Build a Car at Home

One project at a recent Cub Scouts den meeting was building self-powered cars. The components were a bunch of simple, household items: an empty spool of thread, a rubber band, two washers, a paperclip (or two), a pencil, and some tape.

Unassembled car

The first step is to thread the rubber band through the spool so it sticks out both ends (so the rubber band needs to be longer than the spool). Pinching the end of the rubber band helps to insert it but it is hard to get it all the way through. We used a second paperclip to push it through (after we unbent the clip). A skewer works too.

The first step

The next step is to put the paperclip through the rubber band on one end. We used tape to keep it in place. The paperclip holds the rubber band so it can be wound up later.

Securing one end of the rubber band

On the other end of the spool, put the two washers on. Again, pinching the rubber band makes the task easier.

Two washers

Next, put the pencil through the free end of the rubber band.

The penultimate step

Finally, power the car by twisting the pencil in the same direction until it gets moderately tight. Overtwisting will break the rubber band. Happily rubber bands are cheap and are easy to replace.

Winding up

Finally, put the spool/pencil on the floor and let it go! It's fun to figure out if it will go forward or backward. That depends on which way you've wound the rubber band.



The car does tend to curve to one side. Another scout tried replacing the paperclip with another pencil but winding up became extremely difficult, as well as putting the spool/pencils on the floor.