There are two 26TPI series of threads.

BSB (British Standard Brass) with 55deg thread and the BSC (British Standard Cycle) with 60deg thread.

Barry

Well-said, Ian

Another possibility [ Having had a just quick look at the Wyvern illustration ] might be to make the crankshaft components from existing High Tensile 3/8" UNF Bolts; which should be readily available from Automotive parts suppliers.

MichaelG.

On looking at the drawing, I would do a modification to the crankshaft, one of two ways, first way, extend the shaft say about 3/4" beyond the nut, and reduce the diameter to 5/16", or 8 mm to take a pulley. Method two; make a pulley, bore and tap to suit the thread on the shaft, and use that instead of the hex nut. The motor will look more realistic with a means of driving something, maybe a little generator, or a model lathe, anything, motors are made to do work, or at least look like they might. Ian S C

I was just looking a Rod's Wyvern build and you won't be able to use bolts for the crankshaft as they need to be a larger dia on the bearing surfaces.

Pic of the sort of Pully Ian is suggesting here or if it too late you could always go for one that fits to te flywheel spokes.

If you don't want to fit your imperial conversion kit why not make the reduced ends 10mm dia and screwcut a M10 x 1.0 fine metric thread and make the nuts to suit.

Edited By JasonB on 25/01/2014 16:57:37