Saturday, March 11, 2006


Building A Better Mouse Trap Car

A couple of weeks ago my daughter brought home an assignment worth 200 extra points, build a car using as mouse trap to power it. This seems simple enough. Together we tried to design and assemble a car using the wheels and axles off of an old toy, a board, a mouse trap and some string. It worked but just barely.

Before she had taken it to school, she told me another girl had brought a mouse trap car that would go about 4-5 feet while ours would go about 2-3 feet. At this point, I remembered my fallback resource, search the Internet. On my first try I found this site with plans for a simple but very good mouse trap car.

The plans include cutting out wooden wheels about 3" in diameter. (The site is Australian hence the measurements are all metric. I used 3" wooden wheels drilled with a 3/32 hole for the 1/8" axle.) The primary modification we made to the design was to use part of a large paper clip (trimmed) to wrap around the axle and then epoxy it in place for the loop in the string to hook on instead of a short piece of axle rod expoxied to the axle. I believe the use of the paper clip wrapped around the axle is stronger although it doesn't affect performance.

(I didn't let my daughter use any of the power tools.)

One aspect of all this is the competitive aspect of this and many other projects my kids do for school, Scouts, 4H, etc. The other little girl is a very nice, bright little girl. Both her parents teach in the school system. Her mother teaches math at the same school the girls attend. Her father is the shop teacher at the high school.

With the experience, knowledge and resources available to the girl's parents, she always has some of the best, most elaborate projects for school. I decided to make sure my daughter's mouse trap project was as good or better. Thanks to the site linked above I believe I succeeded. In tests at my house the car easily went 20 feet. It would have gone further but 20 feet is about the longest uninterrupted distance in my house.

I always wonder when teachers give assignments like this to children. It would truly be the unusual 9 year old that could successfully design and build a mouse trap car on their own. The spring of the mouse trap is probably powerful enough to break the finger of a 9 year old. Giving children a dangerous, nearly impossible, if done alone, assignment is not my idea of educational enhancement.

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