Roll Cage Material - NEED HELP FAST

[JPhillips-61]

I am in the early stages of building a new cage for my race car and have a question about sizing of steel vs. chromoly tubing.

 

Most sanctioning bodies allow a thinner wall if you go with Chromoly, but NASA doesn't specify a difference.

 

Basically 1.75 x 0.90 in steel is the same strength as 1.75 x 0.82 in chromoly so you end up with a lighter cage.

 

Is this an oversight on NASA's part? Can I go with a Chromoly 0.82 wall?

 

My car 2,800 lbs.

 

Really have to know in the next couple of days!

 

Thanks.

[white_2kgt]

Chromoly is not lighter than steel, it is the same weight, just stronger give the same size (which is why some groups let you use a thinner wall, you reduce weight b/c the wall size is thinner). No, NASA doesn't care if you build it out of Chromoly or Steel since the min size req doesn't change. My guess is they don't have the ability to determine if you used Chromoly or DOM, do you know of a way to tell the difference after it's all painted up nice?

 

Also welding of Chromoly takes more care, if not done correctly the weld can be weaker than one done on DOM.

[JPhillips-61]

Thanks for the reply. I decided to go with the steel primarily b/c that is what the builder has in his shop. The chromoly was the thinner wall. I guess I didn't think about how one would prove their cage is chromoly.

[Renntag]

Correct me if I am wrong, but isn't the typical wall thickness for 1 3/4 '' DOM actually .120 in. ? ...and .095"

 

I assume that you didn't mean .9 in as that is nearly 1 inch thick ! Could you imagine how heavy that would be?

 

Best of luck. share pics during and after if you can. We are always curious to see new cages.

 

edit to include reference to NASA CCR.

 

15.6.18 Roll Cage Tubing Sizes

For the purposes of determining roll bar tubing sizes, vehicle weight is as raced, but

without fuel and driver. Note: There is an allowance of minus 0.010 inches on all tubing

thicknesses.

 

(snip)

 

2201 - 3000 lbs.

1.500â€