Lotus Elan

Performance unlimited driveshaft conversion feedback Please

PostPost by: huggy » Mon Oct 29, 2018 12:19 pm

Interested about feedback of this driveshaft conversion made by performance unlimited on Baby Elan.

They seems commun and good rated on +2 but I do not find feedback for the Baby.

A set have been given to me by previous owner but it was not bolted on car....
Are they a good conversion for the baby? or could be tricky as baby driveshaft are shorter than +2 one

Or performance unlimited made 2 different set ? It seems they are not in business anymore :|
So no infos available from them now...

This UJ come in a box with car at no cost but unfitted (even free) parts means they were perhaps not the solution to go !

What do you think ?
Last edited by huggy on Tue Oct 30, 2018 9:01 am, edited 2 times in total.
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PostPost by: mikealdren » Mon Oct 29, 2018 12:57 pm

Can't comment from experience but you don't really want UJs on the drive shaft, CV joints took over years ago, they're used on most modern cars and kits are readily available.
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PostPost by: Andy8421 » Mon Oct 29, 2018 4:11 pm

UJs are sort of OK, as long as you have the ears of the yokes in line, and the angles of the UJs to the driveshaft equal at both ends. If both of these conditions are true, then the harmonic vibration introduced by the UJ at one end of the shaft is cancelled out by the UJ at the other. There is a pretty good Youtube video that explains this:

https://www.youtube.com/watch?v=gmV4qwLfOMY

On the Elan, with the Chapman strut rear suspension, the requirement of 'equal angle at both ends of the shaft' is just about met. The problem with these shafts is the spline. UJs don't plunge, and the suspension design requires the shaft to change length as the suspension goes up and down. The solution is the spline, but splines lock up if torque is applied to the shaft. The result is that under acceleration, the shaft goes solid, locking the rear suspension. This feeds side loads into the diff casing, and possible suspension instability at gear change points when the spline frees up as the torque is released.

Chapman was aware of this and used fancy and expensive ball splines that didn't suffer from the torque lockup on his racing cars. A better solution these days is to use CVs.

TTR offer a spline / UJ combination for historic racing, which I have on my S3. I don't particularly like it, but the suspension travel is so limited when racing that it doesn't seem to be an issue. I would rather have CVs.
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PostPost by: Orsom Weels » Tue Oct 30, 2018 8:53 am

Tried to fit a set of these to my friends series 3 but found on full suspension drop the 'ears' tangled & locked them up. They would have needed reduced travel shocks as per some CV conversions (or some other form of droop limiting) so we didn't pursue them further & stuck with Rotoflexes.

Regards, Tim
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PostPost by: rgh0 » Tue Oct 30, 2018 9:38 am

"On the Elan, with the Chapman strut rear suspension, the requirement of 'equal angle at both ends of the shaft' is just about met"

On a race car with limited suspension travel this may be the case but on a road car with full travel the angle of the hub shaft versus the diff output shaft changes a significant amount even if the UJ does not bind . Cv's are the right solution for a road car to replace donuts. On a race car you would only use UJ's due to FIA regulations not allowing CV's

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PostPost by: William2 » Tue Oct 30, 2018 11:06 am

I have Performance Unlimited fitted to my car by previous owner although the car was used for track use. It is fitted with SS cables and aluminium fastening blocks as you can see in photos to restrict travel. I make sure I liberally grease the sliding splines with the correct type of grease. The set up seems to work fine and I only cover about 2000miles per year. Long term I might fit CVs' as supplied by Susan Miller but I'm not sure if you need to limit suspension travel with these?
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elan-chassis-finished-003.jpg and
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PostPost by: huggy » Tue Oct 30, 2018 11:15 am

William2 wrote:I have Performance Unlimited fitted to my car by previous owner although the car was used for track use. It is fitted with SS cables and aluminium fastening blocks as you can see in photos to restrict travel. I make sure I liberally grease the sliding splines with the correct type of grease. The set up seems to work fine and I only cover about 2000miles per year. Long term I might fit CVs' as supplied by Susan Miller but I'm not sure if you need to limit suspension travel with these?


Interesting thanks
Could you let me know:
- What grease do you use ?
- Did you make fatsening block and cable yourself or can they be bought somewhere ?
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PostPost by: nmauduit » Tue Oct 30, 2018 11:53 am

huggy wrote:- Did you make fatsening block and cable yourself or can they be bought somewhere ?


I use a slightly different setup, just with a 3mm (iirc) stainless cable loop between the top and bottom plateform, and that can be set in length with a cable clamp (all sourced at Leroy-Merlin, no affiliation on my part). I've seen other similar approaches with a strap rather than a cable.

lotus-suspension-f42/solutions-restrict-rear-suspension-travel-droop-t34803.html?hilit=droop
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PostPost by: Andy8421 » Tue Oct 30, 2018 12:04 pm

rgh0 wrote:"On the Elan, with the Chapman strut rear suspension, the requirement of 'equal angle at both ends of the shaft' is just about met"

On a race car with limited suspension travel this may be the case but on a road car with full travel the angle of the hub shaft versus the diff output shaft changes a significant amount even if the UJ does not bind.

cheers
Rohan


Rohan, is this correct? I thought the whole point of the Chapman strut was to control changes in camber with suspension movement. Eyeballing it, I would have thought that the camber of the rear wheel doesn't move by more than 5 degrees from normal ride height to full bump.

I do agree that CVs are a far better option.
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PostPost by: nmauduit » Tue Oct 30, 2018 12:15 pm

Andy8421 wrote:
rgh0 wrote:"On the Elan, with the Chapman strut rear suspension, the requirement of 'equal angle at both ends of the shaft' is just about met"

On a race car with limited suspension travel this may be the case but on a road car with full travel the angle of the hub shaft versus the diff output shaft changes a significant amount even if the UJ does not bind.

cheers
Rohan


Rohan, is this correct? I thought the whole point of the Chapman strut was to control changes in camber with suspension movement. Eyeballing it, I would have thought that the camber of the rear wheel doesn't move by more than 5 degrees from normal ride height to full bump.

I do agree that CVs are a far better option.


I have the feeling that 2 distinct issues are discussed here, with a possible confusion : Rohan reminding that the UJ are likely to mechanically bind at full droop, while there is an other issue with cyclical vibrations as illustrated by the video (as long as camber is constant and close to 0 the vibrations of properly phased UJ solid shafts would cancel out except for the center portion itself).
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PostPost by: William2 » Tue Oct 30, 2018 1:52 pm

The grease I use is Molybdenum Disulphide (CV grease) and no I didn't make the aluminium blocks.
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PostPost by: miked » Tue Oct 30, 2018 7:32 pm

Elan Plus 2S with long stroke shocks driven on the road for approx 12k miles - no problem.
3 Elan S4's with droop limited shocks. One driven 10k miles, one driven 1k miles. Last one driven 8k miles up to now with 185bhp Zetec pushing it along.
All above TTR style with super glide coating and moly grease.
So in my opinion of actually using them, no problem. Nice video. Yes, need to be ligned up.
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PostPost by: huggy » Wed Oct 31, 2018 6:04 pm

Thanks for all comments: Very interesting.
I will try these UJ with "Rohan style" cable solution
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PostPost by: huggy » Wed Nov 07, 2018 9:02 pm

Little update.
Perhaps it could help someone one day:

- Classic motorcycle fork gaiter could be an alternative solution to perished gaiters
Image

- These ARB mounting block can help to make the travel drop suspension just need la little L bracket on the top of ARB mounting block and a little hole in chassis.
Image
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PostPost by: huggy » Wed Nov 07, 2018 9:05 pm

And I know my wishbone color is strange :roll:
Was previous owner idea but 28 years later this Hamertite paint still protect them quite well.

A little bit like if I own goldfinger car ! :mrgreen:
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