I've decided to go with Humbrol matt black for the wheels. I'd rather use paint than any strong chemicals to colour the wheels, as they could get onto the rims and damage the running surface.
Just a first coat - I'm thinking I should fit the wheels before the second coat. But so far it looks quite pleasing.
I need to fit crankpins to the cranks and the cranks to the wheels. Opinion seems to be divided about what should be done before fitting the wheels and what after. The crankpins are so delicate, it seems to make sense to fit the wheels before adding them, but no harm in doing a "dry run" first to see what it all looks like.
soldered and trimmed
As can be seen I had trouble getting a smooth edge on the cranks. Perhaps more solder would have helped fill those gaps?
trial fitting of cranks
There's plenty of room on the extended axle for the crank. Should it be close to the wheel or at the outer end of the axle?
With the wheels pushed closely together in the underframe, it looks as though there is still room for the crank well down the axle. Probably best to allow some margin for error though, so I'll put the cranks part-way down.
with a crankpin
These are a very generous length. I'm not sure exactly when I'll have to trim them, but even if I cut them short now, they'll still get in the way when I'm fitting the wheels onto the muffs.
Meanwhile I've realised, having painted the wheels, that I've forgotten to fit the balance weights.
Best plan now seems to be, to fit cranks and balance weights, re-do the paintwork, fit the wheels, get the quartering as good as possible by eye then add the crankpins and finalise the quartering.