Cotton reel tank
From Wikipedia, the free encyclopedia
A cotton reel tank is a simple self-propelling mechanical toy which is easy to make at home. At one time, making these was popular, but perhaps has become less so in the age of sophisticated electronic toys, and a decline in home sewing.
To make one, you need:
- A cotton reel
- A rubber band
- Two matchsticks
- A standard household candle
Cut a slice from the candle, carefully withdrawing it from around the wick, so you end up with a thickish (say, 6 mm) washer of wax with a small hole in the centre. Whittle out a groove across the full diameter of the washer on one side. Assemble the tank by passing the rubber band around a matchstick, through the wax washer, through the hole in the centre of the reel, and around a second matchstick cut shorter than the diameter of the reel. Now the tank can be wound up by rotating the longer matchstick. The tension on the band should hold the whole assembly together (though too much tension will lead to uncontrolled unwinding, so you will need to experiment to find the best rubber band and how much to wind it.). The long matchstick is arranged so that it protrudes beyond the edge of the reel at one end. When placed on the floor, the tank should propel itself along as the rubber band unwinds.
