I'm still amazed that the shaft/U-joint is effectively a lower suspension
piece as well. Should have been a half size larger with this in mind.
Peter S
----- Original Message -----
From: Barry Schwartz <bschwart@pacbell.net>
To: <ebk@buffnet.net>
Cc: <spitfires@autox.team.net>
Sent: Wednesday, September 08, 1999 7:05 AM
Subject: Shimming your axle u-joint
>
> >Hi Barry!
> > I'm catching-up on my TR Digest Reading.
> >Question: do you mean that the "shim" goes between the cap & the circle
> >clip? OR Does the "shim" go under the cap? Also- Do you take the shim &
> >have to install it [same thickness shim] on all four ends inorder to the
> >unit "centered" in the centered of rotating axis?
> ***********************************
> It would go between the circlip and the cap. As far as centering, it is
> such a small amount (usually less than .010) that one needn't worry about
> centering it exactly. If you can use an equal shim under each cap all the
> better, but not absolutely necessary. One lister just mentioned that
> Spicer still sells different thickness circlips. It is more important to
> eliminate the slop. After all, if the joint is indeed 'slapping' back and
> forth in the bore then the centerline of the joint itself is changing also
> - Unfortunately, the way this u-joint is used is really a poor design for
> such a joint as whenever you have a "Hooke's joint" of this type you
should
> always have another joint at the other end, and the output and input shaft
> centerlines should remain parallel not unlike your drive shaft (for
> constant, smooth rotation of the input and output shafts). This
> arraignment cancels out the fluctuations inherent in a joint of this kind,
> and the rotation of the output shaft will be consistent with the input
> shaft. With only one joint, unless the input and output centerlines are
> parallel (in this case, concentric) there is actually a fluctuation in the
> output shaft. And the fluctuation increases in proportion to the angle of
> the output shaft (axle) relative to the input (diff inner axle). Given
> that the angle of the axles is less than 20-25 degrees in normal driving,
> it's not a really big problem, but the condition DOES exist. That is to
> say, that whenever your outer axle is not in a straight line with the
inner
> axle of the diff, then the wheel is actually fluctuating in its rotation
> (speeds up slows down) for every revolution. Its small enough that the
> flexibility in the rubber of tire probably absorbs it but it places a
quite
> a cyclical load on the u-joint itself. On top of that ALL of the side
> loads imposed on the tire are handled by this same u-joint as well as
> acceleration and braking. As you can see this poor little joint has QUITE
> a formidable job, and quite frankly does an admirable job of it.
> Fortunately, most of the time, the axle centerlines and the output shaft
> centerlines, are for all intents and purposes, parallel-
> Kinda makes you wonder why the larger TR6 sized u-joint wasn't used.
> It would have fit, and would have only required a very slightly larger
diff
> inner axle flange (I know, I've made a pair) and the yoke on the outer
axle
> would have had to be made slightly larger. The whole setup fits within
the
> confines of the Spitfire frame and body. And the change could have been
> made at the time they were enlarged for the MK4 model line as the flanges
> were changed at that time (although the u-joint itself is the same). Most
> if not all of the parts were in the "parts bins" so to speak. Probably
> cost, as many times that is the determining factor, is why it wasn't done.
> Sorry there, I got a little carried away with the explanation :-)
>
>
> Barry Schwartz (San Diego) bschwart@pacbell.net
>
> 72 PI, V6 Spitfire (daily driver)
> 70 GT6+ (when I don't drive the Spit)
> 70 Spitfire (long term project)
>
|