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RE: Rear Shock Conversion Frame Problems Part 1

To: "Foster, Stan" <stan.foster@hp.com>
Subject: RE: Rear Shock Conversion Frame Problems Part 1
From: "Robert M. Lang" <lang@isis.mit.edu>
Date: Tue, 6 Feb 2007 10:03:56 -0500 (EST)
On Tue, 6 Feb 2007, Foster, Stan wrote:

> So it seems to me that we can probably ensure that the upper bump stop
> will be engaged before the shock reaches max compression by elevating
> the rubber buffer on the TA a tad. Not much thread to work with here
> but enough I think to verify that the bump engages before the shock
> runs out of travel and we can test it with the spring removed.
 
> The rear shock conversion many of us are using has no droop stop
> however, so are we saying this setup is doomed and full droop can
> occur in nature and eventually we will see failure of the cross member
> where it attaches to the frame as the shock bracket takes a pounding
> each time the shock sees full extension with no droop stop to halt it
> ?

This is the kind of example I am citing. In this case (hopefully) the bump
rubber is incorporated within the shock body. Otherwise, you'll either
break the shock or rip the mount off the frame (or both). There's no
question from a design standpoint that the bump stop needs to be
accomodated...

But if the loewr bump stop is not accounted for, then you have a bad
situation.
 
> Or is this theoretical max droop so rare in normal driving that the
> few times it might happen will not have an adverse affect and we
> should relax and worry about something else?

This is a _bad plan_. Once you remove a part of the designed suspension
_system_, all bets are off. What will happen in the absence of the stop? I
have no idea. But loss of control would be high on the list of possible
outcomes. WHy? Because at more than full droop, the camber and toe change
pretty dramtically. Fortunately for our hapless driver, extreme droop
results in extreme toe-in, so the rear _should_ just follow the front...
but the real world is different the theoretical.

> Stan

regards,
rml
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