Re: Subject: Re: HD or sport?

[Mike Klein <klein@xxxxxxxxxxxxx>]

Thanks for the note, Chris.  I saw from another poster that the gas in the
shock contributes a small additional spring rate, but it is much weaker than
the suspension, and the added spring rate that is proportional to position is a
relatively small fraction of the shock's force (because of the effect of the
gas reservoir).  You are correct and your point is well put.

On the issue of energy, though, I worked out a derivation for the ideal case. 
I believe it supports your other point as well.

Start with a fundamental definition of energy:

	energy = force * distance

where force = force applied to shock, and distance = amount of shock
compression.

The fundamental definition of a mechanical damping element (an ideal shock --
no gas):

	force = damping * velocity (the definition of a damping component)

or,
	force = damping * distance / time

or (rearranging),

	distance = force * time / damping

>From this equation you can conclude that to compress two shocks of different
damping factors the same distance, you either:

	- compress with the same force but take longer with the
	stiffer shock (this results in the same energy absorbed
	by both shocks), or

	- take the same time to compress, but requiring more force to
	do so with the stiffer shock (this results in more energy absorbed
	by the stiffer shock, and is the reason for stiffer shocks for
	stiffer suspensions)

The latter case is the one you honed in on, and again you are correct.  I was
thinking of the former case, not having worked out the derivation, and see that
the energy absorbed by using the same force fact is not different; it just
takes longer to compress.

Thanks for the enlightenment,

		-Mike
		klein@domain.elided

'98 323 iC, Avus Blue
'87 911 Carrera coupe, Venetian Blue

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