Re: [T3] Caster and lowering - PART 2

[Russell Wolfe <russella@netins.net>]

As the Bentley book shows for the rear, VW references everything to the top of
the tunnel, directly behind the emergency brake. When I get the VW gage (he
forgot it today) that my Bentley book shows, I will measure the angle there,
and the angle of the axle beam to the frame. This will get us a reference. My
'71 has not been wrecked or altered, since i have known it since it was new.
Also, I will measure the '69 SqBk, and get a reference there too. It will
actually be the easiest, since it has the front fenders off, and the tire well
out.

Russ Wolfe



On Tue, 06 Jun 2000, JaransonT3@aol.com wrote:
> Well, I am more confused then before....here is what I have found out so far.
> 
> I very carefully measured the angle of the front beam mount on my Fasty and 
> compensated for the pan not being exactly level.  I get a beam mounting 
> caster of 9.1 degrees.  I then measured the rubber bushings.  The upper 
> bushing is uniform thickness = 0.45 inches.  The lower is assymmetric.  The 
> rear thickness is 0.55 inches.  The front thickness is 0.35 inches.  Figuring 
> this in adds another 0.9 degrees to the caster of the beam for a total of a 
> nice round 10 degrees.  Sounds like something VW would pick, right?
> 
> Well, this is where the confusion comes in.  Bentley states that the caster 
> at the wheel is 4 degrees.  I built a full scale, 2-D mock-up (pictures on my 
> site soon)  of the front suspension with teh beam at 10 degrees.  The best 
> caster angle that the suspension has as it swings through it travel with the 
> dimensions I previously measured on my car is -0.5 degrees.  Yes NEGATIVE.  
> In order to get the 4 degrees POSITIVE at the wheel the Bentley mentions the 
> front beam angle wouldd need to be 16 degrees!!!
> 
> Now I am sure of two things  VW did not design in NEGATIVE caster and I did 
> not miss the front beam angle measurement by more than 50%.  I am not sure 
> what is going on, yet.  My next step is to remeasure everything and to put it 
> all in a spreadsheet so that I can do a mini sensitivity analysis to see if 
> some combination of small measurements errors could account for my results.
> 
> BTW, the model does show the caster change that I reported last time.  I took 
> several pictures at different travel amounts.  I am going to try to provide 
> an animation of the suspension on my site.
> 
> The plot thickens.  Stay tuned.
> 
> Later,
> John Jaranson
> '71 FI Auto Fasty
> http:/hometown.aol.com/jaransonT3
> 
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