how to make a mousetrap car

Making a fast speed-trap racer

By Doc Fizzix // Published Feb 02, 2005

When you build a vehicle for speed, you want to release the mousetrap's energy very quickly or at a high power output. This way your vehicle can get to top speed as soon as possible. You can change the power output of your vehicle by changing one or all of the following: where the string attaches to the mouse-trap's lever arm, the drive wheel diameter, or the drive axle diameter. The amount of energy released by using a short lever arm or a long lever arm is the same, but the length of the lever arm will determine the rate at which the energy is released and this is called the power output. Long lever arms decrease the pulling force but increase the pulling distance, thereby decreasing the power output. Short lever arms increase the pulling force over a shorter pulling distance thereby increasing the power output. If you are building a mouse-trap car for speed, you will want the maximum power output, just before the wheels begin to spin-out on the floor. Maximum power output means a higher rate of energy being transferred into motion or greater acceleration of the vehicle.

Greater acceleration can be achieved by:
• increasing the power torque
• using a short length lever arm
• having a small axle to large wheel ratio.
• build a light-weight vehicle.
• wheels should have low rotational inertia.

If you are building a distance vehicle, you want to minimize the power output or transfer stored energy into energy of motion at a slow rate. This usually means having a long lever arm and a large axle-to-wheel ratio. If you make the lever arm too long, you may not have enough torque through the entire pulling distance to keep the vehicle moving, in which case you will have to attach the string to a lower point or change the axle-to wheel ratio.

See the following related articles to get started:

• basic mousetrap vehicle propulsions (how to make it move)
• how to make a good distance traveler
• Wheels and axles - the transmission of your racer