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Lifing competition rotoflex couplings

Posted: Sun Mar 04, 2012 4:22 pm
by Nigel Webster (anrw)
Does anyone have any advice on lifing competition Rotoflex couplings? Whilst the stage rallying I do isn't really comparable to circuit racing (we might have 7 or 8 starts at an event and lots of incidence of losing and catching grip) I would be very interested to know what policies people adopt. One either goes down the regular inspection route and only change them when splits or cracks appear, or one takes the lifing route where they are changed at a predetermined interval (say every 6 events) or maybe you change after a time interval (say every year)?

I would be interested in your views because mine after 4 events (two gravel and two tarmac) exhibit signs of use (creases and wear marks) but no signs of splitting or cracking. The dilemma is when you change before they let you down!


Re: Lifing competition rotoflex couplings

Posted: Sun Mar 04, 2012 4:52 pm
by The Nun
I bet when Rootes/Chrysler used to rally them they would be renewed at the start of every event regardless of what the ones on the car looked like.
I dont think you can guess a life when they are used for competition, I would say when they start showing any signs of cracking or cuts, renew them.
Expensive yes, but then serious competition isnt going to be cheap so its to be expected.

Re: Lifing competition rotoflex couplings

Posted: Sun Mar 04, 2012 5:44 pm
by SimonBenoy

I think we give the rotoflexes some stick off the line, but only once per race. I change mine less than once a season (10+ events in a full season) but I inspect them regularly and often have to replace the nuts on the coupling bolts which aren't as tough as the bolts and strip the threads. As you say, there are marks where they wind up, but provided there aren't any splits and the rubber isn't coming away from the plates, carry on.
My old ones go on the road cars, so if I need some for a road car, then I might change them a bit sooner.

Cheers - Simon

Re: Lifing competition rotoflex couplings

Posted: Mon Mar 05, 2012 11:41 am
by ImpManiac
Interesting thread. :) I have been wondering about this too.

May I ask also what the specification of the coupling bolts is? I'd like to get some really good quality tensile steel capscrew bolts and Nyloc nuts to suit. Has any of you any links to where these might be obtained? I won't need them for a while yet but might as well get them sooner rather than later. :)

IM 8)

Re: Lifing competition rotoflex couplings

Posted: Mon Mar 05, 2012 11:53 am
by Rod
Nigel, I think to a great extent it depends on your driving technique. 30 years ago I was forever breaking the blasted things so there was no way of "lifing" them. I was something of a joke on a Monday morning at the Chrysler Special Tuning service counter when I turned up for replacements! :lol: Lot cheaper in those days. One thing I was told, which I'm sure you do, is to always replace the nuts and bolts as well.

The racers I would guess would subject them to a lot less abuse but Geoff Taylor and Mike Hanna should have a lot of experience. I remember reading somewhere that Robin Eyre-Maunsell would change them for every event and maybe even on an event whereas Andy Dawson reckoned on one pair for a season.

ps. Where were the Imps on the Mid Wales Stages? Best of luck to you and Geoff and anyone else giving it a go! :D

Re: Lifing competition rotoflex couplings

Posted: Mon Mar 05, 2012 1:08 pm
by benwick3
Unfortunately the days of lifing and replacing rotoflex couplings on a regular basis are long over. I tend to check them before every race meeting for any visible signs of wear and also check the torque of the bolts after every practice session. At the same time I check for transaxle leaks to ensure that couplings do not become oil soaked. I threw the standard bolts away many moons ago and have replaced them with good quality bolts being the same diameter along their length. Touch wood the above basic checks have resulted in no expensive failures for a good number of years.

Pete Richards

Re: Lifing competition rotoflex couplings

Posted: Mon Mar 05, 2012 1:34 pm
by Nigel Webster (anrw)
Many thanks for the contributions to this thread.

To answer the various questions posed. Paul:- I have found some high tensile cap head bolts (7/16") which I cut down to length (64mm from the underside of the head) for those where the head is on the wheel side and conventional 3" high tensile 7/16" bolts where the head is on the transmission side. These I don't cut down as there is room for them to project more. I have had no difficulty sourcing these from my normal nut and bolt factor. Needless to say I don't use the original stepped type bolts!

We check the torque and inspect them after every event and would of course change them without hesitation if there are splits or signs of oil on them. Following the comments above we now plan to change them after 6 events regardless of their condition - there will be some foc competition couplings available in May for anybody who wants them for a road car. "One careful previous owner etc"

Rod: Geoff and I decided not to do the Mid Wales stages this year as he found it a bit over rough last year. We are both out for the next two rounds of the British Historic Rally Championship (Bulldog 24th March and all being well the Pirelli on 28th April). I will post further details here if any members are likely to be out in the North Wales forests and want details. Can we tempt you up the motorway Rod? Both cars are being service supported by Imp Club members.


Re: Lifing competition rotoflex couplings

Posted: Thu Mar 29, 2012 7:24 pm
by Ian Fisher
I hope I'm not teaching Granny, etc, but I always fit the bolts the wrong way round - the head next to the spider. I think couplings break because a bolt comes loose and then breaks. If a bolt comes loose, it's putting the load on the thinnest part of the bolt. On both occasions I've broken a doughnut (before I started doing the above), at least one leg had no bolt with lump of rubber attached. They're a bitch to fit that way, but I think it's worth it.

Re: Lifing competition rotoflex couplings

Posted: Thu Mar 29, 2012 10:11 pm
by Mike Hanna
Hi. I always used to fit all the bolts with the nuts next to the diff so if a bolt broke it didn't gouge the diff casing. I can only remember breaking the coupling/bolts once in 3 years.It was on a single venue on an old air field near the start of the first stage. I had to run back to the service area to get a spare coupling/bolts and tools. We were 70th after that stage. The rest of the day was a lot more fun. IIRC we ended up in the mid twenties. Apart from that breakage I only renewed the couplings once in 5 years. Better quality then ? Perhaps. Mike

Re: Lifing competition rotoflex couplings

Posted: Fri Mar 30, 2012 7:08 am
by Rod
I was told by the Comps. Dept that the bolts will break before a competition rotoflex so long as it is in good condition. As I said earlier, I broke several and each time I was given a handy tip, make sure the edges of the flanges are rounded off; the driveshafts are level etc. The last time one went I was asked, did the bolts break? Yes. You won't break another one then. That was true but then I only did one more event with the car!

That breakage was particularly annoying, a Rally Sport round, penultimate stage and I was up to second in class behind Steve Bowcock. Mind you Mike was out and Geoff had had a maximum early on and was catching us hand over fist. Even more annoying having gone OTL replacing the coupling in the stage, the other one went half a mile from the trailer park. :?


Just recalled a bit more, I reckon, having walked back a little way down the stage, that I hit the throttle hard out of a bend just as the back wheels went over a large transverse ridge followed by a biggish hole where a lot of stones had been grubbed out. I guess that did for both couplings the second one going accelerating out of a roundabout.