Monday, 22 June 2026

Model A - dynamo drive

 I have been wanting to sort out the dynamo drive for a while - not having it in place leaves a lot of parts laying around on the bench that I want to clear up. It was hindered by having to make a special puller for the dynamo bearings, something that I use infrequently but is very necessary if you're going to rebuild one of these dynamos.

Having finished the puller, I spent a little while turning up a short spacer. For some reason the replacement armature is a little shorter than the original though it fits where it needs to!


And I needed to file up a Woodruff key for the dynamo drive sprocket. It actually took me a long time to get to this place because I had inadvertently assembled the dynamo and fitted it with the dynamo body the wrong way round which caused the sprocket to be something like a half an inch out of line!


Here's the drive in place


That was a chain in amongst the past that came with the bike - is the correct 3/8 inch pitch but the width is way too much. I'll have to look at simply bearings and see if I can find another one, but it really needs to be endless.


You can see here that this over wide chain will rub on the crankcase.


The thickness of the drive sprockets is 1/8" - so that tells us what chain we need.


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