Hi Dave,
Right, the idea is to match the radius of the shoes with the drum. This used to be a fairly common procedure on bikes and cars when drum brakes were commom. I think they called it arcing the shoes. The standard procedure was to set them up on the back plate, space the shoes with shim stock, then turn them on a lathe to the diameter of the drum. Pretty messy, not to say fussy, or dangerous when you figure in the asbestos. The chances of finding someone to do today that is pretty much zero.
So my technique (sorry no photos) is as follows. Start with the turned drum mounted in the wheel and new or very good shoes. Set the shoes up on the backing plate, and disconnect the turnbuckle so the shoes are working independently. Use a thin double sides tape around the inside of the drum. Then using 2 inch emery cloth of about 120 grit, wrap that around the inside of the drum. I think I ripped a thin strip off the 2 inch wide emery cloth so that it was exactly the width of the drum. I used the front axle and a nut to mount the backing plate in the wheel. You will need to make up a simple spacer out of pipe that fits over the axle and takes up the space normally occupied by the lower end of the forks. This gives you a solid axle with the wheel, backing plate all buttoned up, with enough length sticking out either side to drop it onto two saw horses sitting side by side. I used a couple of clamps to hold the axle in place on the two saw horses. The wheel will now spin on the axle, with the backing place centered by the axle. Now if you spin the wheel and apply the brake, using one of the brake arms. the backing plate will spin with the wheel. Obviously this isn't helpful. You need to come up with a method of keeping the backing plate from spinning. Attach some tie wire or good rope around the cable adjuster and nail it to the end of the saw horse so that when when you apply the brake, the backing plate will not spin, and the shoe will be sanded into shape by the rotating drum. After a few minutes disassemble and you can see if you have full contact. If not, continue. Then switch to the other shoe. Result: two perfectly radiused shoes courtesy of your home made "lathe"
Stephen
