Rotoflex couplings?

[Combover]

I'm a bit dim. As a result of this, I have no idea what a Rotoflex coupling is, how it works and pros and cons.

Could someone explain it in laymans terms for me.

Cheers.

Tom

[Richard B]

Big rubber doughnut   ;D



Connects inner driveshaft with outer driveshaft, a design alternative to a U/J or a CV joint. As the rubber allows plunge (change of length) it is more like a CV joint than a U/J which can only provide angular change.

The rubber provides a cushion for drive impact, helping to extend the life of other driveline components.


Downside.

Expensive ones (last 40,000 miles), or cheap ones (last 2,000 miles to 10,000 miles), pain in the arse to change, real pain in the arse to change, in fact a mega pain in the arse to change....  

[Steve AKA vitessesteve]

They look like this.

[Nick Jones]

Pic below shows a rotoflex at home on the driveshaft.  You will see the UJ on the left that bolts onto the diff and on the right the loose bearings where the vertical link would be and the hub.

The UJ on the left allows angular articulation only.  The rotoflex allows angular articulation and plunge (variation in shaft length).  Some say that they also have a cushioning effect on other transmission components.  I say that when really trying, they can also wind-up and let go giving an axle-tramp like effect which is anything but gentle on the transmission.

Another way to do the job is shown below.  The Lobro type CV joint on the left allows angular articulation and plunge and bolts to the diff via an adaptor.  The conventional CV on the right allows angular articulation only.

Cheers

Nick

[cook1e]

Another picture of the original halfshaft being rebuilt with a new rotoflex coupling.

They are a pin to change the first time as most of the suspension bolts are usually seized! However use of copper grease on reassembly fixes that for next time and after changing them a few times it's not too bad a job, a spring lifting tool is a pretty important requirement when reassembinmg the suspension though. Problem with Rotoflex couplings  is that genuine ones are getting very very expensive now, over £180 each from Rimmers!!. genuine ones are by a company called Metalastik. I managed tio pick up a new pair of genuine metalstick ones on eaby about a year ago for around £25, a real bargain!

[npanne]

One question - I know that the coupling come with a metal band around the edge, which I believe is removed after fitting? Is it possible to refit one once the band has been removed?

[Jason]

Yes, sort of :-) If you get a couple of big jubilee clips linked together you can re-compress the coupling and remove/refit ad-nausiem

[Tim Bancroft]

£180 a pop!!!!

Jeez, looks like CV jointed 'shafts are going to become the norm.

Biggest pita with a rotoflex shaft is lining up the suspension joints, pushing against the rotoflex makes this coupling change operation one of the worst jobs involved when working on these cars.

[cook1e]

timbancroft61 wrote:

£180 a pop!!!!

Jeez, looks like CV jointed 'shafts are going to become the norm.

Biggest pita with a rotoflex shaft is lining up the suspension joints, pushing against the rotoflex makes this coupling change operation one of the worst jobs involved when working on these cars.

It's either £180 or £20 for a pattern part that will need changing again in a few thousand miles, probably works out cheaper but you have the hassle of changing it. I agree that CV joints will probably become the norm.

Regarding the lining up of the suspension joints, I've done the job so many times now that I have a well proven method using a selection of prybars, screwdrivers etc along with a spring lifter and I don't find it too difficult now. My method is to leave the bolt that goes through the spring eye until last, everything else lines up OK if you do this.

[Richard B]

cook1e wrote:

I've done the job so many times now that I have a well prove method using a selection of prybars, screwdrivers etc along with a spring lifter and I don't find it too difficult now.

:X
Yeah workshop manual does not state that the rotaflex coupling is pre-loaded when installed and that you need four hands to fit the spring eye bolt. Two screwdrivers, one each side of the vertical link levering it against the spring and two hands to drift the spring eye bolt in with a hammer!   ??)

[cook1e]

Richard_B wrote:

:X
Yeah workshop manual does not state that the rotaflex coupling is pre-loaded when installed and that you need four hands to fit the spring eye bolt. Two screwdrivers, one each side of the vertical link levering it against the spring and two hands to drift the spring eye bolt in with a hammer!   ??)

I've found that the prybar that was supplied as part of the standard toolkit with a Triumph Dolomite for removing the hub caps is just right for this job. You lever the vertical link into place by putting  the prybar through the mounting holes at the top of the link and the spring eye bush . Then you put a screwdriver of a diametr similar to the bolt through the mounting holes and spring eye whilst removing the dolly prybar. Then push the bolt through to push the screwdriver out. No more than a gentle tap required on the bolt to drift it into place, particularly if it's well greased with copperease. Before I found this method I must admit is was a really difficult job though and used to be accompanied by lots of bruised knuckles and swearing  ??)

[Tim Bancroft]

Obviously practice makes perfect, however it is always an awful job.

With the CV shafts, I can get the whole suspension back so quickly. This is great for maintenance and keeping the big bottom bolt and trunnions all nice and clean and of course working as it is should.