I dropped my car off yesterday to have the cage installed and discovered a few interesting things:

1. The Art Morrison 8pt weld in kit that I bought for $200 is actually 4130 chromolly and not DOM as the seller advertised. Upon hearing this, I was initially stoked to hear this since that means a lighter cage.
2. My cage guy tells me that you must TIG weld a chromolly cage, rather than MIG weld. Okay fine.
3. He then tells me that its $300 more to TIG weld than MIG weld my cage.
4. He tells me that TIG welding is MUCH stronger than MIG welding, so I feel better about the $300 since I don't want to go cheap on safety.

Is TIG welding required in NASA/SCCA for a chromolly cage?




[Modified by Steve91, 8:45 PM 12/16/2002]

 

There was a discussion on this here recently.

Chromoly cannot be MIG welded with much success. TIG is possible.

Given that TIG is much more time consuming, I would expect it to cost more. Strength really isnt' an issue, it's more a matter of doing what it takes to get a good weld.

I don't see that you have a choice here... regardless of what a rulebook says.

 

I will second what Jeff said. Tig is much more time consuming, and it takes much more training to do properly. Even I can use a mig welder and get good welds, so it must be easy.

 

One other thing is the cage shouldn't be any lighter. Tubing diameters, and wall thickness rules are the same for chrome-moly and DOM. Drag racers are the only ones that get a break for using chrome-moly. Usually they can run .083 wall instead of .095, so you might want your cage welder to check that before he gets started.

Walt

 

mig (usually referred to as wire feed) can be done with one hand and easy to get into hard places...

so its usually faster...less hours...but i think tig is just as easy as mig..

underwater arc welding is another story

 

mig is easier for a beginner or "back yarder" like myself. wire is automatically fed through the torch along with an inert gas.

tig takes two hands to run; one hand must gently feed in the filler rod, whilst the other carefully controls the torch that contains the tungsten electrode. we have a couple of guys here at work that are welders and they specialize in the tig. they make wonderful, precise, strong, and beautiful welds. its takes some time and patience, though.

I don't do tig. I can use the mig and also the stick welder (arc). The stick is good for thick metal (1/8" and thicker plate, tubing, etc.).

Todd

PS we make garbage grinders, in case you were wondering

 

Well TIG it is. For some reason, I thought the DOM cages had to be .125" and only the chromolly could be .095. Either way, it sounds like I got a very strong cage.

 

fyi,

minimum tubing diameter/thickness requirements are smaller for alloy (chromo) steel as opposed to mild steel for Formula, Sports racer, GT and production cars.

they are the same diam/thickness for both DOM and Alloy, but are different requirements for ERW for SS, Touring and IT classes.

 

I like good old Oxy/Acetylene!

That underwater stuff sounds like a different world! hehe

 

But the welding decision isn't going to change the tube thickness right?

Seems like a good idea to double check and be SURE that the Morrison kit tubing is legal. The only thing worse less money than an illegal rollcage kit is an illegal rollcage welded into a tub.

Kirk

EDIT - Historical note: As I heard it, CrMo tubing was originally designed for cloth covered airplane frames. The joint of choice was bronze fusion welding - brazing.




[Modified by Knestis, 1:14 PM 12/18/2002]

 

I thought that SCCA no longer would issue 'new' logbooks for cars with ERW tubing. Didn't the rules change to DOM & alloy cage materials only?

 

someone pointed out to me that in the January fastrack they are going to push the new ruling back til jan 2004 due to vendor stock still having ERW.

but the ERW thing is not relevent to this thread anyway.