Another Wheel Failure
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From: Bay Area, California
Originally Posted by 949Racing,Nov 23 2009, 05:36 PM
For those that might argue that brake heat has the same effect, it doesn't. Brake heat is transient. Powder curing is sustained unfortunately, not too dissimilar to annealing some fabricators will perform on 6061 T-6 to make it easier to form or repair.
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Originally Posted by Voodoo_S2K,Nov 24 2009, 09:57 AM
What about wheels that are subjected to 25 hours of racing? At that point, is the heat sustained?
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From: Bay Area, California
Originally Posted by 949Racing,Nov 24 2009, 10:43 AM
I wonder the same thing. Cars do pit for fuel and fresh tires though. I get different answers depending on which engineer are rep I talk to.
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Originally Posted by Voodoo_S2K,Nov 24 2009, 10:59 AM
True, but do fuel stops take long enough to allow the core of the wheel to cool down? I know of one car that actually when the entire 25 hours without changing tires, they only rotated them.
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From: Pawtucket, RI
Originally Posted by bpaspi,Nov 24 2009, 07:56 AM
For 15 Minutes??
Anyway, as I have already written some posts before: I have proof for my statement. We found that glass-bead blasting was the cause for a failed aluminium structure part that broked only a few cycles after usage. It was so unusual that we performed further investigations and microscopic visual inspections. We found broken glass particles that had penetrated the surface and initiated a crack.
A sub-contractor of the supplier had blasted (which was strictly prohibited) 2 parts out of 150 and both of them failed...
Anyway, as I have already written some posts before: I have proof for my statement. We found that glass-bead blasting was the cause for a failed aluminium structure part that broked only a few cycles after usage. It was so unusual that we performed further investigations and microscopic visual inspections. We found broken glass particles that had penetrated the surface and initiated a crack.
A sub-contractor of the supplier had blasted (which was strictly prohibited) 2 parts out of 150 and both of them failed...
My point is that it absolutely *is* possible to degrade forged aluminum wheel strength properties by exposure to temperatures above 350F.
Note that I'm not saying that powdercoating wheels is *necessarily* going to reduce properties, only that it CAN, if not done in a manner that ensures the material is not overaged in the process.
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So, moral of the thread is:
PC'ing wheels can cause their failure. However, PC'ing wheels is not necessarily the cause of failure. Sometimes it's because of poor wheel prep prior to the PC. Not all PC needs 400* to cure.
If you decide to PC your wheels, make sure the PC'er uses a low cure temp.
/end thread.
PC'ing wheels can cause their failure. However, PC'ing wheels is not necessarily the cause of failure. Sometimes it's because of poor wheel prep prior to the PC. Not all PC needs 400* to cure.
If you decide to PC your wheels, make sure the PC'er uses a low cure temp.
/end thread.
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Originally Posted by 949Racing,Nov 23 2009, 05:36 PM
There are special low temp powders that can be cured at temps below 150°. Your typical powder coater does not use these powders. The common used powders curing closer to 300° most definitely have an adverse effect on T-4, T-6 heat treated aluminum A356.0 and 6061 alloys used in road wheels whether they are gravity cast, low pressure cast, flow formed, billet or net forged. The stronger the base design, the less likely it is to fail when weakened by improper PC.
Do you know if the AP2 wheels are made of the compounds you mention?
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Originally Posted by RSXLNT,Nov 24 2009, 10:30 PM
Great, I've had my stock AP2 wheels powder coated because of brake dust stains.
Do you know if the AP2 wheels are made of the compounds you mention?
Do you know if the AP2 wheels are made of the compounds you mention?
