Here’s an ingenious little mobile toy that Ruth’s dad enjoyed during his childhood. It’s strong enough to climb up a book, but it’s not motorized.
First find a wooden spool and a small, thin bar of soap. Shape a sliver of soap so that it is about the size and shape of a Lifesaver candy (your job). Remove the flammable end of a kitchen match (your job, again). Place the piece of soap on one end of the spool and thread a small rubber band through the hole in the soap and spool. Insert the matchstick through the end of the rubber band next to the soap to keep it from pulling through (see “a”).
On the other end of the spool, cut a long recess (your job) so that when a piece of toothpick (slightly less than the diameter of the spool) is laid across the hole and is inserted through the other end of the stretched rubber band, it won’t rotate (see “b”). Fine-tune your machine by experimenting with different kinds of rubber bands.
Adjust the matchstick so that part of it protrudes an inch beyond the edge of the spool. Use this end as a crank to wind the rubber band until it’s taut, then place the “tractor” on the table and let it rip!