Here are some set up tips for racing scale drag cars .

 

MOTOR : As in full size drag racing your chances of winning are less if your motor isn’t as good as it could be .

To have a top performing car in heads up racing where the motors are controlled eg ; Super 16D motors as used in the Box Stock and Hard Body classes you need a top performing motor.

If your motor revs high , quickly and smoothly look after it by keeping it clean and lubed , if it doesn’t perform well , fix it or replace it .

 

CHASSIS : In order for a car to run well it needs to run straight , sounds fairly simple but there are a few things that can prevent this from happening .

The driving axle needs to be exactly 90 degrees to the direction of travel , a poorly aligned or bent axle will cause the axle not to revolve on a single axis and therefore develop a vibration within the chassis and cause the car bounce off the line ,

as will wobbly wheels and any loose or worn axle bushes etc .

The slot should be evenly centered between the driving wheels when viewed from above , so the car leaves in the exact line of direction required rather than a general direction .

The wheelie wheels also need to be parallel to the driving axle and with an even gap under each wheelie wheel of approx .3 to .5 mm , so that when they touch the track they don’t impose an uneven load on the chassis which may cause the car to change it’s direction during the launch .

 

TIRES : The size of the contact patch is critical to the level of traction .

Slix that are too wide can cause the motor to bog , as they increase the load .

Slix that are too narrow can cause wheel spin as the motor quickly peaks but time is lost due to lack of acceleration .

Wobbly tyres can cause the chassis to bounce and the car will loose traction instantly .

The slix actually work as a clutch , too much grip = no slip which may cause the motor to take too long to peak , gearing that is too high can also have the same effect .

The slix need to slip just a little to allow the motor to peak quickly , but if they slip too for too long the car will loose time due to wheel spin , not enough slip and the car will also be slow to get to high revs , similar to driving with the hand brake on .

Higher powered cars may need a thin film of goo all the way down the track , otherwise with more power they can loose traction as the slix expand during a run .

Narrow slix and goo is quicker than full width slix without goo .

 

GEARING : This is important as a car with a good motor , slix and a well set up chassis may still not reach its full potential if the gearing isn’t sorted .

Gearing that is too low will help the car to blast off the line quickly but as the motor peaks , the car will stop accelerating and just keep it’s momentum down the rest of the track .

Gearing that is too high will increase the load on the motor which will slow the car for the first part of the run .

A balance between the two is required to allow the car to leave the line quickly and accelerate till near the end of the track for  quick E.T’s .

It is important to note that the “ blast off the line ” sets up the car for the rest of the run , so slix size and goo levels should be sorted before working on gear ratios . An easy way to know if your car is close to the right gear ratio is to gear it so that the motor reaches top revs about 6-8 feet from the finish line . If the car revs well at no load ( free revving ) and peaks near the end of the track , testing of different gear ratios with an accurate timing system may get the car to run quicker .

 

WEIGHT : As long as your car isn’t too much over the minimum weight for the class that it runs in , don’t worry as cars that are not dead on the minimum weight can still be top performers if the rest of it is set up well .

 

SUMMARY : I apply a “90% rule” to the cars I build , this means that - if all of the main factors ( motor , chassis , tyres , gears , weight ) are within 90% of what their best could be , the car will be a good runner that will be hard to beat , you then just have to cut good lights to win races . #21