Wretched Rotoflex

[M.J.S]

Whilst under my +2 recently I noticed both outer rotoflex were showing signs of splitting, so ordered a new pair from Paul Matty.

On the car with the driveshafts level they didn't actually look too bad.

Horror of horrors when I came to replace them they literally disintegrated in my hands. Cannot believe they hadn't failed. The condition you see in the photo was how both actually came off - I haven't pulled them apart.

I think it's a good lesson for new Elan owners like myself to see the importance of getting a car high up with the load off the rotoflex's so they twist and kink, and you can see how bad the splits really are.

Trouble is when replacing the outer I have noticed one inner is just as bad, which looked perfect until it was angled with the weight off it.

Hope the inners are not as troublesome to change as the outers. Horrid 5 hour job, even when up on a borrowed ramp. Don't try and do it on a trolley jack laying on the floor.

Mark.

[Allison]

Mark,

Rotoflex do go but I would not recommend putting them under extreme conditions. They are designed to operate with some movement but even when changing a wheel you need to take the load off them so that they are not at full "flex".

We have remained with the rotoflex and use them on all our rallies - though in a fit of enthusiasm I did change one in Bhutan on the Himalayan rally - using a trolley and a scissor jack on the floor! I think that perhaps they were a bit unsettled when the car took off over a brow of a tarmac road and landed in a rubble track on the other side - we thought we'd really lost it then!

Peter

[gordonlund]

Hi,

Did you say you only replaced the outer? Expect the other to break very soon. You should always replace them in pairs, or better still, all four at once.

I have never replaced a single rotoflex coupling on it's own. They are easier to replace in pairs as the intermediate drive shaft is not fully tightened until the last operation thereby making the fitting operation a little more flexible. They are getting a little bit expensive now so many people are considering the solid shaft alternative.

Gordon

[Lincoln62]

I bought 3 spare donuts from Norfolk Motors in 89 when I was in the UK (it was all they had in stock) after reading horror stories about them. I replaced one that was showing some signs of cracking in 1997 (15000 miles ago). The car was restored in 1984 which means the other 3 are 24 years old and still look fine. The other spares are still in the boot of the Elan unused. Donuts are not all doom and gloom, I try to be smooth on takeoff and they seem to be lasting fine. You hear so many bad stories of donuts I thought I would add mine to the mix.

Peter
66S2

[richardcox_lotus]

What age / mileage have they done Mark ? - my previous set lasted about 9 years, but I also take reasonable care when pulling away - no GP starts for me.

We've all heard the horror stories about "new" rotoflex's not being up to the job - How old were yours ?

[Roy Gillett]

Hi Mark,

I am one who has converted to solid shafts (Sue Miller) after my last set of donuts failed after only 5000 miles. Believe me having one fail is not an experience you want twice (and it cost me a bent wishbone as well) .

My brother in Law is a rubber chemist and when mine went so quickly he said he was not surprised because there are now many nasty chemicals that used to be used in functional rubber products that are now banned ; so 'modern' versions of things like our donuts are nothing like as 'functional' as they used to be. He particularly said that bonding rubber to metal was now a real headache without the nasty chemicals and yours does seem to have separated at exactly that interface (as mine did).

This explains why Peter gets such good life out of 'old' donuts. I am willing to bet he won't get that sort of mileage if he ever has to fit new 'new' parts.

I would go for solid shafts if I were you. Mine have now done over 20,000 miles, including 6 competitive rallies and two trackdays and are still perfect, and they make the car so much nicer to drive. Take-off and gearchange improve beyond belief.

Remarkably they are not much more expensive than 4 donuts and 12 special bolts needed for a donut change. (and fitting solid shafts is simple, not like changing donuts!!)
Best of luck


Roy

[Roy Gillett]

Arithemic was never my strong point. Its 24 special bolts , isn't it

Roy

[M.J.S]

What age / mileage have they done Mark ? - my previous set lasted about 9 years, but I also take reasonable care when pulling away - no GP starts for me.

We've all heard the horror stories about "new" rotoflex's not being up to the job - How old were yours ?

No Grand Prix starts for me either.

Don't know exact age. The car had a major rebuild and new galvanised chassis about 7 years ago so I guess that's when they were last changed.

Given however the car has covered only 31,000 miles in 36 years, and less than 2,500 miles in the last five years, they can't have done many miles.

Will try and buy a new pair today to replace the inners; better safe than sorry. Anyone within 5 miles or Ormskirk had better put their fingers in their ears.

Mark.

[Emma-Knight]

I'm not shure, but Donuts nowadays are "tested" by putting them into an angle they were not designed to work in. This means testing them in tension and may cause the fault that would not have appeared when not testing them. Normal load is pressing rubber and steel together - not twisting them appart. Maybe the old rubber only design was a bit more resistent against beeing twisted.
Maybe MOT is the strongest enemy of those precious round things.

Greetings from Heisenberg....

Anna

[gordonlund]

Hi,

Try post
Things in Common
Posted: Mon Jan 22, 2007 7:02 pm
Dave bean Rotoflex couplings

All the information you will need

Fort Dunlop will never be the same!!!

Gordon

[robcall]

This one?
http://www.lotuselan.net/forums/viewtopic.php?t=14251

[gordonlund]

Exactly!

Thanks for the link, I forgot how to do that.

Everything you need to know about Rotoflexes. If you treat them nice they will last. Like the rest of any Lotus (Lots of trouble usually serious) problems only come if you expect ultimate performance all the time.

Gordon

[chrishewett]

Mark,
My opinion, get rid of them and convert to cv joint driveshafts. I use Mick Miller.
Have some worry free motoring.
Chris

[billwill]

My prior set fell to bits like the photo above, I was horrified. I suppose on average mine have been changed (all 4 at once) about every 10 years.

Somewhere on this forum are pictures of my techniques for fitting them, but I can't find the topic at the moment.


Ah, found it:
http://www.lotuselan.net/forums/viewtopic.php?t=16456