roll bar and roll cage rule

had i guy ask me this the rule book says your roll bar must be 1 3/4 and .118 wall to be nhra legal there are guys in our area running into the 10 with roll cages that do not meet the chassie cert rule as to they are to small/thin as to wall they cant get there chassie cert to go faster then 9.99 but can run faster then 11.50? to have chassie cert they have to be 1 3/4 and .118 wall i thik it was early 1990 when ther changed the rule to be a min of .118 wall i hope you guys can decode what im asking

Mild steel is a minimum of .117 accepted by most NHRA tech when using a sonic tester, they won't accept .116 If they see that the bar/bars where bent on a standard bender, non mandrel bender, they will usually check the inside of the bend as that is where it will normally be the thinnest from crimping, stretching and bending A lot of the mild steel commercial kits sold today are made out of .134 wall mild steel. If you are interested in the lightest weight with the maximum strenght and the strongest tubes buy a chromoly kit DOM(drawn over a mandrel) tubing is suppose to be very consistent on the wall thickest, not eractic like regular electric welded (I think that is the proper name of it ) mild steel tubing is BTW,roll bars have to be 1 3/4 diameter and cages are suppose to be 1 5/8 diameter tubing, mild steel is .120 and chromoly can be .083 I used chromoly for my roll bars in all of my cars, I don't want them to bend in a wreck

That was painful to read but accurate. . . Almost worth the eye strain lol

The outside of the bend is stretched thinner while
the inside goes into compression... but Cab is correct
on the numbers.... a inspector can check anywhere he
wants to check with a sonic checker... they tend to
check some straight areas for the base thickness and
will check some of the outer radius areas if they can
get on it square with the checker... I was asked
the first time I certed my car what the material was
and what wall thickness in different areas and why
I did a couple of things.. once I told him why I did
it that way, he said... thats a real good answer..
it wasnt just show up and they stick a sonic checker
on it... at that time my car was a 7.50 cert and it
passed with flying colors(since then they changed
some of the requirements)