>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)
|