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Ok I have been pricing materials on building my cage and bumpers. NHRA specs for cages is 4130 1 5/8"x.083 and I'm not sure on what the DOM spec it but it is heavier. I do know that .083 4130 is stronger then .120 wall DOM. Anybody have any input on this before I order my tube? Also the .083 4130 is $.06 a foot cheaper then 1 3/4x.120" DOM from the supplier.

Are you planning to weld it with a MIG?

I've heard from credible sources that CrMo cannot be welded with a MIG....you need to use a TIG process on it.


Something to think about, because it might make a big difference in what you choose..... /forums/images/graemlins/thinking.gif





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DOM is a process and not a grade of tubing. You can get many grades of DOM including 4130!

I have read that you can weld cromo just like anything else but you're loosing the benefit of the strength of cromo if it is not tig'd...

Just go with either some 1020-1030 DOM, or HREW...

I went with 1.75" diameter, .120 wall HREW tubing for my cage. I think it will be fine.

For my bumpers and side armor I used the same diameter, .218 wall schedule 80 pipe. It think it will be fine too.

You can MIG or TIG 4340. But, the problem is, you don't really utilize the strength of the 4340 unless you TIG weld it all with 4340 filler rod then have the whole assembly heat treated. Then it will be one had strong SOB. But if you weld it with MIG and just leave it your joints will be weakened, same with TIG but not as much due to less heat. But unless your heat treating the whole thing might as well just use 1020 DOM.

Don't forget 4130 is harder to bend (really need a ram set up) and it chews up bits and blades rather quick. A mig welded 4130 cage won't pass NHRA inspection anyway. TIG is the way to go on cromo because most MIG welds on cromo will look like rooky arc welds on mild steel. I have hrew on all my tube work and haven't broken open a seem yet, or crushed in a bend. And as usual a well designed hrew cage will be safer than a quick job cromo.
MY .02 though.

I will be tig welding it all wether it is 4130 or DOM. You do not have to heat treat it if it is welded correctly. The key to welding 4130 is not to weld it completely at one time because that will create to much heat and make it brittle. You jump around doing little 1/2" welds on different areas and letting it cool.

You don't HAVE to heat treat it no. But it does wonders for strength... But like I said it only works if you use the same filler material as the tube material.

Or you could just by Carroll Smith's (R.I.P.) "Engineer to Win". It has alot of down to earth materials info along with a bunch of stuff on how to design thing to not break. That and "Prepair to Win" I think are the best ones of the series. If you have the money just buy them all /forums/images/graemlins/waytogo.gif

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Or you could just by Carroll Smith's (R.I.P.) "Engineer to Win". It has alot of down to earth materials info along with a bunch of stuff on how to design thing to not break. That and "Prepair to Win" I think are the best ones of the series. If you have the money just buy them all /forums/images/graemlins/waytogo.gif

[/ QUOTE ]

I did /forums/images/graemlins/woot.gif /forums/images/graemlins/waytogo.gif