Tools - dynamo gear holding tool

- by Ian Moorcraft

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Dynamos fitted from the earliest cars until the end of 1929 will be fitted with this stepped driving gear BG2 which has a poor design in that the nut face is 1 1/8” in from the end of the driving gear. This can be a problem if the nut is loose as they often are, especially found loose in the small magneto engine DFL dynamos. This can put a leverage force on the very slim dynamo shaft tapper and then rattle around wrecking the shaft and keyway.

It is extremely difficult to stop the gear from turning in the vice as it tears up the soft jaws and bits of timber, also gripping the gear on the hollow shoulder can distort it if the vice is too tight, and it will still spin before the nut is tight anyway !

This tool is made from a late three bearing conrod of the shell bearing type that I have cut down in width to suit the plain part of the gear. The inner diameter of the conrod is about 0.030 smaller than the gear diameter but will happily spring out and grip the gear tightly when both the 1 3/4” bolts are tightened, I have used this one many times over the years and it still springs back to original size when removed.


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