There is a saying in the Maker community: if you can’t make it perfect, make it adjustable. The corollary is surely that if you can’t make it adjustable, make it perfect.
These drivers are a one-shot deal. Either I get the quartering perfect, or I’m soaking them in acetone to loosen the epoxy, which will melt the spokes and take me back about four weeks. So, my quartering jig is meant to remove as much variability as possible and get the setting perfect on the first try. Time will tell if I was successful.
The quartering jig relies on those ridiculously long axles protruding from the wheel faces to hold the wheels on centre. The axles themselves are hollow, admitting a 1/16″ inner axle that holds the parts of the split axle together. Tiny holes in the quartering jig admit the crank pins, and hold the wheels rigidly in position while the epoxy cures. Finally, two machined L-shaped back to back gauges – one from Alan Gibson, the other by Gérard Huet – hold the wheels against the jig bosses to ensure they are the correct gauge.
Once the epoxy is spread and everything is pushed together, it’s impossible to see how things are going in there. My current favourite epoxy, JBWeld, takes something like four hours to set. For an awful half-day, I thought surely the wheels had gone together too easily and I must have crushed a crankpin. I hadn’t: the wheelsets are as perfect as I can make them.