Kai, I'd just like to offer a couple of observations that may be confusing
the issue :
> the bearing manufacturer -- NTN of Canada --specifically says not
> to preload
> the bearing...
You need to be very careful about terms. "Preload" means something far
different to a bearing engineer than what we're talking about here.
> that is the most reliable source I've heard, and I've had
> conversations with Joachim Gunst in his native German and he has yet to
> provide me with convincing evidence of why the bearing should be
> preloaded.
Probably the best reason is because we're trying to install it on a TR6,
which always used a preloaded (as you call it) bearing. Converting to a
non-loaded design (where the bearing does not always turn) is certainly an
option, in fact that's the way the earlier Triumphs worked. BUT, it also
implies having to periodically adjust the clutch slave linkage.
The bearing itself doesn't "care" whether it runs all the time or not. As
I've already written you off-list, TOB failure is almost never caused by the
bearing itself wearing out (ie reaching it's fatigue life). Even a poor
quality ball bearing will run essentially forever with just the "preload"
we're talking about. Thus, NTN cannot answer your question about whether
the bearing should have the spring to always load it into the pressure plate
... it just doesn't matter to the bearing life.
> I do agree though, that without the spring and strap the bearing
> squeals...
> obviously that doesn't matter who you buy the bearing from.
The squealing is because the lubricant inside the bearing is thicker. The
thicker lubricant means it takes slightly more force to turn the bearing,
and the factory spring does not apply enough force for friction against the
pressure plate to turn the bearing. Thus, the face of the bearing rubs
against the fingers of the clutch plate, and squeals. This is why a
stronger spring stops the squeal. It also means that identical-appearing
bearings may, in fact, work differently in this regard due to different
lubricant or even less lubricant.
> However, to give Gunst the benefit of the doubt, I am going to remove the
> brass sleeve from the bearing tomorrow, get the part number from the inner
> race and contact NTN myself. Time to put this issue to rest.
As I said, NTN cannot answer your question. Ask them instead for expected
lifetime vs load curves, and look up what the bearing's expected lifetime
is, under the load applied by the spring. If it's not measured in tens of
years, I'll be very surprised. (Note that the average "life" operation time
of the car is only measured in months.)
> I've always thought that if you went through such trouble to come
> up with a
> very nice bronze bearing sleeve and a high quality bearing, why did the
> spring setup look so poorly thought out?
Obviously an afterthought.
> another one is
> from a Dodge pickup and is the same exact size as the stock TR6
> RHP bearing,
> but is much more rugged in construction (that bearing in
> particular requires
> no preload). The Dodge bearing is $22 which is a good bit
> cheaper than
> any bearings out now.
Any chance you'd be willing to share a part number or application with us ?
I was just getting ready to order a TOB for my Stag ...
Randall
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