Technical Roll bar 12" Radius

You can see some of the cage here. The front hoop is one piece and has 90degree bends with 12" or less radius.

 

Sorta bit the bullet here with my 40" chunk, secured one end with a plastic cap & a hose clamp, filled with sand & taped the open end, measured off & marked the center at 1'" increments up to 10" (L) to (R) to allow for the radius. The initial bend began in the center with 5 full pumps & alternated (L)to(R) on the marks with 5 pumps on each, back through again until a true 90 degree achieved. minimal dimpling from the rollers & only slight wavy radius on the anvil side. General consensus is acceptable unless the minor dimpling is of concern, good enough for this old racer & getting it back to square one.

 

Your .104 wall is a big part of the problem unless you get precision dies for chrome moly and the proper bender to use them in.. With the bender you refer to you'll have better luck with DOM tubing that has .134 or so wall, the minimum wall thickness for a hoop is 1 3/4 x .118 per NHRA spec, the heavier wall will actually bend better.
I've bent a lot of tubing.

 

I have done this use used 1.25 or 1.5 oil field pump barrels If you anneal them before bending they work fine with the bender you have

 

I bent a lotta tube. I have 1 of those type that uses a bottle jack, 7" radius (I think) and it never failed me. It grabs the tube and pulls it around the shoe. I used to oil the roller and the shoe, no kinks. The NHRA spec is a minimum because all tube gets thinner in the bend. A chassis cert doesn't measure in bends for that reason. .120 DOM bends the best.

 

Heating a pipe that's packed full of water is definitely a "no-no". I was referring to bending without heating. Water or any fluid is incompressable, and it easily fills every nook and cranny within a vessel.....especially a straight pipe with capped ends. My experience with packing sand in a pipe is that it may be easier said than done....as someone may end up with voids when trying to fill a pipe. As I mentioned, I used dry sand with capped ends and didn't get good results......others may have better results than I did. If water is used, (no heat) it will not have any voids and seems like an easier way to do it. That's just my opinion as I haven't tried it......but I probably will the nesxt time I want to custom bend some exhaust. I did get a usable bend for the truck I was trying to work on, but there were no 90 degree bends. My bender has no problem with the thicker material, the problem was when I tried it with thin stuff.

This is what I use for bending, a JD Squared mounted on an old stand I acquired somewhere..........