Roll cage

[Damn True]

So do you think the question is w/o merit or are you unable to answer it? Avoiding it does not make you more credible. Again, your claims regarding Mig/Tig do not apply to the SCCA or NASA tech requirements so I really don't get what your assertions are based on.

Fact is that there are applications in the construction of a cage or other structural member where each is appropriate and where one or the other is less so.

[Rod]

[Rod]

kinda quiet maybe every-bodies out welding stuff to other stuff

[funcars]

Hey, back to the original line of thought and away from I have more amps than you.

A full cage can be dangerous on the street. Think about what would happen if your head hit hard against a steel tube. Not good. If you put a partial or full cage on a street car put padding everywhere you could possibly reach (and that is further than you think in a crash). I can't believe all of the Cobra kit cars I see running around with nice shiny steel tubes inches away from someone's unprotected head. You will probably be much better off to use somebody with experience and talent to design it and put it in too.

Good luck

[ScottT]

Not A TA- Thanks for the advise. I'll look into a 3 point retractable seat belt as I won't be racing. If I do then I will add the cage and I will use padding all over it.

[JohnUlaszek]

Good Tech from Miller's web page, http://www.millerwelds.com/resources...me-Moly-Tubing

[JohnUlaszek]

From a story in the American Welding Society Journal:

"There is a misconception in the race car and street rod circles that GMA welding is not usable for critical welds".

[chicane67]

4130 is a waste of time and considerable money... unless you heat treat the ENTIRE chassis... which... you wont be doing.


Here are a few threads that you should read, specifically on and about roll bars, roll cages and material science... they even include the math:

Cage info 1

Cage info 2

Cage info 3

[chicane67]

Oh yea... and the infamous and gratuitous weld shot that defines TIG welding... and... heat control:

[The GMR]

Oh yea... and the infamous and gratuitous weld shot that defines TIG welding... and... heat control:

oh snap,

A little Dump special!

[Rod]

Oh yea... and the infamous and gratuitous weld shot that defines TIG welding... and... heat control:

those are some sexy welds!!

[Damn True]

So do you think the question is w/o merit or are you unable to answer it? Avoiding it does not make you more credible. Again, your claims regarding Mig/Tig do not apply to the SCCA or NASA tech requirements so I really don't get what your assertions are based on.

Fact is that there are applications in the construction of a cage or other structural member where each is appropriate and where one or the other is less so.

Given that "Chopsmitty" has been logged in a number of times since the question was posed (as recently as 3/30) I am going to assume that the latter half of the above bolded question is the situation at play.

Members,
I would suggest you consider the opinions of more credible contributors to the community.

[Rod]

Given that "Chopsmitty" has been logged in a number of times since the question was posed (as recently as 3/30) I am going to assume that the latter half of the above bolded question is the situation at play.

Members,
I would suggest you consider the opinions of more credible contributors to the community.

Good call True, if you cant admit being wrong as well as right their probably the last one I will ask for advice from, I know I learn new crap everyday!! that proves me right and wrong

[The GMR]

some food for thought...

Lower Arm for a H1 race truck, about 9000 lbs total.

All 4130, MIG for about 90% then I TIG welded in the cup with stainless rod.




Jason

[Rod]

those are some damn sexy welds!!

[Gitter Dun]

some food for thought...

Lower Arm for a H1 race truck, about 9000 lbs total.

All 4130, MIG for about 90% then I TIG welded in the cup with stainless rod.




Jason

WOW! I'd hang a poster in my garage with that on it.

[mikedc]

Interesting.

I was about to ask about this very issue - Now that we've argued ourselves silly over which one is "better", do we have any agreement on specific situations where one is better than the other?



For example, I read a discussion once about TIG possibly being more suitable for bicycle frames because the tubes themselves are such thin material. (The bicycle industry TIG welds a lot of frames from thin 4130, and they're not breaking the welds in the field.)

Thinner = the cool down rate after the weld is a bit more gradual. The thinner tube can't wick away the heat from the weld as abruptly as a thicker one does. So the HAZ spreads out larger and cools down a bit more gradually than with a thicker-walled tube.


Conversely this would imply that thicker 4130 tubes would be more in the favor of MIG because of the heat not being applied as precisely at the weld site. The change in temp is over a larger area and occurs more slowly than a TIG might do in the same situation.



(Once again I am not pushing any of this stuff as if it's factually proven. It is just some interesting theorizing that I read once.)



-----------------------------------------------

[Damn True]

The cage builders I know (one of whom also happens to be a NASA scrutineer) use them both pretty much interchangeably. The deciding factor has more to do with fitting the torch into the area in question & ability to see. You can prep a joint appropriately to work well with either.

[chopsmitty]

Given that "Chopsmitty" has been logged in a number of times since the question was posed (as recently as 3/30) I am going to assume that the latter half of the above bolded question is the situation at play.

Members,
I would suggest you consider the opinions of more credible contributors to the community.

I have stated my point over and over and you apparently are to narcissistic to even read it. It's a waste of time pushing an opinion here. Your point is an opinion, and my point is an opinion. I said my peace. I use 4130 and Tig weld most everything as does Skinny Kid Race Cars, DMC Race Cars, TRZ Race Cars, etc., etc., etc. It is true my current focus is on drag cars, but I have built my share of road race cars as well. Come to me and you get 4130 and tig welds. The finished product is approx. 40% lighter than mild steel and just as strong, if not stronger. Spend some serious time looking at the chassis of a current NASCAR or even a mid pack American Sedan car... You'll see porosity, undercuts, poor penetration, etc. You'll never see poor quality on one of my bike frames or cages, or in any of the above mentioned shops work - all of which use 4130 and tig weld and don't 'stress relieve' the complete chassis :bsjerk:

[Damn True]

I am fully aware that this is your opinion, and I have read said unsupported opinion a number of times I am asking what you have based your opinion and your recommendations on? Thus far your responses have consisted of hostility, insults, anecdotes and reassertion of said opinion.

I am offering statement of fact. The fact is that NASA and SCCA technical regulations do not support your assertions. I have never had a cage on one of the cars I crew for rejected based on the use of MIG/TIG. The cage builders I know (one of whom also happens to be a NASA scrutineer) use them both pretty much interchangeably. The deciding factor has more to do with fitting the torch into the area in question & ability to see. Fact is that there are applications in the construction of a cage or other structural member where each is appropriate and where one or the other is less so and a skilled cage builder can prep a joint appropriately to work well with either.

What documentation are you basing your opinion on? An opinion, I might add that confounds NASA, SCCA, and NASCAR cage construction regulations.

From what I understand, NHRA allows 1010 using GMAW in slower classes but does require GTAW and 4130 for 8sec and faster cars, but I don't recall your mention of that requirement. If you did and I missed it, my bad but I don't know that that justifies your broad brush assessment of cage construction requirements for other forms of motorsport.

We are discussing "safety of flight" items here. This is an area where supported fact is king and opinion is just that. I am by no means closed minded on this and I am perfectly willing to have my mind changed, but it is going to take supported fact to do it. I feel it is irresponsible to make recommendations on "safety of flight" items unless there is something credible behind it. In saying that, I am not attempting to say that MIG is inappropriate, or less safe. Nothing could be further from the truth. But what I am saying is that existing cage regulations indicate that it is not entirely necessary. More accurately, it is but one process which can be used by a skilled builder to construct an cage appropriate to the application. In short, it's more about the design of the cage itself, the care taken to adequately prep the joints, the correct weld parameters (settings) for the joint in question and the ability of the weldor to see what he/she is doing in order to perform a quality weld than which machine (MIG/TIG) is used.