Date: Fri, 19 Jun 1998 14:17:35 -0600
Reply-To: Fred Porter <fporter@EYRING.COM>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: Fred Porter <fporter@EYRING.COM>
Organization: EYRING, Corp.
Subject: Re: Pre-loading Rear Springs re Syncro Suspension (long)
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>
> I think I see where theory departs from reality. Your theory assumes that the
> spring length remains identical with and without the spacer, and that all the
> spacer does is increase the height of the van by the distance of the thickness of
> the spacer.
the length of the spring should remain the same w/ and w/o the spacer
unless something else changes, like the weight of the body/frame or
somehow the suspension leverage on the spring, but i doubt that.
>
> I think that the spacer lifts the van some, but I also think it compresses the
> spring a little too. The result is that with the spacer, the spring is slightly
> more compressed ... it is pre-loaded... over what it would be without a spacer ...
> with the same weight in the van, etc.
nope, with a spacer the spring is still being compressed the same amount
due to the weight of the body/frame which hasn't changed. in this case
there isn't really preload...i was wrong yesterday. inserting the
spacer 'opens' the suspension and extends the shock and the spring isn't
compressed any more than w/o the spacer.
> Doesn't it take more pressure to compress the spring the next 1 cm. than it did to
> compress it that first 1 cm. accomplished by inserting the spacer?
yeah. the force exerted by a spring with constant spring rate is F=kx
where k is the spring constant and x is the travel. the more the spring
is compressed the more force is exerted (or stored depending on how you
loook at it) by the spring.
>
> When you compress a spring, the force required to compress the spring is not the
> same all the way to the point where the coils bind,
right, the more it is compressed the harder it gets
is it...even in a progressive
> rate spring? So, if you shorten the spring by compressing it a little, aren't you
this is hard to describe.....
in a progressive spring, if it takes 3lbs to compress it the first inch,
it might take 9lbs for the second inch and 27 lbs for the third
inch--the rate of increase is increasing.
in a linear spring if it takes 3 lbs for the 1st inch itll take 6 lbs
for the second inch and 9lbs for the third inch--the rate of increase
stays the same
> making it a little stiffer since it requires more force to compress it further
no, its not getting 'stiffer' but it is pushing back the same amount you
are pushing it
> than it would have required to compress it the same distance had you started with
> a completely un-loaded spring?
the only way that would be true would be if the spring constant were a
function of travel also k=f(x) so you'd then have something like F=f(x)x
>
> steve
