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Slot Car Tuning Tips

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#1 GRN


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Posted 06 February 2009 - 10:44 AM

Hi Guys, made up from a variety of sources. thumbsup.gif


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.
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

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 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. 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).

* 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

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.

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. 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. 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. 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.

4. Axles and Bearings

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

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 additional details.

6. Aligning the Drive Train

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.

c. 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.

4.) Another 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

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. 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.

A funny 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 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. 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.

d. 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 the body.

6. Smoke!

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.

3. Weight Tuning

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.

4. Selecting Gear Ratios
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.

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. 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.

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.

1. Chassis
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.

2. Body
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.

b. 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 completely.

3. Wheels
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.

c. 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”.

#2 John Parr

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Posted 06 February 2009 - 03:39 PM

OR................... Just give it to Jim Kelly and say sort it. rolleyes.gif

#3 luckyfour


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Posted 16 June 2009 - 01:07 AM

hey old mate that is some list you have compiled there I would like to visit the club when time permits me to kim got me doing up the house again jp has been telling me about the new tracks and how much fun they are hopefully see you guys soon jimbo
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fail to prepare prepare to fail.

#4 Blade400


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Posted 16 June 2009 - 04:14 PM

Hi Jim,

good to hear from you again. You're more than welcome to visit any race night. Maybe we'll get to see the sponsored Nascar! biggrin.gif



#5 B.Pearce


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Posted 20 August 2009 - 10:11 PM

don't you think that was a bit too much information? I must inquire as to wether you wrote it yourself?
Bradley Pearce

#6 John Parr

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Posted 23 August 2009 - 10:27 AM

Can you have too much information? Digest it and you would soon be able to tune your own cars!!! wink.gif



    Brian Rogers

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Posted 23 August 2009 - 10:48 AM

QUOTE (B.Pearce @ 20 Aug 2009, 23:11) <{POST_SNAPBACK}>
I must inquire as to wether you wrote it yourself?

Which part of:- "Hi Guys, made up from a variety of sources." - didn't you understand then?

Come race with us at Mussel Bay, RAF Marham, Norfolk.
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#8 DH71Tiger


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Posted 23 August 2009 - 02:14 PM

QUOTE (CMOTD @ 23 Aug 2009, 10:48) <{POST_SNAPBACK}>
Which part of:- "Hi Guys, made up from a variety of sources." - didn't you understand then?

Love it.................................................. cool.gif

I do find myself.......................that these days.................... people don't like....................... READING. biggrin.gif biggrin.gif biggrin.gif

Shame for them really..........................that's how most of our learning is done.

Ah well.......................

Tally H

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#9 manic35


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Posted 23 August 2009 - 03:30 PM

Hey GRN, thanks for compiling and sharing all the info. Excellent tips alright.
Visit MANICSLOTS at: http://manicslots.blogspot.com.au/

#10 Jimmy in Greece

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Posted 31 August 2009 - 07:09 AM

Most of these tips are taken from my old tuning article at : http://www.homeracin...otcartuning.htm
There are some other good tips there if you look a bit. Most of the basic tuning is in the first section with other sections devoted to more detailed race mods. The original of this article was written way back in the mid 90's when I first returned to slot racing hence some of the references to rather old cars. Unless otherwise stated all tips were personally tried and used. My wife and I put it together because there was little available for the "new" guy back then other than discussions on a couple forums such as OWH and some of the Slot E-stores.
We're very lucky now with lots of great info coming from members of Slot Forum, Home Racing World, Slot Car Illustrated, SlotBlog, Oldweirdherald and a host of others. you can easily find an answer to a slot car problem now with all these resources available.


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