How to Build a Mousetrap Car for Science Class
My eldest son has come home twice now with instructions from a teacher to build a mousetrap car. There is a lot on the internet that provides video and instructions. The following is the result of the modifications made to various designs seen and improvements made from the first try to the most recent version of this vehicle. A warning: mousetraps are delicate instruments of death to the unwary mouse. Even following the instructions given may result in fingers being snapped accidentally and it will hurt. Slow and steady, as they say, wins the race. Following these instructions but working slowly and carefully and having an extra body around for assistance should reduce or eliminate finger or other bodily damage!
Assemble Materials for your Mousetrap Car
- four eye hooks
- two pencils
- 4 CD's or DVD's
- 4 pop can tabs
- electrical tape
- fishing wire
- wire cutters
Step by Step Instructions for Assembling your Mousetrap Car
1. Drill two shallow holes on each of the short ends of the mousetrap about ½ inch in from each end.
2. Screw in the eye hooks, one into each hole. Make sure the eye hooks are level by placing each short end of the mousetrap against a hard cover book.
3. Using wire cutters, cut the square snap bar where it attaches to the middle bar to the right of the mouse (red V). This step will give greater leverage and greater potential energy when launching the vehicle.
4. Using pliers, straighten the bar so it is parallel to the long side of the mousetrap.
5. Cut the tops of two pop can tabs (where they attach to the can). Bend the cut tabs in slightly. These bent-in tabs will be used to grip the pencil in step 10.
6. Fit a pencil through a pop tab, both eye hooks, and the second pop tab. Center the pencil and mark each side of the pencil about 1 to 1½ inches out from each eye hook.
7. Wrap electrical tape carefully around the pencil at the mark. Position the CD hole over the tape periodically and stop wrapping when the CD will fit snugly onto the wrapped tape.
8. Repeat steps 6 and 7 for the other short side of the mousetrap but make sure the interior axle-length of this side is longer than created in Steps 6 and 7.
9. Drill a hole through the center of the pencil (on the 'mouse' side of the mousetrap).
10. Make sure the pop tabs are very close to the eye hooks and then pinch the cut ends of the pop tabs to the pencil to keep the pencil (axle) from shifting side ways. Bend the tabs away from the eye hooks if necessary to allow the pencil to rotate freely. Make sure the pencil can rotate freely. Repeat this step with the other two pop tabs for the opposite axle.
11. Using pliers, straighten the bar from the point it meets the top of the mousetrap towards the inside so it will not interfere with the motion of either wheel.
12. Measure the fishing wire from the tip of the bar to about two inches past the tip of the mouse's nose.
13. If you have not already done so, remove the straight bar anchored at the tip of the mouse's nose.
14. Cover the edges of the back wheels (mouse points to these!) with electrical tape to reduce slippage at take-off.
15. Slip the fishing wire through the hole drilled through the pencil in Step 9 and knot it securely.
16. Make a loop at the top of the straight bar.
17. Tie the other end of the fishing wire to the loop at the top of the bar and secure it with electrical tape.
Launching the Mousetrap Car
1. Rotate the back wheels slowly to wrap the fishing line around the axle (pencil) until the line is taut.
2. Pull back the bar and continue winding again until the wire is taut (potential energy for the vehicle is obtained in these steps).
3. Hold onto the back wheels and place the car onto smooth ground in an area where there is ample room (at least 20 feet of horizontal distance).
4..Let go of the wheels and watch your car speed away.
5. If the car does not travel in a straight line, adjustments must be made. Check the pop tabs to make sure the axles cannot move from side to side. Ensure that the axles are aligned properly. If you did not ensure that the eye hooks were level with each other your vehicle will not travel in a straight line.
Most importantly, have fun! Rome wasn't built in a day and your mousetrap vehicle may not be built in an hour. Part of the fun is tweaking your vehicle to make it work better and more efficiently. Modifications to the design presented here are possible. GOOD LUCK!