How Did an Empty Thread Spool Become a Rubber-Band Tractor?

The wooden reel left after a household had used its sewing thread already contained a hole through the centre. A rubber band could be threaded through it, secured at one end with a short stick, then passed through a small washer cut from candle wax or soap and held by a longer stick. Wind the long stick, set the reel on the floor and it would crawl forward. Some children cut shallow grooves around the ends for grip; others made obstacles from books and scraps of wood.

Materials and names varied by place. The toy might be called a spool tractor, reel car or little tank. This is a widely remembered type of construction, not one person’s universal childhood experience. It depended on a domestic world where wooden cotton reels, candle ends, rubber bands and offcuts were readily available. They were not a purchased kit but leftovers from sewing and household work.

What children compared was not only speed. A short lever produced little turning force; an overlong one dragged on the floor. A sticky washer absorbed the rubber band’s energy, while a smooth reel spun without travelling. A race therefore became repeated adjustment and testing. The pleasure was less in making an accurate tractor than in giving a still household object its own slow, stubborn movement.

https://blog.adkinshistory.com/cotton-reel-tanks/
https://collection.sciencemuseumgroup.org.uk/objects/co520790/fifteen-cotton-reels-various-sizes-and-makes