In order to relay the track at the South Downs Light Railway I built a set of powered rail rolls which will curve a 12 foot length of rail uniformally in about 30 seconds. These proved very successful, and were later modified to take 6lb per foot rail as well as the original 3lb per foot. I've now built a second set (unpainted) which will take 3lb, 6lb and 14lb per foot rail

The basis for these rail bending machines is three grooved rolls aranged in a pyramid. Each roll bears on the head of the rail and the foot. Some rolls work on the web of the rail, but the mechanical advantage of this arrangment is very poor - added to which, scale and corrosion can create a build up of thickness on the web, which then interferes with the rolling action.
The single roll is powered via a chain, and is adjustable with a screw thread at one end to vary the curvature available.

All rolls leave the extreme ends straight, and this is minimised by having the rolls as close together as possible - although this in turn means you need more power to turn them. A bit of a compromise is necessary....
The motor is single phase, running both in forward and reverse, but is only rated for intermittant use. This means that instead of spending two hours bending every piece of rail you are going to use on your whole railway, you have to roll them as and when you need them. This has never been a problem at all in the past.

If you ever need to hire them - give me a shout.....