This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
If a bicycle rider desires to remove the rear sprocket for changing the gear, or for any other reason, and there is no large pipe wrench at hand, a piece of tube or pipe, as shown in the sketch, can be used as a lever. Fasten one end of the chain in one end of the pipe with a wedge and place the other end of the pipe on a sprocket. The chain is then placed over the sprockets and a leverage equal to any pipe wrench is secured. - Contributed by Jno. V. Loeffler, Evansville, Ind.