Congratulations, you’re coming to the end of your Tech Ed career here at AJ Smeltzer, my final challenge to you is to create a car that is powered by a mousetrap. This is my “Saving the best till last” project, no matter how simple this may seem, you are going to have to buckle down and use your time wisely to be successful at this project. You will be given a mousetrap, that’s it, now make it move. You have two choices for this competition, you can try to build a Sprint car, which must go 5 meters as quickly as possible or a Distance car, which must go as far as possible. I have lots of wood for frames and wheels of various sizes, as well as the equipment in the shop; you may bring in materials from home if you wish.
The
Basics:
Work hard, I can’t emphasize enough the complexity of this project, we could spend two semesters on this unit.
Research, there are so many factors involved in the performance of these cars you can’t ever know too much.
Test and EVALUATE, I’ve been saying this for two years with you, write things down when you make a change, now, is it better or worse?
Use your time wisely, the car DOES NOT need to be painted, have hydraulics or neon lights, look at the Rubric and build your car to the specifics that I have asked, then add your personal touches.
The Rules:
Cars must run under their own power, you may set them down and release them, no pushing .
The mousetrap must be the only power source for the vehicle, no additional aids to assist the mousetrap can be used.
All cars, Sprint and Distance, must go 5 meters.
You must have a complete car ready for testing the day of the competition, you can’t borrow parts from other cars after they make their run.
The Frame must be straight and square, the frame of the car must sit flat unless the design specifically requires it not to. Also the measurement from corner to corner must pass the “X” test, that is, cars must not be out more than 3mm when measured corner to corner. Triangle frames must be symmetrical and represent an isosceles triangle.
The original spring of the mousetrap is retained.
Mousetrap may be modified , clips and latches removed and body cut.
| D | C | B | A | |
| Car completes the 5 meter distance | ||||
| All wheels touch the ground | ||||
| Car passes “X” frame test | ||||
| All objects are fastened not “Bubble Gummed” or taped | ||||
| Car runs consistently, does not self destruct after the first run | ||||
| Car appears solid, frame does not flex when released | ||||
| Car and joints are clean in appearance | ||||
| Wheels are securely attached to Frame | ||||
| Car runs smoothly | ||||
| Car goes straight within the boundaries of the track |
Any Car that can do a standing wheelie will receive bonus marks, you release the car, it wheelies and then completes the 5 meter run.
Any car that can go corner to corner from the largest green rectangle (the Basketball court) in the gym will receive bonus marks.
The fastest in each class will receive bonus marks.
This is a short list of factors that affect the performance of your car.
Mousetrap position: by moving the mousetrap forward or backward on the car, it changes the angle the string pulls on the axle and can help to change the dynamics of your run, moving the mousetrap forward or back can make the “peak pull” of your run occur earlier or later in the run.
Wheel size: the circumference of the wheel changes how far the car goes with each revolution, the larger the wheel, the farther it goes, however, the larger the wheel the harder it is to get rolling, small wheels accelerate very quickly and easily but do not go as far.
Arm length: the longer the arm the more string wraps around the axle and therefore the more times the axle rotates, however, if the arm is too long it produces more leverage against the mousetrap and it cannot get the car to move. The shorter arm produces more torque but it doesn’t rotate the axle as many times.
Friction: Two cars with the same size wheels, frame, and arm length will perform differently if one has less friction….Period
Traction: If your car breaks out, meaning when you release the mousetrap it spins in a circle or doesn’t go anywhere but you can see the wheels turning you need more traction.
Frame: you need to have a good solid frame, if you spend your time gluing and taping the frame back together you will get inconsistent test results and a car that probably won’t go straight, going three meters and turning into the wall is not a 5 meter run.
Gearing: The size of the axle that the string wraps around changes the performance of the car, a small axle is hard to start but will spin the wheels very quickly, a large axle is easy to start but does not spin the wheels as fast.
Break Out: When your cars tires spin violently at any point in the run, this gives no traction thus no speed and no distance.
Peak pull: A mousetrap pulls in an arcing motion therefore it doesn’t have a completely steady pull, take a spring scale and measure the pull at different angles of the mousetraps arc.
Frame Flex: If the frame of your car flexes while moving the torque from the mousetrap is being obsorbed by the frame, not transferred to the wheels.
Junk: A car that has no effort put into it, doesn’t run 5 meters, and no excuse for it being that way…Do Not build one of these.
