pic: mousetrap car

[ay2b]

Originally Posted by Don Rotolo

OK, so all this gets me thinkingf: What makes a winning mousetrap car?

A lot of that depends on the rules of the particular contest. The original poster's contest was distance/<time for first 5 meters>. This means that you want high accelleration. Other contests are just farthest distance. Others are fastest time for a set distance.

Way back when I was in HS, I built a mousetrap car where the score was the product of the mass and the distance traveled. Most of the entries were a few hundred grams and traveled a few meters. Mine was over 2 kilograms and traveled tens of meters. Only one other vehicle came close - it actually traveled slightly farther than mine, but was less than half the mass.

The main winning factor in my design was having a very high gear ratio. The wheels were 3-4 inches in diameter, and the axle was 1/4 inch. The mousetrap pulled a "ripcord" string which was wrapped around the axle. I made sure there was high friction between the string and axle, and low friction between the axle and the berring. Accelleration was very low, but the top speed was quite high.

The other design which did well was a hovercraft. It consisted of a container of dry ice which had a small hole in the bottom, and no other opening. The bottom of the vehicle was very smooth, and the floor was tile. This allowed the whole car to float on a cusion of CO2. The mousetrap was then attached and used to "push off" of a wall-like object at the starting line.

Mousetrap cars, balsa wood towers, popsicle stick bridges - these are all fun easy projects to work on that provide a great intro to engineering. Several years ago my FIRST team did one of these types of projects each week throughout the fall as a way to get the team to get to know each other and to learn various engineering priciples.