Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Mousetrap car wars.

  1. Feb 1, 2007 #1
    1. The problem statement, all variables and given/known data

    Imagine a mousetrap car with weapons, and that is my physics project for you.
    It is essentially a 8 foot long hill (8% grade on each side), with opponents' cars facing eachother, racing up, and trying to go over the crest and force the oppenent's car backwards or off. If neither vehicle has crossed the crest or both finish on the sides opposite their starts, another trial will be completed. But, the vehicle nearest to the top (measured from the back end of the vehicle) will be declared the winner for that round. oh and falling off on the spponent's side still counts!
    It must:(a) go five feet in less than two seconds on a flat surface and, (b) make it up the ramp (no time constraint), be self-propelled, and be 12x8 in.

    Materials: 8 rubber bands, 2 mousetraps, plywood base, cardboard, 2 coffe cans, 4 2-L plastic bottles, 3 ft dowel, glue, 2 wire coat hangers and 4 jar lids, up to 4- 4oz lead sinkers, AND NOTHING ELSE.

    What i need is suggestions for
    1.propulsion(how to best setup/power the car with rubber bands and/or mousetraps)
    2.offense or def.( push other car off/down hill first or prevent the opponent from doing this)
    3.weapons(you could go as far as to make trebuchets, but a simple bulldozer will work)
    4.weight( where should i put it, and how much)

    ALL suggestions will be appreciated! HELP ME

    2. Relevant equations
    i dont think there are any.

    3. The attempt at a solution

    i was thinking a 2moustrap setup, but id really like some delayed energy when it really counts at the top, mayb from rubber bands, but i cant think of how to set that up. I was thinking an offensive vehicle with a bulldozer, and maxing the weight out. I will change my mind with good ideas but im probably gonna need a lot of force for this current idea.
  2. jcsd
  3. Feb 3, 2007 #2
    Hmmmm... I remember making one of these a while back, and while my memory is a little vague, I do still remember some key aspects to making an efficient mouse trap car.

    First of all, use really small wheels. Large wheels increase the rotational inertia while small wheels do not. Also, make sure that your wheels are pretty skinny. When going up hill, you want to divert all energy into a small surface area. Make your car as wide as possible though, you really want to achieve that perfect balance. In addition, you want to make sure that your car has enough ground clearance. The last thing you want is some part of your car scraping the ground, adding more friction, so make sure that you have plenty of room between the ground and your car. One last construction tip you should consider is how to mount the axles. The best way is to have wooden side panels for your car to drill holes in. Drill holes in the sides that are large enough to give your axle plenty of room to move around in; it's vital that the axles have plenty of wiggle room.

    For propulsion, use ONLY 1 mouse trap and attach a short rod to the snapping mechanism of the mouse trap. In case your're wondering, having two mouse traps to drive the car is a terrible idea. Not only is a lot of energy from each spring wasted as a result, but they do not always act in tandem. All mouse traps are not made identically and some springs will be slightly stronger than other, so having two mouse traps with springs of slightly different strenghts will just cause your drive system to slow down and get all tangled up. Reffering back to the construction process, attach to that rod, two linked rubber bands which will then connect to the drive axle. Connect these things using a loop or a staple. Some things to considers are: making sure that the arm travels a full 180 degrees, and the when winding up the rubberband around the the axle, balance out the amount of rubber band wound up of the left and right sides of the axle (basically if you have the band connected in the middle, start by winding the band around the left side first then move it towards the right side of the axle and wind up the rest on that side). Another thing to consider is which axle is going to serve as the drive. Ideally, it's best to make the car front-wheel drive, but rear-wheel drive works also.

    Whoever said that the best offense is a good defense was a total idiot. When it comes to mousetrap cars you want to be strictly offensive, and by going offensive, you want to think big. From my experience, the best possible weapon is a sping loaded catch (this is what you'll use your second mouse trap for). Add to the snapping mechanism of the mouse trap some extra wire from your coat hanger to create a catch (it should kind of resemble a rake with slightly larger hooks in front for grabbing). This catch will allow you to grab your opponent and keep him/her at bay. Catching them also reduces their traction, making it easier for your to push him/her. After attatching the catch to the mouse trap, mount the trap in the front of your car. Make sure that the trap release is towards your opponent so that it is set off when you make contact. This design is proven and will definitely work (trust me).

    Weight is a crucial part of the design, and placment of it is even more important. DO NOT put your weights over your drive axle, doing so will over tax your drive system, thus slowing you down greatly. When going up hill, it is generally BEST to put most if not all of your weight up FRONT. Going up hill causes a weight shift to the back, so you want to balance out that weight shift by putting weights up forward. Because of these weight reasons, this is why rear-wheel drive is good for this project.

    In the end, projects like these are not at all difficult. Just knowing what to do and taking advice (like what I have given you) will put you on track. Take things slowly and you should be fine.
  4. Feb 4, 2007 #3
    Thanks! that was a good idea. Thanks 4 answering my questions about weight displacement and propulsion. I think it will help a lot.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook