Lotus Elan and Lotus Elan Plus 2 Forums

Also posted elsewhere....



It's just come to me...let's all spend five minutes a day just clicking on these links (don't even bother waiting for them to load fully) then Jeff gets a nice little earner..and whoever devised this thing gets their fingers burnt with a loss rather than profit....

John

Thank you all for your advice. Thank you Craig for recounting your experience of both types of shaft, I can now make a choice with much greater confidence. I think the practical solution will be to order a set of splined shafts. John

Have you considered Spyders kit? It's a CV at one end and rotoflex at the other.

I went for it last year, and so far so good. Spyders sales spin is -

Stress is less at the diff end so much less need to worry about the rotoflexs breaking.
Because a rotoflex is at the diff end, is puts much less stress on the (probably very old) diff.
It maintains that windup 'original' feel - if you're bothered about that sort of thing.

Just my pennies worth.

Ian

For what its worth, not all kits are created equal. Here is info about one available in the US by RD Enterprises http://www.rdent.com/
. This kit does more than just replace donuts! It replaces rotoflex couplings, intermediate axle shafts, differential output shafts and bearings, and associated hardware.

Each kit includes two uprated differential output shafts with bearings, axle shafts with Lobro CV joints and adapter for outboard (hub) shaft. Installation is not difficult and can be accomplished by the Elan owner/mechanic. Enjoy the increased reliability of cv axles - no more rotoflex couplings to fail! If you're serious about eliminating the rotoflex couplings (donuts) this is the only way to go! Much better than u-joint conversions! Elan CV Rear Axle Conversion Kit is fully assembled and ready to fit. One kit required per car.

Ref. 26RD0034 Elan CV Kit - $1550.00
Ref. 50RD0034 Elan Plus 2 CV Kit - $1625.00

These have been around for a long time. Mine are at least 30 years old and other than replacing a couple of boots, no issues.
No connection, just thought you should have the info.
Dan

I'll give the spyder driveshafts another thumbs up.. Great so far. The doughnuts at the diff just dont seam to be anything like as stressed as they get with the 4 off them set up... I'm over three years down the line using them now and they are brill'.

Al '.....

joc wrote:Thank you all for your advice. Thank you Craig for recounting your experience of both types of shaft, I can now make a choice with much greater confidence. I think the practical solution will be to order a set of splined shafts. John

I have TTR UJ splined shafts on an S3 that I circuit race. Although I have no problems with this arrangement, the suspension travel is very limited and may not show up the plunge issues with long suspension travel. I have certainly read (but now can't find) reports that Chapman used 'ball splines' to avoid spline lock up in his formula cars. It is certainly true that splines lock when carrying high torque loadings. When I spoke to TTR about this issue, they said they did not use teflon coated splines. For my road going Elan, I will be purchasing CV driveshafts.

Salut Alex and Ian

So Spyder drive shafts are still prone to surging? Their sales pitch says otherwise.

@+

Vernon

Yes you do still get a little surging but not an issue. The diff ends of the shafts have doughnuts but there is little flexing so longer life. the idea is that some rubber still built into the driveshafts protects the transmission from shock. Just as the as the master designed in.. So a little bit of the best of both worlds and not too expensive either..

I would honestly tell you if I did not like them. But, as I say so far so good, very little surging, and a happy diff.

To each their own ....

Alex..

I second everything that Alex says, and here a pic of mine when they were fitted. Spyder generally have a good balance between improving and keeping original in my experience.

Ian

Iyarno wrote:I second everything that Alex says, and here a pic of mine when they were fitted. Spyder generally have a good balance between improving and keeping original in my experience.

Ian

I very much concur Ian..

Alex

Of interest to those thinking of using UJ's and splines. From a forum about Triumph 2000 suspension.

http://t2000.kvaleberg.org/t_faq.html

Rear end twitch

I have a slight problem with the rear end moving when I change gear, do you know what causes this?

You are experiencing what is known as the Triumph Rear End Twitch. The real source of the problem is the rear axle shaft splines, which lock up when engine torque is applied, and is released again when the torque disappears, e.g. when you change gear. The geometry of the rear suspension is such that when the splines lock up, the rear wheels are no longer free to move up and down as they would normally. So, in circumstances where there are load changes when torque is applied, e.g. when accelerating into a curve, you will notice a rear end twitch when you change gear, and the rear suspension settles in the new position.

This phenomenon was present even when the car was new, but a couple of wear points can exaggerate it. The most important point are the rear splines themselves. They need to have a good coat of molybden based grease. Any stale and old lubricant should be replaced by fresh grease. To get to the splines, you have to undo the axles at the flange of the inner universal joint. Also check the condition of the axle rubber gaiter, and renew if it seems to be stiff and brittle.

Wear in the rear suspension trailing arm hinge bushes will also increase the twitch, as will any looseness in the rear axle rubber mounting points.

By design, the twitch will always be present, and more so the stronger the engine is. Fitting stiffer rear springs and stiffer trailing arm bushes will make it less pronounced.

If you want to get rid of it completely, there are two known solutions:

Fit axles that have linear bearings instead of sliding splines. This involves fitting of salvaged Datsun rear axle shafts, as well as some re-machining of the rear axle universal joints [CW].

Fit axles with modern constant velocity joints instead of universal joints, allowing sufficient lengthwise movement. New axles have been purpose made by Hardy Spicer for this purpose. This is of course the most elegant solution, but also quite costly.

My sentiments exactly, I owned a 1977 triumph 2500 TC for many years, lovely car to drive,
and it out handled anything that Ford or GMH (Holden Cars) could ever offer in that period.

Plenty of times I experienced the rear end "jacking effect".... keep the power on
through a given corner, and things are OK... but if you had lift off the loud pedal suddenly
half way through a corner, it all went pear shaped pretty quickly.

You learned to live with it... but it caught many drivers out.... I also used to know
guys who owned crappy Triumph spitfires, the spitfire rear suspension was even
worse... you would have to ask, would you bother?

So, you love rotoflex/donuts, what ever you like to call them, that's fine, learn
to live with them.

But to any elan owner who has made the switch to CV DS... they know from
experience the huge difference it makes.

Drive line harshness only comes from a lead boot type of driver who does not
have much in the way of mechanical empathy.

The argument for or against CVs will never end.

Did Chapman really install rotoflex to add cushioning in the drive line, or was
the company that strapped for operating cash, that the cheap & readily obtainable
donuts solved a production problem, as well as improving the bottom line company
profits.

ceejay wrote:But to any elan owner who has made the switch to CV DS... they know from
experience the huge difference it makes.

Drive line harshness only comes from a lead boot type of driver who does not
have much in the way of mechanical empathy.

Indeed, and why would the Elan driveline without Rotoflex couplings be any more harsh than any of the other millions of cars driving around.

nebogipfel wrote: ...why would the Elan driveline without Rotoflex couplings be any more harsh than any of the other millions of cars driving around.

I have read reports, from some, of increased NVH. Presumably their particular installation generated torsional vibrations, at a particuar frequency, which were no longer damped. Maybe each installation is unique. A bit like the instance of rigidly mounted Webers that worked perfectly until new engine mounts altered the natural frequencies involved ?

Cheers - Richard