assembly with a glued piece of plastic tubing. You can now thread the brass tubing to take a lock nut and washer to prevent up down movement. A third simple method which works on most of the guides is to take one or two flat washers (3mm inside diameter) and press fit them on top of the post. Push them down to take up the slop, but not bind, and put a drop of super glue on them to secure. There are other methods to solve this problem with but these3 examples work well for us. Take a look at the Chassis Weight Reduction and Guide Shoe Modification Section to get more info about fixing this problem. REMEMBER: this area takes quit a bit of abuse and stress so be careful not to weaken the overall structure here. One other simple way to remove slop that doesn’t require any cutting is to try the following: First, remove the guide shoe and coat the guide axle with a liberal amount of oil or WD-40. Second, put a couple of drops of superglue into the chassis guide holder. Third, install the guide shoe and turn it back and forth until the glue sets up. This can be speeded up by having someone add a couple drops of alcohol while you’re twisting back and forth. When the glue sets you should have quite a bit less slop. Add some oil to lubricate and away you go. If you somehow screw this up you can remove the super glue with a little acetone (nail polish remover).
types of track, including Artin and Carrera, offer a wider deeper slot than
Scalex/SCX. Consideration should be given as to whether or not your cars should
be converted to a wider deeper guide such as the MRRC or Parma commercial type
guide or the FLY/Slotit/TSRF guides for commercial tracks. This is outside the
basic section of this article and is covered in the
RACE TUNING SECTION.
* Note: You should not do any rear axle bushing, wheel, pinion, or motor/mount gluing until after you have worked out and tested gear ratios. This process entails axle swapping. If you are planning to race tune the gear ratios you should hold off on the gluing until after final gears are selected and mounted.
3. Motor Procedures Back To Index
a. If you are using a stock motor you can remove any resistors, capacitors, or inductors that are soldered on to the motor leads. This will eliminate one area of possible electrical failure. On cars like Carrera thought should be given to removing all the switchology and EMI components and making simple motor to guide connections. These items have a habit of failing at the most inopportune time and could cost you a race win so take that junk off. Be advised that removing these items may cause your cars to interfere with TVs and other electronic devices. Component failures usually occur when components are being run at 15+vdc which exceeds the design limits on some brand car’s EMI components.
b. Insure that the motor leads are properly soldered to the motor. Cold solder joints appear as a dull silver color and can rob your motor of power and cause intermittent power problems. Reheat any suspicious joints. On SCX RX-type motors, the plug in leads should be soldered in place to prevent accidental disconnects. At the plugins to the guide shoe on FLY, Ninco and other brands, the eyelets should be soldered to the motor wires to make a reliable connection. Further, for competition these eyelets should be soldered to the guide braid at the guide (see step e below for more info). Be careful that you don't over heat this area and melt the guide. One additional item you should consider doing at this point is to isolate motor cable flex away from the motor attach points. This can be simply done by taping the cables to the chassis so that all of the movement occurs forward of the tape. This will lengthen cable life because one prime area of failure is cable breakage at the motor mounting points. On cars with the Copper strip contacts, a small drop of solder at the contact between each motor spring contact and the corresponding chassis strip will insure a reliable connection (see step e below for other options). Contact strips on both the motor and the chassis should be kept free of oxidation. An ink eraser can be used to remove small amounts of oxidation. Finally, make sure that on cars with motor wires that these wires are routed properly so as not to interfere with the body when it is mounted. Many cars have very little chassis to body clearance in some areas so wire routing can be important.
c. Make sure the pinion gear you plan to use is securely installed. If you are in doubt you can add a drop of super glue or, in the case of a brass pinion, super glue or solder. Always use a pinion tool for pinion installation / removal such as Ninco Part #70201. This will reduce the possibility of motor damage. Many of the motors that are used set the motor- armature slop with a cheap interference fit lock spacer inside the motor at the gear end. If you aren't careful when installing and removing pinion gears you can cause the spacer to be moved allowing more forward / aft slop in the motor shaft. If this happens you can take the motor apart and reset it (see motor repair section) or you may be able to correct it enough by adding motor shaft spacers between the gear and the motor end bearing on the outside of the motor.(see the noise section 6c 4 below). When using high torque motors it is better to use solder on brass pinions to prevent "throwing a pinion” during a race. If you notice your car slowing for no particular reason during normal running, especially under acceleration, you may want to check to make sure the pinion is 100% secure. Sometimes it can loosen slightly and go unnoticed except when it is closely inspected. Increased lap times are one symptom of this problem. Brass or solder powder around the pinion area of the motor can be another indication that the pinion is slipping and wearing away slightly. On sidewinder cars, you may want to remove any excess motor shaft on the drive side of the motor. This will prevent possible interference with the tires. FLY Classics typically exhibit this problem as well as cars with larger diameter non-standard tires.
d. Reinstall motor and motor adapters as applicable. If your rules allow, glue these items in place so that neither the adapters nor the motor moves in the chassis. Depending on the difficulty in accessing motor bearings, you may want to lightly lubricate these items at this point with light machine oil. Be careful not to over lubricate these bearings because you can foul the commutator. If you are using motor mounts make sure that the motor is sitting squarely in the chassis before final gluing. A twisted motor could "bottom out" on the track on low clearance cars. Also make sure motor adapters have holes to allow motor bearing lubrication. If they do not, as in the case of Cartrix SCX adapters, simply drill a lube hole in the adapter. This will enable you to lube the bearings without having to remove the motor.
e. Make sure the motor leads plug into the guide securely. I put a drop of conductive paint/adhesive (used for car rear window defroster installation / repair) on each connection. This paint / adhesive is also useful on other electrical connections which could come loose such as motor to copper conductor strips on newer SCX cars. This is an alternative to soldering, which can melt the plastic and damage a good chassis. One type I use is Circuit Works Conductive Epoxy. (view online at http://www.action-electronics.com/chemtron.htm). If you are careful you can also solder all these connections which will give them good contact and security.
4. Axles and Bearings Back To Index
a. Next is the axles / bearings. Check for straightness of axles by rolling them on a flat smooth surface and observe any wobble that would indicate a bent axle. Usually a bent axle should be replaced unless you determine that it can be lived with. Remember high down-force magnet cars are less affected by axle/wheel balance problems than low down-force or no magnet cars but it is still a factor in overall performance especially on high speed tracks. Most Euro-cars have relatively soft axles which can easily be bent in a high impact accident. Consideration should be given to upgrading to hardened steel replacements especially on the rear assembly. Slot-it axle kits (see at: www.slot.it) offer strong replacements with better gear and aluminum wheels. If your budget permits these are good upgrades. On front axles you may want to go to Aluminum or Brass tubing if you have magnets mounted near the axle. This will reduce the flux line braking effect of the magnets on the ferric axles and will reduce rotational mass.
b. Put a dab of glue (super glue works well) in each bearing carrier and, for inline motors, reinstall the rear axle /bearing assembly making sure the axle turns freely in the bearings. Some people advocate using a small amount of super glue in the bearing to tighten the tolerance of the axle to bearing surface. We've found this works okay on metal bushings but doesn't last for many races. If you want to try it then, first put a drop of glue in the bushing holes. One note: Glue the bushings to the chassis before trying to tighten up the axle slop because they may become attached to the axle and begin spinning in the bearing holders. Now, put a drop of oil orWD-40 on the axle and spread it over the entire axle. Insert the axle into the bushings and align before glue sets. After glues sets gently turn the axle to make sure it's free turning. Put a little more lubricant on the axle. That’s it. There should be less free play. You can also do perform this procedure on a built up car by first over-lubing the bearings; then running the motor slowly spinning the rear axle. Allow a drop of superglue to wick into each bearing while the axle is spinning. The glue will slowly tighten up the axle slop. Be sure to keep the axle spinning for at least a minute so that the glue sets up before you stop. If you screw up here, you can use Acetone (used in most fingernail polish removers) to dissolve most CA-super glues. What I usually do instead of using this glue method is to paint the axles where they will be riding in the bushings with thin liquid dry film lubricant, not grease, (Molykote-Molybdenum disulfide found in sports and gun shops) and let it dry. When dry, it bonds to the axle and adds just the right amount of diameter increase to the axle in the bushing to remove excess bearing slop. With greater bushing tolerances you may need to apply several coats letting them dry between coats. Depending on the spec of the coating you use, it should wear longer and be slipperier than the superglue method. NOTE: For sidewinder motor cars don't leave the axle /spur gear assembly installed at this time. This assembly is covered later in this section.
c. There are several designs for front axles. Generally though, axles should turn freely without being overly sloppy. A drop of lubricant may be added to the front axle attachment points to help to reduce wear. Ideally, you want the front tires to just barely touch the track when the car is at rest. Some cars use a stiff front axle set up. On these cars, it is very important to reduce the rolling friction of the front tires (step5c). On FLY/ Proslot and similar with independent rotating wheels, if they are overly sloppy, take each axle and clip about 1 mm off the end of it. This will allow the axle to be press fit on the wheel so that it will have zero slop with the axle carrier. Insert the axle into the carrier like you would for installation. Put some lubricant into the carrier hole so that super glue will not stick. Take the wheel and put superglue into the axle hole. Be careful not to put too much because you don't want any on the rear of the hub. Now press the hub onto the axle so that it is tight WITHOUT binding. Let the glue set up and this should be all you need. I usually turn the wheel as the glue sets up so that it doesn’t wick into the carrier hole. The lubricant on the axle should prevent this. Finally, lube each axle so that they turn freely. I generally use moly-grease (white) since it not only lubricates the interface but also reduces noise level. Your wheel assemblies should now be installed correctly and will not be rubbing any body parts or making any noise because of slop. Much later in the cars life when the axle carriers wear due to use you can drill out the carriers and install brass tubing inserts. The key to the whole thing is the fact that the axles area little too long to snugly fit some wheels to the car. One other method is to use thin metal / plastic washers to take up this extra slop. There are several solutions to the loose front wheel problem so you can choose which method best suits your needs.
d. Solid front axle assembly problems usually show up in several ways. First your car will sometimes unexplainably de-slot in a turn with the car going straight off, not a spin. What has happened here is that something has caused front wheel binding resulting in the front end "hopping" out of the slot. Check for tire rubbing against the body/chassis or sharp tire edges grabbing the track. If you don't see anything obvious, try removing the front tires and running a few laps. Does the problem improve or go away. If so, go to the next step. If not try some weight up front. The second most common front end problem is the car acting sluggish in the turns. This is a too much rolling friction problem. Again remove the front tires and run a few laps. The situation should improve. To correct this problem go to the next step. Finally, sometimes the car floats or even de-slots on the straights. Usually softer guide braids or a little weight up front will cure this problem. More details on de-slotting are provided in the OBSERVATION section of this article.
5. Wheels and Tires Back To Index
a. Check all the wheel rims and tires for roundness and remove any casting residue with an x-acto knife. Then carefully install the tires, making sure that they are completely seated. If you are using soft rubber or silicone in combination with a high RPM motor consideration should be given to gluing the tires to the wheels. Silicone adhesive and rubber cement work well and generally don't damage the wheel. Contact / plastic cement may be used but be prepared for a possible one time replacement use of the wheel. Out of round wheels are not uncommon on some of cars and other than replacement the only thing you can do is try to remove some of the imbalance when sanding the tires. If your car will be running a lot of magnet downforce and or a high performance motor, you need to reinforce your wheel axle insert areas with plastic or brass tubing at this point. This will prevent them from cracking and the wheel separating under racing conditions. Additionally, if you’re going to be using high magnet downforce and hot motors in your car you may want to consider going to aluminium wheels such as Slotit or Patto's designs. These will give you better durability and won't break during hard impacts. You need to weigh the added cost and see. Remember it won't take many broken wheels to justify the added expense of the aluminium ones. You should be able to find proper inserts for these wheels so that your car doesn't suffer appearance wise. If not, you can take the original plastic wheels and make inserts from them. This can be done with a Dremel tool and sandpaper or hobby lathe.
b. Install each wheel on an old axle (straight) and place in a drill / Dremel tool or such. Run at low speed and "round" the assembly by lightly applying the assembly to a flat piece of sandpaper or a sanding block. You should correct major roundness defects here. For front tires, I also find it better to sand off all tread patterns from the tires because you want a smooth non grip surface. After the assemblies are round, sand the inside and outside edges of the tire to round them off. This will help to prevent the tires from digging into the track surface and causing a premature de-slot or flip over in the turns. For the rear wheel/tire assemblies final rounding of the wheel assembly can better be carried out after installation by running the car at low speed with the rears raised off the track, placing a sheet of sandpaper (150-180 for rubber or 600 + for silicone based tires) flat on the track under them, lowering the rear while holding the front end and letting the tires sand themselves round. Edges will then need to be rounded using a small sanding block or similar. You need to be careful when doing this so that you don’t damage the crown gear (This usually happens if you put too much pressure on the tires while sanding or you drop the chassis while the rear wheels are turning at great speed.) NOTE: Wheel assembly gluing (step 5d) should be carried out prior to final balancing so that minor deficiencies caused by wheel to axle rotation can be corrected.
c. If you want to lower the friction of the front tires to the track, and the rules allow, you can put nail polish (clear) or model cement on the tire treads to harden them and cause them to slide better. If you want to get real tricky and think you can slip it past the inspectors try this: Get some hair thin 12-15mm o-rings Dip them in nail polish and slip them on over your front tires to the high point, usually the center. Allow them to dry and you've got stealth hardened o-ring tires. When done correctly these o-rings look like tire mold residue. On the track, only the small "bump" of the o-ring will touch, greatly reducing rolling friction. Consideration may also be given to the possible advantages of installing smaller diameter front tires, such as Pink Cars 16.5mm type (P/N RV003). These tires may also help the car maintain speed in the turns and reduce de-slots on cars where the front wheel assembly, rather than the guide shoe, supports any of the front end weight. A better solution in this case might be independent rotating front wheels or raising the axle. Sometimes slightly filing the plastic axle carriers to elongate the holes removes chassis weight from the front wheels and transfers it to the guide shoe. Be careful that you don't make the situation worse by allowing the tire to touch the inside of the body (step 7a).
d. After you've finalized all
drive train alignment and gear selection and you don't expect to have to remove
the wheels again the last thing you should do is glue the wheel assemblies to
the axles both front and back. What I usually do is rough up the axle end using
sandpaper or Dremel being careful not to remove too much metal/plastic. This
gives the glue a better "biting" surface. Then I add a drop of super glue to the
axle end and press on the wheel assembly to the right position. If the wheel
assembly is to be mounted other than all the way on the axle be sure to mark the
axle so you know how far to press it on. Remember super glue sets up quickly so
you need to get this right the first time. If you are in doubt about your
ability to do this correctly there are slower set up time super glues that you
can find at your local hobby store. If you balanced the wheels before you did
this step be sure to mark the axle /wheel with a scribe before removal for
gluing so that you can reassemble them in exactly the same position. After
you've completed the gluing procedure you should check the wheel alignment and
balance again and correct any deficiencies caused by the gluing. It is probably
better to spin balance the rear wheel assemblies after gluing. For high
downforce configured cars using stock wheels we recommend reinforcing the wheel
axle holders with tubing either plastic or metal. Take a look at the
Wheel drawing for
6. Aligning the Drive Train Back To Index
a. Now to the rear wheels/tires on the inline drive train. On these drive trains the self aligning crown gear takes a lot of the slop out of the axle. However, on most models it may be beneficial to add washers or spacers between the axle bushings and the wheel to take up any extra slack. This will reduce drive train noise dramatically and make the gears mesh better. When you are satisfied with this setup and have finished any gear selection work you can accomplish wheel assembly gluing (step5d). I also add a small drop of super glue to the crown gear to axle joint to reinforce this joint. Be careful that the glue doesn't wick back into the axle bushings. Also a dab of silicone or white Moly grease on the gear self align slot will reduce friction. One note of caution here: It is usually better to remove and replace inline axle assemblies with the motor removed first because of the possibility of damaging the plastic crown gear. If you do choose to remove and replace the axle assembly with the motor installed be extremely careful that the pinion gear teeth don't damage the crown teeth.
b. On sidewinder drive cars washers should be added to first, to provide clearance between the pinion gear and the tire on that side, second, to keep the spur gear from rubbing on the chassis cut-out, third, to take up the slack in the axle assembly and fourth, to get the maximum track width that will still fit under the body. This may sound complex but it can be done quite easily using thin washers and first centering the spur gear in the chassis cut-out using a washer between the spur gear and the axle bushing then adding thin washers to get proper wheel clearance on the spur gear side of the axle (check for body to wheel clearance and track width at this time also). After this wheel is set up, add washers to the other side of the axle to take up the overall slack and to position the opposite wheel assembly in the proper place. When you are satisfied with this setup and have finished any gear selection work you can accomplish wheel assembly gluing (step5d). I also add a small drop of super glue to the spur gear to axle joint to reinforce this joint. Again, be careful that the glue doesn't wick into the axle bushings. One mod to the chassis on cars such as FLY sidewinders that you might want to consider here is to cut out the spur slot in the chassis so that gear/axle assemblies may be removed without removing the pod first. This can save time and wear and tear during gear - axle changes. On cars such as the FLY Classic Porsches the motor pod is not hard mounted to the rest of the chassis. On these models it is important that this pod is mounted squarely so that the wheels are aligned correctly.
One problem that many people complain about is gear noise usually on inline
drive trains. This can be caused by several factors and may be different sounds
which we will try to explain.
1.) The first type of noise is a ticking sound that varies with speed. This is usually caused by a plastic gear that has one or more small burrs on the gear teeth. If you slowly rotate the axle you can usually feel the place where the binding is occurring and if you take a magnifying glass under strong light you will see the burr. You can usually correct this problem by taking a very sharp x-acto knife and shaving off the burr. The main cause of these burrs is not being careful when removing the motor or rear axle. The metal pinion acts like a knife and cuts into the soft plastic of the crown or spur gear.
2.) The second noise is a constant thrashing sound that may be caused by several things. If you are using Slotit pinions they are usually noisy in this way because of their design to get different amounts of teeth into the same diameter gear. You may also get this noise if the mesh is too tight. Sometimes new gears are noisy because they haven't seated themselves. In the case of the Slot-it's and the new gears you can add some paint rubbing compound to the gears and run them at low speed, being careful to cover the rest of the chassis so you don't create a mess (I use a small plastic bag and rubber band). This will slightly polish the gears and make them mesh better. Afterwards make sure you remove all the residue with water and or alcohol. You can also use an abrasive dental tooth paste instead of automobile rubbing compound. Make sure it's abrasive or else the only thing that you'll get is a car that smells good. In the case of the too tight a mesh you simply need to loosen it up.
3.) Some crown gears of some manufacturers do not work with other brands because the diameter of the pinion alignment trough is too great. This will cause binding and noise in the gear area. Unless you want to spend an hour sanding down the trough edges just replace the gear with one that fits.
gear problem which can cause quite a bit of gear noise is a problem with mass
produced motors. Many times there is a large amount of motor shaft forward / aft
movement (slop) because of inadequate armature spacing between the motor
bearings and the armature. This can come from production this way or may be
caused by the improper installation / removal of pinion gears shifting the
interference fit armature spacer found inside most stock motors. In any event,
since most of us would rather not mess around the inside of these cheap motors,
there is an easy way to take up this slack and reduce the pinion gears "in / out
movement" when the motor is accelerating / decelerating. Take some armature
spacers (made by companies like Slick 7, Koford, Mura, etc.) or a piece of
.078"/2mm ID brass tubing and place enough between the pinion and the motor
shaft bearing on the pinion end of the motor to remove all but a paper's width
of movement when the pinion is pressed on. This should make a noticeable change
in the amount of gear noise especially on inline drive trains. This mod assumes
that the slop you remove isn't so much that it causes problems with the
commutator /motor brush interface. If this is the case then the only fix is to
take the motor apart and redo the spacer set up. This is covered in the REPAIRS
section of this article. .
5.) Finally, tightening up the slop in the gear/ axle train will probably do more than anything else to reduce rear end noise so follow the procedures for that first and the rest of this may be unnecessary. If you’re using replacement wheel / axle / gear setups, first set the wheel spacing before setting the gear. Once all the slop is removed from the wheel / bearings the gear can be adjusted using a thin piece of paper between the pinion and the crown gear, pushing them together with the paper in between and then tightening the crown gear holding screw. On sidewinder setups this tolerance is built into the motor adapter and is generally not adjustable except in modified setups such as those identified in the race tuning section of the article.
7. The Body Back To Index
a. Now let's take a look at the body. Many people think of performance only in terms of the chassis but there are a couple of points about the body which can improve overall performance. First and most important is rubbing of any moving part with the body. This usually happens with tires when there isn't enough clearance between the wheel assembly and the body and it can easily be corrected either by adjusting wheel/axle slop on the chassis or by shaving the offending body part with a Dremel tool or x-acto knife to gain clearance. This should only be done to under body areas such as overly large interiors or sloppy factory melt welding of parts such as headlight assemblies, etc. Any modifying of outer body parts such as wheel wells is usually considered illegal at most organized races. Special note should be taken on front solid axle cars that when one wheel is pushed up into the body it does not bind with any body part. This can be one cause of de-slotting in corners; as the car leans the front wheel binds and off goes the car. This is a common problem with some of the older Scalextric Euro-sedans. (Also see OBSERVATION Section.) It may be better to make these moveable axles into fixed ones using brass tubing as an axle holder and setting the wheel to track tolerance so that the front wheels just lightly touch the track. This is explained further in the front end setup section of this article.
b. Any legal body weight reduction will improve your lap times because the Center of Gravity of the car will be lowered. If you want to see by approximately how much, try a few timed laps without the body. Check your track or club rules and take advantage of any weight reduction procedures allowed. This is one area where people like to cheat by shaving or edge drilling into parts such as interiors. Be careful that you stay legal. The best way to remove plastic from the inside of the body is to take a Dremel tool with grinding bit at low speed and slowly remove a layer at a time. One way to make sure you don't remove too much is to place a finger on the outside of the body where you are removing plastic from the inside. As you get close to the surface you will feel the heat / vibration. STOP at that point or you will grind through (and remove a layer of finger). Practice on a scrap piece of plastic to get the "feel" and you'll be surprised by how easy it is to remove a sizable portion of the body weight. Experiment with different bits to find the ones that work best for you. I have found that a set of dental bits work quite well and may be cheaper than Dremel bits. Another area where weight can be saved is on the interior pod. Usually manufacturers mold quite a bit of extra plastic into the interior pod to allow other details such as fuel fillers, radiators, etc. to be attached as one assembly with the pod. You can save weight by removing these parts and attaching them separately and grinding away the excess plastic. You can also remove plastic that isn't seen like the floor under the driver’s seat and plastic beyond the view through the cockpit windows. With careful plastic removal you can get a weight that approaches that of a thick vacuformed body.
c. If your rules permit some cars can benefit from lowering the body on the chassis. Car manufacturers will typically err to the high side on the cars height. This may be due to several reasons some of which have nothing to do with physical constraints. If a car can be lowered to look more realistic and also handle better go for it if your inspectors allow it. Usually shaving the mounting posts will do the job. However, on some cars with full chassis this lowering procedure may just be too hard to do expeditiously. Cars with body parts molded on the chassis will have to have these items removed first and glued to the body. This way there should be nothing inhibiting lowering the body by shaving the mounting posts. If you happen to cut too much off the posts never fear. Just take thin spacers / washers and shim it back up to the desired height. You can then glue them to the post and away you go.
d. Some racers advocate loosening body mount screws to increase performance. Well, on magnet cars with high down force, doing this may result in the chassis dragging on the track since more then a few plastic chassis cars use the body for chassis rigidity and loosening the mounting screws will allow the chassis to sag. On weaker magnet and non magnet cars there may be some merit to letting the body "float". I personally haven't noticed too much difference on plastic chassis cars with strong magnets and I think that this idea comes from the metal chassis / non magnet side of the hobby where it does make a difference. Try it. If it works for you, do it. Small soft plastic or rubber washers can also be used between the mounting posts and the chassis to partially isolate the body. Some cars such as the FLY Corvettes and Vipers have the chassis “snap into place” on the sides because the exhaust pipes on the chassis must fit out the side of the body. If you want to have the body “float” properly you will need to elongate these body holes slightly to get some free play. The chassis part may also be shaved slightly to get the up-down movement required. If you don’t want to elongate these body holes you can also cut off the exhaust pipe representations from the chassis and glue them to the inside of the body leaving the rest of the chassis free to move depending on the mounting screw tightness. This mod alone can reduce your lap times by a tenth or two.
e. Just like gear noise, body noise is something that seems to plague some cars. Usually it can be isolated to one of a couple of causes.
1.) First, interference between the body and some moving part is a prime cause of body noise. Cars such as the SCX Ferrari 333 and Cadillac have almost no clearance between the body and crown gear. On many of these cars a raspy noise will signal that these 2 items are indeed rubbing together. The best cure is to carefully grind out the body area to gain clearance or shim the rear body posts (least desirable because of CG considerations).
2.) On other cars the motor may be vibrating against the body shell or interior. Again the same solutions as previously mentioned should cure the problem. One other option is to take a small piece of sound deadening foam and fit it between the motor and body. This solution also works for some bodies that are just plain noisy because of their design. Sound deadening foam will greatly improve the situation and adds very little weight.
3.) Cracked mounting posts can allow the mounting screws to work loose allowing the body to vibrate. This can be fixed either by gluing the post and retaping the screw or putting a sleeve of plastic tubing over the post and gluing it in place to reinforce the screw hole.
4.) The last item which can cause body noise is loose bits such as headlight covers, window plastic and interiors not being securely glued. You can usually find these noise makers by shaking the body without the chassis installed. Gluing the offending part will fix the problem.
f. On FLY cars that use the sidewinder configuration, particularly the Classics, you may want to check that the motor brush assembly on top of the motor has enough clearance with the body. Without proper clearance this part will cause the chassis to warp when the chassis mounting screws are tightened, the result being a car that sits on 3 wheels and seems to be warped. To fix the problem, either Dremel off some of the brush assembly top or grind off some of the under body where the interference is occurring. You could also put some thin washers on the body mounting posts to fix the problem but this will raise the rear of the body slightly.
g. Although not exactly a body mod, taking advantage of the full track width of the body is important to getting the best cornering characteristics. Make sure that the tires extend out to the maximum track width allowed by your rules. A wider track car usually equals better cornering. Watch out if you are using replacement tires that are larger than stock because some car body interiors may cause interference. If it's not severe usually a little cutting on the interior tray will correct this problem. Also remember that tires expand to varying degrees with axle rpm. Tires that clear the body at rest may have serious body rubbing problems at speed. Gluing tires to wheels can reduce or eliminate this problem in most cases.
At this point, if you are not doing Race Tuning you should run in the chassis for about 50 laps or so stopping every 10 laps to check to make sure everything is breaking in correctly. Check the motor temperature as a hot motor could be a sign of excess drive train friction. Check for uneven tire wear. This could be indicative of unbalanced wheel assemblies or bent axles. Make sure the gears are meshing correctly and that the bushings are not turning in their carriers. A roaring type sound at high speed may indicate that the rear tires are expanding at high speed and that they need to be glued to the wheels. Check that the guide brushes are making proper contact with the track rails and that the guide is seated properly in the slot with the front wheels just barely touching the track surface. Check the OBSERVATION SECTION of this article for other items to watch for. If you observe any problems go back and redo that particular section again. If you note a problem not identified in the first part of this article check the other sections for possible solutions. If all else fails contact this writer by e-mail describing the exact problem. We will attempt to answer any inquires for information.
After this run in period you can still race tune the chassis. This includes: magnet tuning and adding weight, choosing right gear ratios for the right track, selecting rear tires for track conditions and upgrading motors. These items are covered in Section III of this article. Otherwise remount the body and try it out.
heading for slot car tuning, but this is one of the most important tools you can
employ to detect problems in your car's performance. Watch the car as it goes
around the track. Have your friends watch also. You can't have too many eyes.
What are you looking for? Basically, your looking for symptoms of any problem
that might be slowing your car down or causing it to perform below expectations.
Here are a couple of the more important things to look for other than those
mentioned specifically in the General Section of this article.
1. De-slotting: How does the car come off the track?
a. "Normal" de-slotting in a turn: The car spins out with the rear end departing first followed by the front end "twisting" the guide shoe out of the slot. This is what you should see when the car reaches its rear traction limits if your car is balanced well, and all the general tuning tips have been followed correctly. If this happens at too low a speed for your satisfaction follow the Race Tuning Sections that deal with increasing rear down-force and traction. Usually this consists of magnet tuning for more down-force, adding weight towards the rear axle and/or upgrading the rear tires to a width/type that will give more grip. In rare cases you may even gain speed by going to a lower torque motor. This is because less torque translates into less drive to accelerate and break loose the rear tires.
b. Car suddenly flips out of the slot in a turn with both the front and rear departing nearly together and car may roll over. This is usually symptomatic of a car with too high a CG. It can be quite a violent departure when a high CG car has been magnet tuned without consideration being given to lowering the CG first. Your choices in this case are simple, either add more magnet to raise this limit higher (this won't fix the problem) or work toward lowering the CG , first by adding weight (Setting the Vertical Center of Gravity) and second by balancing it with magnets and tire selection (Race Tuning Section). Consideration should be given to also redoing steps 5b and 7b in the General Section of this article.
c. Car suddenly de-slots in a turn while decelerating and the car goes straight off with little or no sliding. This is usually caused by a variety of front end problems that cause the guide shoe to be driven out of the slot. The prime suspect is the edges of the front tires grabbing, loading the front and pushing it up thus raising the guide. Tire rubbing is also a possibility. Recheck step 5b/c and 7b. Also check guide braid adjustment. Sometimes, a little up front weight helps but usually not in this specific case.
d. Car suddenly de-slots in a turn or on a straight while accelerating and the car goes straight off with little or no sliding. This is usually caused by the front end unloading and allowing the traction to push the guide shoe out of the slot. Add weight to the front end of the car behind the front wheels in 5 gram increments until problem is solved (usually less than 15 grams). If your rules allow, adding a magnet just behind the guide will solve this problem also. The amount of magnet you use here can be critical because too little and you don't solve the problem; too much and you cause the car to lose speed. I usually start with a small magnet and drop more magnets to the top until the problem is solved or I reach the point of diminishing returns then I back off one magnet. Consider going to softer guide braids and insure they don't push the front end up too much. One other point, sometimes there is too much grip from the rear tires. This can have the effect of causing the front end to lift. The solution is either more weight up front or a slightly different compound of tire that has a little less grip.
e. Car begins to slide under acceleration out of a turn then suddenly de-slots possibly flipping the car. The car may also "fish tail" a couple of times before departure. This is usually caused by the cars rear tires transitioning from the plastic track to the metal rails and back to the plastic track as the car drifts. This affects short wheel base cars more than the longer ones and narrow track cars more than wide track ones. It is not usually a car problem but a deficiency in the overall design of the track system. Some brands of track are worse due to slightly higher raised power rails. If the problem only happens at a certain point on the track check to make sure the track is flat and that the rails are properly seated into the track. The problem can be helped by using stronger/wider traction magnets that have a wider field dispersal such as flat bars (Slotit type for example) as opposed to the cylindrical type. Adding weight can also help. This is because the wider magnet traction or weight will help to hold the rear down through this transition region. Also make very sure that the inside edges of your tires are properly rounded since these inside edges are the leading edges during rail transition. On some occasions different tire compounds will help also. Other than that, watch how and when you apply power coming out of the turn.
f. Car deslots in tight radius turns with the guide being pushed out and the rear end doesn't slide. This is a classic symptom on magnet cars when the rear traction magnet is either too strong or improperly located or both. What happens is that the car cannot track through the turn because the rear magnet prevents the rear from sliding slightly so that the guide doesn't bind in the slot. This problem can usually be cured by moving the traction magnet(s) forward or reducing the overall rear downforce. In instances where this happens on one hairpin turn, for example, and the car handles in the desired way on the rest of the track, it might be possible to just add some more weight / magnet downforce to the front end to force the guide down more. You will have to experiment here because the solution depends largely on the overall track configuration. Try both methods and use the one which gives you the best overall handling and lowest lap times. You can also mess with different tire combos (compounds / widths) to get less traction as this can also be effective in solving this problem. In non-magnet cars this can be caused by too much rear tire grip. The solution is to go to a slightly harder tire compound
2. Power: Does the car appear to be getting proper power?
Normally a car should respond immediately to any controller input and the motor power should remain constant with a constant applied voltage. If the car does not respond in this manner and/or hesitates at certain parts of the track then something is wrong with the power circuit to the motor. For the purpose of this article we assume that you have a clean serviceable track. So the steps here are for the car part of the circuit.
a. Car slows down on parts of the track: If this happens and only to this one car than the problem most likely lies with the guide braid. Check that it is clean and serviceable. Consider using a soft thin competition variety. Now adjust it so that it makes proper contact with the track. The best way to verify this is to darken the room and drive the car slowly around the track. Any sparks observed means that one or both of the braids have momentarily lost contact with the power rails. This could still be a type of track problem so eliminate that first by cleaning and repairing as necessary. Readjust the braids and add a conditioner if necessary. Remember to readjust your braids if you run on different types of track. Rail spacing / surface height may be different on other track types so readjustment is necessary.
b. If all else fails replace the guide shoe as it may be excessively worn. If there is no sparking but the car still looses power, check the contact serviceability on cars that have sliding contacts such as Scalextric and newer SCX cars. On all others check that eyelets are securely installed and that all wires and solder joints are serviceable. Recheck General Section Procedures 2b&c and 3e. Euro cars are notorious for having sloppy guides. If you can't seem to get the braids to consistently make good contact you might want to consider reworking the guide and guide holder (General Section 2d) to tighten it up. This should help solve any nagging braid contact problems.
c. Though not directly related to power application, one other possible cause of the symptom described is a traction magnet intermittently shorting out to the track at one or more points around the track. As it shorts, it sucks down the power and slows the car. This type of failure is critical because it can cause a controller or the track connections to melt and become unserviceable. If you suspect this problem paint the bottom of the magnets on the car and run it around the track. Carefully inspect the track for evidence of the paint and repair that area as required or raise the magnet. One other symptom of this type of problem is the controller becoming excessively warm after running the car a short time. You may also observe sparks coming from under the car as the magnet shorts out.
d. If you've done all this and still have the problem then change out the motor and see if that fixes the problem. If so, then there is a problem in the motor. You may be able to save/ repair the motor by performing some of the procedures in the REPAIRS section of this article. Sometimes loss of power comes from either a cold solder joint or a wire/solder joint that is about to break. Check the wire to motor connections very carefully if you are having this type of problem and reheat the joints with a soldering iron if there's any doubt about the joint's serviceability. Problems usually occur when the wires are allowed to flex at the motor connection. Placing a piece of tape on the wires to hold them to the chassis will greatly reduce the possibility of this problem happening to your car. Spending a little money for good flexible lead wire can also save you from having these problems in the future.
3. Car slows noticeably through tight turns
a. Sometimes a car will seem to slow down and "drag" through tight turns. This can be caused by several factors. The first thing you should do is take the car and run it by hand through the turn and observe and "feel" what the car does. If it drags here you may be able to determine the exact cause and correct it.
b. The first and most common problem may be that the front wheels are dragging through the turn, in which case, the front end needs to be worked per the general instructions to lower front wheel friction.
c. Another cause may be that the rear magnetism is too strong along the center/forward/aft axis and is causing the guide to drag because the rear is not allowed to track through the turn properly. The best solution here is to either lower the center magnetic traction by going to a multi-magnet setup or move the existing magnet forward slightly to decrease the magnet to guide distance. This is quite a complex problem because you must find the best solution that balances the car for the whole track. A small change to correct a deficiency in one turn may create a whole new set of problems at other points on the track.
d. One other possibility is that the guide shoe is too long, front to back, and is binding in the slot. This is common to Carrera cars used on tracks with tight turns. The easy solution is to remove a millimeter or so off the rear of the guide.
e. Finally, if you are running any magnets close to the front axle you may be picking up flux line friction from those magnets. Many people slap magnets on the car near the guide and front axle assembly and fail to realize that the front axle is ferric metal in most cases and will be affected by close proximity of magnetic fields. The best solution if you think this could be a problem is to go to a non ferric axle, either plastic or aluminium / brass. I like brass or aluminium thin wall tubing because it's light and strong.
4. Car slows on the straights
a. What if the car appears to slow on the straights? Well, this is uncommon in most cases but there are a couple of things to look at if you have a problem like this.
b. First, if the car initially accelerates okay and then seems to bog down you may be seeing the effect of rear tires expanding and either vibrating or rubbing the body. Usually you will notice a “whooshing" type sound but not always. What you need to do is go back and glue the rear tires to the wheels and this should solve your problem. Also check that you haven't bent an axle because this will also give to a similar symptom.
c. Next, if your car seems to get up to a certain speed and just kind of runs out of juice you may need to do some gear ratio work. Different tracks may call for different gears and sometimes even a slightly longer straight section may dictate a change in gearing.
d. Finally, if your car is slow to accelerate you may be suffering from one or more of several problems. First check for lubrication and check that nothing is obviously binding. Check that the front wheels are turning freely. See if the motor is getting excessively hot. This may indicate either binding somewhere in the drive train or that you’re running too much downforce for the motor type.
5. Excessive noise
a. Car noise needs to be isolated to the offending parts before a good solution can be found. What should be done first is to figure out if it's a chassis, body, or chassis to body problem. Running the car without the body should quickly identify this fact.
b. Chassis without the body should be pretty quiet so any racket without the body is either gear, bushing (both axle and pinion shaft; as applicable), motor/mount, gear mesh, front guide or front axle assembly. Removing the front wheel assemblies) and running the chassis will eliminate or identify this area as the problem. Rear axle and pinion shaft bearings should be glued into their carriers. All slop should be removed from the rear axle assembly by using washers/spacers as required. Motor and motor mounts where applicable should be glued in; I like RTV because it is a vibration suppressant and can be removed easily if a motor change is required. Guide slop can be corrected per the info in the General Section. Gear noise can be corrected or reduced after axle shimming by putting a dab of paint rubbing compound onto the gears and running them at low speed for a couple of minutes, stopping periodically to work the compound back into the gears. This should be cleaned thoroughly afterwards with water and alcohol.
c. On the body first take it and shake it thoroughly to see if any parts are loose (See Body section). Prime offenders on FLY cars are the headlight assemblies which are hot melt mounted and sometimes the weld is not good. Super glue will quickly fix this problem or any other loose parts problem. Be careful to use the glue sparingly because it has a tendency to run and you don't want to mess up that beautiful paint finish with it.
Finally put the chassis and body back together and check for any interference
between the gears, motor or wheels/tires and the body. Any interference can be
corrected either by shims or by grinding away part of the body underside that is
causing the problem. With all that done your car should be nice and quiet. If it
isn't than the last thing you can do is add some sound deadening foam between
the body and motor (just a small piece should do it) to isolate the motor from
a. This is probably one of the scariest things that can happen to you. You are driving your car around and suddenly you see and smell the signs of electrical smoke coming from your favorite car as it stutters to a halt. What should you do?
b. First, shut down the power to be safe. Now, figure out what caused the problem. Several things can cause the described symptoms most of which aren't terminal. The most common failure in a car in this situation is that one of the EMI filter Capacitors or inductors has gone "high order" and self destructed. This is quit common on tracks running over 14vdc. Some of the small devices used on the outside of the motors just can't handle the extra voltage that some of the power supplies put out. Removing these components before it happens will save the adrenaline rush of seeing your toy smoking.
c. A second cause of smoke is over lubricating the motor bearings, allowing the excess oil to get on the motor commutator. Short of taking the motor apart to clean the comutator the only thing you can do is to try soaking the comutator end of the motor in alcohol or lighter fluid to break the oil down. Re-lube the bearing and try again. You may have performance problems until all the residue is "burned off" by the motor brushes. See, there's a reason people tell you not to over lube the motor bearings.
d. The third likely cause is a strand of one of the contact braids becoming shorted across the rails. This seldom happens but on Carrera guides it may be more common because of the way it's built and the type of braid used. Removing the offending strand will cure the problem.
e. The fourth likely cause is a motor lead wire that is about to stress break becoming resistive and overheating. This usually happens at the motor connection and can be spotted by looking for broken strands at the solder joint. Stripping and re- soldering the wire will fix this. Taping the wires to the chassis so that they cannot flex at the motor joint will prevent this from happening again.
f. The last and most terminal cause of this problem is a motor that has "given up the ghost". Short of rebuilding the motor which is usually not very practical for this level of motor, replacement is the only solution. Before you do replace the motor; however, you may want to investigate whether there was something such as too much magna traction which caused the failure. You don't want to lose another motor for the same reason.
g. The causes we've identified here are strictly failures in the car. Other track and controller problems can cause electrical failures of the type described. These items are presently beyond the scope of this article. One item though worth mentioning is what happens if you short out the track rails with a traction magnet or similar. Usually the car will stop and if you continue to hold power on the controller something is going to give. This is usually the controller or the track wiring or sometimes the power supply itself. So be careful when running traction magnets and consider fusing your controllers or power supply as a safety precaution.
7. I’m losing my gears!
a. With the introduction of more and more powerful motors particularly in inline drive configurations some people are beginning to experience problems with inline gears stripping. How can this happen with a system that uses an auto align feature on the crown gear? Well quite simply, the chassis is too weak for the amount of motor torque being transmitted through the “differential”. When the motor applies torque to the rear axle the axle bearing carriers are flexing, causing the rear axle to “shift” slightly under stress. This wears out the self align slot which eventually allows the gears to slip, stripping the crown gear in most cases. The solution(s) to this problem is fairly simple in most cases and is explained below:
1. The easiest fix attempt though by far not the cheapest or most desirable is to replace the rear axle setup enabling the use of a Slotit type gear which has a metal self align slot. The axle will still shift under stress but the slot will not wear out nearly as fast as with plastic crowns. The problem is still there but the gear wear issue disappears. Unfortunately, this movement under torque can also cause binding, noise, and other performance robbing events.
2. The next easiest fix is to reinforce the axle bearing carriers. Plastic or metal can be used in this case and be glued around or attached to each carrier so that these carriers do not flex. By eliminating the flex you solve the problem.
3. Finally, the most drastic and usually most expensive solution, but one that can prove the most effective, is to discontinue using the plastic axle carriers and go to a motor “U” bracket made from metal. This will likely take some surgery to your chassis to get a proper fit but in most inline drives it can be successfully accomplished. This solution will give you a rock solid drive train setup.
b. Another area that can cause gear problems on front motor rear drive cars is the driveshaft bearing carrier. Again this is a problem of flex. Here the solution is to brace the carrier with extra plastic or metal to eliminate the flexing movement component. In addition to saving gears the car will run quieter with less torque induced friction.
c. Motor movement in any car can spell disaster for the crown gear. Motors should be secured to and when permitted, glued into the chassis. If there is any up-down movement in the mounting prior to gluing, it is imperative that the motor shaft be aligned exactly center with the rear axle line. If the pinion is shifted, even slightly, up or down in relation to the axle center the crown gear will sustain damage and its life will be significantly shortened. Additionally, the drive train will be noisy and there will be additional friction present.
8. Other observations: Redo applicable General Section procedures related to the problem.
1) Multiple magnet
setup: Many clubs limit cars to just one magnet but there are growing classes of
cars that are allowed multi-magnet setups. In these classes there is usually a
limiting factor that dictates how much magnet downforce may be employed such as
motor, power, or controller restrictions. For the purpose of this explanation
the following restrictions are assumed:
Motor: Plafit Cheetah class or less,
Controller:15ohms or greater
Car: Lemans Sports/Protypes1970-present at least 75% mfgr plastic chassis by weight in stock form including motor mounts and ballast; excluding motor, axle assemblies and magnets.
a) First, almost any car can be made into a winner but some are easier to set up than others. For speed tracks the FLY sidewinder cars seem to be a good choice as well as the SCX LeMans, Ninco LeMans and the Proslot Toyotas inline drive cars. I like the SCX R8 Audi and Proslot Toyota for technical track setups.
b) Perform chassis mods identified in Section7 of RACE TUNING. Major things to strengthen are guide holder and rear axle carrier areas.
c) Assemble your rolling chassis except for magnets. Begin magnet tuning by setting up the rear traction magnets. The main consideration here is forward/aft location in relation to rear wheels. If your racing on a track with no tight radius turns then magnets should be just forward of the rear axle or as close as you can get without interference with the crown gear. If your track has tight radius turns then you will have to set your rear magnets so that your car can track properly through these tight turns. This may necessitate moving your rear magnet(s) forward slightly. You can check this by manually pushing the car through the turn and checking for binding of the guide in the slot or pushing up of the guide as the chassis transitions through the turn. If either happens you have to make one of two choices. Either move your rear magnets forward or add extra magnets / weight to the front to hold the guide down in the slot. The choice depends on testing and using whichever gives the best time. There can be some benefit to using multi-magnet setups for the rear magnet setup. Multi-magnets allow you to tune with individual magnetic fields working together or in opposition to get desired Downforce at different off center positions of the chassis to contact rail relationship. Increasing the downforce off center by a certain amount can increase departure resistance at these angles allowing the driver some extra time to react to rear end departure. Adding magnets outboard of a basic magnet setup can have this effect.
d) Once you've set the rear magnets you can setup the front end. Here you can start with a light magnet setup and add downforce in increments until your times begin to slow. I usually have pieces of magnet I use to set the amount and then I go with larger single ones that add up to the smaller ones for the final configuration. Once you've set the forward you can mess with the rear amounts slightly to fine tune the balance and get the best times. Remember the rear magnets are primarily for traction with some forward guide downforce depending on their distance forward from the rear axle. Forward magnets are primarily used to hold the guide in the slot during cornering and hard acceleration. They affect traction only to the extent they are moved toward the rear axle. Adding too much forward Downforce will have the effect of slowing the car more as the guide friction builds up due to the downward pressure. Forward set ups of 2 or more magnets can often give you a more desirable result since you can tune the front end using more than one magnetic field either working in conjunction or opposition depending on magnet orientation. There is also some advantage to having the forward magnetic Downforce effect increase as the chassis swings off centerline. The reasoning being that the increased downforce will force the guide down as it reaches the movement limit giving the driver an extra split second to try to recover a departure before the guide is twisted out of the slot. CAUTION: if you add allot of forward downforce you will probably need to reinforce the guide holder since the stress loads of the guide being twisted out of the slot during departures will be great enough to break stock guide holders.
e) Here are some other things to consider when magnet tuning. Bar magnets tend to be better then cylinders for field dispersion and should be used when you want the magnetic field spread width wise. Thin cylinders work well when used in pairs and when the setting of fields with less density is desired in one area such as down the centerline of the car. Taking a Slotit bar, for example, and mounting cylinders on each end will give you a stronger field toward the outside of the bar ends and less towards the center. This will make your car more departure resistant in a turn while not overly causing drag on the straights. You need to also be aware that too much downforce applied away from the centerline can have a detrimental impact on the cars corning if it is strong enough to "tip" the car. Additionally, such downforce can slow the car coming out of the turn since it causes the car to want to stay semi sideways because of this strong attraction between these offset magnets and the track rails. Sometimes a little movement of one magnet in one direction can have a dramatic impact on your lap times so take your time and don't be afraid to experiment.
f) Last but not least, when you talk about max magnet cars the primary thing to remember is "light weight is good". Do whatever it takes to keep the overall weight of your car to an absolute minimum. For this reason you should generally not tune a max magnet car with weight. Only use magnets. Also remember that when they do depart the velocity is usually quite a bit higher than with a non-magnet or light downforce car in the same situation so cars need to be built strong.
b. Performance Matched Tuning: If you decide that matched performance is what you are after then that's a little more difficult. Sometimes magnets alone cannot accomplish this to your satisfaction so this advice should be considered along with tire, motor, and gear ratio selection and weight application since these are variable factors as well in changing a cars performance. These subjects are also covered in this article. So where do you start? Well, is the car you are tuning faster or slower than the cars you are trying to PMT to? Faster read on; slower read on anyway.
1) Faster car than the cars you want to PMT to:
a) If your car is faster, usually the first method of slowing it down is to raise the existing magnet further away from the track. If the car has a magnet pocket, placing thin pieces of paper/plastic (I use pieces of plastic coated playing cards) between the magnet and the chassis will do the trick. Add a piece, run a couple of timed laps and repeat until desired time is achieved. Remember, elementary physics states that the magnetic field of a magnet is approximately proportional to the inverse cube of the distance from the magnet. Therefore, if you double the distance from the magnet to the track rails, the magnetic field strength will be reduced (roughly) by a factor of 8. So a little raising reduces the down force by a lot.
b) If raising the magnet isn't possible or feasible then the next best option is probably to replace the original magnet with a smaller one. Magnets come in all shape and sizes and are relatively cheap so you can stock a varied supply. Choose the common shapes (cylinder, flat bar, etc.) in various thickness' (thickness usually equates to strength on small neo-type magnets). I like these or similar Ninco 70223 (8x2), I.M.A. (Spain) #INED0009 (8x3), 70179(8x5), 70229(3x6), 70157 (13x8x3); Wondermagnet #9(3/8x1/16), #10 (6mm); Where do you find them? At your local hobby/electronics store or on the net are the best places. Internet stores such as Fantasy World (www.fantasyworldhobbies.com/) can help you out and I've had good luck with (www.wondermagnet.com). Remember stacking magnets essentially add their individual strengths together, so you can simply drop one magnet on top of another to increase the track down force. With this in mind start with a magnet about 1/2 the strength of the original and add 1/8 or so strength magnets between timed runs until you get the times you are looking for.
c) If you still can't get it quite right read on. The next best option is to shift the original magnet forward toward the guide shoe. As you get further away from the rear axle the amount of rear down force will decrease allowing the car to drift more in the turns and in most cases ultimately if moved further front will allow the rears wheels to spin due to loss of traction. The result then of moving the magnet forward is an increase in lap times. Light to moderate amounts of magnet strength at the center or towards the front will tend to give your car handling similar to that of some of the "classic" makes from the sixties. Cars will drive with controlled drifts and will not have that "stuck down" feel.
d) The fourth magnet option to slow the car down is to remove the original magnet and to use multiple smaller magnets at different points on the chassis to get a desired handling effect. Start with a small base magnet reference (again toward the front if you want drift; toward the rear axle for less drift more rear traction) now you can add small magnets forward or aft, left or right of the base magnet to get desired handling/timing results.
2) The car is slower than the cars you want to PMT to:
a) You use essentially the same methods as for faster cars. In the first method instead of raising the magnet you will want to lower it. This is usually done by opening up a hole in the chassis under the magnet well so that the magnet can be pushed closer to the track. Secure it with super glue once you've established the distance and away you go. If you go with this method you might want to go a step further and make the magnet adjustable. On round magnet cars, I've had good success using short aluminium screw posts with flat screws that are used in document binders. I glue the magnet to the screw head and mount the post on top of the magnet well. Then I can simply screw the magnet up into the well from the bottom of the chassis. I use a drop of rubber cement in the well to give an interference fit and cut a slot in the thread end of the screw so that it can be adjusted with a jeweler's screwdriver from the top of the chassis sitting on the track. A drop of glue or nail polish can be put on the bottom of the magnet will keep it from turning from vibration.
b) In method 2 instead of replacing the original magnet with a smaller one; go to a larger one or better still just add a second to the top of the first. You don't have to glue it or remove the plastic in between. The 2 magnets add their force together (minus a small amount). You can vary the amount of down force by experimenting with different strength magnets. Just pull one off and drop another size on. Like I said you don't have to glue them on. I've used this method many times (one of my Fly Porsche 917s comes to mind) and have yet to have one come loose in a crash.
c) In method 3 shift the magnet towards the rear axle if possible. Better still, consider getting rid of the original magnet and gluing a thin magnet to the bottom of the motor (inline drive) if there is adequate clearance.
d) Method 4 is essentially the same for PMT slower cars except use larger magnets. I use this method when I have a car that I want to drift but at a higher speed than with the original or no magnet. The addition of a small flat bar magnet just forward of the rear axle in addition to a forward mounted stronger magnet will give this affect on some narrow tired cars that originally had no magnet such as Pink Kar's Ferrari GTO and Ninco's Classic Series cars. This method is also the best way to get the most performance out of your car. Strong magnets mounted just forward of the rear axle, toward the outside of the chassis will give you more downforce as the car begins to slide. A weaker magnet either under the pinion gear or just in front of the motor will give you the weaker downforce for straight line traction. Combinations of magnets using variable strengths can help you to tune your car for individual track configurations much as real race cars are tuned to each track. Don't forget magnet tuning is three dimensional up - down for magnetic attraction; in - out - forward - back for balance and handling characteristics. I find that a cheap spring scale can greatly assist you when trying to set up multiple magnet configurations. You can use it to pull your car or chassis sideways by the rear wheel and take measurements as each magnet or magnet set passes across the contact rails. Careful manipulation of magnets can allow you to set up smooth departure transitions for more controllable slide departures and also allow you to set up strong downforce at extreme angle configurations that doesn't adversely affect straight line speed. Also, don't ignore the front end completely. Magnets just behind the guide act to hold the front end down in tight turns and to stabilize sideways movement. Magnet strengths in this area are usually less than at the rear where magnets are used mainly for traction. What I usually do is glue a small value magnet behind the guide, run laps and drop on more magnet until I reach the point of no more time improvement. Then I remove one magnet and use half of it strength value and retest. Eventually I get the optimum value of forward downforce. You may have to play with the back magnet a little to get the exact rear setting after you've set the front. Finally, if you want to increase the downforce slightly of a particular magnet or magnet set you can use thin ferric sheet metal shims on the opposite side of the magnet location to where you want to increase downforce. These ferric shims don't increase the field strength as many people will try to tell you but "squeezes" and redirects the field so that the flux lines are directed slightly off their normal pattern, increasing their density in the area opposite from the shim. You can also use ferric metal shims to "block" flux lines from interfering with steel axles or other ferric components. By placing thin spacers vertically to the magnets you can also set up magnetic boundaries in your traction fields. This can sometimes be beneficial to improving straight line speed. If you want to see exactly what I'm talking about take a magnet and put a small piece if sheet metal on one side now observe the difference in magnetic attraction between the side with the metal and the side without. Remove the metal and see that the magnet side opposite the metal had a greater perceived attraction than it does without the metal on the opposite side. There are some interesting possibilities in using this principle for magnet traction.
c. Measuring Magnet Downforce: Whether you are Max Lap Speed Tuning or Performance Matched Tuning there is usually a need to measure your downforce to get some idea of what it is or how it changes at chassis angles off center to the track rails. There are several methods to doing this, some of which involve fairly expensive scales or cutting up of track etc. What I've found that works best for me is simply to use a cheap set of postage Ketter spring scales (usually available from science equipment stores for less than $10.00 or from China for less than 2) and do pull tests like most of us did at one time or other in high school physics class. The results I get give me a reference that I use to setup cars that race in similar classes. My method doesn't separate weight from magnet downforce specifically (though it can be done easily) because both factors go contribute to the overall downforce of the car. Measurements are taken at the rear axle for traction downforce and at the guide or front axle for guide downforce. I also make one additional test which is not directly a downforce function but does serve an important purpose. That is to measure the horizontal resistance friction of the rear of the chassis to a specific track type. Let's look at each in slightly more detail.
1. First, you need to make a simple pull adapter to hang on the hook of your scale. I use a piece of piano wire bent in an upside down "V" with a small hook at each end of the “V” to engage the rear axle of the chassis under test. Use a flexible wire size so that you can squeeze it to any axle length.
2. Put the chassis under test on a piece of track that is secured to a table (you can use your race track if you don't have a spare piece) so that it is aligned perfectly straight with the track rails. Connect the spring scale and adapter to the rear axle and slowly pull the scale up vertically until the rear of the chassis "breaks free" (If you want to get fancy you can build a scale stand to keep the scale exactly 90 degrees vertical during the test.) Observe and record the reading of the scale when this occurs. Perform this several times so you have a good average reading. This is the overall downforce in oz/gms that is being applied By your chassis rear axle to the track on the type of track you are testing on.
3. Now, you can measure offset downforce at this time if you so desire. What I've done is taken a protractor and marked off 5 degree points off center from the track rails so that I can position the chassis at these offset angles. Using the same setup and method as in step 2 test your chassis at whatever angles you are interested in and record your readings for each angle. This will give you the rear axle downforce at given angles off center and can be used to magnet tune for off center situations.
4. Next, you will need to make an adapter for the scale so you can pull test the guide. I usually just take a thin piece of wire wrapped around the guide tongue but each type of car may need a slightly different setup. The only important thing is that you are pulling at the guide or as near as possible. Set the chassis on the test track, connect the scale and adapter and perform the test as in step2. Record the results. These figures will reflect the downforce pressure being applied to the guide.
5. For the last test, set the chassis as in step “2” and you will have to make an adapter out of wire that wraps around the rear axle at one wheel and extends laterally so that the spring scale can be attached to pull the rear of the chassis sideways. Pull the scale slowly and measure the point where the rear of the chassis begins to slide. (see drawing section for an illustration of this test setup). The readings you record here will reflect the overall friction resistance at the rear tires to the test track interface. This can give you a good static reading of departure resistance with all the components factored in i.e. weight, magnetic downforce, tires and track surface.
6. Those are the tests I make. I use them to give me references for quick setup on any car. These figures will also tell you what the max safe downforce for a given motor type is over a period of time as you build your data base. You can also get a better picture of how different tires compare with different downforce setups on different track types using the drag test. This is perhaps one of the best pieces of data you can develop if you race on different surfaces (since it is a STATIC test it does not factor in inertia components such as chassis flex, tire expansion, etc.). You won't have to listen to "experts" telling you how such and such a tire is the best for a given track type. You can test it yourself and see that in some cases you are being misinformed. You'll also notice that, for my purposes, I don't use the body of the car. This is just a personal preference. I usually do on body tests after I set up the chassis. You can do tests 1 and 3 fairly easily with the body installed. The guide pull test will not be easy though with a body installed. My overall static weight goal on high downforce LeMans cars with standard bodies (lightened) is between 65 – 85 grams. I haven’t been able to get much lighter without some seriously expensive hardware. All additional downforce is strictly magnets and can be quite substantial.
7. One final test setup you may want to have if you have the space and money is a kind of skid pad. This is made by making a 360 degree circular track setup. You can wire this with an adjustable power supply and / or install a timing gantry for computer timing. My setup uses both but I use the computer timing setup most of the time when tuning a car. Here you run the car faster and faster until it finally deslots and check your times. This gives you a dynamic test equivalent for the test in step # 5 adding in the dynamic components. I have found that if you set up the car correctly using the static method though, you almost never need to use the dynamic test because the results coincide. The dynamic test is more important when setting up chassis flex, which generally entails adjusting the tightness of body mounting screws on plastic chassis cars or cutting pieces off the chassis on cars where this is desired. For this reason you may want to forgo the extra cost of this dynamic setup and invest in several different brands of straight sections on which to test using the static method. That way you will be able to set your cars up for any type of track if you have one piece of that type track.
d. Setting up traction on front motor rear drive cars
1. These cars offer a slightly different challenge when it comes time to magnet tune them. Setting the rear up is usually fairly simple since there is ample space where the motor isn’t. Slotit bar magnets or similar provide the best starting point. If the car’s stock magnet is a cylinder I personally either delete this all together and go with the wide bar or lower it to the same level as the chassis by enlarging the hole in the bottom of the magnet pocket to allow the whole magnet to be pushed down flush with the chassis bottom. The magnet is secured in place and 2- 1/16” thick cylinder magnets or similar can be added inside the chassis under the rear axle just outboard on either side of the crown gear. If even more traction is desired another thin cylinder can be stacked to these secured two. This can be combined with the Slotit bar just in front of the drive shaft bearing holder to give enough magnet downforce for the hottest motor setup.
2. Setting the forward Magnatraction can be difficult if there isn’t enough clearance to stick a half 1/16” cylinder to the bottom of the motor. If this can’t be done then about the only choice is to add downforce just behind the motor. This is usually adequate.
As you begin to become familiar with these methods of
magnet tuning, you will come to realize that not only can you PMT for speed but
you can also change handling characteristics as well. Anything from stuck down
like a train on rails to sliding and spinning all over the place is available;
you choose. Though beyond the scope of this article you can also experiment with
opposed force (like-poles forced close together) magnet mounting and magnetic
field directing using ferric metal shims. These let you direct magnetic
downforce so that on the straights it is minimal for greater speed and in the
turns increases with drift off centerline for greater traction. Check your race
rules before using multiple magnets since some rules forbid their use.
On low / no magnet down force cars where magnet tuning is either not desirable or allowed by your rules, adding weight (weight tuning) is the best way to gain traction and cornering speed. A good rule of thumb is to keep it as low as possible in the chassis so the car's center of gravity remains low. How much weight needed and where to put it are determined by several factors:
a. How much weight is needed? Motor torque pretty much dictates what the maximum amount of weight is a car can carry is and still remain competitive. The more torque available the more weight that can be added without bogging the car down or adversely affecting braking and acceleration. This is where the Lead Sled advocates put their money. If the car is well balanced though then heavy or light is pretty much a matter of driver taste although heavier seems to be the current trend. Tire compounds become much more important when running with weight only, so more attention should be given to this tuning area.
b. What do I use? Lead tape, lead sheets, lead wheel balance weights, lead fishing weights, lead or any other metal is okay. Lead because of its weight per volume and softness is usually preferred, but brass, bronze or iron is also used probably for ecological / esthetic reasons or for their soldering properties. When I add weight I usually use lead tape and wheel weights because the adhesive is already applied so I don't have to mess with glue. If you have the tools you can also make your weights out of brass sheet metal by cutting pieces to form fit. This method has the advantage of allowing you to make a belly pan for your car and with mounting screws or glue, attaching it to internal brass balance weights. You can get an idea of this method by looking at the example drawing in the drawing section.
c. Where to put it? It's similar to magnet tuning a car. If you are trying to increase traction then add weight over or near the rear axle. If you need to hold the guide shoe down under acceleration or want controlled drift mount weight further forward toward the front axle. It's usually a good idea to avoid putting too much weight aft of the rear axle because if the CG of the car is too far aft, then normal car drifting in the turns quickly translates into an uncontrollable spin out. Weight applied to shift the CG forward should be applied carefully in 5-10 gram increments so that the minimum amount to accomplish the job is found. Lead tape comes in different thickness' and can easily be applied to the under side of the chassis if there is clearance and rules permit. This allows easy balancing of the car without removing the body. Once the proper weight has been determined I usually put a little spray paint on it so I can see if there is any bottoming of the car around the track. If there is, I can find out if it's a track problem by finding where the scraped off paint is on the track and investigating why it happened. Sometimes when trying to balance a car with weight you end up adding too much weight because you added weight instead of moving the weight around. Always try shifting a smaller amount of weight to see if it corrects your handling problem before adding more weight.
d. When do you use weight and when do you use magnets? Well, what do your rules allow? I will always use magnets over weight because there is less moving mass. This usually translates into less damage in accidents if the speed of the cars is the same. Don't over magnet a car unless you are prepared for sudden departures that you will not be able to react to in time to stop a heavy hit. This often happens when tuning for maximum performance. I use small amounts of weight to shift CG slightly in a car so that the guide doesn't float or use weight when rules prevent the use of multiple magnets and I need more car balance. One important point is that weight should always be used when trying to lower CG. If you try to control high CG characteristics using magnets you will not like the results as the car will be virtually impossible to control at the traction limits and will depart violently when these limits are exceeded (see Observations Section). By using weight first to lower the CG you will obtain a much smoother transition to drift, which you can then tune, using magnets. Some people argue that magnets make the car less fun to drive. My answer to those people is that, when used to PMT cars they actually improve the fun factor. Magnets can also be used to increase the speed of a novice driver (sort of like PMTing of the driver) so that he or she can give a good account of themselves in a race against a more seasoned pro. Nothing is more disconcerting to a new comer to this hobby than to be continually wiped up by others in every race. Using magnets to equalize drivers can keep this from happening all the time. As the new driver's skill increases he can graduate to cars requiring more or varied skills. There are many who disagree with this line of thinking so you will probably hear arguments to the contrary. You choose what you like.
e. There is one final point that I will add here and that has to do with a well known "secret" that some of the metal chassis boys have been using for years; shiftable weight. The principle here is to put a small amount of weight on a chassis in such a way that it shifts to the rear under acceleration giving traction and shifts toward the front under deceleration to give guide stability through the turns. The amounts of this shifting weight are modest due to other factors involved but the principle does have some merit. So how does the poor plastic chassis guy do this? Well the best way is to take a piece of 1/16" brass tubing and mount it cross wise in the chassis between the motor and the guide. Usually mounting it through chassis uprights is the best method. Next take some brass sheeting and cut a couple of small pieces to fit in the side pods of your chassis if it has them. Make them short enough so that they can pivot about the tubing in both forward and aft directions. Now attach the piece of brass tubing to one end of the strips so that you have an axle with piece of brass hanging off at each end. This should be mounted in such a way that it acts like a pendulum if the chassis is held upside down. The brass should be free to move in a 180 degree arc forward and back. If this is done right, when the chassis accelerates the brass weight will pivot aft; on braking it will pivot forward. You can try it on an old chassis to test the principle if you want to. There are other ideas for shifting weight which you can experiment with such as the sliding bar weight which is essentially a brass weight on brass tubing that slides along each side of the chassis on piano wire with small spring at each end to cushion the movement. You can put this mod on a fly chassis for example without too much trouble. Usually, high magnet downforce cars won't be overly affected by this type of modification so its worth on such cars is probably negligible.
a. I'm no pro in this area but a good general rule is that on large tracks with wide sweeping turns gear ratios of 2-3.5 to 1 are usually good. On smaller twisty tracks 3.5-5 to 1 usually works best. (There's a decent chart for ratios at Slot it's site www.slot.it/eng-proaxle.html). Also tire diameter plays a role in the actual ratio obtained (See Tire Section). Another factor to consider is the type of motor you are using. The more torque it has, the lower the ratio that can be used without causing the motor to bog down coming out of the turns. (i.e.. a higher torque motor could operate on a 2 to 1 ratio whereas a lesser torque motor would have to run at 3 to 1 to maintain speed). Also the higher the torque rating of the motor the more motor braking action the car will have. (i.e.. to get the same stopping performance that a high torque motor gets with 2:1 gearing, a lower torque motor might have to run 3:1 gearing. Motors like the NC2, Slotit Boxer, and Cartrix PRO have more torque than say the standard Scalex/FLY motor so they could give the same braking even though they have a ratio that was lower. Thus an NC2 at about 15-18000 rpm (depending on the voltage) with more torque can stay with and beat a 19-22000 rpm motor like the Scalextric (given equal tire size) because the higher torque factor in acceleration and braking allows lower gearing. Some of the "newer" motors have combined and traded off certain factors to try to give us the best of both worlds. Slotit, Plafit and Cartrix to name a few have tightened the manufacturing tolerances of their motors which allow hotter winds and stronger motor magnets without adversely effecting motor life to a great extent.
b. You will have to set up your ratios so that on your longest straight the motor is reaching its top rpm just after 3/4 way then maximum brake and power into and through the turn. I find that on my track this means that I could go with lower ratio gearing on the NC2 fitted cars and higher on the Scalextrics and Fly's. If your track has a lot of tight turns and short straights; however, you might find that keeping the motors at higher rpms by using higher ratios brings you more overall lap speed.
c. One other thing to consider when gear tuning is track power. Most motors have a voltage range that they are designed to work at. Below that range the torque drops off significantly. Above that range the motor gets "torquey" and difficult to control over a range of speeds. Different tracks operate at different voltages usually between 12 and 18vdc. Gearing set up for one voltage may not work at another one so watch this variable. Gearing combines with motor torque, track voltage and controller ohm rating to give you controllability over a range of speeds.
d. I know this all sounds very confusing so let me give you the simple way to set up your car for a particular track.
1) Take the car/chassis that you want to tune and set up several axles with different size (24 27 30 for example for inline motors) gears and use an 8 tooth pinion for a short track or a 10 tooth pinion for a longer track (inline motors).
2) Run each axle combo for around 10 laps and take the times. Also observe controllability with each combo.
3) Next install a 9 or if you have a big track 11 tooth pinion and repeat test. After you do this you should have a fairly good idea of which ratios run fastest with which motors. Play with these combos until you are happy with the lap times and driving characteristics of the car. For inline motors, Slot it's gears and axles along with their pinions should provide all the ratio combos you could possibly need. They are also quick change so you only need one axle in the above procedure.
4) Once you determine the best ratios using the Slotit set you can always go back to standard plastic gears of the same tooth count on standard axle assemblies if you so desire.
5) For the sidewinder drive such as Fly's and Proslots you can use the Slotit pinion set and 3 spurs if the pinions don't give you enough ratios. TSRF has a good selection of gears also. If money is a consideration, TSRF plastic gear sets are one of the best deal going. Procedures are the same as those for inline drives.
6) When using high performance motors that run in the 40,000 rpm range it may be better to increase the gear ratio slightly to gain better control and use of the extra power. Going from a 3 to 1 ratio to a 3.5-4 to 1 can bring you better overall performance depending on the track. Most plastic chassis cars won’t go much faster over a certain point without major structure mods so gains in acceleration and braking using higher ratios can be best for overall performance improvement.
Motors come in many and varied performance levels. The motor you select should be broken in according to manufacturer's recommendations. Running the motor at 3 volts or so for 10-20 minutes usually works to seat the brushes, in absence of factory procedures. If you are in doubt, contact a tech site for recommendations. If you choose to upgrade from a stock motor you should consider the following motor parameters:
a. Motor rpm range: This in combination with gear ratio generally determines top speed. Magnet down force, weight, and tire size are also factors. Go for the most rpms on large tracks with sweeping turns and medium downforce magnet configurations. Control with rear end gearing. On stock plastic chassis, motors exceeding the 40-45,000 rpm range generally don’t provide much top end improvement. These motors should be used with higher numerical gear ratios. Because of chassis flex considerations motors more powerful than the 30,000rpm class FK-130s generally aren’t suitable for plastic chassis setups unless major structural reinforcement is done in the area of the axle carriers (inline drive). Sidewinder setups such as those in some FLY and Scalextric cars can usually handle the hotter FK-130s such as the Falcon/TSRF, Ripper and Cheetah motors.
b. Motor torque curve from stall to maximum: This in combination with gear ratio generally determines acceleration to top speed. Torque is also instrumental in determining how much magnet down force can be used without overly bogging down the motor and causing overheating. Finally, torque is a determining factor in how much dynamic braking a car will possess. Go with max torque over rpms on tight twisty tracks and high downforce configurations. Again control with rear end gearing. Don't forget that traction magnets supplement motor braking and may eliminate the need for it on high downforce configurations. Some motors such as Patto’s Ripper sacrifice torque slightly to gain rpms. These motors should be geared higher to take advantage of this feature. This adds to the perceived controllability.
c. Motor size and shape: Not all motors fit all cars. There are many adapters though so don't just settle for common swaps. For example, any NC2 type motor, using Reprotec RT-10 or Cartrix motor brackets and long pinion will fit any SCX RX-4/6/8/PRO powered car (the shaft may be a little short for the gear self align feature so washers/spacers might have to be used to set up the gear mesh properly) . What does this mean? How about a Slotit boxer motor powered Ferrari 333SP. This would undoubtedly be one the best/easiest SCX car power upgrades presently available, in my opinion, and it just snaps in then a little axle shimming and off you go. Another example, Cartrix motor sets come with a Cartrix Cheetah type motor and Ninco mount for cars with removable motor adapters. How about a Cheetah type motor in the old McLaren GTR for a performance boost? The list goes on and on. Some of these adapters are listed Motors / Adaptors Chart in this article. This is by no means the extent of the replacement possibilities. New manufacturers and dealers are showing up every month. Check with your slot car sources regularly to get the latest and greatest motor/adapter upgrade availability. The only downside to all this is that many of the adaptors are only available with other motors so to get the adaptor you want you may end up with an extra motor. Once you get an adaptor it's relatively easy to make replacements using casting resin. Simple adaptors can also be made using plastic tubing, available at most hobby stores.
d. Motor power consumption: Make sure that the track you are running on will be able to handle the hotter motor. This is usually not a problem except with some of the weaker stock power supplies. One way of checking, on regulated power supplies, to see if you power is adequate to handle the motor or motors you are running, is to take a volt meter (preferably an analog type) and put it across the power supplies positive and return. Watch the meter carefully as you run your cars. If the voltage dips at all then the supply is not giving all the power that the motors are asking for. If this is the case then you should consider upgrading your power supply. Most wall supplies will show fluctuations and need to be supplemented by a second unit if you want satisfactory power operation. Small amounts of meter fluctuation on these wall supplies are normal since they are unregulated and will vary with the load. When measuring these units to see if they are adequate for your motor you need to establish a reference voltage you want to run at. If the meter drops below that voltage at any time while running your cars then the supply is not adequate. If you intend to run multiple cars on one supply it is better to use a regulated unit of adequate output so that each car will get the voltage it requires. If you are in doubt your dealer should be able to help, or check a tech support Internet site. Also don't forget that most stock controllers and track connections aren't built for high current (greater than about 1.5 amps). If you are going to be running motors hotter than say the Slotit motors or high magnet downforce configurations then you should consider going to better controllers that can handle the increased power requirements. Parma or Professor Motor controllers are good cost effective upgrades to consider. Professor Motor controllers are solid state controllers and are adjustable for different motor types and controller "Ohm" requirements. These controllers will save you money in the long run since one controller can run all your car types. Some track systems such as Ninco have printed circuit boards as part of the power interface. These boards can be destroyed by too much current. So if you plan to use more than the manufacturer's recommended amount of power you will need to rewire this interface and eliminate the circuit board.
e. Track Power: This is a very important consideration in motor selection since some motors are designed to run better at 12vdc while others are more efficient at 14.5+ vdc. Motors such as the Cartrix, Slotit V12, and Plafit Fox/Cheetah types work well at both extremes but others such as the RX series seem to do better at the higher voltage. Sometimes certain motors are too “hot” when run at standard voltage levels. This is particularly true when running without Magnatraction. In this situation it is better to have the ability to turn down the voltage to around 9 VDC so that these motors become more drivable. If you can’t adjust your power supply then adding several diodes in series with the motor input will lower the available voltage by approximately .7 VDC per diode. A resistor can also be used but this is a less desirable option choice because of possible heat considerations.
f. Controller used: For most of us, the controller we use is dependent on the motor's characteristics and car configuration. There are times; however, when the situation may be reversed such as a race where the controller type and ohm rating are specified in the race rules. In this situation you must be careful that you choose a motor that performs to your expectations using that particular controller. If you are doing the driving this can be a relatively painless task but if it's for a proxy type race the motor decision could be a bit more difficult. One excellent option when considering controllers is to purchase a unit such as the Professor Motor Controller which allows you to tune the controller to your car and driving habits.
g. One last thing to consider is motor life. The higher
the performance of the motor and lower the quality the shorter the motor's life.
All things wear out so don't be surprised when your motor begins to lose some of
its pep. Most motors for Euro cars will give you hours and hours of enjoyment if
they are taken care of. Cheetah / Falcon type motors with their higher rpms tend
to slow down after one or two good competitions. Since brush replacement isn't
usually considered an option with these motors the best thing to do is retire
them or use them on less demanding cars.
You can rework these motors if you want to
try. Basic instructions are provided in the REPAIR section of this article
Rear tire selection is most important for low and medium down force cars as well as for determining overall rear end ratios and depends mainly on:
a. Track surface. For the purposes of this article I am using my experience with Ninco and Artin plastic track only. It is generally recognized in race circles that Silicone tires rule the plastic track. This may be true on smooth clean surfaces but may not follow on rougher surfaces such as Ninco style track. Silicone tires offer no performance increase over rubber on Ninco track, particularly on high downforce cars. What is said about contact area and traction is essentially true and is proven by the fact that treaded tires do work better on the rougher Ninco track. If you take a magnifying glass and strong light and look at the tire to track surface interface on treaded tires you'll notice that the treaded tire develops "fuzzy" ridges that fit down into the rough surface allowing more contact than silicone because the silicone compound tire won't do this but will tend to "chunk" instead, so the silicone tire will basically sit on top of a bunch of small peaks not making near the contact of the treaded tire on Ninco track. Rubber slicks develop the same fuzziness but it appears to be slightly less than the treaded tires so for the most part the treaded is a better overall tire to the rubber slick also. Over time the track surface acts like many small razors cutting the tread to create this "fuzziness". If you are using silicone what this does is create cuts which eventually expand and cause the tire to disintegrate. During our tests for both the Mania and the Memorial race we experienced silicone tire failure after about 300 laps on a tight turn circuit using high downforce cars. What appeared to happen was that the edges of the tires would get these small cuts and this would cause them to start to separate. Remember Ninco track is so abrasive that you can actually "sand down" your tires with the track if you hold the car down in a stationary position (DON'T do this or you'll make the track smooth at that point by melting the plastic). If you look at most of the competition tires offered by Spanish vendors for Ninco track you will find that most are treaded. Reprotec has a large line of competition tires. These tires are generally meant to replace Scalextric / SCX tires on Ninco track to give better traction (P/N's are AS12301/8/9). I've found that tires such as Ninco soft treaded and slicks, Fly slicks and classics, MRRC classics and Cartrix slicks work well on Ninco track. Most SCX and Scalextric tires are slightly harder compounds and can be used where a certain amount of drift is desired. Some of the newer SCX and Scalextric tires are softer; however, and are good all around tires. Reprotec has a series of tires that have a Silicone component that work very well on Ninco and Scalex/SCX track and are quite durable. In general, the softer the tire is; the greater the traction. Now, on Artin track, things are somewhat different. If the surface is clean then silicones work very well and beat out all the above mentioned rubber tire types. Ninco and FLY tires do not work particularly well on Artin while Carrera and Artin tires (surprise) do. EJ’s narrow tires, for Revel/Monogram classics, also works very well but requires special wheels. There are several makes of new stretchable silicone based tires. These tires offer some of the best traction on clean track.
The recent addition of an Artin track has allowed a better evaluation on smooth track types as well as the rougher Ninco type track. In the last six months this writer has been experimenting with several items used almost exclusively by the Eurosport crowd here in Europe. Among these items was a group of tires in the category known as "sponge". These tires are best known for their traction ability on wood like track surfaces coated with a film of "glue" which enhances the grip of the tires. Well, our part of the hobby doesn't use this tire setup as a rule. These sponge tires do, however, give excellent grip when used with high downforce magnet configurations on the rougher types of plastic track. In fact, the grip is so good on rough track (Ninco) that you may have to reduce your magnet downforce to keep from having too much grip. Sponge tires do not work very well on smooth plastic.
How would you like to have high magnet downforce in the turns but have this downforce reduced on the straights. This would be ideal if it were possible. Well it is possible on some rough types of track (Ninco) where sponge work. Sponge tires can be cut to any diameter and mounted on any diameter wheel. The thicker the side wall of the tire the more it compresses when weight or magnet downforce is added. When the wheel spins this side wall compression expands with the result of its increasing the tires diameter thus raising the chassis. When you raise the chassis you reduce magnet downforce. So what you have is a tire that expands under acceleration reducing downforce and compresses under deceleration increasing downforce. This solves one of the problems which has plagued magnet cars since the beginning; that of having your downforce working against you on the straight sections of track. Now all you have to do is select the right hardness of sponge and side wall height to match your racing setup and track. Several companies already make pre-mounted sponge setups. Sponge doughnuts are also available along with wheels to make your own configurations. If you want to get fancy you can buy a tire machine so that you can cut your own with great precision. The good part is that these items are not much more expensive than your stock tires and wheels but offer you at least a threefold increase in performance and build quality. The only real downside is that some of the softer compounds wear out quickly. A further enhancement to the sponge tire fpr use on smooth plastic track is the silicone coated sponge tire which seems to give good performance on certain smooth types of plastic. You can make these yourself and the procedures can be found at OWH (http://www.oldweirdherald.com/) web site in an article written by Larry Sheppard. So far only wide versions of these tires are available commercially but it may only be a matter of time before someone comes out with some for plastic chassis Eurocars. Patto's (http://members.optushome.com.au/pattosplace/) in Australia is an excellent source for wheels of almost any size to use for mounting sponge tires. In Europe SCD (http://www.scdparma.fsnet.co.uk/) in the UK sells tire doughnut blanks and also has several lines of wheels that can be adapted to plastic chassis setups. In the U.S. most raceways and slot mail order dealers have or can get these items for you.
Generally on smooth plastic most of the silicone based tires are best. Slotit S1, Indy Grips and PPR Supertires are the good choices here.
b. Tread configuration: Whether to select a tread pattern or slicks usually goes back to track surface again. On rougher surfaces, treaded patterns do seem to work quite well with all types of cars from non magnet to maximum down-force types. Slicks are better on the smoother varieties of track. If you are using treaded tires and your car is digging in and flipping in the turns even after you've rounded the edges then consider going to a slick tire or sand off some of the tread pattern on the tire. Here in Europe, particularly Spain, Rally car competition is very popular where tracks are setup with flour and cocoa powder and liquid to simulate different road conditions. In these situations and on dirty tracks treaded tires work best as a rule. If you race normally like most of us though, slick type tires on smooth clean track is the way to go.
c. Car type and configuration: Wider tires of a certain compound generally give more traction then narrow ones and help to cure CG problems on narrow track cars that are top heavy. Go with the widest possible rear tires that: 1. Meet your realism requirements 2. Meet the rules, and 3.Fit under the car. Also be aware that some tires degrade with time much faster than other brands. This may be due to several factors but most often certain chemicals can have a detrimental effect on the tire compound. Be careful with lubricants as some of these may break down certain tire compounds resulting in overly soft or hard tires that lose traction. Further, watch out that you don't heat the tires up too much as this can have the same result. Under most conditions this is not a problem but particularly when sanding the tires be careful not to apply too much force as this will definitely cause the tires to overheat and may damage them; especially if they are silicone type compounds.
d. Track temperature/cleanliness: Cold tracks equal higher lap times on my Ninco and Artin tracks. Dirt and oil on the track really slows things down. I've stopped lubricating my cars and running immediately on the track. I now run the car on a spare piece of track at 6 volts for 20 seconds or so that any excess lubricant is slung off here instead of on the track. Before I start running on the track I wipe it down with a tack rag to remove dust (used to prep real cars for painting) and once a week I wipe it down with WD-40 to clean the rails and then use a soft scrub brush and alcohol and dry with lint free cloth to remove any residue (Fly GT tires don't like WD-40 very much). If you are familiar with chemical safety and use it in a well ventilated area, Carbon Tetrachloride is one of the best solvents for cleaning track rails. Follow all the instructions on the container and use sparingly with plenty of ventilation. As important as track cleanliness is for rubber compound tires it is twice so for silicones and sponge. Any dirt will severely degrade your tires performance so keep everything clean.
e. Rear tire size is often overlooked when performance tuning, but this factor can have a significant impact on your cars performance. First, remember that the larger the tire the lower the perceived axle to motor rotation ratio. So 21 mm tires will give a lower ratio than 20 mm tires given the same pinion/crown gear tooth count and will move over a greater distance in one rotation of the tire. Second, larger tires raise the CG and move traction magnets away from the track rail reducing magnetic traction. Be careful, when you put on new tires, that you consider these two factors carefully. You may have to go back and performance tune for gear ratios and magnet down-force again
f. For front tires hard and smooth are good (see advice in general section). I use low profile tires on modern cars to reduce friction or harden stock tires with nail polish. (This is from the early days of slot cars. We used to do this back in the early 60's at our club track. I'm sure one of the real old guys might know where it originated from). The O-ring on the tire trick (general section) was first used in Da Nang, Vietnam in 1967-68 at a squadron slot track. We salvaged old Amphanol Connector environmental seal o-rings from F-4/F-105 aircraft, coated them with nail polish (we couldn't get shaving cream but there was plenty of Kotex and nail polish at the Base Exchange), and slipped them over the front tires to maintain realism but reduce sliding friction. Eventually in later years way after I left the sport, I guess realism fell by the wayside and O-ring tires became the norm. Today O-rings are readily available in all sizes. Find the thinnest ones that can be stretched over the tire and use them with nail polish or plastic cement. Sand as necessary to round and lower the profile. One last way to lower friction on a front tire is, while you are truing it on a drill, sand the tire down but leave a ridge at the outer edge or on the centerline. On Scalex and SCX fronts sanding off all the tread except for one bead works real well. This is all that will contact the track. Coat the ridge with nail polish or plastic cement and balance tire. To see if your front tires are slowing you down, just remove them and run some timed laps. If the times decrease then you need to work on the front tires and maybe front end setup.
g. This next suggestion is for those who want that last
ounce (or gram) of performance. As mentioned in step f, one of the things that
robs your car of speed most in the turns is the front wheel / axle assembly
since it tends to drag in the turns. Even independent rotating wheels can slow
the car somewhat. So what can be done short of removing the front wheels
altogether? Well the next best thing is to make the assembly as light as
possible. If you are keeping the original front wheels which most of us tend to
do then basically there are three areas. First, lighter axles; going to plastic
or thin wall tubing can save a little weight. I use Aluminium tubing which is
strong and light. Next we have the wheels. You have to be careful here because
you don't want to damage them or weaken them to a point where they break. Since
each wheel design is slightly different my advice here is general in nature.
First, cut as much of the axle holder off as practical, usually flush with the
rest of the wheel. Now, mount the wheel to the tubing axle and fit it to the
chassis. Add thin wall plastic tubing spacers to remove front axle play. After
this is set up remove it. Now take each wheel and make a series of drillings
around the rim under where the tire will mount. Be careful not to drill in too
deep or else you might drill through to the inner detail. Use a drill that's big
enough to drill almost the width of the tire mount ridge minus a little on each
side. If you are shy of using a drill here you can also use a Dremel grinder but
be careful that you don't damage the wheel. Finally, and this will probably save
the most weight, sand down the front tires as much as you can and still remain
legal. Rubber is heavy and adds to the rolling mass. If you have access to
sponge type tires these may further reduce weight. When finished you should have
a fairly light front axle assembly. Remember for front wheels and tires, light
weight is good.
7. Optional: Chassis Weight Reduction, Guide Shoe Modification and Chassis Strengthening
a.. The procedures in this section are usually considered to be illegal in most “box stock” racing classes. Most Euro Plastic chassis cars use a full pan configuration which though esthetically pleasing adds quit a bit of weight in the wrong place to the car. Most cars can gain as much as 2/10 of a second by removing excess plastic from their chassis (This varies from chassis to chassis type.). Before you get out the Dremel and X-Actors though be aware that each car is different and the strength of the chassis can be destroyed by the wrong cut. Fortunately, modern plastic cements allow us to correct any major mistakes so let's go ahead. Also remember that many plastic chassis cars use the body for chassis rigidity. Watch that you don't destroy this interface or if you have to, make sure that bracing is added to compensate for the changes. See diagrams in the Diagrams Section to see drawings of some of the lightening explained in this section.
b. We didn't quite know how to handle this section because of the variety of different chassis. We finally decided to do it by using a couple of examples of popular cars. Number one is the McLaren GTR by Ninco. First, remove all parts from the chassis. Now, looking down to the top of the chassis, the first parts to remove are the side pods. Cut them completely off to the vertical member that runs from the rear to front axle carriers on both sides; DO NOT remove this vertical member. Next remove the pan material from just behind the front "radiator" to the forward mounting posts, staying away from the guide mount, and the plastic from in the little "triangles" on either side on the front. Fourth, remove all the plastic from the magnet well and forward to the front axle carriers but only as wide as the magnet. This leaves about 1/2inch on either side from the motor mount to the front axle. Last, in the rear cut all the vertical plastic from around the exhaust/screen leaving only the section that fits into the body at the rear. If your rules allow lowering of the body, you should cut the front grill work and rear exhaust detail off the chassis and glue them directly to the body. The chassis should now only connect to the body by the screw attach points and the 2 bearing posts at the rear of the interior. What you want to do is File / cut / grind off the screw posts in the body byabout1.5-2 mm so that the tires just clear the wheel wells. I just cut off the two bearing hold down posts because the bearings are glued into the chassis. If you make a mistake and cut off too much of the screw posts you can super glue a couple of washers onto the top of the chassis screw wells to raise the body back up. One caution: watch the screw length so that it doesn't go through to the top of the body. If you are in doubt cut the screw treads off a little. That's pretty much all that can be safely removed and will still allow you to use a high torque motor such as a Cartrix PRO or Cheetah/Fox. You'll notice that we stayed away from the drive train area and the guide mount area. This is because these areas need to be strong as they handle the majority of the torque and track load. If you do make a mistake don't panic. Repair the area using plastic cement, not superglue or epoxy, but glue specifically for plastic. This glue essentially "re-melts" the plastic together with a bond as strong as or stronger than original. In some cases adding pieces of plastic with the glue will strengthen the joint even more.
c. Number two, the Ferrari 333 by SCX. This chassis is one of my favorites because it's strong and well balanced. The newer version with adjustable magnet lends itself well to magnet tuning. The first thing to do when lightening this chassis is to mark the outline of where the chassis overlaps the body so you don't cut that part. I use "whiteout" correction pen since it's easily removed later. You can also make your cuts with the body installed if you are careful. The first thing to do is hollow out the side chassis pods leaving about 1.5 mm all around. Next remove the plastic between the copper electrical "runs" from 1 mm in front of the motor mount to just behind the front axle. Finally, remove the plastic under where the front headlights are. This is a rough circle about 5mm on each side in front. You can expand this to the maximum with the body installed and used as a guide. That's about all you can safely remove. If you really want to get the max though you can also remove two small rectangular portions next to the motor inside the chassis uprights running between the front and back motor holders. With body lightening you can get the weight of this car to well under3 oz.
d. General rules for lightening chassis:
1. Stay away from the drive train and guide mount areas. If you weaken these areas you risk breakage under race conditions.
2. Vertical members on a chassis provide rigidity so be cautious of cutting through them.
3. If the chassis is made from very flexible plastic you may have to add plastic members for rigidity after removing excess plastic from the pan.
4. No mistake is irreparable; if you make an error in cutting repair it with cement and plastic as necessary.
5. With practice you will learn what works and what doesn't.
e. The Guide Shoe: Here is some good information on improving your guide flag set up from Philippe de Lespinay who is a respected authority on both vintage and modern slot cars. We would like to take this opportunity to thank him for his input. We haven't tried this method exactly but we trust Philippe's knowledge on the subject.
" Most 1/32 scale cars come with a "snap-in" guide flag, and the tooling is so poorly engineered that the flag is very loose and rocks forward/backwards in its location. This causes undue wear and arcing to the pick-up brushes, which by the way are too narrow and too stiff, in their front or center. Replacing the flag by another only work if using a decent unit, I.E. NONE from the current 1/32 scale production cars at the notable exception of MRRC and Pro-Track.
1. The first thing to do is to remove the entire guide flag assembly and give it to your dog to chew on. (joke)
2. Then: Slip a 3/8' piece of 1/8"I.D.K&S brass tube inside guide hole on chassis. You can epoxy it if you wish, but it generally fits nice and tight.
3. Select a "proper" (straight shaft) guide, such as: MRRC, older Dynamic, Classic, Cox, Riggen...You may have to trim the frame some for clearance.
4. Slip it in and make sure that the flat surface is at the correct height. MILL the backing surface if necessary (I do this with the Classic guide which I believe is best suited).
5. Get some small bolt-on terminals at an electronic shop along with short 2-56 machine screws.
6. Remove the ridiculous little 'rivets' at the end of the lead wires, and solder the terminals instead. Easy on the solder joints, go to Soldering School if needed.
7. Get some serious 1/24 pro-braid at your local raceway or from your favorite, non-1/32 claustrophobic dealer ("what’s a 1/24 scale car?")
8. Cut the end off the brass clip around the braid, and drill a small1/16" hole through the remaining end.
9. Brush and comb the braid to have all the strands 'loose' and curve the ends oh-so-ever slightly downwards.
10. Tap the holes in the guide flag with a 2-56 tap (you can also use" press-on" guides like 'Jet-Flag' type, but it deforms the guide some and gives you false readings on how far your front wheels are off the ground. OK for 1/24 scale, marginal in 1/32 scale cars).
11. Slide the guide in place, slipthe2-56machine screws through the terminals, then the braid, and bolt to the guide.
12. Go racing for several dozens of hours before you will ever have to replace the braid.
13. This system works great but
can be achieve by other means. However, one thing remains constant: do not
attempt to use the existing flags on those cars, they are too narrow and will
never provide decent
That is a pretty good "quick and dirty” on how to modify your cars guide to make it a winner. It is one more option you can try in an effort to get the car's guide and contact system toy our liking.
f. Strengthening Portions of the Chassis - First we talk about lightening the chassis and now you may ask: why does he want to add weight? Well, the simple answer is that in certain configurations the chassis may have to be strengthened. When? Euro plastic chassis are good cheap designs, for the most part, that are strong within the range of snap in motors and accessories commonly utilized. But when we start hanging multi magnets off them and stuffing Cheetah motors in them then we soon uncover the inherent weaknesses in the plastic chassis design.
1. Guide Holder - When running high downforce magnet configurations and hot motors the guide attachment takes allot of pressure particularly on deslots. Sometimes the pressure exceeds the design limitations of the stock guide holder. If you break a guide holder and gluing doesn't fix the problem, you can make a new guide holder either out of brass plate (preferred) or sheet plastic and plastic tubing. (See Drawing) To do this:
a). Remove all parts of the old holder including the braces so that the chassis pan is flat and smooth in this area.
b). Next, measure out a piece of brass, plastic, fiberglass or carbon graphite sheeting to attach to this area (the top of the chassis).
c). Mark out a hole toward the outer end that is the same diameter of the guide you want to use and drill it out. If you’re using the stock guide you will want to drill out the hole so that a piece of tubing of the proper diameter and length may be fit. If you’re using a replacement guide with guide axle nut then you only need to size the hole for the guide axle and can forget about the tubing. You can adjust this type of guide up and down using thin spacers made specifically for this purpose.
d). Now place a piece of tubing in the hole and cut to size relative to the guide axle. Attach this tubing with plastic cement or in the case of brass with solder.
e). Fit the guide and mount to chassis top taking care to make sure that the guide sits properly in the slot with the chassis on the track. Once you've established this all fits correctly you are ready to glue the assembly to the chassis.
f). Use the strongest glue you have. In the case of the brass you may want to add some small screws countersunk from the bottom and attached with nuts.
2. The Drive Train - In inline configurations, motors such as the Cheetah generate enough torque to cause the chassis to "twist and flex" around the axle bushing carriers. This can cause a number of problems from gears mesh difficulties and striped gears to increased axle bearing friction and wheel hop. Even chassis failure can sometimes happen as the forces act on the chassis to cause fatigue cracks. So what can be done?
a). The problem can be alleviated in large part by adding reinforcement to the chassis in the form of extra plastic or stronger still, brass plating or piano wire. By cutting pieces to fit under the rear axle from the motor extending aft for some amount and gluing these pieces to the chassis one can remove almost all of the undesired flex in the motor axle train. On most inline chassis this should be enough.
b). On some of the older SCX and Scalextric chassis made of softer plastic it may be necessary to add vertical portions to the axle carrier uprights also, attaching them to the previous mentioned plates. That's basically all you need to do.
c). You can get much fancier if you want and make motor attach braces and the like but for the range of power we're talking, this is really not necessary. Look at the SCX/16D drawing to get an idea how such upgrades should look. Other areas of the chassis can be strengthened in a similar manner.
d). Use sheet or scrap plastic if you need moderate strength and go to brass plate or piano wire if you need max strength. Remember angle pieces of plastic or brass give more strength at a given size so consider using these types if you need allot of reinforcement in a small area.
e). If you really want to beef up this
area when using Cheetah/Falcon type motor then a good solution is to take one of
the commercially available "U" brackets which attach to the motor and provide
the bearing holders in a solid mount. These brackets are also useful if you
break a bearing holder and can't make a good repair. Just forget about the
original holders and go with a "U" bracket. In some cases you may have to cut
the bracket down to clear certain bodies. If you’re a real “Cheap Charlie” like
me you can make you own "U" bracket and use 3/32" ID tubing to make "bearings"
for the axle. This is inexpensive and relatively easy to. You can buy
channel pieces (used for door / window frames etc) from your local hardware
store in the right "U" dimension so that the bracket is already bent correctly
and all you have to do is drill the holes for the motor bearing and mounting
screws as well as the axle carrier holes. I keep one of the In Slot brackets
around to use as a hole template so I don't even have to do any high tech
measuring for hole placement. (Talk about lazy). Aluminium brackets are better
for magnet cars since they are lighter. The In Slot type is better suited for
non-magnet setups or non max downforce magnet setups. I've started using these
metal bracket setups on all my inline drive cars when I use high performance
motors such as Cheetah, Ripper or Falcon. The cost is small and the added
stability it gives the drive train is excellent. NOTE: InSlot brackets do not
seem to be available any more but BWA now produces one that is better and
8. Putting It All Together Back To Index
So now we come to the question: How do we put it all together? Well, let me illustrate with a couple of stories.
a. First of all let's take what I call my Classic Class. Initially I had hoped to group all my cars older than the FLY Classic series into just one class but this soon became unreasonable when I began to build an Airfix Sprite using a Reprotec chassis from one of the stock Fiats. The fastest I could realistically get this car to run was 4.98sec on my track. I had already PMTed my other classics to an average time of 4.30-4.50sec per lap. What to do? Well, how about being able to tune for two lap time ranges. This is where I came up with the solution of adjustable magnets on all the Classic FLY cars. It was the best and easiest way to accomplish my goal there. How about the other classics? Well the Ferrari GTO (Pink Kar ) was no real problem. Just pop off the magnet ( I had glued a thin cylinder magnet to the bottom of the motor) and move it forward. The Reprotec Cobra was easy. Swap motor to an RX-4 type and that was it. The Ford GT (SCX) was just a matter of sliding the magnet I had added forward to the front of the motor. So in 10 minutes I could change all my Classics from the 4.30-4.50 sec range to the 4.90 -5.00sec range. One example of PMTing your cars once you know how.
b. How do you know what to do to your car to race tune it? Well let's again take the GTO as an example. When I first got my Ferrari GTO, I knew the motor was a real dog. Straight line speed was missing and it wasn't because the back wheels were spinning. I open the car up and my mood sank when I saw the motor that was installed. I couldn't see any way to easily upgrade the motor until I opened my newly purchased SCX reissue Ford GT and noticed how similar the motor adapters were. Sure enough they were interchangeable and after a little investigation I found out that an SCX adapter was in fact a normal upgrade item. Where can you find out this kind of information? In this article now. After this upgrade, I realized that I would need more rear traction. Wider tires were out of the question because I wanted some realism. My next choice was a traction magnet. Just looking at the car, one will notice that it sets rather high off the track. This made sticking a magnet to the bottom the obvious choice. I found the right place rather quickly ; on the bottom of the motor at the pinion end. I slid the magnet forward and ran several laps but in the end the rear position was the place so that's where I glued it. The car still had a nice smooth transition to drift but at a much higher speed. That's all it needed. I was in the speed range of my Fly Classic cars. I eventually went with an RX-41 motor (about 17,000rpm on my track) which ran cool with no problems. If I ever need more juice I can go to a PRO or NC-2 with adapter. So, knowing what to do to tune a car is a matter of translating your observations into solutions.
c. The next example for those into speed is one of my SCX Ferrari 333SPs. When I got these cars I wasn't expecting much because of some of the bad reviews where I had read about weak motor/too much magnet. Well, I was surprised. The cars had some ingenious items on the chassis. First, as delivered, it did have way too much magnet, but a quick look at a pamphlet that was sent with the car showed that the magnet was in a "trainer position" (for SCX's trainer unit). By turning the plastic holder 180 degrees the magnet became adjustable. The other item was a spring loaded guide shoe. At first this looked kind of gimmicky to me but I soon found that it really worked well. I did most of the general tuning items and found that this car could be made to run real fast. So, I decided to go for maximum tuning on one of the cars for my SCX Trainer Unit. First, I needed a motor with lots of torque. The obvious choice would have been the SCX Pro; everybody said so. Well I guess my years in the aircraft industry must have sharpened my powers of observation because I had my orange Reprotec Cobra open at the time for cleaning and I suddenly realized that the motor with adapters would snap right into the SCX chassis. I put the magnet back to full down, connected the motor wires and proceeded to run 10 of the fastest laps ever on my track. Then I lost it in a turn for some reason and when I re-slotted it, it was vibrating badly. A quick inspection revealed that I had run one of the rear tires half off the rim. I'd never done that with a Euro-car before so I figured I must have been pulling some G's. I glued the tires to the wheels and after letting them dry overnight, I started again. I noticed that this blur was a little slow coming out of my hairpin turn but it didn't seem to be for lack of power. Removing the front tires and running a few laps revealed the problem; too much rolling friction up front. I grabbed a pair of Pink Kar 16.5mm tires and put them on; the corner speed was better but still a little slower than with no tires. Next, I got out the old acrylic clear nail polish and went to work; I let it dry and there it was; no more slow down. I had just gotten a set of Slotit pinions so I decided to do some gear tuning. I found that the motor torque allowed me to go to 11 tooth with no problem. So what was left? I had maximum magnet, proper gearing, and the tires were holding up so the last thing was one last motor change. I had ordered a Slotit Boxer for my CLK but I hadn't gotten around to trying it (I had only just received it). I transferred the pinion and Reprotec adapters to this motor and installed it into the chassis (the gear mesh was set with axle spacers since the pinion shaft is too short to engage the self align feature of the crown gear.) . Second lap out, I broke the 3 second barrier on my track. I never thought that that would ever happen. My 10 lap average time was 2.95sec with a fastest time of 2.91sec. I had my ultimate Trainer Car. One final note, I've chewed up 2 stock crown gears with this setup. It happened accelerating out of my hairpin turn. Some stock plastic gears seem to have reliability problems with high down force combined with motors having 200+ gr/cm of torque. It looks like that's the weak link in the drive train. I've since gone to a new Slotit crown assembly and haven't had anymore problems. These gears are much better suited to the high down force/high torque environment. If you don't have the cash for the Slotit gear sets then putting a spacer between the back of the gear and the axle bushing on that side will reduce the problem by eliminating most of the slop in the gear train. There's an update to this story. I found out that Cartrix had come out with a 30,000 rpm Fox type motor with SCX adaptor. This was the same motor that I'd put in a McLaren with great results. I ordered a couple from Spain and at the same time got a couple of Cheetah motors to do some experimenting with. I installed the Cartrix motor and ran the car for about 30 laps and managed to bring my lap record down to 2.83sec. Using this motor with a Slotit bar magnet mounted between the motor and rear axle. (Some chassis cutting required). Now what? I was feeling pretty cocky at this point so I decided to replace the Cartrix with a Cheetah motor. I should have been burning up the track now, right? Wrong. My times went back to 2.9's again. What had happened? The car was much faster on the straights and boy what torque. Well that was the problem; the torque was causing the rear wheels to spin and I was loosing time particularly coming out of the turns. The solution was quite easy; I increased the gear ratio by going down one tooth on the pinion gear and I added 2 flat cylinder magnets just behind the Slotit bar. The result; 2.73sec the first time out and eventually getting down to 2.57sec with a little magnet adjustment. Adding a small magnet up front completed the tune giving the car a smooth transition in the turns. This is within .15sec of a Fly Porsche /w Cheetah experimental that now has the track record. The only problem I have now is that the car is illegal for our club races so it's only run when I get a "need for speed itch". This particular 333 is now been moved to the experimental pile and has had the chassis cut and converted to a Iso-fulcrum-like configuration which is showing early promise.
d. Number four is a recent addition to our stable that really needed overall lightening; the Carrera Audi LeMans car. This car comes with a Rabbit class motor so it should be able to tear up any stock Euro car and make a good showing against slightly modified ones. Unfortunately, the car suffers from a couple of big problems right out of the box. First, the traction magnet is mounted in front of the motor on a sliding mount set up that while interesting in design suffers greatly in practical use. Second, the car is built like a tank with all the weight associated with such a characterization. Finally, the front wheels support most of to weight up front instead of the guide. To start with the second problem first, we disassembled the car and marked the areas of the chassis that could be removed to reduce weight. The first section that can be removed is the whole sliding magnet assembly and associated plastic. Leave about 1 mm of plastic at the front motor mount and cut from there forward to the front axle. For the rest of the cuts refer to the Carrera drawing in the Diagrams Section of this article. Now, before we could set up the magnets it was necessary to raise the front axle to remove its support of chassis weight. Mounting smaller front tires helped but didn't completely cure the problem. The Carrera axle mounting set up though unique is rather easy to correct. It was simply a matter of elongating the axle bushing with a Dremel until the weight rested on the guide. Be careful not to remove too much or the wheels will rub up in the wheel wells of the body. Next, the magnet downforce had to be set up. The first thing was to remove the chassis detail from around the rear axle area so that a flat surface could be made for attaching magnets. By making these changes to this car we were able to lower lap times from 4.31sec down to 3.45sec on our short track. Handling was greatly improved and the car had more pep under acceleration with the weight trim. The cost of these modifications was "zero" (well maybe a buck for the magnets) not bad price for performance increase. If you want more speed the next logical choice would be a Slotit V12-2 motor and stronger magnet. One small problem though is that you'll have to transfer the pinion gear if you are going to keep the rear axle crown because they're different sizes from the other Euro pinion/crown combos. If you go to a standard pinion you'll have to change crowns which will require some chassis cutting. The Carrera wheels are not so easy to remove so you may run into problems there (axles are different from standard Euro). We haven't tried the car with a stronger motor yet so we can't verify whether the stock gears are strong enough to take the extra power. As soon as we do test it we will let you know.
e. This next example is what you can do with an already fast car such as the FLY Joest Porsche. We needed a car setup that required little tuning once it was configured so that we could compete in proxy races. The FLY sidewinder is perhaps the best configuration for both speed and ease in tuning. What most people have not tried though is to stuff the arguably hottest stock motor around, the Plafit Cheetah, into one of these cars. At first glance, this looked like a formidable task but a little investigation revealed that the motor could indeed be made to fit. A look at the FLY Pod Drawing will show you what was done to put this motor into the FLY pod and make what we consider to be the best plastic chassis speed mod ever. To control the Cheetah's torque a strong downforce configuration was needed. Here Slotit's traction magnet was the ideal solution. The magnet can be glued under the motor to give almost a perfect configuration. A few laps around the track revealed real potential but first the front end had to be reworked. The guide was swapped out with a Carrera unit to give more depth on our Ninco track. Next the independent wheels were discarded in favor of a brass tubing axle with original wheels. Pink Kars 16.5 mm tires were added and all that remained was to elongate the axle carrier holes slightly to remove the rest of the chassis weight from the front wheels. Since our club class restricts this car to one magnet, 15 grams of weight was added up front to hold the guide down. For multimagnet configurations the weight was discarded in favor of a second magnet; we used a Carrera bar for its strength and size. The next thing done to the chassis was to mount the pod using RTV to isolate some of the vibration. This probably didn't add or remove any speed or handling but it did cut down on the chassis noise. Finally, the front part of the chassis in front of the guide was removed to get clearance for the Carrera guide. This left the body which was given our now standard Dremel lightening procedure. The rear wing was cut off the chassis and screw / glue mounted permanently to the body. The front light assembly was modified to gain guide clearance and the little driver's feet were cut off to get front magnet clearance. That was it. This configuration is race proven. Athina's Memorial Race Proxy car was essentially this configuration and but for a mechanical failure this car would have done quite well. This same configuration was recently used in several other competitions with great success. One last item that had to be done after several races was to replace the plastic guide holder with the brass plate/tubing design shown in the Diagrams Section and described previously. The forces on the stock guide holder were just too strong.
f. The great 16D experiment - After seeing the results of the Cheetah mods on several of my cars I decided to experiment on a few of my older SCX cars. I had a couple of old Porsche 911 GT2s gathering dust so these became my test beds for my foray into the world of 16D motors with plastic chassis cars. Why the SCX Porsches? Well the RX motor is the same length as the 16D so all that was required to make the fit was to take the trusty Dremel to the motor mount sides and widen them slightly so that the wider 16D would fit in. I used a Parma Deathstar with an 8 tooth Cartrix pinion. After fitting the motor I secured it with plastic cement and scrap plastic. Prior to installing the axle assembly, I made a magnet pocket on the bottom of the chassis just behind the motor. I didn't have enough room for a Slotit magnet so my second choice was the equally strong but smaller FLY bar magnet. The pocket was deep enough so that the magnet was almost flush with the bottom of the chassis. Next I glued 2 small brass pieces on either side of the crown gear hole to add a little stiffness to the chassis. The axle assembly was next. I kept the stock axle and gear but changed the wheels to the FLY Porsche GT type. The gear mesh was set using a piece of copper tubing as a spacer between the back of the gear and the axle bushing on that side. Everything was glued into place and I moved to the front of the chassis. Here I first reworked the guide to take out the slop and I freed up the front axle so that it floated more. I replaced the axle with brass tubing to remove ferric material and used the FLY front wheels. Finally I added a small cylinder magnet behind the guide to provide downforce to hold it in the slot. After letting the chassis dry over night I was ready to give it a run. I must be getting pretty good at setting downforce because the value that I calculated I would need and that I set up for was right on. The chassis immediately began turning lap times within 3 tenths of my fastest inline Cheetah powered cars. The added motor height didn't seem to adversely affect the handling at all. I ran a hundred break in laps and began timing runs and the chassis was right in the same time bracket as the inline Cheetah powered cars. I felt that given a larger track the 16D would have been slightly faster. Also the gearing was a little tall for the short straights. I converted the second Porsche and went with a slightly higher gear ratio and did improve my times slightly. So was this a success? I'd have to say yes. I now have two 911s that can run right with and occasionally beat my Cheetah powered F-40s. The motors are cheap compared to the less powerful but more expensive Euro type motors such as the V12-2. For SCX cars in an inline set up it seems to be a good option. One final thing to note is that this is not a set up to run with your stock set power or controllers. I'd say 3 amps minimum per lane and Parma controllers are a must if configured with high downforce magnets. After I did all this I finally realized that I could have saved myself allot of work and just swapped the Parma armatures into the RX cans. Though not the same performance as the 16D this set up works quite well in an SCX car. So If you want to mess around with RX motors and make them scream try one of the milder 16D armatures; It's cheaper than most Euro motor replacements and may give you the upgrade your looking for.
g. Artin Freebies - Well not exactly free but almost. Apparently these sets are very cheap in the U.S. right now and a friend of mine sent us 8 cars from 2 extra sets he had purchased for the track. Well out of the box they weren't much on my Ninco track and their weak traction magnet and high CG hurt them badly. These cars come with an NC-1 type motor which is a little weak but okay on 14+ volts. The chassis was surprisingly well laid out and appeared to be a good design. The bodies varied in quality. The Mercedes CLKs were pretty nice cars except for the heavy weight and stickers. Since this is a tuning article I won't get into the aesthetics of the cars any more than that. I decided to tune the CLKs to run with my FLY GTs. The first thing to do was to remove some of the weight. The weight of the bare chassis was reduced by about 40%. Look at the Artin diagram to see where the weight was removed. Next remove the interior and windows from the body. Take a Dremel tool with grinding tip and remove a layer of plastic from the inside of the body. You can remove a good thickness without hurting the body strength. Next, remove all the excess plastic from the windows assembly. This item is quite thick and there's a lot of weight that can be removed. Take the interior next and give it the same treatment as the body. Now take the front and rear body assemblies and remove excess plastic. At the same time remove all screw attachments because these items will be glued directly to the body. Refit the window assembly and interior and glue. Set the body on the chassis and measure how much the body can be lowered. Remove this amount from that mounting posts and, if need be, and it is desirable, cut out a place for the motor to go through the interior (You can paint the top of the motor black and no one will ever notice it). That takes care of the weight and height problems. Take the chassis and remove the original magnet. Use this pocket to put the magnets you use to tune your car. On the 2 CLKs, which I kept with the stock motor, this consisted of 2 half cylinder 1/16"thick magnets glued side by side. On the 2 that had motor upgrades this consisted of a FLY bar magnet. Magnet tuning and Oz-racing (same power spec as FLY) motors were all that were needed to bring these cars up to FLY standards. On the Ninco track the stock tires work well and do not need to be changed, just glued to the wheels. The fronts were sanded slightly to remove the tread and nail polish was applied. Since I'm loaded to the max with Porsches these chassis will be used to mount several vacu-formed bodies I have lying around. So, these cars offer good value for cars that can be made to run with the pack. The chassis are great for tuning and with the 2 wheel base options will fit many bodies. By performing the basic tuning procedures these cars can be made into serious racers.
h. SCX AudiR8 and Proslot Toyota GT super upgrade. Ever since the last Marconi Proxy race where this writers cars faired rather poorly against the scratch build boys I've been locked in my room studying the problem to see if it was still possible to build a plastic chassis car that could compete. The answer I came away with was a definite "maybe" but only with some major chassis work. For the past couple years I have been trying to build a plastic chassis car that would have a guide/ motor assembly isolated from the rest of the car allowing it to function with limited interference from the body and front wheels. Well I finally succeeded in building a reliable configuration that should give the big dogs a run at least in the medium /high downforce area. The surprise for some maybe my choice of car / drive train. I’ve abandoned the sidewinder configuration of FLY for the older layout of inline drive. Why? Well two reasons: the first, optimum magnet placement and second, easy design implementation. My two cars of choice are the ones in the beginning of this paragraph. So what made this crazy idea feasible. A net friend of my late wife Athina, Russell Sheldon sent me an In slot motor bracket for Cheetah/Fox type motors. When this arrived along with many other items that Russell so kindly "donated" I really didn't give it much of a look see since I was concentrating on setting up FLY sidewinders. Later on, I was working on an old SCX F-40 Ferrari and broke one of the rear axle bushing holders. I could have made a good fix with plastic but with a Ripper motor the plastic was just going to be too weak. While searching for a solution I came across this bracket again and quickly discovered that I could mount it along with the Ripper motor in the chassis with little difficulty and so I was able to save my old chassis. This started me wondering, since the bracket was narrow enough to fit between the original axle bushing mounts. Why couldn't I use both bearing holders and allow the motor and bracket rotate around the axle axis? Well the short answer was that I could, with a few mods to the bracket. With this in mind here's what I did:
First, I cut the In Slot bracket so that it was flush with the top of the motor. Next I removed as much bracket weight as possible to reduce weight. This included areas above and around the bearing holes and about 2mm off the bottom of the bracket at the bottom, near the motor, aft the width of a Slotit magnet and from that point back I removed about 1 mm. With this much of the bracket removed the motor now became a structure stiffener for the bracket when the bracket was screw attached to the motor. Finally, I installed and secured a set of ball bearings (good quality oilites also would have worked) so that the flanges were on the inside (for the Toyota since the plastic axle carriers are close together; flanges can go outside on the R8 setup.). Now let’s talk about the chassis.
I started with a Toyota chassis. The bare chassis was fit with the motor / bracket so that the rear bearings all lined up. An axle was installed through the bracket set and then the second bearing set was added to the chassis. I used a single flanged set of oilites obtained from Patto's Place (On the R8 chassis you can use the stock double flanged or better still the Ninco Ball bearings). I insured that the axle turned smoothly and that the bracket rotated in the chassis.
Now the next thing was to mark out the magnet placement on the chassis. Since my setup was for a double stacked Slotit magnet, I took one magnet and marked out its position aft of the motor on the bottom of the chassis. This was done so that the area could be cut out later. I also marked out a strip from the front of the motor forward to the guide holder about 1/2" wide. This too would be cut out later and would be where the guide tongue would sit.
I built up the motor / bracket / guide tongue extension assembly as shown in the R8 drawing in the drawings section. The tongue extension (.032" brass/aluminium sheet) was soldered to the motor body (Epoxy will also work here). I didn't mount the tongue tip or guide at this point since I wanted to position this after the chassis was built up. The Slotit magnets were super glued into the position shown on the drawing in the drawings section.
The chassis was now ready to be cut. I used a Dremel on low speed to cut out the area where the rear magnet would be sitting first. Enough plastic had to be removed so that the magnet on the bracket/motor assembly was free to pivot without hitting the chassis sides. I had to test fit the built up motor / bracket assembly to get this exactly right. After this was completed I cut out the area where the guide tongue would sit. I had to be very careful here since when this area is removed the chassis is almost cut in half and could be broken easily. I took a piece of plastic about .5"- wide and 1.5" long and glued it in the chassis over the tongue cut out in a location approximately where the original magnet was located. What I was doing here was making a brace for the front of the chassis to hold it together securely after the tongue cut out was made. I used plastic glue here so that the bond would be fused plastic. (Epoxy will work here as well.)
The motor / bracket / guide tongue extension assembly and the chassis could now be put together. The critical area was setting up the rear pivot. The right amount of spacers/washers had to be placed between the 2 bearing sets so that there was no slop and that the bracket was centered between the outer bearings. After this, I set the wheels and, lastly, set the gear spacing. Since I used a 64 pitch crown gear with the reversed boss and the In Slot bracket the gear mesh was just about set right automatically. As a note here: You may want to set the mesh up using spacers on the inside of the bracket so that it is exactly correct and there's no possibility that the bearings can shift (I recommend soldering the bearings to the bracket). This sounds complex but the description is harder than the actual task. When it was done I had a nice smooth mesh with a free moving pivot point around which the motor assembly could swing. On two of the cars I subsequently modified in this manner, I kept the stock axle bearings in the chassis carriers. Since they had a little slop in them they acted to let the entire body / chassis “float” in relation to the motor / guide assembly.
The last thing that needed to be done was to setup the guide. First I determined how far forward the guide could sit and not interfere with the car body. Once this was found, I then just mounted the guide tongue on top of the tongue extension in the proper position using solder (Epoxy will also work here). Then I mounted the guide and set the depth using spacers. As a final step I also soldered a piece of piano wire across the guide tongue so that it would engage the chassis as the tongue fell down. This would limit the amount of pivot downwards to a couple of degrees which was all that was needed.
When all this was done I set the forward magnet on the tongue and mounted the body. On the Toyota, I had to make a new forward body mount since the old one was removed with the tongue cut out. I used plastic tubing and threaded inserts to make mounts on each side just behind the front wheels. (The R8 needs no mod in this area.)
On the track this setup was well balanced because the body had little or no effect on the tripod other than support to prevent leaning in the turn. I've made several minor tweaks to this design to add several flex points. I won't reveal these details just yet as they may be part of my next Marconi entry design. By using this setup as a base though you will still have a well performing car that you can personalize with your own little tweaks. One area on the Toyota that I needed to reinforce was under the rear plastic bearing carriers. After about 20 hrs of operation the chassis broke at this point so I glued two thin brass strips under the car to reinforce this area and on the inside with piano wire epoxied to the chassis. That was the only place where I've had a problem. On the R8, I have had no failure to date after 25+ hrs of operation with several huge crashes. This mod can be done to almost any inline drive car. The only restrictions are: 1. enough space between the rear bearing holders so the bracket can fit and 2. enough body clearance for the bracket on some LeMans type cars. Ninco cars such as the McLaren GTR, CLK, or BMW and most SCX cars are good candidates for this type mod.
19 Nov 2002 update: After much testing and tuning I’ve decided that using the long tongue isn’t necessary unless you need the extra .1 sec. As an alternative, just adding a fixed guide holder rather than the one that pivots with the motor seems to give the best compilations of speed and reliability. Side loads on the rear bearings is extremely high with the full mod and lifetime of the bearings/holders is reduced somewhat and the chance for damage is greater in a high speed crash.
One note of interest on the R8, the 2 rear side mounting screws can be used to adjust the suspension effect of the complete motor pod assembly if you do not glue the rear axle bearings into the chassis carriers. Tighten the screws reduces the allowed slop in these outer bearings. This translates to less movement of the complete motor assembly. By using bearings with some slop you can also build in some flex into the motor assembly without compromising the motor to rear axle stability (inner bearings are the load bearings for the drive train).
November 2002- This setup was proven at the latest Marconi Proxy Race where An SCX Audi R8 with the “U” bracket setup finished overall first in the magnet class. 2 cars were also in the top 5 in qualification
I. This next setup was made because of the continuing increase in speeds for high downforce racing. Magnet cars present a basic problem. They need to have enough downforce to hold them through the turns yet not have so much that they overwhelm the motor. Up to now the general feeling was that the lighter the car the better for magnet cars since the more mass a car had the more magnet downforce that was required to keep in on the track in the turns. The fact is that this may not be completely true. What if the weight added was in the motor area which would make available double the torque of a similar car of lighter weight. This would allow a doubling of downforce at a weight cost of only a third of the original weight. The result a greater magnet downforce to overall weight ratio.
THIS PROJECT WILL BE DETAILED NEXT UPDATE IF IT PROVES IT'S WORTH.
So, what these stories should tell you is that in the end you decide which items can give you the performance you are looking for. If I had to choose an order for the speed crazed, it would be first magnets and motor and then tires and gears. Body and chassis general weight reduction are essential for maximum performance. Use specific weight to balance out any CG problems. When tuning cars the easiest tuning is with magnets and/or weight. Go to the expensive stuff later only if you still want more boost.
a. SCX Ferrari 333#1 #2 d. Ninco F-1 g. Toyota/AudiR8 Super Upgrade j. AudiR8 mods(2 pages)
b. Ninco McLaren e. Carrera Audi h. Brass Weights k. Guide set up
c. Fly Porsche Joest #2 f. Cheetah/Fly Pod Mod i. Guide Holder Repair(2 versions) l. Measuring traction
1. Need more power to run your Cheetah motor on stock power? If you’re running an unregulated power supply like many of us do or a low current regulated take an analog volt meter and watch your power when you rev up your motor or run with high magnet downforce around the track. Does the voltage drop when you add more throttle? Then your power supply needs a little help in the form of a charged capacitor. This mod is simple. If you’re running on Scalextric or similar with no brakes just take a 2200ěF capacitor rated at 20-25 volts and solder it across the motor terminals. Remember the capacitor is polarized so make sure you got it correct. You can easily tell by running the motor and momentarily touching the capacitor to the terminals. If it's correct the motor will rev up slightly. Make sure you insulate the capacitor's leads so you don't get a short. Also make sure you mount it in the chassis where it won't interfere with body mounting. It can be superglued to the chassis or RTVed. This mod will also work on tracks with brakes though slightly less efficiently. If you want a better set up in this situation combine this mod with the next one on Brake Disabling. NOTE: One additional advantage to running a capacitor in the car chassis is that it helps to prevent power loss from poor brush to track contact. Sometimes due to a number of factors not all of which are easily correctable, your car may experience power loss because the brushes just aren’t making good contact at some points on your track. During those times the capacitor will discharge and fill in part of this loss. Is your car too small to fit the proper size capacitor? Well remember that capacitors in parallel add their values together and so several smaller ones may be substituted and mounted in various small spaces. Still don't have enough room? Well you can always hide them in your controller but you will lose the "power during poor brush contact" capability. One last thing that these capacitors provide you is an extra "cheat" factor when power is removed from the track so that lanes can be switched. You will get that few moments of extra power which could make a big difference in your track position. Finally, don't get carried away with adding capacitance. Don't forget there's charge and discharge times to consider. You do want your car to react precisely with your controller inputs so be careful how much capacitance you use.
2. Let’s disable the brake circuit in the car - Your first question may be: Why do this? Well sometimes either you can't do it at the track or the rules mandate the use of brakes. In the case of high magnet downforce cars brakes may actually cause lower performance because the combination of magnet braking and dynamic braking is just too much. So if this is the case why not just put a switch in the car that will switch out the brakes if so desired. The circuit is simple again because all you need is a 3 amp diode in series with the return wire from the motor mounted in the direction of normal voltage flow. When the motor short is provided by the controller during brake initialization it will be blocked by the bias of the diode. The diode's only disadvantage is the voltage it drops under normal operation. This can be minimized by using Schottkey Diodes that drop only .3volts. The speed gain in decreasing braking will more than offset this loss in voltage on tracks with more turns.
3. Mod 1 and mod 2 may be combined to give you both functions. Just make sure that the Capacitor is mounted before the diode in the circuit (See the drawing).
4. The next mod in this area is not one that is done to the car but one that can be done to the track to reduce the effectiveness of the cheaters in mod 1 and to give your weak power system a slight boost. Just mount a large value capacitor across the input lines of your track. 6000mF+ at 25V should do the trick. This will help to prevent those nasty acceleration problems on one lane when the other de-slots. Again watch out that you keep the polarity correct or else you'll be in for an unpleasant surprise. These caps can also act to smooth any ripple still in the voltage. As a side note any of you that are using battery chargers as power supplies, adding capacitors across the output lines can be very helpful in cleaning up the voltage especially on those cheap Chinese made chargers.
5. Lighting circuits – To be added in next update
As you can see it doesn't take any fancy circuitry to get more performance from certain power situations. There are some more exotic ways of getting an advantage using voltage circuitry tricks, power inductors and the like but for right now I think these should remain on the list of "beyond the scope of this article" items.
This section is written to give repair procedures for certain items that may break on the chassis or body. Some of these items are covered in their particular topic section but we felt that a section was needed to make locating these repairs easier.
a. Guide Holder - Sooner or later you are going to break a guide holder and will need a good repair that is both strong and easy. There are several methods mentioned in this article at different parts but the most reliable that we've found is the one that utilizes a brass plate and tubing guide axle holder. Using the Guide Holder diagram as an example cut the plate and tubing and solder them together. For most applications, gluing this plate to the chassis will create a strong enough bond. If there is some doubt you can use small countersink screws to add additional bond strength.
b. Axle Bushing Holders - If you’re running high downforce and hot motors you may run into a problem with broken Axle Bushing Holders. Is the chassis ruined if this happens? Well not exactly. You can try re-gluing the broken part to the chassis. Use plastic cement since you want to re-bond the plastic together. What I do is mix the glue with plastic filings to make a paste and apply it liberally to the broken joint. Let it dry for 24 hours and file off any excess if it is necessary. The new joint should be stronger than the original material. If you’re planning to use high performance motors etc. you may want to take some preventative measures in this area by reinforcing the holders with extra plastic and glue. Pieces of brass can be fitted here also and glued into place if and even stronger set up is desired. Next to the guide holder this is the second most failure prone area when very high performance components are used such as Cheetah motors and strong magnets. If you intend to run plastic inline chassis with these items you might want to consider going to a motor "U" bracket so that you can have the extra strength in this area.
c. Cracked or Broken Chassis - Once in awhile a chassis gets broken in a high impact crash. Usually the best fix is to first remove everything from the chassis and set the chassis up so that it is back together and properly aligned; you may want to clamp it in place if the break is in an area where the chassis doesn't naturally come back together. Once everything is lined up use superglue to get it attached together in a temporary joint. Now take plastic model glue and mix it together with some plastic filings to make a paste. Apply this freely to the chassis area under repair. If a stronger bond is desired a piece of scrap plastic may be added over the joint and covered with the glue mixture. Allow to dry for 24 hours and clean up the joint as necessary. As in the case of axle bushing holder repair, a brass piece may be glued over the original break to obtain a stronger joint.
d. Motor Mounts - It is not at all uncommon to crack or break a motor mount on fixed mount chassis after several motor removal / installations. If the mount is cracked usually the repair is simply a matter of rebonding the plastic using plastic glue. Sometimes it may be desirable to add a piece of plastic reinforcement so that the mount is strengthened. If you break a mount particularly at the pinion end then the repair is a little more difficult. The problem is that you have to make sure that your repair keeps the motor pinion to crown gear alignment perfectly zeroed. This usually means that the motor will have to be glued into the chassis with the mount so that this alignment can be made at the time of the bond. Using liberal amounts of plastic glue with plastic filings will insure that the mount will be stronger than new. For inline chassis, going to a motor "U" bracket will give you a much better fix.
e. Quick Fixes Under Race Conditions - What can you do if you have a failure of any of the above during a race and you need a quick fix that will get you through the event and until you have the time for a proper fix. Well one of the best "combat" repair tools is a hot soldering iron. Remember your car is plastic and plastic melts. You can get a pretty decent short term bond by melting the broken parts together. It's not pretty and the fumes are noxious but it works. You should only melt the plastic enough to make the minimum repair otherwise you will have allot of work to do when you get it home and want to make a permanent fix. Also remember that you can take scrap plastic and melt it to your chassis if a stronger bond is required. I recommend you practice melting techniques on scrap plastic so that you can get a feel for making these kinds of repairs then you will be prepared when the need arises.
a. Body Mounting Posts - Body mounting posts on most cars can be repaired by sliding a length of plastic tubing over the post and securing with superglue. Screw holes can be filled with glue and retapped.
External Pieces Such As Mirrors - Keeping small pieces attached to the body is
always a problem. Other than removal or continued re-gluing your options are
limited. One thing you can try is to take small pieces of straight pins and
inserting them into the mirror or small part base from the inside of the body.
This is neither easy nor useable in all circumstances. What you do is heat up
the pin and insert it carefully into the component from the inside of the body
and once it's inserted fully add a drop of glue to add strength. The difficulty
is in getting the correct pin length and not pushing the pin through the part
a. Loose Hubs - This is a chronic problem with plastic press on wheels. Sooner or later they all come loose or begin slipping. Sometimes this is due to a hub crack (see next section) or just stress and wear. Various methods can be employed to repair these items but the methods I've found that works best is as follows. First, rough up the axle with course sandpaper or Dremel tool. Now, clean both the axle and wheel with alcohol, including the inside of the axle hole of the wheel. Parts must be absolutely oil free. Next take either slow set up super glue (thickened) or a mixture of plastic powder and plastic glue and apply to the INSIDE of the wheel axle hole. Press the wheel onto the axle, twisting it slowly as you press it on. Let dry for the recommended glue drying time. That should give you a good long lasting mount. In addition to Super and plastic glue, certain epoxies and casting resin may be substituted. If you’re attempting to put a wheel on an axle that is very loose, wrapping the axle with plastic thread or "horse hair" prior to assembly can tighten up the fit so that you will get a more satisfactory result. The key to any wheel / axle joint is to a good interference fit. Roughing up the axle will usually do this nicely. Adding the thread will help those situations when that isn't enough.
b. Broken Hubs - Plastic wheel hub axle holders are a particularly weak part on the wheel. Even from the factory you will sometimes get wheel assemblies that are cracked. The best repair is to remove the wheel, take a piece of plastic or brass tubing and superglue it over the axle holder; the tighter the fit the better. Let it dry and remount the wheel using the procedures above in "step a". If a wheel hub axle holder breaks completely you still may be able to repair it using this method.
Wheel removal – Most plastic wheels will come off the axle by simply them off.
Sometimes you may have to turn them while pulling but this should be kept to a
minimum so that the holes don’t become elongated.. One problem brand is Carrera
because they use serrated axles. You still remove them by pulling but it is much
more difficult and there is a greater chance of damaging the wheel. When you
remove a wheel with the intension of reuse you may want to consider adding
tubing similar to what is mentioned step “b”.
a. Silicone tires – Some people can run sillies for years and never have a complaint. I, on the other hand, have had several incidents where these tires have come apart either due to improper installation or to too many rpms on an unglued set of tires. Since these tires don’t grow on trees here in Greece, when one comes apart it can spell disaster. Well I’ve found that these tires can be repaired enough to finish a race or in some cases run for months with a little CA glue and some luck. Here’s what I’ve done on several occasions to save a set of tires. First, see if the tires can be squeezed together on the wheel so that it looks “normal”. If so, then take some CA glue and put it in the break and squeeze and hold the tire together for about 20 seconds or so until the glue sets up. Now take the CA glue and run a bead around the wheel rim / tire bead interface so that it wicks into the joint. Do this to both the front and inside sides if possible. This step isn’t necessary 100% of the time but it keeps the tire from expanding off the wheel under high rpm conditions. Now run the rear tires on a piece of sandpaper (for silicone tires use 600 grit or finer since coarser grits decrease silicone tires traction slightly) to balance and remove any excess glue on the tread area and away you go. I’ve been able to fix 4 out of 4 split tires this way and haven’t had any problems with them. Of course as with any “shade tree” fix, your mileage may vary. You can also fix the tire off the wheel and make an even better repair. Glue it together as in the on wheel fix. Now take some liquid silicone or RTV and rub a small amount on both the outside (make sure it’s clean) and inside of the tear joint. Allow it to dry and it should act as reinforcement to the joint. Make sure you use a sparing amount of sealant especially on the inside so that you don’t have a mounting problem. The outside can be sanded gently as in the on wheel method to smooth everything out.
5. Basic Motor Repairs
First, I’m no motor expert but there are times when you may need to take one of your motors apart to check something or make a basic repair. This section will not cover things like rewinding, setting timing, reworking the commutator, or any of the fancy items that motor builders do. What this section does include are some basic things inside our motors that we may want to fix without the aid of any sophisticated equipment. There are 3 basic types of motors covered here: 1) the FC-130 which includes all the basic Scalextric / FLY / Proslot / Slot It etc motors 2) the FK-130 which includes all the Cheetah / Falcon / Ripper / etc. (NC2 types are similar) motors both closed can and with vent holes 3) 13uo (FT-130?) which includes SCX / later Teamslot type motors.
a. Parts: Before we take one apart let’s look at the basic parts of the motors we will be referring to: 1.Can assembly including the motor magnets 2. Endbell assembly including brush assemblies 3.Armature assembly including spacers. Each of these assemblies contains smaller parts but these will not be detailed except where specific inspection or repair is required.
b. Disassembly: Each motor type comes apart slightly different so each will be dealt with separately.
FC-130 (Most common type used by most manufacturers)
1. Remove the pinion gear with an appropriate gear puller tool. If the gear is a Cartrix type with no hole on the end or if the motor has a front motor-rear drive assembly then carefully take and grasp the motor shaft between the motor can and pinion / spring with a thin needle nose pliers. Take a second set of pliers or a small diagonal cutter and wedge them between the first pliers and the pinion / spring. Gently pry the pinion / spring up until it is removed. If you don’t have the first set of pliers to hold the shaft you can still pry off the pinion / spring but you may move the fixed motor spacer inside the motor. If this happens you will have to reset the armature spacing.
2. Check the amount of “in-out” movement of the armature shaft. If it is excessive, make note to adjust armature spacing.
3. Using a small screw driver, pry the 2 tabs, one on each side of the motor, open.
4. If the motor is endbell drive (shaft comes out of the end bell end of the motor), grasp the armature shaft and pull the armature assembly along with the end bell out of the motor can. If the motor is can drive, press the pinion end of the shaft against a hard surface to separate the end bell / can assemblies. Carefully grasp the armature and pull it along with the end bell out of the can. The idea is to keep the end bell assembly on the armature.
5. Take the armature / endbell assemblies and with a pair of closed face tweezers gently push the brush assemblies on the end bell apart enough so that the armature along with its spacers can be removed from the end bell. Be careful here so that you don’t damage the motor brushes or lose the shaft spacers.
6. To remove the magnets from the can remove the 2 spring clips; one on top, one bottom, by taking a small screwdriver and prying them toward the open end. Be careful not to let them spring away from you or you’ll be searching the floor for some time. Now pop the magnets away from the case and slide them out. Sometimes the point of and Exacto knife between the magnet and the case can expedite this action.
7. To remove the brushes from the endbell take an Exacto knife and separate the brush holder from the endbell by gently pry the assembly loose at the top of the endbell at the joint. The brush assembly sits on an axle so once you loosen them they will slide off.
13uo (SCX and Teamslot use this type motor)
1. Same as step 1 above.
2. Same as step 2 above
3. Remove the brush tension springs and mark brushes so that they can be reinstalled in the same retainer as they are removed from; remove the brushes.
4. Same as step 2 above.
5. Remove the end bell from the can assembly being careful not to lose any of the armature shaft spacers.
6. Remove the armature from the can assembly.
7. To remove the magnets from the can remove the 1 or 2 spring clips; one on top, one on bottom (depending on motor brand), by taking a small screwdriver and prying them toward the open end. Be careful not to let them spring away from you or you’ll be searching the floor for some time. Now pop the magnets away from the case and slide them out. Sometimes the point of and Exacto knife between the magnet and the case can expedite this action.
FK-130 (Cheetah / Falcon / Ripper, Cartrix Pro, New FLY Racing motor; Ninco Stinger; NC2 is the same basic structure in longer can)
1. Same as step 1 above.
2. Same as step 2 above.
3. To remove end bell assembly carefully open the 4 small press tabs at each corner of the end bell. If you can’t do this then take a Dremel tool and remove them. (In this case you will have to glue / solder the end bell back together with the can assembly when you rebuild the motor.)
4. Press the pinion end of the shaft against a hard surface to separate the end bell / can assemblies. Carefully grasp the armature and pull it along with the end bell out of the can. The idea is to keep the end bell assembly on the armature.
5. Take the armature / endbell assemblies and with a pair of closed face tweezers gently push the brush assemblies on the end bell apart enough so that the armature along with its spacers can be removed from the end bell. Be careful here so that you don’t damage the motor brushes or lose the shaft spacers.
6. To remove the magnets from the can remove the 2 spring clips; one on top, one bottom, by taking a small screwdriver and prying them toward the open end. Be careful not to let them spring away from you or you’ll be searching the floor for some time. Now pop the magnets away from the case and slide them out. Sometimes the point of and Exacto knife between the magnet and the case can expedite this action.
7. (Required for brush replacement and replacing endbell bearings) To remove the brush assembly from the endbell plate you must first cut off the 4 tits that hold the brush assembly to the endbell plate. This is done by taking an Exacto knife and cutting each one flush with the back of the plate. Now take your knife and gently work it into the joint between the endbell plate and the plastic brush holder. Do this on both sides until the brush solder contacts work free of the plate. Now the two pieces will pull apart easily.
c. Inspection and repair
1. Armature Assembly (All types)
a. Visually inspect armature for any obvious defects such as broken wires severe burn marks on the commutator. If any major problems are observed armature should be considered un-repairable at this level of maintenance unless you want to try re-soldering a loose wire back on a commutator post. This is usually not possible since, when a wire comes loose, it usually results in a catastrophic failure.
b. Clean commutator with a soft cotton cloth and alcohol or lighter fluid. Make sure there is no metallic accumulation between the commutator leaves that could be shorting 2 poles together. If there is something there take the BACK side of an X-acto blade and gently run it up and down each leaf gap. Try to remove any carbon residue or oil build up. Remove carbon marks, not dissolved by fluid cleaning, with a soft rubber eraser. If there are small grooves or ridges on the commutator that might be detrimental to motor performance, you may be able to polish it slightly using auto rubbing compound and soft cloth. 1200grit sandpaper can be used as a last resort. Don’t expect miracles here because most of these commutator's are very cheaply made and are generally not designed for rework with tools like a commutator lathe. Slotit and the newer ScaleAuto motors are the exception with quality commutator's that can be reworked.
c. Check between each set of leaves to make sure you have some ohm reading (varies from motor type to motor type). Reading should be > 0 ohms and < 10ohms again depending on the motor type. If the motor was running okay before disassembly with no abnormal heat build-up or no great loss of power this check should be good. If it’s bad the armature is non-repairable for this level of maintenance.
2. Can Assembly (All types)
a. Visually inspect can to make sure magnets are secure and armature shaft bearing is okay. If magnets are loose for some reason you can remove the spring clips that hold the magnets in place and bend them open slightly to provide more pressure on the magnet. If you still have problems, then you can wick some superglue between the magnets and the can. This should hold things together. If the bearing has problems your better off replacing it with a spare from an old motor or just replace the whole can assembly.
b. Clean the inside of the assembly thoroughly with a small brush and either alcohol or lighter fluid. You can remove the magnets before you do this but make sure you mark them so that you can reinstall them exactly the same way.
c. Take a strong Neo magnet and run it over the inside of the case and motor magnets to remove any accumulated ferric “dust”.
d. If you think you need to replace the magnets, do so at this time. Not all motors have the same strength magnets. Typically stronger magnets provide more torque and brakes while weaker ones provide more rpm if compared in an identical environment. Other factors are involved such as magnet to armature gap but these are beyond the scope of this discussion.
e. Reinstall the magnets by sliding them into the can until they touch the front stops. Now take each spring clip and place them at the front of the magnet flat against the case. Take a small screwdriver and slide each, one at a time, completely into the can.
3. Endbell Assembly
a. (FC/FK-130) Check motor brushes for wear. This is the most likely cause of performance degradation especially on high performance motors such as the Falcon / Cheetah / Ripper. (FK-130) If the brushes are worn excessively you have a choice: discard the motor, put it back together and use it for other than competition, or take a motor end bell / brush assembly from another motor and replace the defective component with it. This last option should be considered if the original motor has a particularly good armature that you want to continue using.. Cheap motors are available from several sources to use as donor motors but be careful that they have the carbon tips on the brushes as some just use the copper spring strips without these tips. Likewise some end bells on cheap motors do not have a metal armature shaft bearing but instead use just the plastic end bell case as the bearing. These should be considered unsuitable for normal slot car use.(FC-130). There are brush assemblies available for this type of motor for about a dollar a set. To replace just pry the old set loose from the mounting post and replace with the new set. Insure that the spring tension is proper on the new set (the brushes should be touching each other with slight tension.). Make sure that each brush is mounted squarely in their holding slot. If the fit is loose take a drop of superglue and put it inside the slot while holding the brush assembly in place. Check some of the Mini-X RC sites for sources.
b. (FC/FK-130) Insure that the brush assemblies are providing spring tension so that the brushes will engage the armature properly. Check that they are not bent out of shape and that they ride squarely on the commutator. This can be verified by trial fitting the armature commutator end onto the end bell assembly and visually inspecting the brush seating. Spring strips can be moved / adjusted by carefully using a pointed tweezers to grasp the strip and reset it to a proper position. Insure that the spring strips are aligned exactly vertical. If they are not take a needle nose pliers and adjust them in their individual plastic slots. Add a drop of superglue to each slot to help to hold them in the proper position.
c. (13uo) On RX type motors the brushes are mounted in holders and small external springs provide brush tension. These brushes are easily replaced when worn and motor disassembly is normally not required for this task. Springs may be bent to increase or decrease brush tension. You can usually get a general feel if adjustment is required by taking a small screwdriver and increasing or decreasing the spring tension with the motor running. If the sound pitch goes up with the increase or decrease tension then adjustment may improve performance.
d. (All) Inspect the end bell bearing for excessive “play”. If this is a problem your better off replacing it with a spare from an old motor or just replace the whole end bell assembly. Ball bearings are available for these type motors for about 2 dollars a set. This is a worthwhile upgrade on hotter motors. Check the motor modification section for instructions.
d. Re-assembly -
1. Setting armature spacers (All types)
a. Basically you want the armature to turn freely in the bearings without excessive back and forth slop. This back and forth movement should be no more than a paper’s thickness. This small amount of play is necessary for thermal expansion as the motor heats up and expands under use. Excessive movement will cause more bearing wear, loss of performance and gear mesh noise / problems. In addition to minimal movement, the armature should be set so that the armature poles and windings lie completely inside the motors magnetic field. Additionally, it must be insured that the motor brushes ride on the commutator without interference.
b. Most armatures have an interference fit spacer on the can end of the armature shaft and several thin spacers on the end bell end. Usually proper spacing can be set by manipulating the interference fit spacer to reduce or increase the amount of “play”. If desired this method can be replaced by using shaft spacers to set the gap exactly. The advantage with this method is that the gap cannot be changed by external forces such as pinion installation / removal. If you stick with the interference fit, a very small amount of epoxy on the armature side of the interference fit spacer will help to insure its security.
c. Spacers on the commutator end of the armature shaft can be of several types. Usually there is a plastic / phenalic type that rides next to the commutator to prevent shorts in motors where the commutator sits near a metal bearing. Some motors have a spacer which acts as a lubricant stop to prevent excessive oil from reaching the commutator. It is best to reinstall spacers exactly as they were removed so that you maintain the manufacturer’s configuration. If you must add spacers to this end of the shaft it is better to add them between the existing spacers so that you don’t defeat any purposeful spacer locations.
d. The gap can usually be set using a spare end bell that has had the brush hardware removed. This will make set up easier and will reduce the chance of damaging the motor brush assemblies while setting the gap.
2. Putting it together (All types except where noted)
a. Once you’ve set the spacing it’s time to put the motor together. Basically this is the reverse of the disassembly procedures.
b. (FK-130) Install the brush assembly onto the endplate by adding a drop of super glue to each of four tits and then gently pressing both sections (endbell plate and brush assembly) together. There will be no space between the assemblies when they are completely joined. Hold together until glue sets.
c. I’ve found that it is easier for me to assemble motors without damaging motor brush assemblies if I first install the end bell onto the armature assembly and then together join these assemblies to the case. You must be careful because as the armature is introduced into the case the magnetic field will exert a pulling force on the assembly. You can maintain control on can drive motors by grasping the shaft as soon as it clears the case bearing and by then slowly guiding the armature / endbell assemblies into place. On endbell drive motors install the armature while grasping the shaft on the outside of the endbell. You may find another method better fits your skill level.
d. (13uo) Insure that you install the brushes in exactly the same place and orientation as they were when removed.
e. (FK-130) When joining the armature and end bell assemblies to the case insure that the endbell “snaps” into place and that the armature turns freely. If the security tabs have been removed then you can either run a bead of glue around the case / end bell joint or spot solder the two assemblies together.
f. After securing the end bell assembly to the case by bending the security tabs into place you can put a drop of glue on each one to make sure they remain secure.
g. Lubricate each motor bearing lightly and then slowly run the motor to 3 volts observing that there is no arching at the brush assemblies. If there is reduce the voltage until it stops or if it doesn’t until it is minimal and run motor for 10 minutes. Check to make sure that there is no excessive friction or heat. If everything looks good the motor is ready for reuse.
6. Motor Modification
a. Installing Ball Bearings
1. Installing ball bearings in a cheap motor such as the FC, FK, and 13UO type used to be rather useless since the bearings were more expensive than the motor. Today, though, things have changed. With slot cars and mini-rc becoming more and more popular replacement parts are becoming a profitable venture at a reasonable cost to the customer (about two bucks a set). With this in mind the following is a general set of procedures for replacing your stock bearings with ball bearings. What are the advantages? Well, the main one is friction reduction. On low rpm motors you can see gains of up to 1000rpms and on higher speed motors the result is even greater. This is a measurable performance gain. Also with the reduced friction the motor runs cooler and the motor brushes are stressed less. All this at the cost of a couple dollars and a little time (about 30 minutes with practice). So let’s start.
a. (All) Disassemble the motor completely including the magnets and brushes per the disassembly instructions in this motor section.
b. (All) Take the can assembly and place it bearing up on a flat surface.
c. (All) Take a punch or similar and with a hammer firmly tap the can bearing until it is punched out of its holder.
d. (FC/13UO) Take the endbell and place it bearing up on a flat surface and repeat step c.
e. (FK) Take the end cap and place it outside up in a vice or similar and repeat step c.
f. (All) Determine the outer diameter of your ball bearing (usually 5.8 or 6 mm) and select a reamer (preferable) or drill (useable) of the same size. If you use a drill you may want to slowly work up to the bearing size in several stages using a couple size of drill incrementally. This will prevent damaging the hole or drilling off center.
g. (All) Place the can in a vice or similar. Take the reamer with a handle (don’t use drill or Dremel) and run it through the bearing hole expanding it out to the desired diameter. Note: don’t worry about the bearing crimp flange on the can this is to be removed anyhow.
h. (FK) Now, repeat the process with the motor end cap.
i. (FC) There are several designs for these. Basically, you want to make a pocket for the bearing. This can be done with a small grinding tool and Dremel. It is not necessary to enlarge the small hole that the shaft sits through in most cases. If you run into problems you can take the reamer and open the small hole out to the proper diameter and glue the bearing in. This is slightly less desirable than the first method.
j. (13UO) Putting ball bearings in the 13UO endbell is very tricky and can only be done using bearings of 5.8mm or less in diameter. Place the endbell in a vice and carefully ream out the hole to the desired diameter. Be careful that the plastic doesn’t grab the reamer/drill and begin to twist the whole end of the endbell. This will destroy the endbell and make it unserviceable.
k. (All) Insure all metal around the bearing holes on both sides is clean and free of paint and oxidation. Clean as necessary.
l. (All) Install the ball bearings into each whole. If you made the holes correctly they should press right in. If the hole is too tight run the reamer (or a drill of the right size) back though the hole several times. If the hole is slightly big don’t worry at this time.
m. (All) Now take the armature (or old spare armature) and put it into the can and reinstall the endbell. The shaft should push into the bearings easily. If it doesn’t smooth it up a little with some fine sandpaper.
n. (All) The motor should now be together with the armature inside. The armature should turn freely. Next, the bearings are to be aligned.
o. (All) If the ball bearings are aligned the armature will turn freely by hand and not stop abruptly as it decelerates. The sound should be very fine with no sound that indicates the balls are stressed. If the armature stops abruptly one or both of the bearings need alignment. This is a kind of trial and error method but with a purpose. Use the play in the armature (in and out) to gently tap the bearings. This will usually allow them to find their center. Use a little patience here. Some units align right away while others take some time. If the bearings are loose you may need to add a drop of thick superglue to the bearing/motor joint to set the bearing in place as it is turning. Just a drop of this is not the permanent joint.
p. (FC/13UO) After the endbell end bearing is aligned, superglue the bearing / endbell joint. This will hold it in place so that you can apply epoxy to this joint. Mix your epoxy per kits instructions and run a bead around the bearing – endbell joint (on FC may not be necessary) . Be careful not to contact the free moving center part of the bearing. Remove the endbell from the motor can and run an epoxy bead on the inside of the bearing – endbell joint.
q. (FC/13UO) Reinstall endbell and make sure bearing alignment is still set correctly before the epoxy sets up.
r. (All) Heat your soldering iron, place the can armature assembly in a vice or similar so that the can bearing can be soldered.
s. (All) Freely add flux around the bearing and hole being careful not to get any on the bearing free moving center joint.
t. (All) Verify bearing alignment one last time and apply heat to the bearing – hole joint and flow solder in and around the circumference of the bearing. Note: you can apply a heat sink to the motor shaft to keep excessive heat away from the armature. This shouldn’t be necessary if you solder quickly and properly.
u. (FK) Repeat step -(s) on the end cap end of the motor.
v. (All) Clean up the joints with alcohol, smooth any rough spots in the solder / epoxy with light sanding ,and check the bearing operation by spinning the bearing by hand. Armature should “freewheel” and not stop abruptly. If there is a problem then you must redo the whole thing again.
w. (All) Reassemble per instructions in this motor section.
2. That’s all there is to it. When the motor is reassembled run it slowly for 5 minutes to make sure everything is okay. You may want to lightly lubricate the bearings with ball bearing oil. Don’t get carried away because oil attracts dirt and dirt is BAD for ball bearings. Clean the bearings frequently with a soft brush and liberal amounts of alcohol.
b. Setting the air gap.
1. This step is optional to get more torque from your motor and can be performed 2 ways. The first way is to add tape to the backs of the magnets to move them closer to the armature. This method is fairly easy and doesn’t take any special skill.
a. Disassemble motor per instructions above.
b. Take a piece of masking tape and stick it to the back of each magnet and cut to fit.
c. Reinstall magnets in case and replace armature and endbell.
d. Check to make sure the armature doesn’t touch magnets.
e. Repeat steps b – d adding layers of tape until armature touches magnets then remove one layer of tape.
f. Reassemble motor and test. Gap should be at minimum acceptable.
2. The second method below is a little more complex and takes more time and effort. It is as follows:
a. Take the armature and carefully wrap one wrap of masking tape around it, making sure that the ends just meet but not overlap.
b. Put a small amount of oil or grease on the out side of the cellophane tape. This will make the armature easier to remove after the glue dries.
c. Reinstall the magnets into the can but do not reinstall the holding clips. Now slide the armature into the can. As you do this, the magnets should suck down onto it.
d. Make sure the magnets are positioned correctly and check the amount of space between the magnets and the case to see approximately how much glue/epoxy will be required to fill the gap.
e. Remove the armature and magnets prepare and apply glue to the back of the magnets and the motor case. Reinstall the armature with the magnets attached to it. Position the magnets so that they are squarely against the armature sitting in the can in there normal location with the epoxy between the magnets and the inner can.
f. Now temporarily install the endbell and position the magnets exactly right. Leave everything together until the glue sets up. Now carefully remove the armature and endbell. Take the tape off the armature and reassemble the motor per the instructions in the previous section. The motor should turn freely and the air gap should be set to a more desirable setting (the width of the tape) without the use of special tools.
c. Swapping Armatures Between Motor Types (FC – FK)
1. Some people may ask, why not just put an FK-130 armature into an FC can or vice versa? Some people ask why? The answer to the second is because you can. To the first question: Well, it could be done but a small problem must be addressed first. The motor timing between the FK and the FC is different because of the brush mounting position inside the motor. The FC brushes come down from the top of the motor and contact the commutator on each side (approximately aligned with the magnets) while the FK motor brushes come in one from each side and ride on the top and bottom of the commutator (approximately 90 degrees to the magnets). To get one type of armature to work reliably in the other type can setup the timing would have to be changed. To do this right one would need to open the crimp wire holders on the commutator, carefully remove the wire, shift the commutator to the proper position and then reinstall the wire. This is a pretty delicate operation that isn’t easy or always successful. This article will not be addressing this type of mod; at least not at this time. What you can do though in many cases is turn the commutator enough on an armature to realign it to a position that will work in either the clockwise or counter clockwise direction depending on the amount of wire slack on the armature. Most Eurocar motors seem to be timed close to zero (they run pretty much the same speed in both directions) so what you need to do is VERY SLIGHTLY turn the commutator in one direction to change the timing. Don't do this if you're not prepared for the possibility of messing up the motor (broken wire). If you look at the wire connections on the comm you will see a little slack in the 2 wires attached to each segment. This slack is all that you have to work with when turning the commutator. Exceed that slack and a wire breaks. Here is how to do it:
a. Disassemble the motor per the disassembly instructions.
b. Take the armature and look at the relationship between the commutator segments and the armature poles. Mark it with a felt pen so you can always return the armature to it’s original setting. For an FC can the commutator slots should align up with the center of each armature pole. The FK should have the slot toward the left or right side looking at the comm end depending on the direction of rotation the motor was setup for. Now I get confused with the whole clockwise - counter clockwise thing and direction of rotation so I just turn it one way a little and try it. If it's wrong for the direct of motor rotation I want I go back and turn it the other way.
c. Turn the comm by gently grasping the area between the wire attachments with a needle nose pliers and turn it VERY SLOWLY. Turn it only a little at a time and make sure you don’t break any wires or the whole thing is a loss. Keep an eye on the wires to make sure you don’t stress them.
d. Reassemble the motor per the Assembly instructions and try it out. Don’t forget to set the armature spacing.
e. Changing the timing can effect the motors torque curve, rpm range and operating temp. Changing the timing slightly in stock motors can help you gain a little performance. Back in the old days guys used to cheat by changing the timing in so called sealed motor races. The evil doers used to change the timing without taking the motor apart. I’m sure no one who reads this would do something like that.
1. Don't run magnets too low or else your going to short out to the track rails. This can damage track, controllers, and power supplies.
Don't pick up the rear of high downforce cars and run the motor at high speed.
If the car rear accidentally
drops, say good by to your crown gear
because the wheels won't spin so the weakest link will go: which is usually the gear.
3. Don't run more than one car on a track at a time. If you've got stock controllers and hop up motors you can over heat the controller wiring.
4. Don't use too much oil on your motor bearings. Besides making a mess it can foul the commutator and cause you problems.
5. Do keep your car clean. Dirt accumulates naturally and a good cleaning every so often will help to keep it's performance at the peak.
6. Do check brush/braid alignment and adjust often. Good electrical contact is essential to good performance.
7. Do check tires for cleanliness and, if they're not glued, fit. Nothing will defeat you faster than poor handling due to tire problems.
check your car carefully after each competition. Look for any wear and tear and
correct it. Also check all alignments and make sure everything that's
glued is still secure.
use your powers of observation when competing. See what the competition is using
that may be better suited to the particular track. Remember, the
locals usually know what works best on their track.
10. Don't eat yellow snow. Oh, sorry. Wrong Article.
Well that is the end of the procedures sections. If you did even some of the things we suggested, your cars performance will be much better than out of the box. We hope we covered what you were reading this article for in the first place. If we didn't, contact us at email@example.com and we'll try to answer your questions or you might try some of the other technical sites on the net. After we completed this article we discovered a nice piece on club racing in the UK that might help some of you. It’s at http://www.pendleslotracing.co.uk/.Take a look at it. Since this article was first written the hobby has exploded in popularity and with that there have been many new and updated web sites that offer good technical support and advice. Almost every E-Tailer that handles slot cars exclusively has a Tech board. These can be great sources of information if you have a problem. Use them. There are also several “Slots” forums that can give you access to many of the experts in the hobby. Home Racing World (http://www.homeracingworld.com), Slot Car Illustrated Magazine (http://www.slotcarillustrated.com/) and Fantasy World Hobbies (http://www.fantasyworldhobbies.com/index.html) both offer excellent Tech discussion sections to help the hobbyist. Old Weird Herald (http://www.oldweirdherald.com/slotcartalk/) offers excellent forums for the slightly more seasoned hobbyist but newbie's are also welcome. One word of advice though, there’s no such thing as a stupid question but take a little time and look at the archives of these tech boards before you ask your question. Many times the answer lies there and is discussed in much detail. Both FW and SCI have excellent tech areas with “How To” articles.
The last sections that follow are Appendices that include:
1. A "what's hot what's not" list for quick reference in motor selection.
2. A general consumables list which will give you more information on what was used in tuning the cars. These are items you should think about stocking at home.
3. A motor / adapters chart to give you some idea of what's available. I’m sure this will never be complete since new products come out all the time. It should, however, give you a general guideline to allow you to ask the right questions when you decide to up grade motors. I would encourage anyone with inputs for this chart to send them to us and we will include them. An unfortunate problem with adapters is the fact that most of them only come with motors. This is true of Cartrix and Reprotec adapters which are used for Slotit Boxer to SCX and Cheetah to SCX or Ninco. One note of caution, not all the examples on this chart have been tested by us. This is the only part of this article which hasn't been but we felt that the chart was important enough to make since the data is scattered all over the internet. This is still in rework because I haven't figured out an easy way of presenting the information so that it's not confusing.
5. A tools chart and an internet sites chart will eventually be included. They haven't been completed at the time of this revision. Sorry, I still haven’t had time to get this finished yet (I really do intend to do it some day).
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Appendix:WHAT'S HOT AND WHAT'S NOT FOR HIGH DOWNFORCE CARS
This is what's hot or not for cars with high downforce magnets. New motors are released all the time so this list may not have the latest and greatest. Check the slot forums for what’s the latest and greatest. Many of the NOT motors work well for medium/low downforce configurations and where power is restricted to less than 1 amp. Their main problem is a weak torque curve. 25ohm controls are about as high as you want to go with the hot combos except for the Slotit's which work well at 40 ohms.
Scalextric Cars: Slotit V12-2 and Scale Auto S07. Motor mount must be cut and modified to use Plafit Cheetah, Patto's Ripper or JK's Falcon/TSRF.
FLY Cars: Slotit V12 and ScaleAuto S07 again the best drop in. Plafit Cheetah, Patto's Ripper or JK's Falcon/TSRF can be fit into the motor pod with a little work and is the ultimate upgrade.
Ninco chassis with separate adapter: use Cartrix 1173, if that's too weak use the adapter and install a Plafit Cheetah, Patto's Ripper or JK's Falcon/TSRF (requires long pinion from Cartrix unit and lots of magnet to control torque). SlotitV12-2 good unit also but doesn't come with the traction magnet option that the Cartrix unit does. On short tracks, Ninco’s NC-4 offers excellent torque and with adapters will snap into most Ninco cars.
Ninco NC2 only chassis use either Slotit Boxer especially at 14+vdc(high rpm; slightly lower torque) or Cartrix1164E or NC3(lower rpm more torque) depending on the track. Cheetah, Patto’s Ripper or JK's Falcon/TSRF upgrades can only be made by fabricating a rear motor mount adapter.
SCX: Cartrix 1173E is best drop in; for still more power use the adapters/pinion with Cheetah, Patto's Ripper or JK's Falcon/TSRF. Slotit’s recent release of their motor with SCX adapters is also now a good upgrade.
Proslot: Slotit V12-2 is all around best. Plafit Cheetah, Patto’s Ripper or JK's Falcon/TSRF can be fit with a little work.
Carrera: Slotit V12-2 is best but stock pinion must be used unless a complete drive train swap is acceptable. Slotit makes a replacement setup for the rear axle.
Teamslot TS3/4 RX type motors offer very good rpm and good torque (much better than SCX Turbo Pro) for SCX cars
Cartrix 1162, Reprotec Nitro and Proslot EVO-4 have good rpm and good torque and can be used anywhere1173 can.
Slotit V12-1 Good rpm and torque for Scalextric and Fly.
OzRace / Proslot / Fly/ Ninco NC1 / Scalex can motor slack the torque to handle high downforce cars. Most will overheat and slowdown if pressed. These motors are best used only where stock is the rule or if you need to have a slower car. SC03 and EVO3motors are best of the lot. Quality varies within each group so that you may get a fairly good one or a dog; it's just by luck. Acceptable performance can be obtained on low downforce traction magnet configurations.
SCX RX-Series open can motors also lack power particularly RPM. Only use for stock classes. RX-6 and Turbo Pro the best of the lot. Operate best at the higher voltage levels approaching15vdc.
Appendix : Consumables List and Adaptor Chart
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DC-11 Silicone Grease
Any hardware store
On guide shoe pin and crown gear
Light oil ( lube set#80925 from Micro-mark is good start)
Local hobby shop also www.micromark.com
On all axle and motor bushings and front axle carriers
Make sure it doesn't harm plastics
Auto parts store or gun shops
On axles to build up surface that rides on the bushings
Use the type for sliding and bearing surfaces
Don't use your wife's or mother's
On front tires to reduce rolling and sliding friction
Clear acrylic is best.
Local hobby shop or hardware store
To condition and clean guide braids
also Wahl Hair Clipper Oilworks
Auto parts store
Use to secure electrical connections when soldering isn't practical
Make sure that it has conductive properties similar to or better than copper. Also stay away from thin liquid type.
Local hobby shop or hardware store
To balance the car CG and handling
This item can be difficult to find sometimes.
Glues, Epoxies, and Cements
Local hobby shop or hardware store
Used in various places to secure parts
Specific plastic glue usually bonds to plastic better than most epoxies. Use epoxy when added strength is needed.
Brass or Copper Tubing
Local hobby shop or plumbing and hardware store
Various sizes used to make axle spacers and front axle carriers.
Easily cut to size with Dremel Tool.
Thin Metal or Plastic Washers
Local hobby shop or hardware store
Used to fine tune axle adjustments and tighten guides
You can usually find suitable washers cheaper in a good hardware store than at your local Slot shop.
Plastic Sheet and Tubing
Local hobby shop or hardware store
Used to make repairs to chassis, wheels, body posts and motor mounts
Get various sizes that can be telescoped together.
Local hobby shop or hardware store
Used to round tires
around 150-280 grit works fine
Local hobby / electronics shop or hardware store
Used to secure electrical wires to motors
Do not use acid core.
Fingernail polish remover
Use to dissolve Super glue
Be careful when using with some plastics
Any SCX or Teamslot closed can motor to PinkKar Ferrari
This is the same bracket that's used in SCX classics like Ford GT40with RX-4 motor
Any RX motor to Ninco's that allow removable motor adapter
Any can drive motor like NC1orslotit to Ninco NC2 chassis cars
NC2 adapter for Ninco
NC1 adapter for Ninco
Allows this motor or otherNC2typeto fit SCX chassis
Basically gives NC type motor the same footprint as RX-4 motor
Allows RX-4 type motor fit team slot w/ older Exin open motor
This is the same as Pink Kar adapter RV-17; see above
Same as 52003 but with magnet provision
Regular endbell drive to fit older Exin cars
Endbell drive to Rx?
1174 Motor plus adapter
Just like Reprotec RT-10
Basically gives NC type motor the same footprint as RX-4 motor
1171/2/3 Motor and Ninco adapter w/magnet
Allows these motors to fit any Ninco cars with 70105 NC1 adapter capability
Puts magnet in right place on these cars
1172E/73E Motor and SCX adapter w/magnet
Snap in fit these motors to any SCX RX motored chassis; need long pinion for SRS chassis
Has extra magnet for more traction will allow Cheetah to snap in also Use Reprotec long pinion AS28099
Technical Drawings Section