[QUOTE=Hotrod46;578637]Seems to me when I was researching rule books for guidance on a roll bar for my car, that .120 was the minimum wall thickness for mild steel.

I know you said weight is important, but for the added hassle of getting moly welded properly, I would just use mild steel. Much simpler to weld, cheaper, and more than adequate for the use you described.


Nice car, thanks for the link! It's for sure a stout chassis, when you're building for John Q. Public one has to do the overkill on tubing sizes just to try to make them idiot proof so some fool doesn't try to pull a trailer with the car or some other poorly thought out plan the car wasn't intended to do! I had to do the same thing when I had my shop and sold to the public. Building my own, just for me, I can saw off some pounds and go minimal on some things.... I know .120" is the standard wall thickness for most frame rails, just planning now so it's easy to 'lighten up'!

Yeah, moly is a pain in the butt to work with and weld, but it's light and strong. I guess I'll have to decide how much extra time and $$$$ the weight is worth to me. I've taken a few nasty rides in moly cars and walked away from all of them just a bit dazed and confused!!!

The next size up from 14 ga. (.083" wall) is all the way to .125" (advertised) that averages out at about .120" wall, I don't recall right off the difference in weight per foot but it is a considerable amount. DOM has always been my choice after moly, more strength then mild steel and welds like a dream with a MIG, maybe round tube 1 5/8" at about the .110" wall thickness and a round tube chassis would be a better choice? Lots more labor, but stronger and lighter then the usual 2 X 4 .120" that seems to be the norm. I'm in the process of doing some significant weight reduction on the body (ie aluminum door skins and quarters, 'glass hood, etc.) which is my rational for lightening up on the chassis.... My initial calculations (round tube DOM frame and cage) bring the car in at about 2600 pounds....


Thanks much for the input! Asking knowledgeable people the questions for me is still the best way to come up with a workable plan! I certainly appreciate the help!