I am recently back in the ‘Lunatic Lotus World’ after a 30 year absence having just bought a 72 Sprint that appears reasonably well sorted, but with memories of my 65 S2 still bright in my mind, I want to head-off some of the old disasters - and the first action is to fit solid driveshafts.
I have seen lots of discussions regarding solid driveshaft conversion, but I do not remember any definitive information regarding the relative merits/advantages/disadvantages of the two different types i.e. UJ and CVJ.
I plan to do a conversion sometime over the winter and would appreciate some advice in order for me to make the “correct” technical decision.
Lacking definitive information on a Lotus? Sell it and buy a Porsche. If you insist on the Lunatic Lotus, and must give up the perfectly acceptable rubbers, I highly recommend CVJ over UJ.
My next change to my Elan was going to be the Spyder combo CV/roto-flex shafts. Alas I sold my Elan before I could execute. I simply did not feel comfortable removing all of the cushioning of the rotoflex joints, no other reason. The Spyder’s also have the anti flail construction, so failure of the roto-flex is not catastrophic.
Perfect! Three choices if you forget the UJs due to undue stress on the upper frame tower. Some axle shifting is required in an Elan.
I’ve seen photos of much more powerful mid-engined race cars with rotoflexes on the half shafts…
Buying a Porsche would not give a retired automotive engineer much of a challenge. With 35 years experience in the only slightly less lunatic world of Ford, GM and DC, I have a great yen to get back to basic engineering that does not depend upon electronics to work properly. My last 5 years were spent working on VW/Porsche transmissions - albeit the Touareg/Chayenne models, and these vehicles would not turn a wheel without the most complex of electronics.
I did consider a Boxster and Elise, but with depreciation in mind and the fact that it will be for fun use for about 10 weekends a year, and without the need for expensive garage servicing, I reverted to my original wish and bought the Sprint. Please, no comments on the fact that I shall spend a small fortune updating and maintaining it during my ownership ? that?s how I know I?m back in that lunatic world.
By the way, I don?t think that any Lotus is lunatic, but I still believe you have to be loony to own an old Lotus as one of my abiding memories of my old 65 S2 was that the hood had to be lifted weekly in order to do some sort of maintenance in order to be sure of not breaking-down during the following week ? I have no elusions that a 72 Sprint will be any different.
Brian…the CV shafts from Sue Miller seem to have had good press on the forum over the last couple of years and certainly don’t have the problems that the TTR ones used to on road cars of ‘locking up’ on full suspension reach. I’m rebuilding a late Plus 2 and upgrading an S4 currently and they’re both going to receive the Miller treatment!
Come along to the Club Lotus spares event at Stoneleigh in November, where Sue Miller, Paul Matty, TTR and Spyder usually attend, and you can inspect the items for yourself.
It seems that folks with CV shafts haven’t had any problems caused by not having the isolating rubbery effect. I guess if you have no mechanical empathy, drop the cutch at the lights evey time and snatch through the box then something will go…but that’s true for all cars. With Rotoflex couplings at about ?200 a set plus nuts and bolts, and CV driveshafts at ?400ish, it’s not such a daft price to upgrade. And a lot easier to fit! And the drive has to be a lot better, especially in the heavier Plus 2.
I have an early Plus 2, that was fitted with a 170bhp Ford BDA engine in 1971. That kept blowing the doughnuts at approx 1000 mile intervals, and did so when tested by Motoring News in 1972. The owner had a set of CV joint driveshafts made for it in '73 (there were no standard ones available then), and it’s still running on them today, with no failures in the diff or hubs. Good enough for me!
Mark
I fitted Sue Miller?s CV/CV solid driveshafts to my Sprint at the back end of last year without any real problems. Since which I?ve done about 2k of reasonably aggressive driving and am more than happy. Incidentally, they do not need a strap to prevent ?full droop?.
The only minor problem (as others have reported) was that the ears would not align to let all 3 bolts go through. Any 2 bolts were fine, but the 3rd was a bugger!
Careful inspection showed which was the culprit, and I simply drilled through oversize by half a mm. Then tried it again. I kept drilling different ears so as to keep everything as concentric as possible (I only had to drill twice, by the way).
Again, as Mark said, Stoneleigh is an ideal opportunity to inspect them. In fact you might care to ask Sue to bring an extra set with her (at no obligation) and then if you decided to purchase, you?d save the considerable postage. Many of us pre-order parts in general, precisely for this reason.
In addition, this year Brian Buckland will be giving four technical seminars (chassis, bodywork, suspension and engines). The featured Lotus model is the ?baby? Elan.
here in the states we have the excellent Dave Bean CVJ option. I have no regrets. I think people with donuts believe there is some kind of added harshness, taking some of the slack out of the system, but personally, didnt feel it at all.
I fitted the TTR UJ & sliding spline driveshafts to my S4 last winter. I have done my usual 3k miles this summer and all is well
They certainly make driving in stop start town traffic much easier, no more bouncing. Same goes for quick take offs getting out of busy junctions. More details on www.stig.uklinux.net
I’ve also fitted the TTR sliding splines. Done 5K miles so far with no problems. Used droop limited shocks (also from TTR) to prevent lock ups and all seems well.
Interestingly, like the sue miller CV conversion, the boltholes didn’t line up that well and needed some fetling
Cheers
Tim
The main reason for posting this question at this time was in order to make a decision before the Stoneleigh fair in November.
The level of research I did was to consult the three different design suppliers with the inevitable result that each was the best for the baby Elan application.
Its not that I am ignorant of CVJ or UJ designs as in a previous lifetime I had engineering responsibilities for propshafts and driveshafts while working for Ford. My experiences did not make me any authority on their applications - particularly to the Elan. And that?s why I thought it best to try to get the latest owner feedback from Lotus.net members.
My ?gut feeling? was for the Mick Miller design, and I think this has now been confirmed by the messages received.
Forgive my ignorance, but isn’t the TT a single UJ and sliding spline vs. a double UJ?
If so, your answer is to go with the CV’s. The combination of a single UJ and anything else other than a rotoflex creates an undamped velocity change as the axle revolves. This would be likely to wear related components, and especially the UJ.
Two UJ’s on an axle (like the Europa) creates a CV joint, with the motions cancelling each other by design. A CV and anything but a UJ is the same (there is no off-speed motion to cancel). But a UJ paired with anything that cannot damp its velocity change is a less-than-perfect solution.
In practice, this may not make much difference, though in theory it is flawed. And my experience with pre-MKIV Spitfires suggests that either their driveline parts were made of paste or the single UJ swing axle was really hard on the driveline bits. Maybe both given the state of BL in those years.
Yes and they get changed between after around 15 or so hours, Btw the quality of teh current donut is suspect .
Does anybody know the legality of the cv joints for historic racing ? My assumption is that the sliding splines are the safe way through tech inspection.