On Wed, 1 Jul 1998, David Bayer wrote:
> >| Now on to pre-loading.  If I have a spring, and I
> >| stick a piece of threaded rod through it and assemble together
> >| some washers and nuts and such and clamp the spring down
> >| an inch shorter than it normally is, I've pre-loaded it.
> >|
> >| Suppose I have a non-linear spring, like is on the motorcycle,
> >| which at its full extension requires 150 lbs to compress it
> >| one inch.  Now I clamp it down an inch.  A load of 150 lbs.
> >| placed on this pre-loaded non-linear spring will now compress
> >| it LESS than an additional inch.
>
>         In this case, you have to put 150lbs. on it to over come the
> restraining force exterted by the threaded rod. As you apply the 150lbs
> to overcome the threaded rod, you will compress the spring an infintesimal
> amount. The reason being that the rod is a fixed barrier and
> will not apply additional force once the weight is moves the spring off the
> rod. Even in a nonlinear spring, when the "preload" is caused by a fixed
> barrier, as soon as the fixed barrier is removed from the forces acting on
> the spring, that fixed barrier can have no effect on the spring.

Oooooh, I see!  So pre-loading _does_ have an effect, be the spring
linear or non-linear.  Makes perfect sense.

Thanks for the hint, now to go sit down and think about it for a
bit ;)  And also to read the rest of your post...

        Gary