Lotus Elan

Are my donut’s distorted?

PostPost by: Fergus » Mon May 09, 2022 10:40 am

Hi I bought a nice Elan s3 with lots of non standard Spider bits last summer and I’m slowly finding my way round it. The car was rebuilt pre 1980 and hasn’t covered many miles, it’s a great runner but I noticed going into reverse sometimes there’s maybe a bit of wobble in the drive shaft. Checking out the “donuts” they look a little distorted, I’ve bought new ones but before I get dirt could could someone please check out my photos…. maybe this distortion is within limits? Thanks
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PostPost by: m750rider » Mon May 09, 2022 2:33 pm

That one looks a little bit out, but maybe this picture is with the suspension not in compression.
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PostPost by: smo17003 » Mon May 09, 2022 4:44 pm

It appears (unless it's a trick of the camera) that there's a washer between the spider and the rotoflex - I don't think that should be there.
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PostPost by: types26/36 » Mon May 09, 2022 5:30 pm

The coupleing bosses have a high and low sides which must be fitted the correct way round.
Its hard to tell from the pictures if they are correct, here is a pic from the manual that explains which way they should be fitted although I'm not sure if it makes any difference with the Spyder set up you have.
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couplings.JPG and
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PostPost by: 512BB » Mon May 09, 2022 8:10 pm

It stands to reason that no matter what shaft arrangement you have, if it encorporates a donut or donuts, it needs to run as true or flat as possible, unlike in the picture. It appears that the shaft has been connected to the low bosses, which is not correct, and will seriously shorten the life of the donuts and may cause vibration.

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PostPost by: Fergus » Mon May 09, 2022 8:34 pm

Thanks to all of you. The photo shows the donuts under compression so I was pretty sure they should be flat and running true and yep why’s that big washer there? I’ll dismantle the shafts and probably put in new the new bits. Cheers
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PostPost by: sprintsoft » Mon May 09, 2022 9:27 pm

Hi Fergus,

I think you have a Spyder driveshaft conversion fitted, you can see the sliding spline in your pictures, the outboard end connecting to the disc should be a hook joint, not a second rotoflex.

The inboard end you are showing should have the Spyder fail-safe boss installed between the diff output shaft and the rotoflex, if it is missing or wrongly assembled then its probably contributing to your misalignment.

I'm attaching a pic here of the conversion, I marked in red where you can just see the Spyder internal boss that prevents the shaft detatching in case of a rotoflex failure.
SpyderDrive.jpg and

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PostPost by: Fergus » Tue May 10, 2022 11:28 am

Hi again. It looks like the shaft was connected to the low boss and the head of the Spider “fail safe” insert was rubbing, due to insufficient space. I’ll connect the shaft to the high boss and re-assemble using the new donuts. Thanks again.
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A2EDB8CF-FA17-4E87-9816-D9F815C52C18.jpeg and
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PostPost by: Fergus » Wed May 18, 2022 10:20 am

My troubles aren’t over. I replaced one donut with great difficulty and it distorted in the same way as the old one! The photo shows the car sitting on the wheels at ride height - the Spider drive shaft is fully home in the splined coupling pushing the donut evenly into the distorted shape.

I’d say the shaft assembly is at least 1cm too long. Re- assembling without the spider “fail safe” fitting would solve my problem but I shouldn’t have to do that unless maybe the spider bits were for a plus 2? Any ideas very welcome.

The car (rebuilt in the 80s) has fatter tyres and wheel arches, could that be a factor?
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AF09F0E6-0487-4B70-AB6A-B1D50935C471.jpeg and
New donut, shaft running close to straight to wheel.
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PostPost by: alanr » Wed May 18, 2022 10:37 am

That donut from the photo looks to be even more twisted than the original fitment did!
Have you considered that the rule of 'High lug to the shaft' doesn't apply to the Spyder shaft variant because it looks to me as though fitting the donut with the original spec shaft rule applied is wrong and the low lug needs to be to the shaft due to Spyder fail safe insert.
Why not give Spyder a call and ask?

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PostPost by: Fergus » Wed May 18, 2022 10:45 am

Thanks Alan. I tried connecting the shaft to the high boss but that made it longer but with the spider fittings I don’t think it matters.

I’ll maybe try and call Spider again but they no longer stock donuts and didn’t return my last call asking when or if they’d get them in.
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PostPost by: smo17003 » Wed May 18, 2022 12:24 pm

I think that you have a problem with the overall length of the drive shaft. Is the splined shaft "bottoming out" in the yoke at the hub end? If it was able to slide freely I don't think it could distort the donut.
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PostPost by: Fergus » Wed May 18, 2022 12:52 pm

Yes the splinned shaft is bottoming out in the hub, distorting the donuts.
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PostPost by: Andy8421 » Wed May 18, 2022 2:03 pm

Fergus,

Movement in the splines should allow the rotoflex to run undistorted when the suspension is level. Assuming your rotoflex have the same distortion on both sides of the car, and that the splines are bottoming on both sides of the car (so it isn't a single side butchered spline problem), I think it quite likely you have plus2 shafts which are longer than Elan shafts.

The splines shouldn't bottom, so possibly taking up all the movement in the spline and also distorting the rotoflex is just enough to compensate for the extra length of the plus2 shaft.

If so, you need different shafts.

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PostPost by: Fergus » Wed May 18, 2022 3:45 pm

Thanks Andy it’s starting to look like the wrong shafts were fitted. I’ve phoned Spider and they asked me to call back tomorrow to speak to a technical guy. If any one has dimensions of these shafts or knows were I can get them I’d greatly appreciate it. Cheers
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