mousetrap cars and vehicles

May 12, 2008

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What is a mousetrap powered car and how does it work?

How do you build a mouse trap powered racer?

What are the "perfect" instructions for making a mousetrap vehicle?

What is the difference between a good speed-trap racer and a good distance traveler?

How far can a mouse trap car travel?

How did Doc Fizzix get started?



What is a mousetrap powered car and how does it work?
A mouse trap-powered racer is a vehicle that is powered by the energy of a wound-up mousetrap's spring. The most basic design is to tie one end of a string to the tip of a mousetrap's snapper arm and then the other end of the string has a loop that is designed to "catch" a hook that is glued to a drive axle. Once the loop is placed over the axle hook, the string is wound around the drive axle by turning the wheels in the opposite direction to the vehicle intended motion. As the string is wound around the axle by the turning of the wheels, the snapper's lever arm is pulled closer to the drive axle causing the mousetrap's spring to "wind-up" and store energy. When the drive wheels are released, the string is pulled off the drive axle by the mousetrap causing the wheels to rotate.



How do you build a mouse trap powered racer?
There is no one "right way" to build a mousetrap powered vehicle. The best approach is to apply your best understanding of the laws of physics without over exaggerating any one concept to your design. To build the "perfect" mousetrap racer you must try and find a harmonious balance between all the elements and variable that will affect a mouse trap vehicles performance. Do not be fooled into thinking there is only one way to build a winning mouse trap racer, we have been building mousetrap cars for over 15 years and our designs continue to change; one year everyone is designing cars with huge big wheels and the next year everyone has moved on to pulley systems. Be willing to try something original, it might be the next "thing". The first step to making a good mouse trap powered car is simple, put something together and find out how it works, it may not be pretty but it is a start. Once you have something working you can begin to isolate the variables that are affecting the performance and learn to adjust to improve your results. Building mousetrap cars is a simple process of design engineering, you build, you test and experiment, you change, and you do it all over again.



What are the "perfect" instructions for making a mousetrap vehicle?
Again, there is no one "perfect" set of instructions for building a mousetrap racer. There are many good and proven designs that will work for most first time builders but there is never a set of the "perfect" plans, there is always room for improvement with any design. Doc Fizzix continues to experiment with new ideas and designs in order to go further and faster, he never settles on one design. If you are going to build a record setting mousetrap car you must to be willing to make changes to your designs or any set of plans once it is built. Many students expect to build a mouse trap car from a set of plans and have it work perfectly right after they are done assembling it. This is just simply not the case, you need to test your vehicle and make changes if you want to set a new record. Doc Fizzix has a great selection of mousetrap racer plans that will get you started in the right direction.



What is the difference between a good speed-trap racer and a good distance traveler?
A good distance car will not be a good speed-trap car and so on. When you build a mouse-trap car for distance, you want a small energy consumption per second or a small power usage. Smaller power outputs will produce less wasted energy and have greater efficiency. When you build a vehicle for speed, you want to use your energy quickly or at a high power output. You can change the power ratio 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 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 mouse-trap car for speed, you will want to maximize the power output to a point just before the wheels begin to spin-out on the floor. Maximum power output means more energy is being transferred into energy of motion in a shorter amount of time. Greater acceleration can be achieved by having a short length lever arm and/or by having a small axle to wheel ratio. 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.



How far can a mouse trap car travel?
The sky is the limit! The first mouse trap car Doc Fizzix ever made only went 26 meters. Currently, Doc Fizzix has made a car travel over 182 meters. His has a new system that he feels will even double that distance, we will have to wait and see the final results. 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.



How did Doc Fizzix get started?
Doc Fizzix is actually Alden J. Balmer, an award winning physics teacher from Mc Neil High School in Round Rock, TX. Doc Fizzix had discovered through his years of teaching, that students had very little experience working with their hands or building things. As a boy, Doc Fizzix was always making strange creations and contraptions. It was Doc Fizzix love of science and engineering that brought him into the classroom and he was determine to share his excitement with his students. In 1990, Doc Fizzix decided to have his students to build a mousetrap powered racer instead of a semester exam. He thought this was one way to get his students to experience building or creating something on their own. Students had to also do a full write-up about their mouse trap car that explained how the different concepts of physics applied to their racer. What a success, the students had more fun than they ever dreamed they would have making their own mouse trap car and Doc Fizzix had seen the students develop a true understanding for the concepts that were taught during the course. Doc Fizzix spent a lot of time traveling around the country sharing his teaching methods and activities with other science teachers and would also appear on local television shows as the resident "Mr. Science". As here traveled he would share his mouse-trap-racer activity with more and more groups of teachers and before long he had people asking him for a book on the subject. He wrote the now top selling Mouse Trap Cars: the Secrets to Success in 1995 making it the first and only publication written just about mousetrap vehicles.