AAK z28

iTrader: (18)

is it against nhra rules to run a chromoly cage that has been mig welded with special chromoly wire?

MADMAN

iTrader: (4)

Its against NHRA rules. Even if you use Er70S MIG wire.

LongIsland63SS409

iTrader: (22)

Can it be tacked with mig than completed tig welded later?

The mig tack would just be used to keep the members in place till final tig
welding.


Mike

JL ws-6

iTrader: (50)

That is a somewhat common practice (tack with a mig then tig weld 100%), not really right though.


You can mig a mild steel cage, and you can build a mild steel cage to 25.5 cert (7.50) but if you want to go any faster then that you will have to rip it all out and start over.

ATwelveSec02Z28

iTrader: (17)

Supposed to cut out any GMAW tacks before completing with GTAW.

You can do mild steel but look at the wall thickness differences. Lots of extra weight

custm2500

iTrader: (11)

That is cazy they you are supposed to cut out mig tacks even!!

Without a 4 page report why is mig welding chromoly so bad?

JL ws-6

iTrader: (50)

I've actually done the weight comparison on a piece of 1.75 chromoly vs 1.75mild steel, it's .1 lb difference per foot of tubing.

So, if you were doing a 6 pt rollbar with say 60 feet of total tubing it would be 6 lbs. The weight difference is pretty close to the same for 1 5/8 mild steel vs 1 5/8 chromoly.

So a 10 pt cage that probably has 120 feet, it's about 12 lbs, a 25.5 that probably has closer to 200 feet in it would be about 20 lbs.

Main reason I think that mild steel will not cert past 7.50 (madman correct me on this if I'm wrong) is that there's actually a schedule of black iron pipe that meets the requirements for mild steel... and there's no way that would be safe.


One other thing to think about, about 6 years ago, a regular 10 pt cage used to be good to 7.50, not 8.50. It was somewhat recently that all the spec's were updated for certain speed levels, etc.

IMO, which isn't worth much, I think they're off a good bit. You can go buy a brand new mustang or corvette and just by putting a drag radial on them go 10.x at 130 or so... so the rollbar rule, really needs to be changed, to 10.50 or faster from my perspective, 11.50 for a convertable, and those should be good to about 9.50 before you need a 8 pt cage in a car, and that 8 pt cage should be good to 8.0, once you get to 7.99 then the 25.5 makes sense, but that should be good to 7.0, etc.etc.


I know you'll get that old clunker someone put a bbc in that will go 9's and the car isn't safe to push down the road nevermind 140+ but no matter what you do someone will show up with something like that.

Just a perspective, looking at what you can buy today off a showroom vs the current rules, and the rules that were in place not too long ago.

JL ws-6

iTrader: (50)

I can tell you that other industries will mig chromoly material, it's not allowed for nhra or scca, but it is an acceptable practice elsewhere... there's some science etc. involved with the materials and whatnot, I can't tell you exactly the reason.

I can tell you that I have mig'd chromoly threaded inserts to mild steel tubing for go karts and the like and it's held up with NO problems, and these kids beat the things up pretty hard. A simple hole thru the tubing to put a plug weld in, and then wld around the end and I haven't had one fail yet. I've had them bend he tubing after crashing into stuff at speeds that would have probably totalled a car LOL, but the weld joints, and material around the weld joint didn't fail.

mrdragster1970

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I was always told they don't like mig because anyone can slap something together, and it will look & test good.
With a tig, you need more skill & experience to get the proper heat & penetration to look right???
Now I know for a fact, that my Camaro had no business going 8.50's, and it was completely insane
they gave me a 7.50 sticker for all those years.
Yes it was legal, but I don't think sticking a cage on a 6" plate made it 7.50's safe!!

I'm also leaning towards the whole mild steel is junk at 7.50 rule being ridiculous!!
Make them tig it if you're worried about quality and penetration, but I think it's more then strong enough!!
Anyone see the nascar guys on the news??
Those are mild steel cages in those crashes!!


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No Hope

The reason why they would want the cage Tig welded is because 99% of Mig welding is done with globular transfer. You have to be a professionally trained welder to get full penetration with this process. Tig welding uses DC- polarity for this application and full penetration can be easily achieved. Tig welders as a rule have more training than a Mig welder.

GTAW or HeliArc is Tig welding

GMAW is Mig welding

If you grind all the Mig weld off no one will know if you Tig weld it after. Make sure you use the proper filler rod and I would back purge the pipe just to be safe. Do Not resell the cage.

JAX04

iTrader: (17)

Good read, and good to know. Thanks for posting up the question and thanks for the responses guys. I've been wondering this stuff for the last week since i went with MS for my 10point. I highley doubt ill ever make it faster then 7.50 so, works for me.

JL ws-6

iTrader: (50)

You'll need the 25.5 as soon as you get to 8.49, you can do that with MS so it's not a big deal to add on to what you have, and then you're good to 7.50...

To go faster then 7.50 takes CUBIC dollars... if you can afford that, then redoing the cage probably isn't going to kill you.

JAX04

iTrader: (17)

Lol, Works for me i dont have CUBIC dollars, and Wont for along time, lol

JL ws-6

iTrader: (50)

I never will.... and if I ever do come into it, I probably won't be spending it on this stuff. I'll make that money, make me more.

SuperSlow02

iTrader: (16)

for less then 10lbs on a 6-8pt cage/bar, why spend the money for CM? I understand every pound counts..but your almost doubling costs. I mainly do arc welding at work, but i also do alot of mig welding when i dont feel like being showered with splatter and you would be amazed out how some awesome looking mig welds dont burn in for crap.

Thats another thing...whats the reasoning behind no arc welding for roll cages...I know it cant be a strength issue. Just something ive wondered, done a lil research but no concrete answer

JL ws-6

iTrader: (50)

I understand you can mig a weld and have it look nice, but not penetrate. When I was first learning how to Mig stuff it was easy to tell when there was no penetration at least to me... you could pull on the pieces and you'd get the weld to break off the surface of one side. Easy fix, higher power level stopped that at least for me and the welder I have (Lincoln 180)

Since I've gotten the hang of it, and know what looks right, anything I have tried to pull apart absolutely will NOT come apart. I had someone I know that's a certified welder take a couple sample weld's I did and go inspect them @ his work.. he came back with a thumbs up on the joints.. made me happy to know.

But, that being said.. I still won't weld a cage in a car. I don't feel confident enough to do that yet even a MS deal. Just not something I want to do, if something were to happen and it had to hold up to keep someone alive I don't want that in the back of my mind.

Exhaust, frame connectors, all that, yes. Cage, no I leave that to people that do it for a living.


As for not allowing arc weld's on a cage, I would guess the filler material isn't up to par maybe, or the amount of heat, or the porosity of the weld would be the reason.

One of the welding guru's in here will have the answer in technical terms I'm sure.

SuperSlow02

iTrader: (16)

I hear ya on that. Ill do my own mild steel cage. Ive had others ask if i would do theres and that was a big no, i dont want that responsibility.

hopefully somebody will chime in on arc welding. I guess i like to defend it since i do it all day long, if done correctly its an exellent welding technique. I build steel containment tanks and when we do verticle storage tanks in the 20-30,000+gal range, we will never use a mig, always arc weld. may just be what were comfortable with

00Wildcat

I'm pretty sure as others have said it's about the dumb asses pushing the wire. Anybody that owns a MIG welder thinks they are super welder. I'll give you a couple of examples and leave the pics big.
This is a mild steel sub-frame that came with a complete strut Chevy II clip that I purchased from an unnamed vendor that is popular with the Mustang crowd. When asked why the Chomoly suspension parts looked so much better than the sub frame it was explained to me that the mild steel was mig welded.

00Wildcat

So then I sent the company owner pics of my rearend housing that I MIG welded and explained to him just because it was MIG welded didn't mean that some F*Tard had to lay down a dog **** weld on the joint! So they are now sending me a replacement chromoly subframe.

00Wildcat

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