Lotus Elan

Solid Driveshafts - Which Way Round?

PostPost by: William2 » Thu Dec 22, 2016 5:37 pm

A while back when I was rebuilding the chassis I fitted the U/J style solid splined driveshafts with the sliding inner spline half attached to the wheel side as opposed to the diff. Is this the correct way round or doesn't it matter??
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PostPost by: Apx » Thu Dec 22, 2016 6:30 pm

According to the diagram that i was supplied with mine the female part of the central sliding spines is attached to the diff via uj. therefore the male part goes to the wheel. I will try to scan it later. Cheers Neal
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PostPost by: Davidb » Fri Dec 23, 2016 3:23 am

William, If you think of the unsprung weight, the lighter end is to the outside where there is greater movement and hence, greater effect of weight. So, heavy end to the inside where it is supported by the diff which is directly attached to the chassis.
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PostPost by: Andy8421 » Fri Dec 23, 2016 1:05 pm

William,

It is unclear from your picture, but the 'ears' on the two ends of the central shaft need to be in the same plane. If I recall correctly, the splines can be pulled out and slid in at any angle, so it is possible to move the ears at one end of the shaft relative to the other.

If they are not in the same plane, the harmonic effect of the UJs will introduce significant vibration when suspension movement causes the UJs to run at an angle.
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PostPost by: pharriso » Fri Dec 23, 2016 1:34 pm

Andy8421 wrote:William,

It is unclear from your picture, but the 'ears' on the two ends of the central shaft need to be in the same plane.


Well spotted, looks to me like the ears are not aligned at all...

This drawing shows how the ears should be aligned:
performanceunlimiteddriveshaftad1984.jpg and
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PostPost by: Apx » Sat Dec 24, 2016 9:44 am

Diagram from TTR as promised
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scan.jpeg and
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PostPost by: William2 » Sat Dec 24, 2016 10:51 am

Thank you for your help. I must confess that I didn't realize that the U/J ears had to be in alignment. At least I got the drive shafts the correct way round so I only have to remove the wheel side to slide out the splines and turn them.
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PostPost by: vincereynard » Sat Dec 24, 2016 12:53 pm

William2 wrote:Thank you for your help. I must confess that I didn't realize that the U/J ears had to be in alignment.


Here's a nice demo. Out of phase is shown at about 4 minutes.

https://www.youtube.com/watch?v=T4P75ZQvpws
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PostPost by: stevebroad » Sat Dec 24, 2016 1:49 pm

Back in the 70s I destroyed a doughnut, pushing a caliper into the boot in the process. I thought that there must be a better way, so went about looking for one. I was wandering around my local breakers yard (you could back then) and spied a propshaft with a splined section. AhHA! I thought and immediately bought a couple. A little bit of measuring, design and welding resulted in a pair of solid driveshafts.

I won a Club Lotus Sprint meeting and North Weald with them so thought that I could market them and make a few bob. However, a few days later I saw an add by Performance Unlimited (similar to this one) for basically the same thing! A few expletives were said and I dropped the idea.

My design did require a little updating as the original steel tube couldn't cope with standing starts with slicks. I replaced the tube with aircraft spec seamless and that solved the problem.

Image



Image


It has been mentioned in various mags and forums that this type of splined driveshaft can lock up under load. 168bhp at the wheels said different. My only recommendation is not to leave the ground unless you have droop straps fitted as there is a good chance that UJs will lock up on full droop.
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PostPost by: Davidb » Sat Dec 24, 2016 4:47 pm

I had a frightening experience with sliding spline driveshafts when racing 26/R5 in the mid eighties. It was fitted with sliding spline driveshafts and a Hart 416B engine putting out 180 odd bhp. At full throttle when going over 'Deer's Leap", near the end of the main straight as the car settled it went into a series of swerves (at 135 mph) that were very frightening in an Elan with minimal roll-over protection (the good old days)! On subsequent laps I lifted off the throttle as I crested the rise and had no further problems. The only cause I was ever able to determine was that the driveshafts locked under full power and 'lifting' had reduced that power just enough to prevent it. The series 2 26R was fitted with roller spline driveshafts...

(I edited it! I meant to say the S2 26R was fitted with roller-spline driveshafts-not sliding spline)
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PostPost by: RogerFrench » Sun Dec 25, 2016 3:38 am

I was taught that the ears should be at right angles to each other.
In either case the cross- pieces are aligned, so I wonder if it matters.
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PostPost by: alan.barker » Sun Dec 25, 2016 8:55 am

The YouTube link as mentioned above is good watching
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