Date: Tue, 30 Jun 1998 20:30:16 -0700
Reply-To: "Steven X. Schwenk" <sxs@SCHWENK-LAW.COM>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: "Steven X. Schwenk" <sxs@SCHWENK-LAW.COM>
Subject: Re: Pre-loading Rear Suspension and P ogo-sticks
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Thanks for the tip, Ken. 25 years of setting up suspension on off-road motorcycles has taught
me a couple of things about suspension, though...I'm not just flying by the seat of my pants
here...I know what I am talking about....and I do have books. Even posted one. take a look.
Why is what's in this book any different what I am saying. It isn't.
http://www.concentric.net/~Sxs/preload.shtml
Thanks for the feedback,t hough.
steve
kenstich wrote:
> Steven,
>
> Rainer is exactly correct - as I splained in an earlier message - but for
> grins - giggles and guffaws, consider the following analogy that is exactly
> correct from a mechanism/physics perspective.
>
> You, Steven are on a pogo-stick - remember these things - the sprung stick
> with footweights that you can bounce around on - they also have a lower stop
> that results in spring preload, but preload is of no matter as you will see.
> OBTW - because you have perfect balance, you can stand on this stick virtually forever.
>
> So Steven, you're standing on the stick and suddenly get the urge to do a
> daring feat - you pogo upstairs - yep, upstairs. The bottom of the spring is
> now elevated (so are you - aren't you).
>
> Next. because you are a mechanical dude, you want your pogo to ride higher, so
> you put some washers in the pogo between the spring and the lower spring
> bracket. Do you ride higher when at rest on the pogo - of course you do - the
> spring preload is greater, but that doesn't matter because your constant
> weight compresses the spring to the same length.
>
> Because:
>
> 1) The free length of the spring hasn't changed
>
> 2) The spring constant hasn't changed
>
> 3) Your weight hasn't changed
>
> If you wanted to really get into spring application/design, (do it!) go to a
> college library and get a book on Mechanical/Machine design - go talk to
> someone in a Mechanical Engineering department. A reference that you may find in a college
> library: Marks Standard Handbook for Mechanical Engineers; McGraw Hill - If you draw a
> freebody diagram with the forces and geometry, you can
> fairly precisely calculate the deflections for any load condition. Its not
> rocket science!! (no calculus or differential equations required) And then
> have a beer or two.
>
> Best Regards,
> Ken Stich
>
> BS Mechanical Engineer
> MS Aerospace Systems Engineer
> 80 Vanagon-L
> 85 Prelude Si
> 57 Beetle
> ============================================================================================
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