We've this pipe bender where I work and it's completely useless, the points of contact are so far apart it kinks the tubing every time regardless of OD:
Northern Industrial Air/Hydraulic Pipe Bender — 16-Ton | Pipe + Bar Benders | Northern Tool + Equipment We've (me and a buddy) have been yappin' about giving this one a shot, a roller/mandrel tubing bender that is reputed to make nice bends in tubing w/o flat spots or kinking:
Woodward Fab Tube and Pipe Bender, Model# WFB2 | Pipe + Bar Benders | Northern Tool + Equipment
...but be warned of a coupla things - "pipe" benders are typically ill suited for the comparatively small OD & thin walls of bike tubing, "tubing" benders are usually better, used by racing car drivers to make chromoly cages, where things like flats & kinks are simply not allowed. The problem is while the above links are for affordable benders, the dies for tubing benders are rarely included and get pricey
quick - but they usually include one die of your choice w/purchase... Ya might have some luck diggin' around & llokin' through the links ere in GH's thread:
http://motorbicycling.com/f36/huge-list-frame-builder-suppliers-24414.html
There
is a buncha DIY solutions like cutting your own (stationary) dies out of hardwood, even packing the tube with sand & capping it off before bending it etc. Try "DIY tubing bender" in google and ya will get a ton of returns...
BUT - while I've played w/metal for a good long time - I'm new to the bike frame fab game & I'd love some feedback from our fabricators too
BTW - should ya decide to go the packed sand & endcap route, if ya use heat - make sure your sand is DRY & have pinholes in the endcaps or you mighta just made yourself one heck of a steam-powered pipe bomb