mousetrap car instructions

DVD/CD Wheels

By Doc Fizzix // Published Nov 17, 2005

Try the following :
Compact disk make great wheels for several reasons:
• first they are very aerodynamic
• second, they have very little rotational inertia.

The idea with any mouse trap racer is to displace the vehicle over some distance, either the furthest possible distance or a pre-determined distance in as little time as possible. Understanding the concept of energy, more of the mousetrap's potential energy should be converted into the kinetic energy of the frame of the vehicle and less into the kinetic rotation energy of the wheels. The less kinetic energy that gets transferred to the wheels and the more kinetic energy that goes into the body of the car the better. It is very important to have wheels that have the least amount of rotational inertia as possible.

At Doc Fizzix, we actually use DVD Layers. A DVD is made up of two parts that are glued together, we manufacture just the layers before they are glued together. As you can imagine since a DVD layer is only half a full DVD, the DVD layer has half the rotational inertia and is even more aerodynamic compared to a normal CD. With DVD layers we see the same car travel 5-15 meters further than with CD wheels.

The biggest challenge with CDs is getting them to attach to an axle. Doc Fizzix recommends using a rubber 1/4 L beveled sink washes that can be purchased from a hardware store. Be careful, not all 1/4 L beveled washer will work well with your CD, make sure you try several samples in order to find the best fit, if possible, select one that has a lip the will prevent it from passing through a CD.

Doc Fizzix manufactures sink washes so you can get them here from our online store.

SPECIAL only from Doc Fizzix, 1/2 DVD disk. DVDs are made in two parts and one single part is 1/2 the thickness of a CD and 1/2 the rotational inertia, more aerodynamic and greater performance, get the whole set-up - CD space, axles, string, axle hook, and DVD layer slices.

See the following related articles to get started:

• basic mousetrap vehicle propulsions (how to make it move)
• how to make a good distance traveler
• how to make a good speed-trap racer