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Discussion Starter · #1 ·
Me and my sons have a 75 Camaro with a 496 and went fast enough to need a cage... The first pass out on the re-built motor was 11.11 with no tune to speak of, just put the engine together set timing and went to the track. I think we will be well into the 10's when we get time to sort things out...

I have been trying to figure out what to do and, here are my thoughts and questions.


moly must be tig welded so I don't think I'll do that so, it's either DOM or mild steel.

Questions I have are,

What exactly are the rules for the use of DOM over mild steel? Are there any?

Is there a weight difference between the two?

DOM is stronger than mild steel but how much stronger?

What makes the difference between SW and Comp. engineering cage?
I know fit was mentioned but aren't they both "fit to the car? How is the fit different?
 

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a Mild Steel RWS or DOM cage is fine to the 10's. a 6 point rool barr is good till 10.00. To go faster you need a 10 point. the difference in the cage between RWS "Rolled Welded Seem" and DOM drawn Over Mandrel " Seemless" Could be substantial. I know the SCCA rules have varying thickness and I belive the SFI specs for that cage is the same. I think DOM is .120 and RWS is .154 IIRC.

About 20-40 lbs in a typical 6 and or 10 point cage.

Mild steel is RWS and DOM its the way the tube is formed that changes it's designation. Both RWS and Mild steel may be mig welded.
 

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A full bodied car with stock floor and firewall only needs a 5 point bar down to 10.00 by NHRA and IHRA rules. DOM is hard to find in unwelded "kits" but is usually .120" wall. Commonly found mild steel kits are .134" wall. Chrome moly is .083" wall but must be TIG welded. TIG is cleaner and less chance of spatter harming glass or other stuff in the car that is not fully protected or removed during welding. Comparative weights for a 6 point bar with swing out side bar on driver's side, GM A body, would be 45 lb in .083, 65 lb. in .120" wall, 73 lb. in .134 wall.
 

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DOM is stronger than mild steel but how much stronger?
DOM has about a 37% higher tensile strength than RWS/ERW if I recall correctly. I think its 80ksi versus 58ksi. But all that does is allow you to use a thinner wall thickness, so overall the cage 'strength' is about a wash between the two.

Craig
 

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Discussion Starter · #6 ·
Great info...I really appreciate it....

I don't have access to a tig welder unless I can rent one for a couple of weekends... 1 weekend to practice and 1 to weld the cage. lol
I do have a miller mig 230v 175a and can weld tubing pretty good with it so I suppose I'll go with the DOM from the info I've seen so far.
 

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Make sure it is DOM Mild steel. Also make sure it is a low carbon alloy. The high carbon steels are a PITA to weld well.

Other Advice get a few piece of scrap to work with and get the copping and fit up really good. then practice welding those joint together. Make sure to destructively cut a few piece up and look at the root of the pass. don't just super glue it with the welder make sure to Bond it with the welder. You going to want to weld around 80-90 amps in short pulese most likely. Maybe hotter or colder depending on the wire and the tubbing thickness. I would also recomend using a thinner 0.023 wire maybe one step down and really using the wire speed to make a clean weld. Don't just pile on the filler make sure it penetrates.
 
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