Dave bean Rotoflex couplings

[nitch]

Hi all,

As my Elan +2's overhaul advances, I need new Rotoflex couplings.
Ken from Dave Bean offered me Normal ones or Heavy Duty.
Does anyone have any comments on those? Are the Heavy Duty ones recommended?

Thanks,
Liad

[gordonlund]

See attached,
Non interleaved couplings were Hillman Imp. Believed to be slightly sronger rubber. Lotus & Hillman had Dunlop introduce the interleaf type which is much stiffer for uprated applications. We are looking at the 96mm PCD ones. 210 lb ft vs 140 lb ft normal torque rating. If you do the sums, the stiffer ones are not really rated for CONSTANT traffic lights sprints!! Hence treated gently they might last a couple of seasons. Used hard don't expect a long life.

One can understand the popularity of modern constant velocity driveshafts, but they put additional strain on the drive train. Follow the manual exactly as they only go on one way.

[pmallinson]

Hi

Could you please re-attach the excellent rotaflex pictures but this time in A4 format so I can read them they are just too small for my old eyes

Cheers

[gordonlund]

The original pic would not download as it was too big. I'll try and make it a little bigger. These are as big as I can get the web site to handle. See me on my stand at Donington Lotus Show and I'll get some copies.

[prloz]

Hi all,
Anyone tried the rotoflex centring devices as sold by Dave Bean and others ?
Thanks.
Regards,
Peter.

[gerrym]

Try this attachment for part number and dimensions (PCD 96 interleaved type)

Gerry M

[thor]

Gordon, I didn't quite get the meaning of your answer here, which ones are you talking about only lasting a couple of seasons, the normal ones? And what are the differences between the two types, in your opinion? Constant traffic light grand prix efforts notwithstanding..

[gordonlund]

Thor,

The interleaf type is the only one available for Elans now and is is far superior to the non interleaf type. They only have limited life however 2- 5 years max depending on mileage) due to they being used outwith their design parameters. ie Excess torque in first gear and greater angle of inclination. These couplings are used in Formula Ford single seaters but they have very small rear suspension movement hence they have an easier life than in an Elan be it with more power.

Thats the downside. The positive side is that they enhance the drive in an Elan by smoothing out the inherant vibrations and harshness that would be transmitted through solid driveshafts.

Hope that answers your question. A bit vague I know but a lot depends on what you want from the car.

Gordon Lund

[thor]

Hm. Good points Gordon. I'm doing a proper inspection of mine this spring when I do the servicing. What are the tell-tale signs of excess wear on the couplings, cracks?

[gordonlund]

Thor,
Jack up the rear of the car, remove road wheels, and with a good light just look at the couplings with the suspension on full droop. If you need a closer look put chocks of wood under the sills near the rear jacking points.

If the rubber is starting to delaminate from the bolt bosses and /or the interleaf metal strips then change them immediatly. If these let go, specially on the early cars the results can be disastrous as well as expensive. Later cars had a spigot extension on the inboard drive shafts but i'm not convinced they would restrict the movement of a wayward drive shaft much. Follow the workshop manual to the letter and you shouldn't go far wrong. Obtain new HTS nuts & bolts also, I had a bolt break a few years ago but managed to rectify before any more damage occured

Nice web site, car and lady. Have a look at Rhubarb on the Elan Gallaery of this web site. I'll post some more pics later.
Gordon

[thor]

Excellent advice Gordon, am making a note of this! -8C here today, so I'M VERY MUCH looking forward to spring......

[nebogipfel]

The topic of drive couplings has understandably cropped up many times, I would like to add a couple of points.......

Unfortunately there is a serious question over the quality of some drive couplings and indeed other bonded products such as engine mountings which are being manufactured these days and premature failures are being reported.

Hence the reason for conversion to CV Joints

Which brings me to my other point - I must contradict Gordon on his statement that there is "inherant vibrations and harshness ........transmitted through solid driveshafts." I admit before I converted my car I wondered if there would be a difference in the feel of the car but can now say that the only change is that Rotoflex wind-up is (obviously) absent. My Elan is as smooth as any other

The question of the longevity of the rest of the drive train has pretty much been answered by the number of cars now converted and the subsequent trouble free mileages reported by owners.

[thor]

These have been my own thoughts too, I must admit.
There is the initial large cost, but the job to change to CV joints (Sue Miller ones, not the ridicilously expensive US ones..!) seem a LOT easier than changing the Donuts, then that's it! 80% of my logical reasoning says yes to this for the spring...

[nebogipfel]

Thor, I think you should stick with your 80%

A set of Rotoflex couplings and bolts is pretty expensive and if you have to replace them again as soon as 3,000 miles (it has happened!) then A CV conversion begins to sound like a bargain.

It's not just the inconvenience but the potential damage done by failing couplings which has to be considered

I fitted Sue Miller shafts and am very impressed with them.

I suspect if modern CV joints had been available and cost wasn't a consideration Colin Chapman would have fitted them to the Elan

[thor]

And for the argument of extra strain etc., the +2 has a pampered life with a limited mileage and no track days... and a speed limit here in Norway of about 65mph tops, and that's on VERY few stretches of motorway.

And it would be nice to lose the elastic wind-up effect of the donuts.