Lotus Elan

Spyder Driveshafts

PostPost by: richardl46 » Sun May 08, 2022 12:49 pm

After nearly 4 years ownership and a lot of body/engine restoration I decided to give my 1972 +2 130S a short run.

Unfortunately there is a knocking sound from the final drive above 15 mph. The only possible cause I can find is that the metal segments of the rotoflexes are making contact with the safety tube that fits through the inside, although the rubber appears quite sound. Attached photos show rubbing marks on the safety tube. Also shown are the existing rotoflex /safety tube fitting which has plenty of space to move around, compared with a new rotoflex that is a tight fit over the safety tube.
Is there anything special about the rotoflexes used by Spyder? The installation looks similar to photos I have seen on line but I don't have the original instructions from when the conversion was supplied to the PO in 1998. Can anyone PM me a copy?
It would certainly be useful to get some advice before I start the struggle to rebuild the shafts.

Thanks, Richard

IMG_4435.JPG and
IMG_4441.JPG and
IMG_4480.JPG and
attachment=0]IMG_4481.JPG[/attachment]
Attachments
IMG_4481.JPG and
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PostPost by: elans3 » Sun May 08, 2022 5:02 pm

Can't quite see what's wrong here, but all I can tell you is that I have the same shafts on a late S3 Elan and find them perfect. I like the idea of a cv on the outer side, and a doughnut on the inner, virtually zero wind-up, and having the doughnut on the inner is much kinder on the diff.
Hope you work out what the issue is,
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PostPost by: richardl46 » Mon May 09, 2022 6:45 pm

Thanks for your comments Steve.

The more I think about it the less I believe the rotoflex/safety tube could be causing the noise, which is a definite knock at drive shaft/wheel frequency. I'm now part way through changing the rotoflexes, having already bought a new pair.
If the noise persists I plan to remove the new 14" MInilites and try it with the original 13" Lotus wheels. I've already change one UJ and turned the propshaft through 180 Deg, so now running out of ideas. Hopefully there is nothing wrong with the gearbox, diff or hubs!

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PostPost by: 661 » Tue May 10, 2022 7:54 am

Have a look on the inside of the wheel faces and check the outer wishbone bolt heads are not fouling
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PostPost by: richardl46 » Tue May 10, 2022 8:27 pm

Thanks for the suggestion Graeme.

The wheels and tyres are quite close to the wishbone bolts and spring bases but no sign of any contact. The fact I am not getting the knocking noise until 15mph is making it difficult to pinpoint the location. Having stripped the rotoflex out of one side; the diff, outer CV joint and hub appear to be turning smoothly. It will take a few days before I rebuild that side and tackle the other one.
If the new rotoflexes don't cure the noise I will put the old 13" wheels back on. With hindsight that would have been a more sensible course to take before changing the rotoflexes. I'm hoping to make that job easier with some motorcycle spring clamps to raise the shafts in line with the diff.

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PostPost by: Donels » Tue May 10, 2022 9:49 pm

Are you sure the new wheels are tight?
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PostPost by: Andy8421 » Wed May 11, 2022 5:59 am

FWIW, I had a difficult to diagnose rear suspension knock that turned out to be a failed rear wheel bearing. I was running rotoflex couplings, and when I jacked the car up, the suspension droop caused the rotoflex to pre-load the bearings and no play or noise was apparent. It was only when I jacked up under the bottom of the strut so the driveshafts were horizontal that the play and noise became apparent.

In your case with one cv, it may not have the same effect, but may be worth checking out if all else fails.
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PostPost by: 512BB » Wed May 11, 2022 7:57 am

Have you checked the nut that secures the top of the damper for tightness? That knocks like Black Rod if it is loose.

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PostPost by: richardl46 » Fri May 13, 2022 7:48 pm

New rotoflexes fitted and I was pleasantly surprised how well that job went. Whilst drive shafts disconnected the diff, CVs and wheel bearings appeared to run smoothly. With 14" wheels and 2.5mm hub spacers there is ample clearance between wheels and wishbone bolts.
However, although the gap between tyres and spring perches looked adequate I remembered the advice from Spyder when I bought the 14" Minilites and fitted their recommended 185/60 tyres. They said the spring perches may need tapping back to give clearance. So I hammered them a little just to flatten the curve where the tyres may be touching.
Road testing showed the previous noise had gone, but now with increased speeds I am getting a clunk when going on or off throttle. Not enough to put me off taking the car up to 60 mph but obviously something moving in the rear suspension that needs sorting.
The engine ran nicely for a couple of miles but then was reluctant to pull cleanly from say 30 to 50 mph. A bit like fuel starvation and dropping down to 3 cylinders before picking up when a lot of throttle applied. Time to get the Dellorto book out and work through the possible causes.
Thanks again everyone for the advice. Impending holidays will slow progress for a few weeks but I hope to put in some decent running-in miles during the better weather.
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PostPost by: billwill » Sun May 15, 2022 2:39 pm

I had a similar CLUNK a long time ago, I think it turned out to be the bolts that hold the diff. The nuts were a tiny bit loose. Not detectable by hand.

Needs a mole wrench or person to hold the nuts in the boot, and a second person under the car with a socket set with two extension bars plugged into each other to tighten the bolts from below.
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