Okemo 2 caged car crashes

Mopar 151w2
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Re: Okemo 2 caged car crashes

Post by Mopar 151w2 »

Ain't suckin nuthin up. Not every car we see is new, or built especially for this series. We generally like vintage race cars, and don't seem to mind good stock cars - either of which is apt to be decent ERW. According to my sources, DOM was virtually nonexistent in stock car racing before the advent of the "factory built" race car in the early 80's, and is still widely used in entry level oval cars.
IMHO, we would be far better off learning how to visually inspect welds and examine bends for evidence of kinking and flattening (from use of improper tooling and bad technique) Decent ERW does not split if bent CORRECTLY - and such bad technique is A) well known and B) detectable. We have far worse problems to deal with in homemade cages - DOM ( which has a welded seam too) is far from stupid-proof when it comes to poor fit-up and bad design - like being welded onto to a .035 rocker panel with poor prep and plenty of paint for "flux". The key to success with most cages is preparation of the car for cage installation - like welding a "doubler" plate to said rocker panel or floor, and holesawing a socket for the tube to fit into. the small gap around the tube allows full root penetration, and the added thickness of material allows a weld of sufficent size and "heat" to assure a complete bond. Don made a good point, backalong, about reinforcing the car for installation of a bolt-in cage, and plating from the "feet" of the cage to nearby seat belt mounts (strongest point in the unibody). gotta go, more to follow.
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sdwarf36
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Re: Okemo 2 caged car crashes

Post by sdwarf36 »

Somebody with better google skills than me please show me a ERW cage that failed at a weld ? I keep hearing "I heard (3rd hand) of one. Not defending the stuff-but with all this talk of bad quality chinesium metal, where's all the failed cages from the last 25 years?
Translating road racing to hillclimbing:
Proper tire selection== nothing hooks up on moss or wet leaves.
Staying on the racing line==anything paved is considered good.
jkale
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Re: Okemo 2 caged car crashes

Post by jkale »

sdwarf36 wrote:Somebody with better google skills than me please show me a ERW cage that failed at a weld ? I keep hearing "I heard (3rd hand) of one. Not defending the stuff-but with all this talk of bad quality chinesium metal, where's all the failed cages from the last 25 years?
Well Sherm, not very many people like to post their fabrication failures so I'm sure it is difficult to find.. Here is some useful info that I stumbled across though..

http://www.thefabricator.com/article/hy ... ced-metals

It shows the difference in how erw reacts compared to a tube that has been normalized.. It briefly describes what happens to the microstructure of the material when formed as ERW is... and shows a nice split at the welded seam during a free-expansion test(cap the tube and pressurize).. I'd say it is pretty apparent that the ERW has one very long brittle seam..
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jkale
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Re: Okemo 2 caged car crashes

Post by jkale »

Mopar 151w2 wrote: Decent ERW does not split if bent CORRECTLY - and such bad technique is A) well known and B) detectable.
Correct, you can position the seam in a manner so the tube remains in tact during cold-working process. BUT, does that mean it will react the same as a normalized tube under stress? No. That is the important part.
-Joey Kale #111
Kale's Custom LLC.
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sdwarf36
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Re: Okemo 2 caged car crashes

Post by sdwarf36 »

jkale wrote:
sdwarf36 wrote:Somebody with better google skills than me please show me a ERW cage that failed at a weld ? I keep hearing "I heard (3rd hand) of one. Not defending the stuff-but with all this talk of bad quality chinesium metal, where's all the failed cages from the last 25 years?
Well Sherm, not very many people like to post their fabrication failures so I'm sure it is difficult to find.. Here is some useful info that I stumbled across though..

http://www.thefabricator.com/article/hy ... ced-metals

It shows the difference in how erw reacts compared to a tube that has been normalized.. It briefly describes what happens to the microstructure of the material when formed as ERW is... and shows a nice split at the welded seam during a free-expansion test(cap the tube and pressurize).. I'd say it is pretty apparent that the ERW has one very long brittle seam..
Interesting read--but not really applicable. (but all gained knowlodge is a good thing! :) ) They made the failure from pressurizing the pipe to 3600 lbs. And they were comparing it to a one piece tubular blank. I'm looking for an impact failure of a ERW cage at a seam--BECAUSE of the seam.
Translating road racing to hillclimbing:
Proper tire selection== nothing hooks up on moss or wet leaves.
Staying on the racing line==anything paved is considered good.
Mopar 151w2
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Re: Okemo 2 caged car crashes

Post by Mopar 151w2 »

Mightily impressed by your ability to find completely irrelevant information, as this pertains to making blanks for hydroforming. Further, the press-formed blank is made of softer material, and welded by a different process, than DOM tubing. Which starts as roll-formed, welded tubing - the weld seam tends to be homogenized by cold - working the material as it is redrawn - so the materia, welding, and forming process is completely different than the "good" sample shown. And we are not interested in the hydroforming properties of tubing, but in it's mechanical properties as part of a weldment. I know a bit about hydroforming - made a bunch of dies for it backalong. In the case of the part shown in the article, a preform - a bent tube - is shut inside a multi-piece die, with a heavy rubber bladder inside. The bladder is filled with extremely high pressure hydraulic fluid, which stretches the preform into every little crevice of the die. In order to do so successfully, the material must be very soft, and have the ability to stretch (elongate) from the size of the preform to the size of the finish part. So the object of the test has little to do with our problem, other than it had a picture of a piece of split tube, which was deformed by internal pressure - completely irrelevant to our issue.
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sdwarf36
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Re: Okemo 2 caged car crashes

Post by sdwarf36 »

I'm so glad that this thread seems to be getting everyone informed on alot of things that people were anxious to choose a side on voting for new rules.

To review: DOM IS NOT A MATERIAL-ITS A MANUFACTURING PROCESS.
ERW IS NOT A MATERIAL-ITS MANUFACTURING PROCESS.
DOM STARTS OUT AS ERW.

I've been wanting a breakdown of rules from tin cans to tube cars for years. Anytime a rally group decides that putting another bar from here to there to keep that 20 ga floor from moving- it might be double redundant at best-to compromising a planned crumple zone at worst -to one of our cars. And since our rules are one size only, thats it.
our rules " must be ignored to accept many of the cars in our current field."


" round tubing...which is fine for cages. But if you are fabricating a chassis where parts of it are going to essentially act as a cage but you need to use square or rectangular structural tube

about the dividing line between chassis and cage on a "tube" frame car. Since a number of good cars are build with a rectangular/square tube chassis onto which round tube is welded for supports and cage elements, and the rectangular is not made in "DOM", simply requiring DOM and/or CDS everywhere is not realistic"

Hurray! I've asked before where my frame ends + cage begins. Easy to tell on a Subbie...
Translating road racing to hillclimbing:
Proper tire selection== nothing hooks up on moss or wet leaves.
Staying on the racing line==anything paved is considered good.
jkale
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Re: Okemo 2 caged car crashes

Post by jkale »

Mopar 151w2 wrote:Mightily impressed by your ability to find completely irrelevant information, as this pertains to making blanks for hydroforming. Further, the press-formed blank is made of softer material, and welded by a different process, than DOM tubing. Which starts as roll-formed, welded tubing - the weld seam tends to be homogenized by cold - working the material as it is redrawn - so the materia, welding, and forming process is completely different than the "good" sample shown. And we are not interested in the hydroforming properties of tubing, but in it's mechanical properties as part of a weldment. I know a bit about hydroforming - made a bunch of dies for it backalong. In the case of the part shown in the article, a preform - a bent tube - is shut inside a multi-piece die, with a heavy rubber bladder inside. The bladder is filled with extremely high pressure hydraulic fluid, which stretches the preform into every little crevice of the die. In order to do so successfully, the material must be very soft, and have the ability to stretch (elongate) from the size of the preform to the size of the finish part. So the object of the test has little to do with our problem, other than it had a picture of a piece of split tube, which was deformed by internal pressure - completely irrelevant to our issue.
It is a good example to show everyone what exactly we are talking about. The failure of the seam on an erw pipe.
-Joey Kale #111
Kale's Custom LLC.
802-448-3790
jkale
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Re: Okemo 2 caged car crashes

Post by jkale »

sdwarf36 wrote:
To review: DOM IS NOT A MATERIAL-ITS A MANUFACTURING PROCESS.
ERW IS NOT A MATERIAL-ITS MANUFACTURING PROCESS.
DOM STARTS OUT AS ERW.
Correct. Drawing the welded-seam pipe over a mandrel normalizes the HAZ(heat affected zone) and relieves the concentrated stresses that are left behind. The HAZ is a weak spot that runs the whole length of the tube.

Creating a rule that defines tube frames vs. unibody cars w/ roll cages should not be that difficult Sherm.
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KevinGale
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Re: Okemo 2 caged car crashes

Post by KevinGale »

jkale wrote:It is a good example to show everyone what exactly we are talking about. The failure of the seam on an erw pipe.

I'd have to dispute that. It's not really a good example. I'm interested in crash failures in a decently constructed roll cage using a good material that happens to be ERW. And even then it would need to be clear that the failure was because of the seam. Hard to find probably, but in a way that is the point. It's not at all clear that this is a danger that makes it worth excluding existing cages.
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