Item Subject: cc:Mail Text
     James, et. al.

     1.  Are you the fellow who had a few SA grilles avec lights for sale
     before your escape to Aspen?  My memory fails me on the supplier.

     2.  On the matter of spring rates.  The unsprung weight includes those
     things not really firmly attached to the chassis.  Wheels, lug nuts,
     tires, some percentage of the driveshafts, swing arms, outer cvs and
     so on.  The sinking crow has considerably more sprung weight than the
     standard and for a similar ride height will require a "stronger"
     spring.  If my fizzix doesn't fail me now, it's F=K*x  Where F is the
     resisting force, K is the "spring constant" and x is the deflection of
     the spring (in our case, compression).  Now for F=K(x)*x or a
     progressively wound spring the spring constant is a function of the
     compression distance.

     3.  In practice to support a 1000KG weight, the spring must have an F
     of 1000KG.  How much x is given up depends on K or K(x).  With a
     spring constant of 1000KG the compression is 1M (MKS)  With a K of
     10000KG the compression is 0.1M or 100cm. With a K of 100000KG the
     compression is 10cm.  More like what the reality of Westie springs.

     4.  All well and good for static operation and measuring ride height
     when stopped.  For dynamic operation such as actually driving the
     vehicle,  the F required depends on the motion of the sprung weight as
     dictated by acceleration due to high speed slalom events,  berm
     gelandespringen, curbs, dead animals or gravity warps.  Once again
     F=MA, where M is the percentage of the mass of your conveyance
     supported by each spring, A is the acceleration you applied by
     turning, hitting a bump or braking severely or just bouncing along on
     those oversize tires.  It's the same F as in 3, above.  The more A you
     have the more F you'll need to avoid the dreaded bottoming out. The
     more F you need the more K you need.

     5.  Bottoming out is the condition where the spring no longer
     compresses as the coils touch and the spring becomes a fixed cylinder
     which transmits any additional A directly to the frame and spring
     mounts resulting in higher elective dental restoration bills for the
     unfortunate occupants and structure damage to the beloved conveyance.
     So don't do that.  Put in a resisting thingy that resists as a
     function of A.  Like a shock absorber.  The gnomes at VW did that for
     us thank goodness.  We just have to make it right for our use and
     replace the deteriorating parts now and then.

     6.  The second function of the acceleration damper is killing off
     harmonic transients or keeping the wheels on the ground so to speak as
     the M dangles merrily on the spring.  Too much damping factor or too
     stiff shocks and you approach the fixed cylinder state.  Too little
     and you have the bottoming and boinging effect.  All dependent on K
     and M and damping.  Change M significantly and you are out of the
     ideal operating range of the damped spring system.  Perhaps not at the
     gross limits but not ideal.

     7.  The unsprung weight has an effect but not nearly what one would
     think.  It's effect has to do with transmitting motion to the sprung
     weight via A.  If the balance is such that the unsprung weight is very
     small compared to the sprung weight then the only effect has to do
     with keeping the wheels in contact with the road at some relatively
     constant ground pressure.  The damper helps here.  The spring pushes
     down from the dynamic inertia of the sprung weight to try to keep the
     wheel on the ground when the sprung weight goes up.

     Now there's more of course with a compound spring connected masses
     system (the tires have their own K and M and damping factor) between
     the ground force and the sprung mass.  The ideal answer is " probably,
     for a limited range of motion, mass, forces etc.  I can make you a
     compensator device that will guarrantee an absolute smooth ride and
     ride height using parts from a Citroen DS-19/21, but you wouldn't like
     the maintenance cost".  Or sense all that stuff in real time and
     adjust the damping and resisting force in real time using a computed
     ride map of preset parameters that are selected based on the last
     several samples and applied for the next sample time group.

     Simple, eh?
     Now back to our regularly scheduled programming...

     al NOT ON THE SAFARI due to motor problems and gnashing and snarling
     therewith.