A set of rolls with a slot to take one 1 leg of the angle is the best way. You can mimic the action of pyramid rolls by having two curved blocks fixed to each end of a vice jaw and a third in the middle of the other jaw. Just nip up the vice so it puts a small bend into the part, move along 1/4" and repeat, I have used this way to bend steel tyres for traction engines.
To fabricate you can take 3/16" strip, bend to your radius. Then rest the bent strips on edge onto some 1/16" plate and silver solder. Its then just a case of cutting them out and trimming the leg to a constant 1/4". Thats how I did the two angles above the axle here.

Edited By JasonB on 26/08/2014 11:52:19