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Thread: Mousetrap cars

  1. #1

    Default Mousetrap cars

    I'm sure many people have heard of these, but for the very small percentage of you that haven't, A mousetrap car is a small car that only uses a mousetrap's spring for power. My school recently decided to do a competition, and I just submitted mine for the competetion a couple of days ago. The competition is on distance traveled from the starting line. I saw most of the other entries and none of them had the idea to add gears to the car like mine to allow instead of only about 10 CM of string wrapped around an axle, it has the effect of nearly 100 cm of string wrapped around the same axle.

    I will post pics of the car after the competition as i do not have it in my posession ATM, but I will after 4/19.

    If anyone else has experience with these, go ahead and put it here.

  2. #2


    I built one when I was in high school, in engineering Explorers. It was fun, and technically I won the competition, but there wasn't much competition: there was only one other entry.

    Anyway, the car I built didn't have gears, exactly, but rather a "cam". Basically, there was a largish disc attached to the axle, but it was cut so that its radius decreased (at the point where it contacted the string) as the axle turned. That way the gear ratio was higher at the beginning of the stroke, when the force from the spring was the highest, and it gradually decreased as the spring reached the end of the stroke. The idea was that would provide more efficient transfer of energy from the spring to the axle.

    I like your design though, and your chances against the competition. And it's really cool that you thought of adding the gears yourself. (I was closer to 17 or 18 when I built my car, and, if I remember correctly, it was one of our engineer advisers that suggested the cam design that I used.)

    Good luck!

  3. #3


    At my school it was a physics project. Mine was too heavy so it went about 2.5 meters I think, anyway the needed displacement was 10 meters. I still passed with an 80, probably because most of the other cars went about 4 meters.

  4. #4

  5. #5


    We had to do one as part of our first-year engineering class in college. Every year, they added a little bit more to the requirements. By the time I got to the class, the requirements were:

    -Go forward exactly 10 meters, +/- 2.5 centimeters
    -Stop and fire a 1-gram payload (think catapult) at a staircase
    -Hit the specified step (numbers 1-11; you wouldn't know what number you had to hit beforehand, so your catapult had to be calibrated and adjustable)
    -Reverse direction and travel 10 meters backwards, with the car stopping entirely behind the line

    This was to be accomplished with two mousetraps (one for drive, one to fire the catapult) and a length of string. We made the car body out of foam core board and the wheels out of CD's. Axles were dowel rods. Duct tape provided traction on the wheels. An incense burner was attached to the drive mousetrap and actually functioned as the control for going forward, stopping the car and triggering the catapult, and causing the string to re-wind itself around the axle to change directions.

    Once the car left the start line, there could be no human intervention. We met all of the requirements, except that our payload missed its target by one step. Considering that many in the class didn't have cars that could even travel the 10 meters, let alone reverse direction, I'd call it a success.

  6. #6


    I think that a lot of people have knowledge on mosetrap cars here, my idea behind the car is very little weight and gears. my car weighed only about 40 grams, while most of the other cars weighed something like 100+ grams. someone elses used a rat trap, but was disqualified due to the danger involved with the rat trap

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