Thinking ahead, while I had the fork in hand, I measured the carbon brush socket in the steerer. The carbon brush was missing, but luckily the spring and insulator are still there. The inner diameter of the insulator measures 5mm. I'm going to buy some 5mm pure graphite rod from Ebay (I guess used as old-school carbon arc lamp or really old-school carbon arc welding electrode) and give it a try. There's continuity in the original wires through the frame and insulation from it, so no reason to change anything!
I did look for actual motor or alternator brushes, figuring they'd be sintered with copper and possibly more durable and/or more conductive than pure graphite, but they don't come in 5mm round, and any less lathe work I have to do on this thing will be better. Anybody have any ideas, or know whether the brushes he used would have been pure carbon or something better?
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Owner & co-founder, Cycles René Hubris. Unfortunately attaching questionable braze-ons to perfectly good frames since about 2015. With style.
Last edited by scarlson; 10-02-20 at 11:37 AM.