Lotus Elan

Tasteful updating

PostPost by: Grizzly » Sun Oct 08, 2017 3:15 pm

Ok so when you say they have been use you mean on race cars.

Spot the difference (unless i'm mistaken thats a +2 drive shaft as well so less angle)..... (BTW these pictures are straight off Google so i hope the owners don't mind me using them)
spyder_shafts.jpg and

11a-dd.jpg and


Can't tell you the 'Worse' that can happen is but i've had a Rotoflex fail and smash the rear caliper off my +2 Hub which wasn't much fun.
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PostPost by: Foxie » Sun Oct 08, 2017 3:47 pm

Grizzly wrote:Can't tell you the 'Worse' that can happen is but i've had a Rotoflex fail and smash the rear caliper off my +2 Hub which wasn't much fun.


Happened to me too.

At the traffic lights. In the outside of three lanes in the morning rush hour :shock:
Last edited by Foxie on Sun Oct 08, 2017 9:39 pm, edited 1 time in total.
68 Elan +2, 70 Elan +2s
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PostPost by: mbell » Sun Oct 08, 2017 4:15 pm

One of my rear hubs and chassis show the signs of a similar incident in my cars past. So not an area I would be experimenting with.

But you're a grown up and I am sure you well aware of the possible damage and risk you are taking on trying these. I'd be interested to have some more solid feedback on if they work or not, as I've seen some comments but far from enough to convince this doubting Tom.
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: Davidb » Sun Oct 08, 2017 6:31 pm

I am surprised that nobody has mentioned u jointed shafts. They were used in period in the early 26Rs and while they do have limitations, sudden failure is usually not one of them!
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PostPost by: Chancer » Sun Oct 08, 2017 7:38 pm

Yes, I think that I can spot the difference, one photo is taken on a ramp with the wheels at full droop and the other is taken with the vehicle at normal ride attitude with the weight on the suspension.

Modern rotoflexes can fall to bits without even taking them out of the sealed bag, I understand everyones doubts but the reinforced couplings aren't likely to let go like a Rotoflex in my opinion but its only conjecture, I can see another metallic element either driveline or suspension letting go if they are too stiff.

I'm just frustrated that I cannot get on a give it a go to see what happens.

Does the BMW propshaft use one U/J and one guido coupling? in theory U/J's should be used in pairs with the correct phasing, one U/J with a rotoflex like in the photo, as on the bike engined Caterham and the BMW prop if it is that way should theoretically not be done, that said the single seaters were always like that and BMW sure know what they are doing, i know from the Caterham prop that the coupling can adequately damp out the non constant velocity accélérations and décélérations from a single U/J but it hammers the hell out of the bolts especially if they are not in correctly toleranced holes (the guido couplings are for larger bolts IIRC) and/or bearing on the threaded portion, I had one let go at V-MAX right beside my clutch foot at 3 times the RPM that a driveshaft would, not one I wish to repeat but the coupling itself did not suffer in any way.
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PostPost by: mbell » Sun Oct 08, 2017 11:09 pm

The BMW shaft is gumbo to gearbox (very high torque bolts and machined faces), u joint at the center near center support bearing and cv type joint to the diff.

Guibo failures are common, prob 60k to 100k life, but sudden failure is rare. They have a lot of string type material so you normally have a lot of vibration & noise before they go.

The one I pictured had at least 60k on it and was only changed as I fitted new prop shaft as center bearing had gone.
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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