General objectives when setting-up a slot car

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General objectives when setting-up a slot car

Post by gordon »

Several months ago I started writing down points to remember when setting up my cars. They eventually evolved into the 11 items listed below (just added a 12th item). I'm sure some of you can add to this, however for what its worth, here are my points of reference whenever I'm prepping my cars. Hope this helps you get yours running better.

General objectives when setting-up a slot car
  1. Whole car, particularly the body, should be as light as possible.
    Some classes allow substitution of an ultra-light plastic cockpit or you can use a very thin sheet of plastic and a driver head to reduce weight. Be sure to check the rules for the specific class though as some classes require that the original cockpit be retained. For classes which require a minimum weight, if ballast has to be added to meet this requirement, add it as low in the car as possible to keep the centre of gravity low.
  2. Should have as much downforce as possible or needed for its class to ensure good road holding and drivability, without compromising acceleration or top speed.
    This is a trial and error area and more so in classes which stipulate the USD rule. One of the things I do when testing for the USD rule is use a rubber band to temporarily hold the body to the chassis instead of having to be screwing and unscrewing the body for each test. Any weight added to allow the car to pass the USD rule should be located as far away from the magnets as possible, whilst obeying the location requirements ("Any weight added to the car must be positioned within 2.5" (64mm) and ahead of the rear axle").
  3. No-magnet and low-magnet cars should have free body roll without interference.
    You can loosen the body and/or motor pod screws slightly to create a little body roll which can improve handling in no-magnet classes. Be sure to cover the loosened screws with adhesive tape so that they cannot fall onto the track though.
  4. Should have minimum resistance to rolling on track.
    All bearings/bushings should be lightly lubricated. A small amount of grease should be applied to the gears. Gear mesh should be as smooth as possible. Axles should roll freely when you spin the wheels by hand (test this on the rear axle when the gear is not connected to the motor or motor is not installed). Front wheels should barely make contact with the track and front tyres should be as "slippery" as possible. A good way to achieve this is to coat their rolling surface with clear nail polish.
  5. Should have lowest possible centre of gravity.
    Make sure that there is some ground clearance in the magnet locations to prevent the car from bogging down on uneven areas of the track. Also check that there are no parts dragging on the track surface. Some classes require a 1.0 mm minimum ground clearance under any magnets installed, so be sure to check this. FRC can supply a plastic 1.0 mm gauge for this.
  6. Should have best possible rear tyre traction.
    There are a large number of slot car tyre manufacturers. Do some research and acquire the best tyres for your car's particular wheels that are within the regulations for the class.
  7. Should have optimal gear ratio. This must take rear wheel diameter into consideration.
    Remember that a 3:1 gear ratio with 19mm rear wheels will have a lower overall gear ratio than a 3:1 ratio with 22mm rear wheels. With any given gear ratio, smaller wheels will give more acceleration and less top speed and larger wheels will give slower acceleration and higher top speed. A lower overall gear ratio will also give more brakes than a taller one, however the car will be tricker to drive in the turns because of sudden acceleration which may cause the rear end to slide.
  8. Should have best motor for its class.
    Don't just consider the motor's maximum RPM. A very important factor is its torque (usually measured in Gm/cm). The more the torque, the more "get up and go" your car will have. Check out Slot Car News Motor List ... -list.html for the tested torque values of many popular motors.
  9. Should have lightest possible drive train to reduce inertia, giving you faster acceleration and better braking.
    Where legal and possible, use light gears and wheels instead of heavy ones. For example, you can get good quality Slot.It inline gears with brass hubs, however Slot.It also make the same gears with aluminium hubs and these will reduce inertia. Likewise, lighter wheel and tyre mass will have a positive effect.
  10. All 4 wheels should be properly aligned and tyres should run true without high spots or wobbles.
    True the raised areas on plastic wheels (but not too much, as this can cause tyres to become concave, reducing traction) and true rubber and urethane tyres so that wheels and tyres roll with no high spots. Best way is to use a tyre truing machine, however you can also do so using an old chassis with motor and some emery on a piece of track.
  11. Car should be properly balanced left to right (50/50) and front to rear (~35/65).
    Of course if you've added ballast to fine-tune for the USD rule or to meet a minimum weight requirement, this can alter the "ideal" setup. For magnet classes, bottom line here is that the car must comply with the regs and at the same time get the best downforce that is legal. For non-magnet classes (eg. our Rally class), try to get the best weight distribution. You can use a small digital scale and a block of wood to measure the left to right and front to rear weights. If you have two digital scales, this will make the process even simpler.
  12. Remove all "wobble" to eliminate loose items in the drive train.
    Make sure that the axle bearings fit tightly in the chassis. If not, glue them in place with an axle in both left and right bearings for proper alignment. Make sure that the axles do not "rock" in the bearings, otherwise change or shim the bearings. If the motor tends to rotate under acceleration or braking, screw or glue it in place.

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Re: General objectives when setting-up a slot car

Post by RameshB »

Thanks very good tips.
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