Light-Weighting the Wheels

An experiment about the moment of inertia of the wheels.

Taking material off of your car’s wheels is perhaps the most controversial aspect of the pinewood derby. Most competitions don’t allow you to modify the wheels at all -- but each pack and district is responsible for its own rules. In this section, we use a computer model to analyze the effects of light-weighting the wheels on a car’s run time. We conduct a very simple experiment -- using soup cans -- to show how the placement of mass in the wheels can make a big difference in rolling speed.
The moment of inertia of standard wheels.
The moment of inertia of wheels with some material removed.
The moment of inertia of wheels with a lot of material removed.