Howdy, all.
I've got to apologize for not having followed up with my advertised
comments on C/V joints yet. The thing is, I was kinda planning to go
back and content search a bunch of the Lotus-Cars digests, to dig out
some old messages on the subject, that I know are lurking in there.
But my accustomed (NT based) content search methodology is not
working, since my unix user account has moved to a different server
(and I'm not a very accomplished GREP user...)
Anyway, I'll make a few comments now, because I'll be be gone again
on travel next week, and I should try to get *something* posted
before then...
Rotoflexes seem to be pretty reliable, if changed on a reasonable
maintenance schedule. "Reasonable" for the sprint donuts probably
means every three years oe so, although some have used longer
intervals with good success...
In my personal view, the principal arguments *against* donuts are:
1) Changing them periodically (this appears particularly miserable
on the GT6, although I hated doing the job on my '67 Elan, too)
2) Donuts don't work at all well, in combination with a Hewland
limited slip differential.
Chris K. wrote about 240Z half shafts, as being the "contemporary"
racers solution for the Spit/GT6. Yeah, U-jointed shafts were used a
lot on Elans too, although I think 240Z shafts would have been too
long to work. (I had a pair once, and gave up on trying to adapt
them...) Other U-jointed solutions were typically fabricated from
parts, and they were used on many Elan race cars in the States.
The 26R came from the factory with splined, U-jointed half shafts.
One of the comments Fred McClung made, that I found very interesting,
was that the reputation the splined U-jointed shafts had for binding
and causing dramatic handling problems, was largely undeserved...
apparently, that scenario mainly comes about when the splines are very
worn out.
For modern race cars, no one would use U-jointed shafts unless they
are forced to (or, if they somehow *perceive* that they are forced to)
by the rules of their particular venue. The C/V jointed shafts are
just a really superb deal, in comparison. Most racing rules (if they
make any kind of distinction) usually describe that the joints must
be of the same general type... and guess what... the Rotoflexes are,
in fact, of the constant velocity type, unlike the Hookes jointed
widgets which undergo significant instantaneous velocity changes when
operating at high angularity.
People usually use VW C/V joints on Elans and +2s. There are a
couple different species of VW joints that have been used, and my
recollection of details about the different options is very poor now.
Maybe others on chapman-era can help some more (Keith?) or Chris you
could contact DBE, and they can probably tell you quite a bit more
about it.
Ted Rogers has his own design (he has put considerable effort into
it, and he has the expertise to do it properly) which I believe is
also intended to allow full travel, but uses considerably beefier
Porsche C/V joints. I'm not sure if such a hefty joint is really
necessary, though...
There is much, much more that ought to be said on this topic, but
for now, a key discussion a while back on Lotus-Cars was regarding
whether Elan C/V joint axle conversions typically allow full
suspension travel. Rod Bean posted a comment about limit straps
(possibly) being required on Elan C/V axle conversions.
I think that may very well have been true, for some early Elan C/Vs.
The thing is, the shafts end up so darn short, that considerable
angularity is required and it might be easy to get something just a
little bit wrong (underestimating the shaft length, as Keith
mentioned, for example) and as a result have them bind before full
travel is achieved.
I had no limit straps on my '67 Elan, which had about '85 vintage
John Kouba C/V half shafts. (Kouba's C/V half shafts were excellent,
but don't take this as a blanket endorsement by me of his products or
service. I have certain reservations about Kouba, and I personally
don't do business with him any more.)
The thing is, I vaguely remembered that I could let the suspension
all the way down on my '67, and rotate the shafts freely. But I
wasn't very certain about this recollection.
When I was at the McClung's, we tried this *exact* experiment on their
'65 Elan (which has C/V axles on it that are essentially of a type on
which the Kouba design was based). It worked. In other words, at
full droop, there was no bind.
OK, enough for now...
Regards,
Erik Berg
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