how to make a mousetrap car

Making a long distance traveler

By Doc Fizzix // Published Feb 02, 2005

When you build a mouse-trap car for distance, you want a small energy consumption per second or a small power output. Smaller power outputs will produce less wasted energy and have greater efficiency. You can change the power ratio of your vehicle by changing one or all of the following: where the length of the mouse-trap's lever arm, the drive wheel to drive axle ratio. 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 and power output but increase the pulling distance. Short lever arms increase the pulling force and the power output by decrease the pulling distance but increasing the speed.

If you are building a distance vehicle, you want to minimize the power output or the transfer of stored potential energy into kinetic energy of motion at the slowest possible 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

most important is reducing friction, the more you can reduce or eliminate friction, the farther your racer will travel. In a perfect universe, a mousetrap vehicle will travel forever, just like an object thrown in space should travel forever or until it hits something. This is the challenge that makes building mouse trap powered cars so much fun, seeing who can reduce friction the most

Greater distance can be achieved by:
• using a longer length lever arm
• having a large axle to large wheel ratio.
• eliminate friction

Slow Moving vs. Fast Moving Vehicle Here are my thoughts on the ultimate distance vehicle. In sharing my thoughts with you please understand that I am not telling you how to build the perfect Distance Car but I am pointing out the application of physics as I applied it to my mousetrap powered vehicles. I tend to design my distance cars to travel extremely slow. One of my cars that travels 100 meters or more may take over 5 minutes to travel that distance. My idea is to reduce the power output to a minimum, only supplying enough energy to the vehicle to overcome the friction. By traveling slowly you will reduce the air resistance to a minimum vs. a fast traveling car that will have more air friction acting against it. Also, I feel that a quick accelerating car will create more heat energy during a quick acceleration than a slow accelerating vehicle which will reduce the energy needed to travel a great distance. Building a mouse trap car for distance means minimizing the wasted energy and converting more energy into displacement of the vehicle. With that in mind, I like to build cars that have very low frictional forces acting against them and are slow moving. I try to find a harmonious balance between the movement of my vehicle and the length of the lever arm. My cars tend to have long lever arms and large wheels. If a lever arm is too long the vehicle will not travel the full distance because you must have enough torque to keep the car going and the torque changes with spring angle.

See the following related articles to get started:

• basic mousetrap vehicle propulsions (how to make it move)
• wheel and axle gearing
• how to make a good speed-trap racer