Lotus Elan

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PostPost by: The Veg » Mon Feb 26, 2024 3:21 am

And remember, almost no car is the result of some divine alchemy, but rather an amalgamation of compromises made for a staggering variety of reasons, but in the case of Lotus*, most of those reasons are cheepness. :mrgreen:

I'd bet donuts to drain-plugs that *nobody* in Chunky's employ deliberately determined after much contemplation that Rotoflexes would be the absolutely perfect thing for this application. More like, 'what already exists that will do the job and meet our price-point?'

*And most cars, when you get down to it.
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PostPost by: 2cams70 » Mon Feb 26, 2024 8:01 am

The Veg wrote:And remember, almost no car is the result of some divine alchemy, but rather an amalgamation of compromises made for a staggering variety of reasons, but in the case of Lotus*, most of those reasons are cheepness. :mrgreen:

I'd bet donuts to drain-plugs that *nobody* in Chunky's employ deliberately determined after much contemplation that Rotoflexes would be the absolutely perfect thing for this application. More like, 'what already exists that will do the job and meet our price-point?'

*And most cars, when you get down to it.


I completely disagree with that statement. Lotus (and Ford UK) mostly did what was the most smart and intelligent thing to do within the constraints of what was available to them at the time. They would not have been so successful if they had not.
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PostPost by: Andy8421 » Mon Feb 26, 2024 4:24 pm

Veg and 2cams70,

I think underneath it all you are both saying the same thing. I'm an ex design engineer, and money is always the ultimate constraint.

Chapman was apparently fond of saying 'an engineer does for 10 shillings what any fool can do for a pound' (or some variation on this). Unless you are designing for the military, or the Apollo program, cost always matters. You can always make a better job of something if you can spend more money on it.

Lotus used ball splines and UJs in their racing cars and on the 26R. Apparently the Elan was going to have inboard rear brakes until it was established that Rotoflex weren't up to it and Tony Rudd mentioned in his book that Rotoflex failures were the biggest cause of warranty claims on the Elan.

I think it would be reasonable to assume that the choice of Rotoflex was primarily a cost and not performance driven decision.

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PostPost by: SCElan » Mon Feb 26, 2024 5:18 pm

and compared to anything else at the time was the best solution where 'adding lightness' was the aim (and cost).

The CVDS's have cleared customs and are in Coventry might have em in the morning! :D
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PostPost by: mbell » Mon Feb 26, 2024 7:54 pm

Andy8421 wrote:I think it would be reasonable to assume that the choice of Rotoflex was primarily a cost and not performance driven decision.


I suspect rotoflex we're the cheapest solution that met the basic requirements.

I think engineering is a lot about requirements and finding a solution that addresses all the requirements, where low or lowest cost is one of the significant requirements. Often it's a trade off between the requirements.

Then there the fact that as owners we have different requirements and different weighting on requirements to the manufacturer, so we often decide to modify cars.

CV axles are a good example, a lot of people prioritize reliability, safety and low maintenance. That along with the quality issue for rotoflex and high cost means CV axles are a better solution for a lot of people.

However some people prioritize originality more so keep to the rotoflex. The difference between the groups is in the requirements and there weighting, which are a personal thing.
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PostPost by: SCElan » Mon Feb 26, 2024 9:04 pm

I had the rotoflex on mine for many years. It came to me with a CV joint and rotoflex combination drive shafts goodness knows where they came from. The guy who had it a few years before was an engineer and did all sorts to it. Theres a chance he made them.

The crucifix on one side snapped so went back to 4 couplings. My local chap is a staunch believer in RFC's as they are more forgiving on the drive train. Lately due to experience with quality of the RFC's and degradation of fairly recent units we have decided CVDS's are the way to go.

I have driven the car with vigour in the past and always 'made progress'' how on earth it ran I have no idea because most of it was worn out. Its been across europe and even round the ring for a lap and a half - well scary and it never let me down on any of those trips...well not that i couldn't fix it with wire, tie wraps and/or duct tape :oops:

If its possible to say any Elan is standard when no bugger has a clue where the sprint stripes should officially go then mine definitely is not standard.

I like it the way it is and anything to increase reliability so I can drive it with confidence is a must.

With all these cockwombles 'in charge' we don't know how much actual driving there is left to do! :|
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PostPost by: 2cams70 » Mon Feb 26, 2024 11:14 pm

Andy8421 wrote:eg and 2cams70,

I think underneath it all you are both saying the same thing. I'm an ex design engineer, and money is always the ultimate constraint.

Chapman was apparently fond of saying 'an engineer does for 10 shillings what any fool can do for a pound' (or some variation on this). Unless you are designing for the military, or the Apollo program, cost always matters. You can always make a better job of something if you can spend more money on it.

Lotus used ball splines and UJs in their racing cars and on the 26R. Apparently the Elan was going to have inboard rear brakes until it was established that Rotoflex weren't up to it and Tony Rudd mentioned in his book that Rotoflex failures were the biggest cause of warranty claims on the Elan.


Perhaps I should have explained myself a bit better. When I said that Lotus used what was the best available at the time I meant that constant velocity joints (the Birfield type as we commonly know them) were new technology at the time the Elan was developed. The first car to use them was the Mini and they weren't commonly available or necessarily reliable back then.

So instead of using a metal constant velocity joint Lotus used a constant velocity joint made of rubber. Those doughnuts are constant velocity joints just not metal ones. The rubber flexes to accommodate variation in shaft speeds as the shaft rotates around it's axis. A standard universal joint as was commonly available at the time the Elan was developed cannot do that so you get more vibration and stress in the driveline compared to a constant velocity joint.

As a matter of interest Mk2 Ford Escorts with the 2 litre Pinto engine always had a centre Birfield constant velocity joint in the driveshaft. Same was true for VB/VC Holden/GM Commodores. The Germans on the other hand always use rubber couplings in the driveshaft and not Birfield CV joints. Look at the driveshaft on a modern rear wheel drive BMW and you'll see rubber couplings used not CVJ's. In that application they are entirely reliable and help achieve a very smooth drivetrain.

I too am an engineer and I work in the automotive industry and I know for a fact that cost is just one consideration.
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PostPost by: h20hamelan » Tue Feb 27, 2024 3:28 am

Mercedes Volvo also still use rubber inline, but none of the BMW Volvo Mercedes have much or any deflection from straight inline.
There is good supply of quality, I have never experiment to see if size is similar, but I do have all above on shelf and Lotus so could measure.
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PostPost by: 2cams70 » Tue Feb 27, 2024 5:32 am

h20hamelan wrote:Mercedes Volvo also still use rubber inline, but none of the BMW Volvo Mercedes have much or any deflection from straight inline.
There is good supply of quality, I have never experiment to see if size is similar, but I do have all above on shelf and Lotus so could measure.


You will not be able to use a RWD driveshaft rubber coupling from another car for the Elan. They aren't intended for that purpose and yes they don't need to flex as much (still rubber though!),
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PostPost by: alan.barker » Tue Feb 27, 2024 12:34 pm

2cams70 wrote:
h20hamelan wrote:Mercedes Volvo also still use rubber inline, but none of the BMW Volvo Mercedes have much or any deflection from straight inline.
There is good supply of quality, I have never experiment to see if size is similar, but I do have all above on shelf and Lotus so could measure.


You will not be able to use a RWD driveshaft rubber coupling from another car for the Elan. They aren't intended for that purpose and yes they don't need to flex as much (still rubber though!),

You can from another car "Hilman Imp" like the early Elan, for Kangaroo jumps lol.
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PostPost by: 2cams70 » Tue Feb 27, 2024 12:53 pm

alan.barker wrote:
2cams70 wrote:
h20hamelan wrote:Mercedes Volvo also still use rubber inline, but none of the BMW Volvo Mercedes have much or any deflection from straight inline.
There is good supply of quality, I have never experiment to see if size is similar, but I do have all above on shelf and Lotus so could measure.


You will not be able to use a RWD driveshaft rubber coupling from another car for the Elan. They aren't intended for that purpose and yes they don't need to flex as much (still rubber though!),

You can from another car "Hilman Imp" like the early Elan, for Kangaroo jumps lol.
Alan


I meant you can’t use a RWD car propellor shaft rubber coupling. It won’t have enough articulation. Apologies I should have said propellor shaft not driveshaft.
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PostPost by: alanr » Tue Feb 27, 2024 9:33 pm

alan.barker wrote:
2cams70 wrote:
h20hamelan wrote:Mercedes Volvo also still use rubber inline, but none of the BMW Volvo Mercedes have much or any deflection from straight inline.
There is good supply of quality, I have never experiment to see if size is similar, but I do have all above on shelf and Lotus so could measure.


You will not be able to use a RWD driveshaft rubber coupling from another car for the Elan. They aren't intended for that purpose and yes they don't need to flex as much (still rubber though!),

You can from another car "Hilman Imp" like the early Elan, for Kangaroo jumps lol.
Alan


I wouldn't recommend using Hillman Imp rotoflex doughnuts on an Elan. Whilst they will fit ok being the same size they are a lower grade being for lower powered car and will definitely not be up to the job on an Elan.

Alan.
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PostPost by: rgh0 » Tue Feb 27, 2024 10:42 pm

The Imp style donuts were what was used on Elans up until the donuts with the additional metal interleaves were introduced around 1970 with the Elan Sprint to try to limit the surging.. So if you are truly after the original design intent of Lotus then you would use these !!

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PostPost by: Gordon Sauer » Tue Feb 27, 2024 10:47 pm

Interestingly, on my Elan that I’ve had since 73 the original ones have held up the best, even though most of the time the car sitting, but on the interleave ones, always splitting away at the metal plate, Gordon
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PostPost by: alan.barker » Wed Feb 28, 2024 6:24 am

When i bought my Sprint i said to the seller that it must have a mot.
To pass the mot the seller told me he had fitted new rotoflexes. Yes you guessed he fitted the cheaper Hilman Imp ones.
There was also another car that used rotoflexe the Triumph 1500 FWD.
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