Lotus Elan

CV Joints suspension droop

PostPost by: quaybook » Mon Apr 05, 2010 12:08 pm

I'm just fitting Mick Miller CV jointed driveshafts to my S2. The fitting instructions say that the diff must be fitted in the lowest possible position when using these shafts, which implies the need to minimise the angle of the driveshafts. This is presumably either because CV joint life is affected by its operating angle or, more likely, because at full droop the suspension is close to or at the maximum angle/elongation the CV joints will take. My diff is positioned at the lowest point, but I'm concerned because my offside suspension has a 9mm spacer inserted between lotocone and the suspension tower in order to level the car, which otherwise sat low on the drivers side (as discussed in a thread on here last year) and so full droop will effectively be extended beyond the normal geometry. I have a Lotus replacement chassis and, but for the spacer, standard rear suspension and dampers. I've asked Susan Miller and she says she thinks it will be ok but, with her customary honesty, she says that Mick was the technical expert so she cannot give me a technical response with maximum droop measurements or driveshaft angles.
Can anybody with experience of the Mick Miller shafts throw any light?
With these shafts, is it necessary to avoid letting the suspension go to full droop when jacking the car?
I've been trying to figure out a droop limiting strop arrangement without much success. I've seen Rohan's version elsewhere on this forum, but he has a Spyder Chassis which provides a convenient aattachment point unlike mine. Any ideas?

The annoying thing is that my Rotoflex couplings were fine, but speaking with a guy who had had a dramatic and traumatic Rotoflex failure made me loose faith in them and decide to change to CVs. Now it looks as if I'm going to be worried about an unexpected yump in the road or excessive body roll in spirited cornering popping a CV joint instead! Still, at least it won't flail and rip the car to pieces.

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PostPost by: alan71 » Mon Apr 05, 2010 1:46 pm

If you can rotate the rear wheels with the car jacked up then I wouldn?t worry about it, you?re not going to damage anything.

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PostPost by: nebogipfel » Mon Apr 05, 2010 2:11 pm

Vernon.

When my car is jacked up and the Mick Miller shafts are at full droop they are actually starting to bind and will not rotate freely.

When I first assembled the car I thought the angle looked too steep and would cause problems. In practice however the shafts run at a perfectly sensible angle when the car is on the road and it just isn't a problem. Unless you plan using the Elan as an off-roader then it's not a problem!

Five years on I am very happy with the conversion and happily recommend it.

The only suggestion I would make is that if you intend leaving the rear jacked up for long periods or rotating the wheels on full droop I would add a jack under the wishbone to reduce the droop angle.

My car is standard suspension and wheels and FWIW I wouldn't trust the Rotoflexes available these days
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PostPost by: elansprint » Mon Apr 05, 2010 3:09 pm

Vernon when i was rebuilding my engine i remember speaking to Mick at the time & the CV joint has a droop angle of 22.5 deg from memory if you are worried fit a belden cable to the wishbone to limit suspension droop
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PostPost by: lightwait26 » Mon Apr 05, 2010 7:37 pm

TTR sells shorter travel rear shocks, which eliminate the problem.
art
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PostPost by: alexblack13 » Mon Apr 05, 2010 9:02 pm

Hi Guys,
I bought a set of Perf....ce Un....ed drive shafts many... Errr ..moons ago, and they were supplied with the brilliantly designed droop limiter device. The said bit of wire rope about 2' long. 1 pc for each side. Following the instructions to the letter resulted in complete destruction of the drive shaft 1st time out. They had to be rebuilt. The 'anti droop cables' went straight in the bin. Hopeless and def' not fit for purpose. However.... Thinking droop limitation, I decided to shorten the travel by taking a bit off the shock rods... as you do! and just got stuck in. I set the suspension up minus the springs etc and got me a measurement and off I went. Re-machined the ends of the rods and built the suspension back into the car. Sorted. Full droop and free as a bird, rotating sweet as a nut... The cables were a joke...

The car still managed to break the drive shafts another twice before I took them off and went back to standard. They were hopeless too!! :lol: :lol: I gave them to someone who spotted them in my workshop and asked if he could buy them. I said no, but you can have them and told him the history. Don't know if he ever got them to work.

Did I ever tell you about giving away my +2 steering wheel?? :shock: Boy was that a mistake... Ah well! :?

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PostPost by: ceejay » Mon Apr 05, 2010 9:44 pm

Hey Guys.
Have you seen the extreme operating angles that our CV drive shaft
will cope with... no need for limiting cables... or chopped and re-machined
strut rods... designed & built to work straight out of the box.
DS will work at 3.74" droop & 3.74" Bump... with no sign of binding or lock up!
http://www.youtube.com/watch?v=nfuqmifnEPU
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PostPost by: elansprint71 » Tue Apr 06, 2010 11:05 am

Would it not have made more sense just to put packing pieces between the chassis and the body in order to "level the car", by which I think you mean level the body?

I have no issues with droop on my MM shafts which, incidentally, are used with Spyder twin-wishbone RSC suspension.

Cheers,
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PostPost by: miked » Wed Nov 30, 2011 2:04 pm

Hi Alex,

I am interested in the type of failure that you encountered with the P U drive shafts. I have seen these used without peolpe having problems. I know the plate that converts from 4 bolt to 3 bolt is quite thin and 4 countersunk bolts that go through might be a problem if the UJ flange is not bolted up tight. Would you mind elborating?

I have actually had sliding drive shafts made up (in the past) and used the same principle but with thicker discs and larger cap screw type fasteners. Ran for miles on them, without problems. Did track days etc. Same size shaft, UJ's and flanges.

Mike :)
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PostPost by: alexblack13 » Wed Nov 30, 2011 3:33 pm

It was a long time ago Mike. Friend and I and our wives were staying in London on holiday and we went along to Southend (I think) and we both bought a set each. I could not wait to get back and fit them to my +2s130. The 1st thing that I encountered was the droop limiters which didn't...

Got round the droop problem and checked all free with no binding issues fully up or fully down and all looked well. Ran them for a very short time before I lost all drive one night and had to get a tow back home... Inspecting the shafts revealed that the weld had failed where the round bar was pressed into the splined sliding section. Can't remember whether the male or Female end but the very neat weld turned out to be very light and not a lot of penetration. Fixed this side and carried on. Same thing happened to the other side shortly afterwards. Off they came! Maker did not want to know, so they became Garage furniture after that and lay about for years before I gave them away..

I think the splines were locking up under load and not sliding as they should have. They were well greased up too and had neat rubber boots .... They went of with a fair bang when they broke..

I personally would not entertain these now. That's why the various makers went CV route was it not? :shock:


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PostPost by: miked » Wed Nov 30, 2011 6:58 pm

Thanks for explanation Alex.

Some human error then one the manufacturing process. :shock: They are pretty old, I believe, and many of the suppliers of parts that we buy from have gone through periods of quality issues. I have a friend running a Plus 2 with a set fitted. I will mention to him. He has had them on for about 8 years. Worth having a close look.

Re: CV's, no experiece with them. Have run TTR UJs and the ones I had built. No problems whatsoever. Rubber motor cycle fork gaiter boot over the spline joint to keep lube at bay.
Couldn't knock the drive or handling experience myself (or new owner).

Mike :)
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PostPost by: Orsom Weels » Thu Dec 01, 2011 3:44 pm

Hello chaps.
I droped in on Sue Miller last week to get a few parts for the +2 & took my freind along to sort a few things out in readiness to start the rebuild of his S3 Elan. One of the things he needs to sort out are his drive couplings & with the scare stories of modern Rotoflex's was interesred in a set of Sue's CV conversions. Sue said she was no longer able to supply them for the Elan as she had had problems with new pattern CV joints failing, the originals were genuine Ford items, no longer available & she felt the failures were down to the pattern joints not being good enough to cope with the angles acheived on full suspension travel, the +2's, due to their wider track, dont reach the same accute angles & she's had no problems with them so is still happy to supply those. She offered to sell us just the shaft's & adaptor plates, she apparently has a large stock & would like to recoup some of her investment, we would then need to source the CV joints to complete the job, that way she would not be resposible for any failure of the joints. We had a chat about using alternative joints but apparently, the Ford items were the only ones Mick was happy with & nothing else has been found to replace them, the only thing she could think of, was to sell them with a modified shock to limit suspension drop but that would make the kit too expensive. I should point out that she said she had sold 800 & some odd kits & had only had problems recently but it does show how close to the limit they are so any discrepancy in shock absorber travel could prove problematic.

I hope this is of interest/help to some of you, it's a brief resume of our conversation, I'm sure Sue would be happy to provide more detail if you give her a ring.

By the way, my friends take on all this was "why the .... cant someone make good Rotoflex's then, after all, they were ok 40 years ago !"

My, how we've advanced :roll:

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PostPost by: nebogipfel » Thu Dec 01, 2011 6:58 pm

Just to add to Tim's info' regarding the Mick Miller drive shafts. I must admit when I first fitted them I was somewhat alarmed by the angle of them at full droop.

That said, on the road they are excellent and so far my concerns have been unfounded and they seem to work very well. (I will have my fingers crossed from now on). They certainly make an Elan much nicer to drive and I would be disappointed to have to go back to rotoflex couplings.

It is worth adding that from day one I have always been careful to support the wishbones if I raise the back of the car. Not allowing the shafts to droop fully.
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PostPost by: miked » Thu Dec 01, 2011 8:38 pm

Guys,

I could be wrong but is it not about driving angles (hence mm's of diff' height businesss) that give them the Sh*ts, not the odd time that they are hanging on droop. I know very little but was talking with a guy who said the will only tolerate very slight angles and it is this driving deviation that damages them.

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PostPost by: nebogipfel » Thu Dec 01, 2011 9:56 pm

miked wrote:Guys,

I could be wrong but is it not about driving angles (hence mm's of diff' height businesss) that give them the Sh*ts, not the odd time that they are hanging on droop. I know very little but was talking with a guy who said the will only tolerate very slight angles and it is this driving deviation that damages them.

Mike


I don't think, under normal driving conditions it's an issue. The Miller shafts and indeed other similar ones have done thousands of miles with no problems. I haven't spoken to Susan Miller about this subject but I believe she told Tim the problem is with the unavailability of quality CV joints of the type Mick (Miller) originally designed the shafts to work with.

My car doesn't get raced or rallied :D and I would be interested to hear the experiences of others using the shafts, perhaps more aggressively than myself?

Meanwhile I hope to continue to enjoy surge free motoring, safe in the knowledge that I will not get my backside flailed by a driveshaft :shock: :lol:
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