When a Cage is needed?

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Re: When a Cage is needed?

Post by ZIGGY » Sat Jul 19, 2014 12:22 pm

Alan Roehrich wrote:Tig weld is absolutelly necessary to chrome moly tubbing?? Will be hard to find someone that can fab roll cages tig welded overhere.
Find a top-notch old fashioned gas welder?

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Re: When a Cage is needed?

Post by BrazilianZ28Camaro » Sat Jul 19, 2014 12:30 pm

Ok Alan, got it.

In your experience, how heavier is a mild steel roll cage compared to a chrome moly one?

You're right, I'll reconsider the way I'll weld the bars to the pan floor. Probably I'll be welding the bars directly to the frame like you told me.

I'm thinking about add a horizontal bar under the dash, from the curved section of the H member to the bottom half of the shoulder bar if space permits. Might help I believe.
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

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Re: When a Cage is needed?

Post by Alan Roehrich » Sat Jul 19, 2014 12:53 pm

ZIGGY wrote:Tig weld is absolutelly necessary to chrome moly tubbing?? Will be hard to find someone that can fab roll cages tig welded overhere.

Find a top-notch old fashioned gas welder?
I did not write what you quoted under my name. Please avoid attributing things to me that I did not post.

I would not be inclined at all to trust my life to a gas welder fabricating a chrome moly cage. Yes, I'm fully aware that aircraft were welded that way for years. I am also fully aware that if you evaluated 10,000 welders, you would be extremely fortunate to find one who was truly capable of gas welding a chrome moly cage and doing it correctly.

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Re: When a Cage is needed?

Post by Alan Roehrich » Sat Jul 19, 2014 1:00 pm

BrazilianZ28Camaro wrote:Ok Alan, got it.

In your experience, how heavier is a mild steel roll cage compared to a chrome moly one?

You're right, I'll reconsider the way I'll weld the bars to the pan floor. Probably I'll be welding the bars directly to the frame like you told me.

I'm thinking about add a horizontal bar under the dash, from the curved section of the H member to the bottom half of the shoulder bar if space permits. Might help I believe.
Directly comparing 1-5/8" x 0.125" wall DOM to 1-5/8" x 0.090" wall chrome moly, in a 8 to 10 point cage, maybe up to 50 pounds. Using 1-3/4" x 0.134" wall ERW is another story entirely, and if you look carefully, that is what many of the kit companies are selling for mild steel cages. The reason is purely money. To buy 1-5/8" x 0.125" wall DOM costs considerably more than the 1-3/4" x 0.134" wall ERW. If you buy 1-5/8" x 0.125" wall that is not certified and DOM, you will find that the wall thickness is not consistent, and here in the U.S., it may not pass certification tests because of thin spots, especially on the outside radius of a bend, where the metal is stretched, not compressed. With certified DOM, the wall thickness is guaranteed to be above the spec, so that you do not have a thin spot in the tubing that drops below the minimum thickness spec to have the chassis/cage certify.

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Re: When a Cage is needed?

Post by BrazilianZ28Camaro » Sat Jul 19, 2014 1:03 pm

I'm wondering why the 4130 steel is so difficult to weld? Maybe it hardens on the welded area but with only .03% carbon it wouldn't be a problem?

I did a quick research and the above steel is roughly 35% harder than SAE 1020 steel in normalized condition.

What if it could be slowly cooled or stress relieved after welding? :-k
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

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Re: When a Cage is needed?

Post by ZIGGY » Sat Jul 19, 2014 1:05 pm

Alan Roehrich wrote:I did not write what you quoted under my name. Please avoid attributing things to me that I did not post
Sorry. Unintentionally pulled quote from wrong area.

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Re: When a Cage is needed?

Post by BrazilianZ28Camaro » Sat Jul 19, 2014 1:09 pm

Alan Roehrich wrote:
BrazilianZ28Camaro wrote:Ok Alan, got it.

In your experience, how heavier is a mild steel roll cage compared to a chrome moly one?

You're right, I'll reconsider the way I'll weld the bars to the pan floor. Probably I'll be welding the bars directly to the frame like you told me.

I'm thinking about add a horizontal bar under the dash, from the curved section of the H member to the bottom half of the shoulder bar if space permits. Might help I believe.
Directly comparing 1-5/8" x 0.125" wall DOM to 1-5/8" x 0.090" wall chrome moly, in a 8 to 10 point cage, maybe up to 50 pounds. Using 1-3/4" x 0.134" wall ERW is another story entirely, and if you look carefully, that is what many of the kit companies are selling for mild steel cages. The reason is purely money. To buy 1-5/8" x 0.125" wall DOM costs considerably more than the 1-3/4" x 0.134" wall ERW. If you buy 1-5/8" x 0.125" wall that is not certified and DOM, you will find that the wall thickness is not consistent, and here in the U.S., it may not pass certification tests because of thin spots, especially on the outside radius of a bend, where the metal is stretched, not compressed. With certified DOM, the wall thickness is guaranteed to be above the spec, so that you do not have a thin spot in the tubing that drops below the minimum thickness spec to have the chassis/cage certify.

Thank you very much for the clarification Adam.

PS : I saw the pics on your website, Awesome machines you build there!!! Congrats =D>
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

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Re: When a Cage is needed?

Post by Alan Roehrich » Sat Jul 19, 2014 1:17 pm

BrazilianZ28Camaro wrote:I'm wondering why the 4130 steel is so difficult to weld? Maybe it hardens on the welded area but with only .03% carbon it wouldn't be a problem?

I did a quick research and the above steel is roughly 35% harder than SAE 1020 steel in normalized condition.

What if it could be slowly cooled or stress relieved after welding? :-k
There are a lot of variables there, and how do you intend to properly control stress relief on it without being able to provide a completely controlled stable environment.

Yes, there are all sorts of things you can possibly "get by with". But there are reasons that the FAA and racing sanctioning bodies require very specific procedures for welding and fabricating using high strength alloys. Those reasons are failures by some to properly execute other procedures, resulting in failures, some of them catastrophic.

Sure, the right well trained, experienced, and dedicated craftsman could MIG weld or gas weld chrome moly tubing. But people of that level of skill, dedication, and talent are extremely rare. For example, world renowned welding expert (NASA consultant as well) Richard Finch developed a strictly controlled process to MIG weld chrome moly tubing to fabricate seat frames in general aviation aircraft for one company. But read that again, and note the qualifications of the guy who developed the process, and the conditions of the process itself.

Of course, there are people who can turn on a TIG welder and strike an arc, who will completely screw up chrome moly tubing welds.

It is your car, and your life, only you can decide what it is worth to you.

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Re: When a Cage is needed?

Post by Alan Roehrich » Sat Jul 19, 2014 1:21 pm

BrazilianZ28Camaro wrote:
Alan Roehrich wrote:
BrazilianZ28Camaro wrote:Ok Alan, got it.

In your experience, how heavier is a mild steel roll cage compared to a chrome moly one?

You're right, I'll reconsider the way I'll weld the bars to the pan floor. Probably I'll be welding the bars directly to the frame like you told me.

I'm thinking about add a horizontal bar under the dash, from the curved section of the H member to the bottom half of the shoulder bar if space permits. Might help I believe.
Directly comparing 1-5/8" x 0.125" wall DOM to 1-5/8" x 0.090" wall chrome moly, in a 8 to 10 point cage, maybe up to 50 pounds. Using 1-3/4" x 0.134" wall ERW is another story entirely, and if you look carefully, that is what many of the kit companies are selling for mild steel cages. The reason is purely money. To buy 1-5/8" x 0.125" wall DOM costs considerably more than the 1-3/4" x 0.134" wall ERW. If you buy 1-5/8" x 0.125" wall that is not certified and DOM, you will find that the wall thickness is not consistent, and here in the U.S., it may not pass certification tests because of thin spots, especially on the outside radius of a bend, where the metal is stretched, not compressed. With certified DOM, the wall thickness is guaranteed to be above the spec, so that you do not have a thin spot in the tubing that drops below the minimum thickness spec to have the chassis/cage certify.

Thank you very much for the clarification Adam.

PS : I saw the pics on your website, Awesome machines you build there!!! Congrats =D>
I did not do the chassis work on those cars. I build the engines, transmissions, and other components. The Beretta is a full tube chassis car, built by a legend in the chassis business here close to me, Gary Jennings. That car was a state of the art Pro Stock car when it was built, and was then converted to an A-arm car to withstand the rigors of throttle stop racing. It may possibly be one of the top 5 cars in the country with regard to consistency and predictability.

I have gotten away from building cars, I no longer have the time and space. But when I was doing it, Gary and another local builder taught me a great deal.

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Re: When a Cage is needed?

Post by af2 » Sun Jul 20, 2014 10:28 pm

Alan, Remember why chrome molly was introduced?

They did not have TIG at that time only O/A for the planes. I am saying in good hands either will be excellent. MIG? NEVER.
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Re: When a Cage is needed?

Post by Alan Roehrich » Sun Jul 20, 2014 10:40 pm

af2 wrote:Alan, Remember why chrome molly was introduced?

They did not have TIG at that time only O/A for the planes. I am saying in good hands either will be excellent. MIG? NEVER.

Chrome moly was introduced for its strength to weight/mass ratio, which was necessary for the evolving high performance aircraft. It certainly was not because it was easier to gas weld than mild steel.

This is not the nineteen fifties, or more to the point, the nineteen thirties. The number of craftsman that can correctly weld 4130 chrome moly tubing in any given area can be counted on one hand, at best, being generous, and that's here in the U.S., never mind where he is. There is no person nor school I'm aware of teaching the process anymore. You'll have an easier time finding a craftsman that can do body work in lead.

Further, consider the amount of time, effort, and gases necessary to gas weld a chrome moly roll cage. It would cost him less to buy someone a small TIG welder. It takes 3-5 times as long to gas weld as it does to TIG weld, which takes 3-5 times as long as it does to MIG weld. It's a simple matter of economics and common sense. He's far better off to go with DOM mild steel, if he cannot find anyone who can and will TIG weld chrome moly for him.

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Re: When a Cage is needed?

Post by af2 » Sun Jul 20, 2014 11:08 pm

Alan Roehrich wrote:. He's far better off to go with DOM mild steel, if he cannot find anyone who can and will TIG weld chrome moly for him.
I Agree big time, it is far superior than .135 mild seamed tubing.

I was just suggesting an option.

Alan, my dad is still alive and you would shit watching him weld molly with a torch..

It blows me away the technique he has.
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Re: When a Cage is needed?

Post by BrazilianZ28Camaro » Mon Jul 21, 2014 4:07 pm

Great replies fellas, but excuse me the question:

Which problem occurs when a CrMo tube is welded with MIG?

Can I guess the different metal compositions from the MIG wire and the tubes won't match well or the weld points become brittle like glass after the weld ? Or maybe the CrMo tube realese impurities that must be eliminated by a torch heat? Not arguing just asking. :D

I can say I have some skill on a MIG welder, I remember one time I welded Stainless steel with ordinary wire and no problems but obviously is a entire different alloy.

Sometimes weld SAE 1045(wich have a higher carbon content) is necessary and the brittle condition of this material is easy eliminated with a simple heating process with a torch, per exemple, just watching the steel temperature by its color, when a furnace stress relieve isn't possible.
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

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Re: When a Cage is needed?

Post by ZIGGY » Mon Jul 21, 2014 5:55 pm

The one's I've seen break on circle track cars typically break not at the weld but within a inch or two of it.

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Re: When a Cage is needed?

Post by BrazilianZ28Camaro » Mon Jul 21, 2014 6:02 pm

ZIGGY wrote:The one's I've seen break on circle track cars typically break not at the weld but within a inch or two of it.

Interesting, I'd say the breaking point wouldn't be affected by the weld heat at those distances, but I never worked before with this CrMo steel and may be wrong;

Did you noticed some deformation (elongation) on the bars near the rupture point?
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

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