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Rotoflex to swing spring conversion


David Kirk
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ive come across a couple of swing shafts failures  all from a crack eminated from reversed torsion ie  LH second hand shaft fitted to a RH side  so the torsional memory has been reversed 

ends up with nice smooth split almost looks like its been cut off .

most rotaflex couplings of original specification do last for many years , it the crap after market copies that give up early 

there are some nice poly/neoprene type ones used in marine drives , no idea if they would take the torque of driving wheels ,  not done any homework on them .

Pete

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11 minutes ago, Dick Twitchen said:

Lotus used them in the Elan and their GP cars, as did Alfa Romeo and the Hillman Imp had them.  All the rage at the time and fine with Metalastic Ltd manufactured items?

Dick

Yes, I am aware of that. But the 2000 range used a sliding splines/double UJ setup, which is better, and others (1300fwd?) CV joint which is what Dave at CC used on his CV conversion. But using a rubber donut is an inferior solution to the problem.

I know that bubber donuts are used in many propshafts, I assume to soften take-up, which is a plausible theory with the triumphs to reduce diffs breaking/warranty claims.

As to reproducing decent new ones, it will be the usual problems. (a solution in CV shafts exists at a price, but mainly that many will see a cheap/nasty £30 donut and won't understand that £100-200 version is worth the extra. So a quality version will sell is such small numbers nobody will bother unless there is a large volume of demand elsewhere)

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I agree the dougnut design is a tortuous use , far simpler on Imps etc  as a straight fit inboard not the  contorted  inside out fitting  inside the wishbones of triumphs idea, 

it does make you wonder why when CV were used in much of the BL range of the day , maybe futile independance like the stag engine 

icant see it was to protect the diff as whilst not the best they had they are not particularly  explosive in normal use 

its anther love it hate it thats lasted 50 years 

pete

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What we tend to forget these days, now that CV joints are universal and dirt cheap, is that in the 1960s they were still expensive. And unnecessary. You point to the other BL cars that used them - remember two things: Triumph and Austin were not the same company when the Mk2 GT6 was designed, and the cars that did use CV joints were FWD, where the joint needs to perform round a very wide angle. Even the Triumph 1300 only used CV on the outer - the inner was a Rotoflex.

As to the tortuous fitment, it allows the doughnut to be further outboard than would otherwise be the case.

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53 minutes ago, NonMember said:

What we tend to forget these days, now that CV joints are universal and dirt cheap, is that in the 1960s they were still expensive. And unnecessary. You point to the other BL cars that used them - remember two things: Triumph and Austin were not the same company when the Mk2 GT6 was designed, and the cars that did use CV joints were FWD, where the joint needs to perform round a very wide angle. Even the Triumph 1300 only used CV on the outer - the inner was a Rotoflex.

As to the tortuous fitment, it allows the doughnut to be further outboard than would otherwise be the case.

+1 to that; you must remember that at the time, they were fitted as a simple and innovative solution to large suspension movements and flex and if anything went wrong they could be replaced by the garages of the time, as much as a service item requiring regular replacement. I don't think Triumph expected them to last forty years, or for owners to have problems sourcing replacements.

1768326574_rotoflexad.thumb.jpg.07dff4baf3ea35c6663cdb1ec07eaa2f.jpg 

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12 hours ago, Nick Jones said:

 

Built our Spit up as roto (with CV shafts) in considerable part due to the number stories of lost rear wheels....... Three wheels on my wagon and no brakes.....  no thanks!

Another angle to that is that all the OE shafts are at least 40 years old now, so fatigue has had time to do it's work.  So you might think that new ones are a wise investment - and on the face of it, you'd be right.  However, having heard a few stories and seen a few pictures of new shaft failures, or near failures in the last couple of years..... perhaps not.  Problems seem to be mainly with the way that the UJ yoke forging is attached to the shaft and being rather less secure than the OE ones - which very rarely fail at that point.

Nick

Myself and american Bill were exiting a roundabout just outside Bude in Cornwall,going uphill at about 30 when the rear started wobbling,the wheel came off with the brake drum still attached,car slid along the road on the twin box exhaust,managed to pull to the side ok,the wheel ended up in a ditch.

I looked at alternative swinger shafts,Sommers Bros in the US,i think Chris Sherrington used them on his T6,but they were nearly a grand a pair.

CV virtually fit and forget,about £700 all in.(diy fit)

Steve

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Handbrake guides are different, they are chassis mounted for swing spring and body mounted for Rotoflex. You'll need to cut the handbrake guides off a swing spring car and weld them on to your chassis plus maybe  cut the old guides off your bodytub as they might be in the way. I have heard of people neglecting to change this and the handbrake either binds or doesn't work depending which way around you are converting. 

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19 hours ago, Cookie said:

Handbrake guides are different, they are chassis mounted for swing spring and body mounted for Rotoflex. You'll need to cut the handbrake guides off a swing spring car and weld them on to your chassis plus maybe  cut the old guides off your bodytub as they might be in the way. I have heard of people neglecting to change this and the handbrake either binds or doesn't work depending which way around you are converting. 

You don`t need to cut off the guides,mine is a Mk 1,just needs careful setting up of the brake balance and handbrake,mine works fine.

Steve

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On 23/07/2020 at 19:05, clive said:

I think"rotoflex" suspension refers more to the style rather than the actual components. At least these days. And yes, goodnessknows why Triumph used an "iffy" rubber donutrather than the CV which was used in other Triumph cars. Possibly cost? Or I did hear a whisper it helped diffs to survive.

Yes, I've been told that it helped the diffs survive too.

Cheers, Richard

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