The quality of your axles and wheels may be the most important factor in building a fast car. Here’s how to choose and polish your axles and wheels.
1. Start with a set of raw axles.
2. Can you tell the difference between the axles in the top row and the ones on the bottom? The ones on the bottom aren’t straight and will slow your car.
3. To tell which are straight and which aren’t, mark each axle with a marker about 1/2 inch from the pointed end.
4. Have an adult clamp a power drill into a vise, a device that will hold it perfectly still.
5. Have an adult help you clamp each axle into the drill at the location you marked in Step 3. Have the adult turn on the drill.
6. Bent axles will wobble as they turn in the drill. Straight axles will hardly wobble at all. Pick the ones that wobble least.
7. Once you’ve selected the four straightest axles, use a file or fine-grit sandpaper to remove small burrs and mold marks that can cause friction and slow a car. These imperfections should be removed from both the axles and the wheels.
8. Use polishing compound from the auto supply store to polish the wheels and axles. One easy way to do this is to clamp the axles back in the drill and let the drill spin the axle while you polish it.
9. When you install the axles and wheels, make sure they are aligned perfectly straight. You can test the alignment of your axles by pushing your car across a smooth floor or table. It should roll in a straight line.
10. Don’t forget to add graphite or another dry lubricant to your wheels and axles.