[ST] FW: Suspension upgrade (was: Sprint ABS)

["Emile Nossin" <Emile@xxxxxxxxxx>]

I think this was also meant for the group (interesting enough anyway), but was to me directly
because somehow my reply went to both Matthew and the group (so the re-reply went to me).
 
-----Original Message-----
From: Matthew Heyer [mailto:matthewheyer@xxxxxxxxx] 
Sent: Wednesday, February 15, 2006 03:11
To: Emile Nossin
Subject: Re: [ST] Suspension upgrade (was: Sprint ABS)


Yes in some sense the change in spring rate on its own provides a retarding / impeding effect on the compression.  But, how
compressed the spring is determines how much.  If the progressive spring is not compressed much, it won't impede much.  It will
impede more the more it is compressed.  So the spring acts like a stiffer spring when it is compressed more, and acts like a softer
spring when compressed less. But again, not the same as damping.  With damping, the effect is through the entire range.  So you can
damp when you are cruising (least compression), hard on the brakes (most front compression), hard under acceleration (most rear
compression), or hard cornering (some compression on both ends).  A progressive spring works on the assumption that you would want a
stiffer spring under more agressive circumstances (which is generally the case).  
 
Use this to picture it:
 
With damping you can have a soft, supple (relative) spring for overall suspension travel, but still not have the suspension compress
quickly under something hard (braking, cornering, accelerating).  For example, think of having a blow-up raft (or blow-up g/f,
whichever your pleasure...lol).  When just rolling around on the raft, it is soft and supple all around.  If you are trying to
deflate the raft to store away you can jump on it, and it will seem harder.  While it is actually soft and supple, it will feel a
bit harder at first, but will eventually compress, and does so at a slow rate.  That's just like damping.
 
As for the leaf springs, that is correct.  The springs are a certain rate; but with the friction between the leaves, that friction
will slow down the movement, no matter where in the range as the friction is always there.  That is exactly damping - although a
fairly nominal amount in most leaf spring applications.
 
 
Matt Heyer

----- Original Message ----
From: Emile Nossin <Emile@xxxxxxxxxx>
To: ST@xxxxxxxxxxxxxx; Matthew Heyer <matthewheyer@xxxxxxxxx>
Sent: Tuesday, February 14, 2006 8:48:20 PM
Subject: RE: [ST] Suspension upgrade (was: Sprint ABS)


>From: Matthew Heyer
>Progressively wound springs do not act with damping effect. Where the
>similarity might arise is that when riding hard. A progressively wound
>spring just changes the actual spring rate as it is compressed. Softer
>initially, and then stiffer the more the spring is compressed. Damping
>is completely different in that it works to impede either the compression
>or rebound of the spring.

Well, I know that they are different things. But does the change in spring
rate on its own not provide a retarding / impeding effect on the compression,
just like an oil orifice does for a constant wound spring? The higher the
force on the spring (speed of approaching / departing terrain), the higher
the resistance of the spring or oil density. Right? I mean the oil determines
with what speed the compression changes, but a change in spring rate also
changes that speed in a similar fasion... doesn't it? 

A similar thing I read here about multi-leaf springs, which also progressively
change spring rate with compression:
http://transport.tuthill.com/Reyco_Granning/reyco_granning-susp-basics.htm
"The multi-leaf spring has a rudimentary ability to increase damping with load,
due to an increase in inter-leaf friction."

Emile
www.piloot.com <http://www.piloot.com/> 
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