min radius for roll cage tubing

[mom'sZ]

I'm attempting to 'design' a piece of roll cage. What is generally considered the minimum (smallest - tightest) radius bend that can be made to a piece of 1 1/2" DOM roll cage tubing. Not the apsolute min, but what most tubing benders can handle. Please state the measurment is inside, outside or on the centerline.
Thanks

[lateapex911]

If this is for SCCA, the good book will list the main hoops min legal radius, IIRC.

Ninja edit: Words "main hoops" added..

[mom'sZ]

Good call Jake, thanks
9.4.G.3 states:The radius of all bends in the roll cage (measured at centerline of tubing) must not be less then three times the diameter of the tubing.
So.... 1.5" tubing x 3 = 4 1/2" radius at centerline. So my question then becomes is your average tubing bender capable of bending 1.5" tubing that tight?

[joeg]

Normal dies for that size would be in a 6 inch radius.

[mom'sZ]

Thanks Joeg, that's what I was looking for. That would be 6" radius on the inside then (I assume)

[tom_sprecher]

I'd think it would be 6" on the centerline as it sure would make everything easier to design but I'm just guessing.

[betamotorsports]

A tubing bender die uses CLR (center line radius) for its measurement. So a die with a 6" radius means a 6" radius measured at the centerline of the tube. The radius on the inside would be 1/2 the tube OD less then 6" and the radius on the outside will be 1/2 the tube OD more then 6".

[ddewhurst]

The fab shop that did my 1 1/2 O.D. Miata hoop did an inside radius of 3 7/8. NO wrinkles. The main hoop, halo & front down tubes fit within 1/4 inch of the roof/body full length of all tubes other than the corners, but they are as tight as one can get them. Ya need the room in a Miata. I figure this is my last race car therefore I'm being real anal. :cool:

[DoubleXL240Z]

I use the JD2 bender and have the dies for a 4 1/2 ctc radius. That is the min. for 1 1/2in tubing, I have never had any issues with crinkle/wrinkle etc. with bends. I also have had no problems with following contours with 4 1/2 radius. I' in Orlando if you need anything built let me know. 407.463.0312

[mom'sZ]

Just wanted to give Chris Leone (DoubleXL240z) a big thumbs up. I called him Wednesday afternoon, sent him my little sketch of what I needed done and Friday evening the new roll cage member was waiting on my doorstep. Great work, fast and cheap!!! Thanks so much Chris and I'll ring you up when I need more stuff done!!
Highly recommend Chris's work and service.