2015 Rules Submission and Discussion

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walterclark
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Re: 2015 Rules Submission and Discussion

Post by walterclark »

I think its worth a good discussion at the rules meeting as to how we grandfather existing cages and ones that are built to other acceptable standards, and what from the past just isnt going to fly.

I think John took a good stab at doing that in 7 and 8.

If it isnt already, we need to be sure it is clear that materials we accepted in the past are not to be used for construction from this point forward. John's mention of things like A500 Class A and A513 type 1 are an acknowledgement that such materials are below our new construction requirements but where they have been previously accepted they will continue to be for existing cars. That statement does specifically not limit acceptability of existing cages using these materials to those on cars that have previously hillclimbed with us and been accepted as suitable cages, only that they were built before this rule goes into effect. We may want to further limit this...or not. It is very clear that cages built from materials below that listed in 7 as "marginal" are no longer going to be accepted regardless of whether they previously raced with us or not.

Schedule 40 pipe is not considered structural tubing at all but I am sure it has been used for roll cages. It is about 50% thicker (in the 1.5" nominal size) and with larger OD than our requirement for 1.75" tubing, but soft... being below the proposed minimum strength at about the same strength numbers as ASTM 1008-1010. So the added thickness and diameter compensates some for the softer metal. Based on that, I think it it does fall into the same general category John labeled "marginal" and "accepted principally for existing" cages. Schedule 10 on the other hand, possesses the same low tensile and yield strength numbers 40, but is just about the same thickness as we require of suitable tubing. So 10 really should be unacceptable.
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Kiwi
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Re: 2015 Rules Submission and Discussion

Post by Kiwi »

We probably should have started a separate "Roll cage discussion" thread, the title of this thread doesn't tell people we are discussing cages...

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KevinGale
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Re: 2015 Rules Submission and Discussion

Post by KevinGale »

Mopar 151 (J.Reed), posting from Kevin's computer:
Part2, short version: A very particular driver, Rusty Wallace, started driving for Roger Penske. Penske's most notable driver, Mark Donahue, was a degreed engineer, and Penske's shops are known tobe some of the best fabricators in the sport. Penske South cars were built with the best available tubing (likely 1026 DOM), and 100% tig welded. Then Rusty(c.2002) was involved in "the big one" that occurs during every race at 2.66 mi., 33deg. Talladega, AL. There were tubing failures - specifics are hard to come by. Rusty's agent/business partner, Don Miller, became an advocate for better tubing, and few people in the sport are better connected. Steel mills, and distributors, will make you nearly anything, if you buy enough of it - these are generally referred to as heats or mill runs. Some of the initial tries (Roger bought a LOT of tubing) were done with 1018 seamless tubing, with the OD machined (turned, by a process known as skiving) to produce a consistent wall thickness. Due to several developments in the steel business, like Thyssen/Krupp building a new mill in the Birmingham area (aka "South Pittsburgh") and a new distributor willing to do whatever it took for the motor-sports market (Stock Car Steel), the "state of the art" has changed. 1018 Cold Drawn Seamless, in ground finish for enhanced weld-ability, is the new "best stuff there is". Virtually every "name" chassis builder in oval track is in love with the stuff now, and the price from SCS is little more than DOM. - Less, if you'll take import (Id think twice, particularly about Far Eastern sources). The big reason, IMHO, is better weld-ability, and much better % of Elongation.
Again, anyone thinking hard about materials should read the excellent article by Jon Asher, as republished on Bill Miller Engineering's website. As far as my "playing metallurgist" - I used to work for one. All he ever told me to do was look it up - so I did. The specifications cited in the change proposal are based on the specifications cited by the steel distributors used for specialty tubing, and past practices throughout motorsport.
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