Rotoflex couplings

[pimkeirle]

Does anyone have any experience of using Triumph GT6/Vitesse Rotoflex couplings in place of the Lotus originals, which can now cost up to £200 each compared to £40 each for Triumph ones? I would be using them in conjunction with Spyder semi solid driveshafts.

[alanr]

£200?...Surely not?
SJS Rotoflex couplings are £94.79 +vat.
https://www.sjsportscars.com/parts-and- ... D0034Z.htm

Alan.

[Sadbrewer]

£99.00 at Classic Team Lotus if it's closer to you.

https://www.parts.classicteamlotus.co.u ... 3409-c.asp

You may see some really cheap ones that were for the Hillman Imp...don't touch them with a bargepole, they won't handle the power from a Lotus.

[Baggy2]

You may see some really cheap ones that were for the Hillman Imp...don't touch them with a bargepole, they won't handle the power from a Lotus.

+1 !

[rgh0]

The Imp style non interleaved couplings were used until the Sprint interleaved coupling was introduced so it apparently handled Lotus power for many years.

My understanding was the interleaved coupling were introduced to eliminate the surge by reducing the coupling flexibility. The stiffer Sprint coupling has other issues due to doubling of the bonded steel to rubber joints under higher stress due to lower coupling flexibilitydue to shorter rubber section lengths between steel sections

All of this is historical and no longer directly relevant given the poor quallity of the modern couplings. I would just use Cv's and be done with it as i did 40 years ago

cheers
Rohan

[Sadbrewer]

The Imp style non interleaved couplings were used until the Sprint interleaved coupling was introduced so it apparently handled Lotus power for many years.

My understanding was the interleaved coupling were introduced to eliminate the surge by reducing the coupling flexibility. The stiffer Sprint coupling has other issues due to doubling of the bonded steel to rubber joints under higher stress due to lower coupling flexibilitydue to shorter rubber section lengths between steel sections

All of this is historical and no longer directly relevant given the poor quallity of the modern couplings. I would just use Cv's and be done with it as i did 40 years ago

cheers
Rohan

I'm not sure that's completely correct Rohan...apologies but I can't find the article now, but going from memory it said interleaved couplings were introduced on S4's in mid 1969, and that two couplings were available for a while, the 'A' coupling and the 'B' 'competition' coupling. As I understand it the 'A' coupling was dropped, and from the Sprint onwards only the 'B' was made available.
We were in the trade at the time, and whilst I only remember us having one Elan in ( besides my own) we did quite a number of the Imp variants, and ( admittedly this is a memory from 50 odd years ago ) I seem to think the Imp coupling was a softer compound and cheap as chips to buy.

[trw99]

Tony Rudd was reported on his investigation into Rotoflexes in a 1971 Motor Sport article:

“When I [CR of MotorSport] visited Lotus some months ago I spent quite a while discussing the relative merits of Rotoflex couplings and sliding spline and universal joints in the rear drive shafts with Tony Rudd, the firm’s Director of Engineering. Rudd had been dubious of the Rotoflex or doughnut coupling before he joined Lotus and agreed that the diabolical surge they caused had to be cured. To this end various experiments were tried when he joined the firm, one of which was the use of the more conventional u/js.

However, for some reason, concerned with the elasticity of the doughnuts, the handling undoubtedly deteriorated considerably using the metal joints. So Rudd did quite a lot of research on Rotoflex couplings and after a couple of improvements has now come up with one that almost entirely eliminates the wind up. These are naturally somewhat more rigid and perhaps, because of this, the ride seems to be a little harder than on the earlier and exceptionally smooth riding Elans.” [Copyright Motor Sport]

Tim

[Sadbrewer]

Tony Rudd was reported on his investigation into Rotoflexes in a 1971 Motor Sport article:

“When I [CR of MotorSport] visited Lotus some months ago I spent quite a while discussing the relative merits of Rotoflex couplings and sliding spline and universal joints in the rear drive shafts with Tony Rudd, the firm’s Director of Engineering. Rudd had been dubious of the Rotoflex or doughnut coupling before he joined Lotus and agreed that the diabolical surge they caused had to be cured. To this end various experiments were tried when he joined the firm, one of which was the use of the more conventional u/js.

However, for some reason, concerned with the elasticity of the doughnuts, the handling undoubtedly deteriorated considerably using the metal joints. So Rudd did quite a lot of research on Rotoflex couplings and after a couple of improvements has now come up with one that almost entirely eliminates the wind up. These are naturally somewhat more rigid and perhaps, because of this, the ride seems to be a little harder than on the earlier and exceptionally smooth riding Elans.” [Copyright Motor Sport]

Tim

Thanks for that Tim...there is some conflicting information though...in the same article it states that interleaves were available from April 1969.
'' Let us begin by looking at the set up for the Elan. Four rubber couplings, manufactured by Metalastik Ltd of Leicester, were used at the end of each drive shaft; they were called Rotoflex couplings and they gained some notoriety. Lotus list two types of coupling in the Elan Parts Book: A026 D 0034 for all Elans and B026 D 0034 for the Sprint. The book states that the second B type was introduced from Elan Unit No 8930 on 11 April 1969. The A type was made of pure rubber, whereas the B type had aluminium interleaves around the bolt holes. For the +2 again two types were listed: A026 D 0034 and 050 D 0034 for the +2 until replaced at Unit No 1550 on 26 June 1969, when the part became A050 D 0034, which in turn was replaced by B050 D 0034 at Unit No 7101010335L in February 1971. Essentially these were the same couplings for both Elan types. ''

Edit...having read it again it seems Rudd's work was to improve the existing interleaved coupling...or possibly Rudd was talking about his work that took place in 1969.

[rgh0]

The Imp style non interleaved couplings were used until the Sprint interleaved coupling was introduced so it apparently handled Lotus power for many years.

My understanding was the interleaved coupling were introduced to eliminate the surge by reducing the coupling flexibility. The stiffer Sprint coupling has other issues due to doubling of the bonded steel to rubber joints under higher stress due to lower coupling flexibilitydue to shorter rubber section lengths between steel sections

All of this is historical and no longer directly relevant given the poor quallity of the modern couplings. I would just use Cv's and be done with it as i did 40 years ago

cheers
Rohan

I'm not sure that's completely correct Rohan...apologies but I can't find the article now, but going from memory it said interleaved couplings were introduced on S4's in mid 1969, and that two couplings were available for a while, the 'A' coupling and the 'B' 'competition' coupling. As I understand it the 'A' coupling was dropped, and from the Sprint onwards only the 'B' was made available.
We were in the trade at the time, and whilst I only remember us having one Elan in ( besides my own) we did quite a number of the Imp variants, and ( admittedly this is a memory from 50 odd years ago ) I seem to think the Imp coupling was a softer compound and cheap as chips to buy.

Nothing about Lotus is ever completely correct

cheers
Rohan

[EPC 394J]

I’ve been using Rotoflex couplings in conjunction with Spyder half shafts for some years now. Absolutely no problem at all with the Rotoflex, and quite like the driving experience which, unsurprisingly, feels like a halfway house between Rotoflex and CVs.

The advantage of the Spyder arrangement is that even if the doughnut fails, the drive shaft always remains retained inside a metal cup. So no flailing damage/danger!

[Sadbrewer]

Nothing about Lotus is ever completely correct

cheers
Rohan[/quote]

''a riddle wrapped in a mystery inside an enigma''

[alanr]

I’ve been using Rotoflex couplings in conjunction with Spyder half shafts for some years now. Absolutely no problem at all with the Rotoflex, and quite like the driving experience which, unsurprisingly, feels like a halfway house between Rotoflex and CVs.

The advantage of the Spyder arrangement is that even if the doughnut fails, the drive shaft always remains retained inside a metal cup. So no flailing damage/danger!

I am still using regularly checked all round fitted Rotoflex couplings on my car with no problems at all. If in the future though I change my current thinking the Spyder solution with an inner Rotoflexx for cushioning of the driveline with an outer CV would be the way I would go.

Alan.

[pimkeirle]

Thanks to all concerned for the wealth of knowledge shared. My understanding of Rotoflex is much improved. I think I will try the GT6 ones for a while and see how they fare. I usually find that the couplings need replacing because of perishing with age rather than breaking (my driving style has mellowed over the years) so hopefully these will last as long as the Lotus ones, which still cost almost 3 times as much with the VAT.

[alanr]

Interesting...
Are you confident that the size of the GT6 Rotoflex coupling, PCD etc, is exactly the same size as the Elan ones? I may be wrong but I think the GT6 ones are a different size?


Alan

[alan.barker]

just looked at GT6- rotoflex GCD301P for £48 incl vat.
where the Bolts go through it is solid metal just like the second type of Lotus rotoflex.
Like said question is the PCD of Bolt holes.
When i bought my Sprint the seller had fitted Hillman Imp rotoflex to get it through the MOT. I was very happy to discover that
Alan