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I am building a mouse trap car and I have several design issues.

  1. Mar 15, 2009 #1
    1. How to attach my wheel, plastic lids with rubber bands around, and axle, a wooden dowel rod 5/8 in diameter, to the car body, which is a board of wood?

    I used a wood block and attached the too the body and drilled a hole big enough to slide the axle. I also put a piece of aluminum around the dowel rod inside the block to reduce friction. However the wheels weren't spinning very smoothly. There was also graphite between the aluminum and the dowel rod.

    2. What is a good material to use to attach to the mouse trap and to the axle, which will be wound around the axle after opening the trap so that the spring is compressed?

    I used ribbon that is about a cm wide. I might try fishing line if that is stronger/ more effective.

    3. What is a good material to use to extend the lever arm?

    Possibilities are wood, wire coat hanger, and that's basically it. I was thinking wood with a hook screw inside it attached the the mouse trap bar would work.

    4. How to increase the distance traveled by the mouse trap car?

    My prototype went several inches and it needs to cover a slope that rises to 3 cms and falls for a total distance of about one meter. I believe making the axle thinner will allow for more revolutions and less energy consumption from the spring.

    5. What wheel setup would be optimal?
    Currently I have four wheels for simplicity. All are the same size, but I'm thinking about uses smaller wheels for the front.

    6. The back wheels of my car are powered by the mouse trap. Should I convert to a front wheel driven car?

    I think the problem in my car lies with the wheel and axle and probably the mouse trap. My next prototype will add a longer lever arm. The wheel and axle don't spin smoothly enough. I think most of the energy from the spring is lost due to friction or maybe the angle that the ribbon is acting on is causing much more force to spin the wheels. Also for my first prototype, the axle was on the top of the car body along with the mouse traps for ease of winding the ribbon around the axle from the mouse trap u-shaped bar. Thus the axle will get in the way of the lever arm when I lengthen it. I'm thinking of ideas of an effective way to wind the ribbon or whatever i decide to use around the axle if i put it beneath the body. I would have to have something to wrap the string around so that it won't get tangleg or hit the wooden body and waste the potential/kinetic energy. On the other hand, that would slow down the lever arm from returning which would be more distance traveled. However I am guessing the amount of energy being lost due to hitting the wooden board would mean less energy turning the wheel. I will continue making prototypes.

    Thanks for any responses!
  2. jcsd
  3. Mar 16, 2009 #2
    Well I have one idea I think is pretty good. If your car needs to go up a hill and then down, ideally you would have some sort of gear system so you could use a big gear to help you accelerate up the hill and then a small gear to get you maximum speed going down. Obviously it's not very feasible to put a gear box in a mousetrap car. But you have an advantage in that you know you have to go up the hill first.

    When I built my mousetrap car, it worked by having a lever attached to the mousetrap that pulled a string wrapped around the axle. If you use a thick and wide material instead of just a string, you can get a sort of continuously variable transmission. Imagine you glue a paper towel roll to the outside of the axle, and the loose end of the towels attaches to the lever on the mousetrap. When the mouse trap first starts pulling on the roll, it is all the way rolled up, i.e. it is big. As it unwinds, it shrinks in size. So in effect you continuously transform from a large gear to a smaller one. Tell me that's not awesome.
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