Sprockets and Chain

Like most electric motorcycles, this design does not use a traditional transmission.

If a transmission is not used, the gear ratio needs to provide the right balance of acceleration, top speed, and range.  Most do-it-yourself electric motorcycle conversions use a reduction ratio between 3.5 and 5.5 (number of teeth on the aft sprocket divided by number of teeth on the front sprocket).

I chose a 50-tooth rear sprocket, which is the largest one available with the Royal Enfield changeable-sprocket rear hub, an aftermarket item.

Rear sprocket

It easily fits on the hub and clears the swingarm, and gives me the ability to use a 13- or 14-tooth sprocket on the front.  If I had used the stock 38-tooth rear sprocket, I would have had to use a 10- or 11-tooth front sprocket.  I was afraid that a front sprocket that small might not allow the chain to clear the swingarm pivot, or might not run smoothly due to chordal action.

Front Sprocket

The front sprocket is a 13-tooth with attached collar and 7/8 inch bore.  A 3/16 inch square key and two set screws are used to secure the sprocket to the motor shaft.

The chain is size 530 heavy duty (ANSI 50-H) roller chain.

Chain

It is the same gauge of chain as on the original motorcycle.  The chain was bought in bulk (10 ft length), broken to fit, and connected with a master link.

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