Wheels and Axles

1. Friction is your enemy. If you want a fast car, you need to polish the wheels and axles.

2. Wheels can be polished by spinning them with hand-held power drill while lightly sanding with 400 grit wet sandpaper. Scout and craft stores sell special "mandrels" for holding the wheels in the drill chuck but many Cubs find that a nail can work just as well. The objective is to remove all mold marks and other imperfections.

3. For the axles, start by carefully picking the four best, straightest, smoothest nails from your kit. To polish each one, put it into a drill chuck and first use a jeweler's file (if available) to file away any obvious marks or burrs (especially near the head) while you turn it with the drill. Then use wet emery paper to finish polishing it.

4. Rub a little graphite with your finger on the car body where each wheel will go, then fill the hole in each wheel with graphite, insert the axle and push it into place on the car. Don't pound the wheels in with a hammer. If the fit is nice and tight, you're lucky, because that will let you check the alignment before you glue everything.

5. The fastest car is one that rolls straight. Test your car by rolling it across the floor or down a ramp. If it rolls to the side, it'll probably be hitting the lane guide in the race and losing speed. Many Cubs have found that if only three wheels (one in the front and two in the back) actually touch the ground and turn, the car goes faster because the friction is lower. Also, some Cubs believe that if you push the axle in a slight downward angle (5 to 10 degrees), you'll get a faster car because only the inside edge of the wheel will touch the track and because the wheel will be pushed to the outside and won't rub against the body.

6. When you're satisfied the wheels are aligned just the way you want, the axles should be glued in place with hot glue or epoxy, taking care not to get the glue near the wheels.