chromoly tubing for cage ?

[RickM415]

hello,where can i get some chromoly tubing in northen california and what size
i am wondering if its 1 5/8 .83 or .120

i want to build a 10 point cage for my 69 camaro

open to other options

[Blake Foster]

not sure where you can get it but the size depends on what rules your trying to meet
NHRA for a "Roll cage" is 1 5/8 x .083 CM or .118 MS
for road racing it is more dependant on the car weigth but most likley 1 /34 x but i would double check that spec.
also if using it for NHRA it MUST be TIG welded

[deuce_454]

Originally Posted by killer69

not sure where you can get it but the size depends on what rules your trying to meet
NHRA for a "Roll cage" is 1 5/8 x .083 CM or .118 MS
for road racing it is more dependant on the car weigth but most likley 1 /34 x but i would double check that spec.
also if using it for NHRA it MUST be TIG welded

Thats funny.. if you use Chrome moly for any areospace application it must be welded with an oxy acetylene torch, or the weld must be annealed if tigged....

[Apogee]

I would personally use DOM mild steel over chromoly unless you're planning on post heat-treatment at the weld zones like duece_454 pointed out. There was a big fuss a few years ago about mandating chromoly cages in some of the SCORE desert classes which boiled down to the cost versus safety...the debate was about whether a chromoly cage is really safer than a DOM cage. Racing is an inherently unsafe activity, however nobody wants to pay more for something that doesn't definitely improve the safety of the rigs and/or give them some competitive advantage.

While there's no doubt that chromoly is stronger for the same wall thickness so long as it's welded properly, the debate centered around how rigid you wanted your cage to be? Cars have crumple zones for a reason and that's to distribute the force of an impact over a greater period of time since the impact is typically what does the most damage to the soft and squishy thing inside called the "driver". I think we can all agree though that once a crash begins to occur, the "driver" is really a passenger at that point.

Tobin

[NOT A TA]

I went through the whole cage thing a little over a year ago. Chromo Vs. DOM , sizing, and sanctioning body tech requirements. Here's a couple links to threads you might find informative. Beware of assuming that rollbars and cage structures you see in PT type cars are legal for any sanctioning bodies. Get the rulebooks for any sanctioning bodies where you might run the car.

https://lateral-g.net/forums/show...light=chromoly

http://www.pro-touring.com/forum/showthread.php?t=48151

[Blake Foster]

i have herd that the Tig om CM process is acceptable if you wrap the weld and let it cool slowly???? not that any one does it.
i think in reality to make it PERFECT you would want to heat treat the entire cage after welding, but no one is going to do that.
DOM is definatly cheaper. and the fit is not quite as critical and it can then be mig welded..

Deuce454 i know the procees is different but tig and gas welding would be esentially the same? no just that tig would be more controlable would it not?

and what is the BEST filler to use on CM if anyone can shed some light there, we use a 312 rod. only because no one sems to know what if anything is better. my fab guy has been building roadrace cars for 15 years and that is the best material he has found to date.

[mfain]

To support Killer69's point that you should check the rulebook for the type of competition you plan to participate in, I have included an excerpt from the NASA (Road Race) rule book for roll cage tubing size. The Ultimate Track Car Challenge uses the NASA rules, and the unlimited rules for the Silver State Classic are very similar. There are lots of other cage construction "rules" in this and other CCRs (SCCA, Proautosports, NHRA, etc). I've included the website for the NASA rulebook -- pages 59-64 contain NASA cage rules. Some sanctioning bodies let you use thinner wall Chrome-moly because of its strength, but NASA, for example, specifies the same wall thickness for DOM and Chrome-moly.

http://www.nasaproracing.com/rules/ccr.pdf

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. Minimum tubing size for the roll cage is:
Up to 1500 lbs.
1.375” x 0.095” Chrome-moly / Seamless mild steel (CDS or DOM)
1501 - 2500 lbs.
1.500” x 0.095” Chrome-moly / Seamless mild steel (CDS or DOM)
1.500” x 0.120” ERW* (No issuance of log books for cars with ERW cages 04/30/03)
*Note- Specifications listed for reference for inspection of grandfathered vehicles.
2501 - 3000 lbs.
1.500” x 0.120” Chrome-moly / Seamless mild steel (CDS or DOM)
1.750” x 0.095” Chrome-moly / Seamless mild steel (CDS or DOM)
1.750” x 0.120” ERW* (No issuance of log books for cars with ERW cages 04/30/03)
*Note- Specifications listed for reference for inspection of grandfathered vehicles.
3001 - 4000 lbs.
1.750” x .120” Chrome-moly / Seamless mild steel (CDS or DOM)
No ERW allowed.

[RickM415]

ok so lets say i go dom tubing then 1 3/4 .134 would get me in to all the pro-touring events ?...and where to get it in nor cal ?

[Apogee]

Originally Posted by gEtyOpAPiOn

ok so lets say i go dom tubing then 1 3/4 .134 would get me in to all the pro-touring events ?...and where to get it in nor cal ?

Based on what I've seen, 1-3/4" x .0120 DOM mild steel will get you onto most tracks, but the design has to be compliant as well as the material. If you go too thick on the wall, you limit your bend radius options for conventional mechanical die/follower type tubing benders, hence the reason I wouldn't exceed .120 on the wall thickness.

Tobin

[RickM415]

ok so now that we got the material figured out ....where can i get it