Lotus Elan

CV drive shaft conversion

PostPost by: rgh0 » Fri Feb 02, 2024 3:18 am

The max amount of droop depends on the CV joint used and also the boot. For example the VW combi CVs allowed more droop due to its suspension design

Not all the conversions use the VW CV either

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PostPost by: UAB807F » Fri Feb 02, 2024 6:34 am

From my limited knowledge, as Rohan says, not all the conversions use the same CV joint. I have a hazy memory of Ford (Sierra ?) joints being used at one point and presumably they are different specs to VW joints.

For me the "lock up" feature hasn't been a problem, just limit the droop on the damper and job done. And it's not as if I'm lifting wheels or catching air when I drive anyway, I haven't been a hero for years !

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PostPost by: ill_will » Fri Feb 02, 2024 7:08 am

I understand some later/federal(?) cars were fitted with a failsafe stud and cylinder arrangement so that if the doughnut let go it would be contained. (I've never seen one in the flesh.)

Can anyone with this setup confirm that it works? Given the risks with doughnuts I'd probably opt for this setup if using them.

FWIW I had doughnuts on an S3 when I first got it, but they were looking a little tired and I didn't like the surge, so they got swapped for Susan Miller CV joints which were great. Only downside is weight, as mentioned previously.

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PostPost by: oldelanman » Fri Feb 02, 2024 8:27 am

rgh0 wrote:The max amount of droop depends on the CV joint used and also the boot. For example the VW combi CVs allowed more droop due to its suspension design

Not all the conversions use the VW CV either

cheers
Rohan


Also, according to the Elantrickbits website the CV joints are modified so they don't limit droop on the Elan.

Screenshot 2024-02-02 082451.png and
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PostPost by: Andy8421 » Fri Feb 02, 2024 11:37 am

ill_will wrote:I understand some later/federal(?) cars were fitted with a failsafe stud and cylinder arrangement so that if the doughnut let go it would be contained. (I've never seen one in the flesh.)

Can anyone with this setup confirm that it works? Given the risks with doughnuts I'd probably opt for this setup if using them.

FWIW I had doughnuts on an S3 when I first got it, but they were looking a little tired and I didn't like the surge, so they got swapped for Susan Miller CV joints which were great. Only downside is weight, as mentioned previously.

Will


I had the pin and tube arrangement on my Sprint. I recall posts sometime back that suggested it wasn’t a man enough arrangement, and under certain conditions would also fail in the event the rotoflex failed. I think it is telling that lotus felt the need to introduce this modification which would indicate that there were enough failures of a serious nature to warrant it.
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PostPost by: 661 » Fri Feb 02, 2024 12:41 pm

Andy8421 wrote:
ill_will wrote:I understand some later/federal(?) cars were fitted with a failsafe stud and cylinder arrangement so that if the doughnut let go it would be contained. (I've never seen one in the flesh.)

Can anyone with this setup confirm that it works? Given the risks with doughnuts I'd probably opt for this setup if using them.

FWIW I had doughnuts on an S3 when I first got it, but they were looking a little tired and I didn't like the surge, so they got swapped for Susan Miller CV joints which were great. Only downside is weight, as mentioned previously.

Will


I had the pin and tube arrangement on my Sprint. I recall posts sometime back that suggested it wasn’t a man enough arrangement, and under certain conditions would also fail in the event the rotoflex failed. I think it is telling that lotus felt the need to introduce this modification which would indicate that there were enough failures of a serious nature to warrant it.


Indeed, and although the pin and tube arrangement might perhaps contain the driveshaft, the rubber and bolts are still being flung around
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PostPost by: types26/36 » Fri Feb 02, 2024 1:39 pm

This article may be of interest to some regarding CV’s.
http://blindchickenracing.com/How_to/CV ... ts_101.htm

For those who dont know VW’s.
The type 1 is a Beetle (air cooled)
Type 2 is Kobi/bus.
Type 3 (bigger then Beetle)
Type 4 is the VW 411/412 model.
I can confirm that (at least) the early MM CV’s were Ford Sierra 100mm diameter cv’s. I don’t know about the later ones which may be VW type.
I used to work for VW back in the day so knew them pretty well at the time.
I can also confirm that the Ford and VW types are not interchangeable as the number of spines the cv’s fit on are different between Ford/VW.
I made a couple of sets twenty years ago, one set using VW 100mm Golf GTI/Kombi cv’s which I believe are the same.
The other set using 95mm VW Beetle cv’s.
The 100mm ones are still in use and given no trouble (apart for a failed adapter) which was not the fault of the cv’s.
I don’t know of the 95mm set as I sold that car.
Back to the 100mm set, I never restricted the droop but was always carful to jack up the car and not let it go into full droop, a couple of years ago I did add a limit strap after reading numerous accounts of failed installations but I had not experienced problems except for the adapter.
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PostPost by: pharriso » Fri Feb 02, 2024 2:20 pm

ill_will wrote:I understand some later/federal(?) cars were fitted with a failsafe stud and cylinder arrangement so that if the doughnut let go it would be contained. (I've never seen one in the flesh.)

Can anyone with this setup confirm that it works? Given the risks with doughnuts I'd probably opt for this setup if using them.
Will


It's not a Federal thing.

My 130/5 had them in the UK, did absolutely nothing when a doughnut failed launching onto the A1 late at night :(
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PostPost by: rgh0 » Fri Feb 02, 2024 5:46 pm

Andy8421 wrote:
ill_will wrote:I understand some later/federal(?) cars were fitted with a failsafe stud and cylinder arrangement so that if the doughnut let go it would be contained. (I've never seen one in the flesh.)

Can anyone with this setup confirm that it works? Given the risks with doughnuts I'd probably opt for this setup if using them.

FWIW I had doughnuts on an S3 when I first got it, but they were looking a little tired and I didn't like the surge, so they got swapped for Susan Miller CV joints which were great. Only downside is weight, as mentioned previously.

Will


I had the pin and tube arrangement on my Sprint. I recall posts sometime back that suggested it wasn’t a man enough arrangement, and under certain conditions would also fail in the event the rotoflex failed. I think it is telling that lotus felt the need to introduce this modification which would indicate that there were enough failures of a serious nature to warrant it.


I had them on my 73 Plus 2S 130/5. It did not work. When the donut failed it just sheared of the pin and then the shaft flailed around damaging the chassis.

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PostPost by: UAB807F » Sat Feb 03, 2024 7:24 am

Reading these reports from you guys who have had the failsafe driveshafts and also had them falling apart is a bit unsettling.

When I first read about the Lotus modification I was still using rotoflex and thought "I bet that was in case they got sued in America for a failure". Then later, after considering how Chapman did the minimum to get performance and keep costs in check, I changed to thinking "these things must fail badly and it's cheaper to weld on a bit of tube and round bar than it is to redesign the rear suspension".

I drove on rotoflex from getting the car in the mid 70s and in those days I would be tinkering with the car on a regular basis so you could say they were inspected weekly. I'd replace rotoflex and bolts whenever I saw cracking around the steel inserts. In those days you could get good quality parts so it was no big deal and not worth the cost of changing to UJ & sliding spines which was the option back then. (although I did consider it at one point)

The Elan went off the road for a while around 2003-4 and when I came to get it roadworthy again, the rotoflex were old rubber, the start of delamination at the steel inserts on droop and not trustworthy. And that's why I went CV.

Lotus themselves obviously thought there was a problem with the rotoflex in the Elan application otherwise they wouldn't have introduced the fail safe driveshafts. (which clearly don't from your comments). Add in the comments I hear on the internet about variable quality in rubber components and where they're sourced from and it became (for me) a no brainer.

After reading Rohan's posts it should be clear to everyone that if you want to use rotoflex on a daily basis then it's a weekly check-up because once delamination starts you have no idea how quickly it will progress..
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PostPost by: EPC 394J » Sat Feb 10, 2024 2:18 am

As another contributor has posted, I too have the Spyder half and half solution. Each drive shaft has a CV plus a doughnut. I really like the set up. I bought my first Plus 2 in 1982. My current one gives the same (unique!) driving experience. As an aside, the drive shaft at the doughnut end is captive within a cup, so should the doughnut fail, any flailing is greatly restricted. I’ve been driving the car now for almost ten years on the same doughnuts, though with a ramp in my garage it’s not difficult to check them.

Somebody else also mentioned “sprung weight” which I think is definitely a consideration in the Lotus driving experience.

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PostPost by: mjbeanie » Sun Feb 11, 2024 5:53 pm

Just got my CV kit from Elantrikbits down under, in Australia. Very nice. Machining looks very well done. An email was received from Col, with detailed instructions as well. I will generate a separate thread when I am installing them on my +2, as this seems a popular topic. Here's a photo:
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IMG_3381.jpg and
IMG_3384 (1).jpg and
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PostPost by: TonyA » Sun Feb 11, 2024 10:08 pm

Love to hear how your installation goes: I am about to fit the Sue Miller driveshafts on my Plus 2

Of particular interest is where to support the car to get the job done..

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PostPost by: Lotus54 » Sun Feb 11, 2024 11:27 pm

When I recently fit my Elantrikbits axles (66 Elan) I had the rear suspension all apart. So it was super easy to fit. I did not take them apart (like instructions say)- but did keep the allen screws loose until all fit.
I had the upper damper fitted, but put the axles on before the A-Arm. That worked quite well.
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PostPost by: alan.barker » Mon Feb 12, 2024 7:33 am

Lotus54 wrote:When I recently fit my Elantrikbits axles (66 Elan) I had the rear suspension all apart. So it was super easy to fit. I did not take them apart (like instructions say)- but did keep the allen screws loose until all fit.
I had the upper damper fitted, but put the axles on before the A-Arm. That worked quite well.

Sorry but as i understand the Fitting Instructions don't say take apart.
It says unscrew one turn each Allen Screw one turn.
Ref: fitting instruction paragraph 2.
Correction just reread and it says remove inside adapter plate
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