Roll cage Manufacturer question?

[Notso Swift]

Well engineered an alloy cage is fine in 99% of circumstance
The issue is that you cant really tell if too much heat has been put into the alloy which makes it brittle

Mind you a FIA cage is no guarantee:

Full FIA spec CrMo cage from 1998, built for international rally and did about 6 (converted to circuit in 2005), died in 2009, passenger side T boned

[Paul D]

Originally Posted by Notso Swift

Full FIA spec CrMo cage from 1998, built for international rally and did about 6 (converted to circuit in 2005), died in 2009, passenger side T boned

It's difficult to tell from the photo, but has that fractured with almost no distortion prior to fracturing? I'm no metallurgist, but I would have expected significant bending and stretching of the tubes before reaching the fracture point. I'm sure ductility is an important property of a decent cage, as surely it's this that allows it to absorb and dissipate energy.

It's interesting to note that it hasn't fractured at the welds though - it appears to have let go just adjacent to the welds. It does rather prove a point though - no matter how good your cage may look, do any of us really know how good it is until it's tested to destruction? And that's not really the time to be finding out it's not up to the job, is it?

[phoenix]

Originally Posted by Notso Swift

Well engineered an alloy cage is fine in 99% of circumstance
The issue is that you cant really tell if too much heat has been put into the alloy which makes it brittle

Mind you a FIA cage is no guarantee:

Full FIA spec CrMo cage from 1998, built for international rally and did about 6 (converted to circuit in 2005), died in 2009, passenger side T boned

A lot of welders don't stress relive 4130 as they should:

http://weldingweb.com/attachment.php...1&d=1332256871

A process not required with UK spec CDS, as welding CDS does not cause brittleness

[terence]

The welding leaves a lot to be desired though. Its surprising how many fabricators dont know how to stress relieve,some thing that,judging by the photos,is fairly obvious.

[FastDB2s]

Originally Posted by roco

Im not making any allegations,, im simply stating that i have seen people with brand new cars, fitted with brand new cages, turn up to scrutiny and be failed as the cage wasnt up to standard. that person after spending their hard erned money now has to go and get it fixed or done again properly, which means they miss racing, costing money and hassle, all im asking is there a governing body that regulates the cage builders so that if a cage builder is approved by them then a customer knows that the cage they are buying meets a minimum spec and has a better chance of passing scrutiny! basically like electricians or any other trade has to be, you see it on their vans, reci approved, or rac approved, ect.

Hi Roco, are you from Eire

[zefarelly]

Originally Posted by Peter Mallett

Agreed, although a fully welded in cage is a lot different and performs a different job too, which is why they cost so much more. We aren't allowed to run fully welded in cages in Group 1 or FIA App K. But we can in Group A .

Are you sure Peter? When I built my car it was 6 point bolt in . . . I've not seen a tin top, or any other App K car recently prepared with anything lees than the Carlos Fandango hand fabricated super cage, I think you could be forgiven for thinging bolted cages where now outlawed!

[JohnD]

Originally Posted by phoenix

A lot of welders don't stress relive 4130 as they should:

http://weldingweb.com/attachment.php...1&d=1332256871

A process not required with UK spec CDS, as welding CDS does not cause brittleness

Thnaks for posting that link, phoenix!
But I was puzzled; it's called 'stress-relief' and that explanation relies on brittleness due to air and material quenching. So I looked for more information and found this:

http://www.thefabricator.com/article...ess-in-welding

Still says the same thing, pre- and post-weld heating, but in terms of weld distortion due to the weld metal expanding and contracting with temperature; much more likely, IMHO. It also appears to me authoritative and includes much more detail on techniques and methods, some beyond the amatuer, but anyway.
You have stimulated me to learn - thank you!
John

[TEAM78]

Originally Posted by phoenix

A lot of welders don't stress relive 4130 as they should:

http://weldingweb.com/attachment.php...1&d=1332256871

A process not required with UK spec CDS, as welding CDS does not cause brittleness

WOW

I have never seen anything like that before, what possessed the manufacturer to cut the tubes and weld like that? I have seen some real shockers out there before but not as bad as that. I have always trusted www.tavikess.com for rollcage design and manufacture. They seem to have a good understanding of testing the design of rollcages and are very good at doing one off projects from ground up.

[roco]

Originally Posted by Notso Swift

Well engineered an alloy cage is fine in 99% of circumstance
The issue is that you cant really tell if too much heat has been put into the alloy which makes it brittle

Mind you a FIA cage is no guarantee:

Full FIA spec CrMo cage from 1998, built for international rally and did about 6 (converted to circuit in 2005), died in 2009, passenger side T boned

Hard to tell by the pics but that looks Mig welded?

[roco]

Originally Posted by FastDB2s

Hi Roco, are you from Eire

yes im from Ireland

[morninggents]

Difficult to tell from the picture but the wall thickness appears too thin.

[Peter Mallett]

Originally Posted by zefarelly

Are you sure Peter? When I built my car it was 6 point bolt in . . . I've not seen a tin top, or any other App K car recently prepared with anything lees than the Carlos Fandango hand fabricated super cage, I think you could be forgiven for thinging bolted cages where now outlawed!

Sorry Zef, just noticed this. I was under the impression that fully welded was, as I said. I guess things have changed then.

[Notso Swift]

Originally Posted by morninggents

Difficult to tell from the picture but the wall thickness appears too thin.

It is CrMo,

It was TiG and full FIA spec of the time ('99)

[zefarelly]

That snapped cage looks more like Farmers Arc than Tig, I can weld better than that!!! either way, its snapped and moved, but appears to have done its job, if it wasn't there it would have been a lot lot worse.

[GORDON STREETER]

I remember in "the old days" that the Hot Rod roll cages left a lot to be desired !
You had to have a hole drilled in the B post upright to show the wall thickness and "some" (to save weight) used to make the rest out of nothing more than exhaust pipe !