This is NOT a mandrel bender ($$!!!) but it IS the type that is used/approved for roll cage bending and so on in race car shops. Does not kink tubing within the limits of its operation. Roll cage tubing, for example, is 1 5/8" and can be bent to a centre line RADIUS of 6" without kinking.
These types of benders typically use what looks like a chain of steel balls maintain the tube's diamter through the bend, don't they?
You may have hung yourself with this announcement BTW.
I've had a couple of crazy ideas flinging around my head lately that could probably take advantage of a tight radius bend or two. So when I get around to making the ideas become real, and if you're willing... Heck I'll even contribute toward the die purchase if it requires one which you don't already have!