Okemo 2 caged car crashes

jkale
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Re: Okemo 2 caged car crashes

Post by jkale »

KevinGale wrote:
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.
So even though John admits that future built cages should use something stronger than ERW and it is very obvious that the seam is weaker, you still NEED to see a picture to admit that ERW is a bad choice?

Maybe we can suck it up and build a cage structure here at the shop from ERW and see what happens when it gets crushed...
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KevinGale
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Re: Okemo 2 caged car crashes

Post by KevinGale »

jkale wrote:So even though John admits that future built cages should use something stronger than ERW and it is very obvious that the seam is weaker, you still NEED to see a picture to admit that ERW is a bad choice?
Yeah, life is about risk. I certainly wouldn't pick tubing that is ERW for a new cage. I probably wouldn't even pick DOM since CDS is better still assuming we are taking about the same material in all the cases. But that mostly about the fact that the cost difference isn't that significant and I'd be worried about where the cage would be accepted.

But if I already had a well built cage with good materials that happened to be ERW would I throw it out? I think not. I haven't seen anything that says the added risk is significant. People don't crush their old street cars and buy a new one when the new model gets a higher crash rating. Sure the newer car is slightly safer but real world it's not that big a difference for the costs involved.
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sdwarf36
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Re: Okemo 2 caged car crashes

Post by sdwarf36 »

My complaint isn't which material is better for a new construction- but as this all started at the rules meeting was any car that never ran with us before could be told no if it was made of ERW
And the reasoning behind it was because of " I heard of cages failing ". I just want to see an example.
My car was 1st built in 1998- there was plenty of ERW in it .( I cut it apart and did a new main cage in 2004- with DOM). But while its unclear what part of my cage is a cage and what is the frame, the line is fuzzy. Are the bars going forward from my front hoop forming the nose of my car frame or cage?
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walterclark
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Re: Okemo 2 caged car crashes

Post by walterclark »

KevinGale wrote: It's not at all clear that this is a danger that makes it worth excluding existing cages.
Couple of points.

I dont think anyone intends to exclude cages that met our previous rules regarding materials, or for that matter cages that met rules of other sanctioning bodies, provided they were not less that what we have required in the past. Defining what is meant by "existing" may need some work. I am pretty sure it would include any cage that passed our tech and raced with us in the recent past.

I think this rule change should be aimed at giving a fabricator information needed to pick acceptable materials for new construction. We are not in a position at tech (and I dont think we want to try to get there either) to determine if the material meets our requirements beyond some easily measured dimensions. We are in a somewhat better position regarding observing weld quality, but not much. And we can determine if the cage has acceptable structural attributes because they too can be observed. So at the end of the day if someone says their cage is A513 Type 5 1026 we will have to accept their word unless something obvious is apparent that brings that into dispute such as a magnet will not stick to it, the diameter is not one that is available in that material (happened at a rally) or there are pipe threads visible at the end of the main hoop (again, actually happened at a rally).
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Re: Okemo 2 caged car crashes

Post by Super1303 »

walterclark wrote: or there are pipe threads visible at the end of the main hoop (again, actually happened at a rally).
LOL!! Awesome!! I was going to ask about that being a wise ass but that's even better. I bet someone was embarrassed.. :lol:
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jkale
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Re: Okemo 2 caged car crashes

Post by jkale »

Walter, What you just said ^^^ is exactly my goal in this discussion.. I am hoping the end result will bring about an agreement on wording that will help guide a semi-informed fabricator as to what material to use if they are building their first race car.

Just out of curiosity, who showed up at a rally with black pipe as a rollcage?
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walterclark
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Re: Okemo 2 caged car crashes

Post by walterclark »

jkale wrote:Just out of curiosity, who showed up at a rally with black pipe as a rollcage?
I will never tell. Don might.
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sdwarf36
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Re: Okemo 2 caged car crashes

Post by sdwarf36 »

That sounds great Walter-a solid guideline to set someone in the right direction will do the most good in the long run.
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.
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Re: Okemo 2 caged car crashes

Post by Mopar 151w2 »

At the time, this was considered about the worst wreck you could live through. I see no major structural failure.


Or you can watch all this action - where are all the rollcage failures that we are assured are occuring? Any I ever heard of (Eddie Flemke at Malta, Don Diffendorf at Riverside, Cloutier Bros @ The Pines) had to do with using electrical conduit as door bars to save weight.



I would concur that we need to define the critical tubes in the cage, and spell out their requirements quite thoroughly and reasonably I'll look into a portable hardness tester (B scale), and then come up with an allowable range on actual tubing sample.
The stuff the scares most of us is either gooey soft (EMT, 1005 exhaust, hydraulic tubing) or has hard spots near the welds (improper 4130, bad DOM {there is a chassis made with this in Art Heath's yard, not for sale - tube failed in middle of span}, or work-hardened stainless.
I think we can come up with a reasonable definition of critical structure outside the main cage, for tube cars - and what we will accept for side bars, bumpers, etc as energy absorbing structures.
Further, I think that it is incumbent on the proponents of unibody cars to advance a standard of acceptibility for caging and reinforcing them. We HAVE repeatedly seen failures in these areas, and I'm beginning to regard this entire debacle as a smokescreen,
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KevinGale
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Re: Okemo 2 caged car crashes

Post by KevinGale »

walterclark wrote:
...I dont think anyone intends to exclude cages that met our previous rules regarding materials, or for that matter cages that met rules of other sanctioning bodies, provided they were not less that what we have required in the past. ...

I think this rule change should be aimed at giving a fabricator information needed to pick acceptable materials for new construction. ...
Makes sense to me. I don't want exclude good cages and if we need to make a recommendation (which we probably do) then we need to steer people towards good stuff for lots of reasons.
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