From: hotrod@dixie.com (The Hotrod List)
Subject: Re: Watts linkage, etc.
Date: Fri, 08 Jan 93 06:19:00 GMT
Organization: Dixie Communications Public Access.  The Mouth of the South.
To: hotrod@dixie.com
Reply-To: hotrod@dixie.com
Posted-Date: Friday, Jan 08 01:18:55
X-Sequence: 3268
X-Gifs-To: met@sunset.cse.nau.edu
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On Jan 7, James W. Swonger wrote:

>  Somebody had asked about Watts linkage sources etc.; I remembered a Car
> Craft issue which gee, whizzed about a '68 Mustang which had a custom 
> rear suspension setup. I brought the article in, FWIW.
> 
>  The Watts setup looks to have a custom mount welded to the butt of the 9"
> Ford rear, around 2 o'clock position and near the rim (about 1" in). The
> arms and the pivot piece have unequal lengths, the arms being adjustable.
> The mounting points to the frame are up on the frame arch over the axle.
> The article intimates that this work was done by Mike Ruth's Pro Chassis Shop
> in Hacienda, CA; however the linkage does not look very hard to do if you're
> any good at welding. If you want to look at the pictures try rounding up the
> September '92 issue. This guy also added a custom torque arm that runs up
> the driveshaft tunnel; a good looking setup all in all.
> 
>  Just out of curiosity, why not a Panhard setup? A bit simpler, and the 
> Watts looks like similar, if not more, weight and complexity. I've seen
> add-yer-own Panhard kits in either the Jeg's or Summit catalog (can't
> remember which) for fairly cheap (although probably overpriced for two
> stampings, some rod ends, a tube steel length and instructions).

The Watts link setup is the best if you are looking for ultimate (99th
percentile) handling, and don't mind the added complexity, weight, and
fiddliness.  A properly designed and symmetrically installed Watts
link will exhibit symmetrical displacement of the instant centers for
body roll in each direction- which will give identical handling
characteristics for turning either direction, which is what you want
for roadracing.

This asymmetrical installation you talk about sounds like it is
intended for a circle track car- the aymmetry in the installation will
result in different behavior for rolls in opposite directions, which
is what you want to control (and in fact encourage) weight jacking on
an oval. But for that application, the panhard probably makes more
sense- it's simpler, lighter, easier to tweek, and oh by the way
asymmetrical by its nature.

If you want the "perfect Watts", you'd set it up with the bellcrank
attached to the chassis, the centerline of the pivot on the centerline
of the car, and equal-length arms attached to the axle such that they
were dead parallel to each other and the axle centerline at static
ride height- then you'd have perfect symmetry, right up until you
added fuel, a driver, a bumpy track, end engine and brake torque
reactions. In short, once you actually try to drive the car, a lot of
the paper advantages that the Watts offers kinda go out the window. At
that point, the difference between the two for anything other than a
top-notch, built-to-the-hilt Trans-Am or GT-1 car would probably be a
wash- so use the friggin' panhard, and don't sweat it.

For the ovals, the panhard can be set up to be _insanely_
asymmetrical, which is just what the doctor ordered. For the
club-level roadracer, the asymmetries can be dialed out well enough by
just making sure that the rod is horizontal at the static ride height,
and going out to run the car. If you're running for fun, make it
simple. If your'e running for money, then feel free to go for the last
2 or 3 percent- since you know your competition certainly will...

Bottom line seems to be- whatever floats your boat. My car's going to
grow a panhard for next season, though.

-skod

--
Scott Griffith, Sun Microsystems Lumpyware
expatriate SCCA New England Region Flagging/Communications worker
(and sometimes driver, of anything that turns both right and left,
and can pass tech...) Return Path : skod@trenco.Eng.Sun.COM

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Posted by: emory!Eng.Sun.COM!Scott.Griffith (Scott Griffith, Sun Microsystems Lumpyware)
Newsgroups: alt.hotrod,wiz.hotrod