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matters of human endeavor...

Eric

> Date: Wed, 18 Jul 2007 10:44:16 -0400
> From: "Taka Mizutani" <t44tqtro at gmail.com>
> Subject: Re: [s-cars] Woah! pics link
>
> I do recall something about the improvements that ECS made to their brackets
> after the whole cracking thing came to light several months ago.
>
> I do know that ECS will replace existing brackets at no cost to the
> customer, other than shipping, IIRC.
>
> After the whole ECS debacle, there was another debacle about BIRA and debate
> whether or not BIRA's brackets may do the same thing, but I don't think any
> cracking reports have occurred with the BIRA brackets.
>
> I thought the ECS brackets placed the caliper in the same orientation as the
> RS2 brackets. If that's not the case, then using RS2 brackets would
> necessitate a custom hat or the use of A8L one-piece rotors. At least the
> RS2 brackets are forged steel, so the chance of stress cracking is much
> lower.
>
> Taka
>
>
> On 7/18/07, Paul Gailus <gailus at mindspring.com> wrote:
> >
> > While I'm not a metallurgist, I have a suspicion that this failure
> > could've been caused by stress corrosion cracking and/or fatigue cracking
> > along the grain of the aluminum alloy. Hot-rolled plate stock will tend
> > to have some unrecrystallized grain structure in layers that can act as
> > slip planes in a fracture.
> > For example, see the discussion at:
> > http://www.key-to-metals.com/Article114.htm
> >
> > Being in the "salt belt" probably didn't help either, Bill ;-)
> >
> > Some suggested alternatives in the design would be:
> > 1. use an alloy more resistant to stress corrosion cracking, and include
> > ferrous alloys in the selection process
> > 2. counterbore for a steel nut so that the aluminum bracket doesn't have
> > to be threaded and therefore be more susceptible to stress/corrosion.
> > 3. the existing counterbores for bolts to the strut housing could
> > have a larger radius applied with a ball mill to minimize stress
> > raisers.
> >
> > Perhaps the redesigned brackets have some improvements in these or other
> > areas.