Vanagon EuroVan
Previous messageNext messagePrevious in topicNext in topicPrevious by same authorNext by same authorPrevious page (July 1998, week 1)Back to main VANAGON pageJoin or leave VANAGON (or change settings)ReplyPost a new messageSearchProportional fontNon-proportional font
Date:         Wed, 1 Jul 1998 13:21:02 -0600
Reply-To:     Gary Shea <shea@GTSDESIGN.COM>
Sender:       Vanagon Mailing List <Vanagon@vanagon.com>
From:         Gary Shea <shea@GTSDESIGN.COM>
Subject:      Re: spacers and sproings
Comments: To: "Steven X. Schwenk" <sxs@SCHWENK-LAW.COM>
Comments: cc: Vanagon@VANAGON.COM
In-Reply-To:  <359A6AAA.AD31042E@Schwenk-Law.com>
Content-Type: TEXT/PLAIN; charset=US-ASCII

I can't believe I'm this stupid, but I'd like to stick my .02" of spring travel in here. I've been listening to some of this thread and it seems to me that if we accept Steve's observations about bikes, then we have to accept that the bikes do not have the same kind of springs that we compressed in Physics 101.

That seems entirely possible.

A 'normal' spring takes some amount X of force to compress it one inch. If the spring is already compressed 1 inch or 4 inches, an additional force of X applied to the spring will compress it exactly one more inch... assuming you aren't about to compress the spring flat or break it or something.

To put it a bit more simply, if you have a normal spring that compresses one inch when you place 150 lbs on it, then if you put another 150 lbs on it, it will compress another inch. I'm going to call these 'linear' springs.

The spring that Steve is talking about doesn't seem to work this way, and it has been pointed out in this thread that such springs do in fact exist. Apparently they are found on off-road motorcycles. Call these fancy springs 'non-linear' springs.

The next question is: what kind of spring does the Vanagon have? A 'normal' spring, or a non-linear spring? Got me. I'd certainly expect a 'normal' spring, but I'm not in a position to know for sure.

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.

Now suppose I have a linear spring, the common everyday Physics 101 kind of spring, and I compress the spring down 1 inch, and then apply that 150 lbs, and the spring compresses 1 more inch. Now I tighten up the nuts and compress the spring down 2 inches. Applying the 150 lbs will once again compress the spring 1 more inch! So pre-loading is meaningless with a linear spring. Make sense? I've at least got myself convinced so far.

So the two questions that I see as being relevant here are: is the Vanagon spring non-linear, and if it IS non-linear, is addition of a spacer truly pre-loading, i.e., forcing the spring into additional compression before any load is placed on it? If both of those questons are answered in the affirmative, then we are seeing useful results from pre-loading the springs.

If the answers aren't yes and yes, then we're seeing another effect and need to work out a better explanation.

I'm hoping that my re-explanation of springs will help someone, anyone figure out what's going on. If not, well, at least it wasn't written in anger or with the intention of making anyone else look stupid ;)

Gary

----------------------------------------------------------------- Gary Shea shea@xmission.com Salt Lake City http://www.xmission.com/~shea


Back to: Top of message | Previous page | Main VANAGON page

Please note - During the past 17 years of operation, several gigabytes of Vanagon mail messages have been archived. Searching the entire collection will take up to five minutes to complete. Please be patient!


Return to the archives @ gerry.vanagon.com


The vanagon mailing list archives are copyright (c) 1994-2011, and may not be reproduced without the express written permission of the list administrators. Posting messages to this mailing list grants a license to the mailing list administrators to reproduce the message in a compilation, either printed or electronic. All compilations will be not-for-profit, with any excess proceeds going to the Vanagon mailing list.

Any profits from list compilations go exclusively towards the management and operation of the Vanagon mailing list and vanagon mailing list web site.