RML:
Given that the crack originates (seemingly) on the lower side of the
casting, and given that it originates between the hub and the shock, a
hypothesis is that it is cracking because;
The spring is too strong;
or
rebound damping is excessive;
or
both.
The crack originates on the bottom of the arm, implying that there is
a bending force being applied to the arm near the crack. The bending force is
such that the lower edge of the arm is in tension, and the upper edge is in
compression. The only time that will happen is during rebound. Under those
conditions the spring is trying to force the arm down, while the shock is
resisting with a net result of a bending force on the arm.
Unfortunately, the damping must be matched to the spring rate for
optimum handling. If there is too much damping, then the answer may be as
simple as going to standard shocks. If it is correctly matched to the spring
rate, then you must reduce both the spring rate and the rebound damping to
maintain control of the suspension, at the expense of increased body roll when
cornering.
If that is not acceptable, then you will need to MIG weld some
additional aluminum to the bottom edge to increase it's strength - and inspect
regularly for cracks.
Just some random thoughts.
Vance
Vance Navarrette
Cogito Ergo Zoom
I think, therefore I go fast
-----Original Message-----
From: Robert Lang [mailto:lang@isis.mit.edu]
Sent: Wednesday, August 13, 2008 12:02 PM
To: Navarrette, Vance
Cc: 6pack@autox.team.net
Subject: Re: [6pack] Race Car Quandry
On Wed, 13 Aug 2008, Robert Lang wrote:
> It's not very radical... most of the lowering comes from tire profile
> (23x9x15 slix)!
Note - these tires are insanely sticky. I pick up 1/2 pound of gravel
driving around the paddock on each tire when they are warm/hot.
So we could be just seeing a combo of very high CoF and higher than usual
bending moments... it's possible the ding on the driver's side was a piece
of the casting breaking away, but I'm pretty sure that's not the case.
>> Cheers,
>>
>> Vance
regards,
rml
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Bob Lang NER/SCCA | This space for rent
Solo Chair 2008 TR6 40 F Prepared | Triumph!
Voice:781-438-2568 FAX: 617-258-9535 | Cell: 339-927-4489
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