[s-cars] Woah! pics link

[LL - NY]

Steel can be designed for "infinite life", although such a part is heavier
than if it was not designed for it. There are many factors including shape,
expected stresses, preloads of bolts, stress factors such as bolt holes,
etc. used in designing for such. Stress reliefs include rounding of sharp
surfaces, round rather than shaped holes, etc. Doin these adds
to the cost of parts, due to the added labor to round things, etc. Threads
are stress risers, in general.

There is NO WAY (at least within the engineering education I received, to do
so for aluminum. You can overdesign to a specific no. of cycles, called
"finite life", but never
for infinite. This is the reason that airframes on airplanes are carefully
tracked for #hrs of operation, and parts that appear perfectly fine are
replaced. I have often wondered how
those mfgs of cars with aluminum suspension components (which includes my
Saabaru)
deal with the potential liability, since most cars last varied periods,
undergo much more
varied levels of stress, and cars aren't inspected in the proper method (dye
check or
X-ray analysis) for their alloy suspension components. As far as I know,
this is the only
way to catch minor cracking prior to the stress cracks becoming
catastrophic. This is what we used when I was in the Nuclear Power industry
for ALL sorts of alloys, both Aluminum and steel based. Of course the risk
of failure there was much more critical than the loss of control of one
persons car, so the expenditure was justifiable.

On 7/20/07, QSHIPQ at aol.com <QSHIPQ at aol.com> wrote:
>
>
> Depends on how you make the bracket, and out of what Eric.  I've got a
> couple dozen of the Big Red kits running around right now, that uses a
> huge  block
> of tempered Al billet, and none of them are showing any signs of
> fatigue  (as
> far as I know) or stress cracking.  I don't agree that steel is hard to
> fabricate, you get good tempered aluminum, it eats up cutting bits really
> fast
> (our machinist was swearing).  We didn't use Aluminum for economy (it  was
> way
> more than the steel in price for the billet), Carl and I used that for
> a  weight
> target.  IOW, the total weight of the G60 anchors was ~33lbs IIRC,  the
> weight of our big red kit was 32 and change, including 345rotors.
>
> I just don't see all the fancy cuts in the aluminum on the ECS bracket not
> one of the causes of the problem.  I also wonder if some of this is due
> to  the
> lower deck height of the S caliper vs the Turbo Caliper.  If the
> design  of
> the bracket was to use a fastener for the turbo caliper, and someone used
> an  S
> caliper, the bolt could bottom out.  IIRCII, even if you 'hole  tap it'
> the
> standard metric 12mm Allen isn't threaded far enough up on  the shank to
> not
> cause some problems.
>
> It's been a while since I looked at all this, Carl and I stopped producing
> the kit ~2000.  That said, I just serviced a set of rotors last fall on
> a  10
> yo kit, and the brackets are still crack free.  The rotor hats tend to  be
> a
> problem, but IME, all AL rotor hats with recessed mounting bolts are
> a  problem.
> BTST on a lot of different kits.
>
> My .02
>
> Scott J
>
>
> In a message dated 7/19/2007 10:54:50 P.M. Central Daylight Time,
> gcmschemist at gmail.com writes:
>
> Ah, but  then there's "fatigue limit"
>
> Aluminum doesn't have one.  Steel  does.  IOW, at a certain level of
> bending (stress), you can bend a  steel part forever without fatigue.
> Not so with aluminum.
>
> Steel is  hard to fabricate, while aluminum is frightfully easy.
> Aluminum is often a  very economical choice for parts-making.
>
> Eric
>
>
>
>
>
>
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