Rail bender

I need a rail bender for a project, to suit code 40 rail. As far as I can tell nothing is available to suit code 40, so I made my own. I already own a KB Scale bender, but this is made to be used with code 83 for building O14 track, and is designed to give specific radii. As I had it already I made a replacement set of rollers to suit the finer rail, just as an experiment. My rollers worked well enough but as can be expected the bender didn't give the amount of curvature that I require. It did however provide a basic design that I could adapt for my own use.

Here's the KB tool, fitted with my code 40 rollers with the KB rollers next to it;

I started with a length of 25mm x 5mm aluminium bar, cut and faced to 50mm long. I chose 5mm thick bar as it will be easy to hold in my bench vice when in use. I then marked out positions for the centre slot (mine is designed to be adjustable) and two separate hole positions, at 26 and 34mm centres. This is for adjustability, whether I will need the inner holes or not I will only know when I start using it. Once the bar was marked out it was held in a machine vice and the holes and slot machined, the holes being drilled 1.8mm to suit 8BA and the slot had a series of 1.7mm holes chain drilled before being milled 2.2mm wide (again to suit an 8BA bolt).

New rollers were machined from brass, to the same dimensions as before but drilled and reamed 6mm dia. Hubs for the rollers to spin on were machined from silver steel, drilled 2.2mm (8BA clearance) and turned to suit the rollers allowing them to spin freely when the hubs were tightened up. The middle adjustable roller is held in place in the slot by means of a thumb nut underneath the baseplate.

The unit assembled;

Here it is in use;

It appears to work well enough, but I do need to test it properly.

Notes on design;

The rollers should ideally act on the web of the rail (the thin middle section), the KB Scale one certainly does, but with code 40 being only 1.1mm tall that is impractical as the web is tiny. So, my rollers act on the head of the rail, with an undercut at the bottom of the roller to suit the wider foot of the flat bottom rail (the KB Scale rollers also have an undercut). I also copied the upper flange of the KB Scale rollers, this holds the rail in place as it moves through the bender. Hopefully the fag-packet sketch below will give some idea of how the rail sits;

I've not added any dimensions, the sketch is just there to give the general idea and hopefully can be adapted to suit other rail profiles.

Paul.