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Old Rotoflex

PostPosted: Sun May 08, 2022 3:29 pm
by Temmck
The S4 I just purchased has been off the road for 30 some years. One of the reasons may be due to a broken rotoflex coupling that apparently flopped around and broke the brake disc. I was able to remove the drive shaft after much difficulty. The bolts are all rusted and fused to the rotoflex AND spiders. I was able to break free about half of the bolts, enough to remove the drive shafts with rotoflex still attached. I tried unscrewing the the bolts (no nuts) with liberal use of anti-sieze but could not get any movement. My 12 ton press couldn't budge them either. I finally able to smack them out with a hammer.

The car came with an extra set of "new" couplings. These still have the original band around them and there is no sign of cracking. But, they are the solid drilled out spacer variety so I assume they are old. My question is, should I use these new-old couplings or buy new?

Also interesting is the diameter of these couplings. I placed the "new" couplings over the holes in the spider and the coupling was too tight. I cut the band off and let the coupling relax a couple of days and they are still a little "small". Are these the wrong couplings?

The other side couplings look good, no cracking. But, boy, I really don't want to go through this nightmare again. And to think I haven't even installed the first side yet. Where's the pulling-my-hair-out emoji?

Re: Old Rotoflex

PostPosted: Sun May 08, 2022 3:44 pm
by h20hamelan

Re: Old Rotoflex

PostPosted: Sun May 08, 2022 5:01 pm
by ericbushby
Hi Terry,
Is it possible then that these couplings are also 30 years old. It is rubber or something similar. Would you fit a 30 year old tyre.
I think are suitable for landfill only.
Eric in Burnley
1967 S3SE DHC

Re: Old Rotoflex

PostPosted: Sun May 08, 2022 7:31 pm
by billwill
The band is there because without it the rubber expands and will be 'too big' to fit the connections.

Use 3 jubilee clips instead, that gives you much more control.

See my fulll topic on changing the doughnuts/rotoflexes.



Re: Old Rotoflex

PostPosted: Sun May 08, 2022 7:45 pm
by mbell
Was there two sizes of rotoflex's? My memory is that there two bolt patterns for rear brake discs, and outer shafts with smaller ones for early elan cars. Maybe these are for those ones rather than the common larger later types?

Unless it's a trailer to show car, I'd be likely fitting CV shaft to the car.

Re: Old Rotoflex

PostPosted: Mon May 09, 2022 2:06 am
by Temmck
The left side of the picture below shows the two rotoflex's that were removed from the car. The one on the right is the "new" one that came with the car. All three are from different companies and different designs. The 'new" one is a smaller diameter. I guess I need to buy all new couplings. Apparently, I have to change my 30 year old tires too. :cry:

Re: Old Rotoflex

PostPosted: Mon May 09, 2022 4:54 am
by Andy8421
Tony Rudd in his book 'It was fun' mentions that in period the item with the highest number of warranty claims on the Elan was the rotoflex couplings.

If you search the forum, there are threads with pictures of strange mangled areas around the diff where a driveshaft has whipped around after the rotoflex has failed. If you are lucky, you can bring the car to a halt before the driveshaft wedges against the frame and locks the rear wheel.

Looking at your pictures, you have one 'pre-sprint' rotoflex without the metal interleaving plates (that has failed), one 'post-sprint' rotoflex with interleaving plates that is intact (edit: on closer inspection, it appears to be delaminating), and a replacement vintage rotoflex that is also 'pre-sprint'.

Your call, but were it me, I would show all the rotoflexes the bin, and buy CV joint replacements. The rotoflex don't 'fail safe', and they have a well documented history of failing.

Re: Old Rotoflex

PostPosted: Mon May 09, 2022 4:57 am
by UAB807F
If I'm understanding the photo correctly, you've had a mixture of rotoflex on the car, the top one is the later "sprint" version and the broken lower one is the original type first fitted to the early Elans. Also, IIRC, to Hillman Imps to transmit their massive 40bhp to the rear wheels.... :wink:

The mixture would make me suspicious of the maintenance history so I'd replace the complete set, both sides and keep any good ones as spares. I'd also do the tyres because after standing in one spot for 30yrs they may well have deformed slightly. I'd probably do the drivetrain first and if the tyres held pressure/no cracking then I'd drive the car round the block a few times and make a "to do" list, but even then the tyres would be somewhere on the list.

I guess this is the time to consider alternative drivetrains. When I resurrected my Elan from a long term slumber the rotoflex looked ok but I decided to change it for a CV system. More expensive for sure, but hopefully a longer term solution although to be honest I'd driven with the donuts for years with no real issues other than wear/tear.


Re: Old Rotoflex

PostPosted: Mon May 09, 2022 1:19 pm
by m750rider
As others have recommended, replace all the donuts with new that have the interleaved inserts, as you don't have the correct ones. Or change to CV joints - your decision.

I've owned my S4 for almost 50 years and just recently replaced the donuts once more. But for me they have not been problem. Others have had different experiences.


1969 S4 SE

Re: Old Rotoflex

PostPosted: Tue May 10, 2022 1:39 am
by Temmck
Thanks all. I have new rotoflex couplings, nuts, and bolts on order. I was tempted by the CV's but I want to experience the original feel of the car before diving into CV's so that I can make my own judgement on which is better (for me).

And yes, I have new tires on the car. The 30 year old tires were only used to roll the car onto and off of the trailer. This is not my first barn find Lotus.