Drive train parts:
Imp Rotoflex joint
Left the Unipart/Quinton Hazell etc after market rubbish;
Right the NEW correct type.
The ones previously avaliable .
Did not last for longer than 1 year and would often be the reason of hugh repair costs when early and timely inspection did not disclose disruption/breakage risks.
The issue with manufacturing these parts was that the original design and required materials have not been avaliable for a long time.
The original design is quite complicated, requiring 12 machined parts, proper welding (not spotwelding!) and bushed (round) holes where the hardened drive bolts go in.
Also this rotoflex has 3 "low" and 3 "high" leveled bushes. This to equal out the limited space left between the driveshaft and the engine shaft in the imp rear suspension setup.
The other aftermarket / replacement designs are primarily designed for industrial use, They lack the specific flexibility that an Imp drive train needs.
Being mounted on the rear drive half shafts, Imp rotoflex joints will have to withstand over 25 degrees tilt. The industrial design is limited to 2-4% tilt maximum.
The one on the left has none of these specifications.
The original Dunlop made rotoflex was made with a soft-but-strong type of rubber.
This rubber used to be made from NEW natural rubber compound in combination with additives.
Today natural rubbercompound is a very diificult product, as many environmental and safety rules are limiting the suppliers to continue on natural products when working with small productions ( say less than 10.000 pieces).
Therefore more and more "re-generated" rubber is being used nowadays (like old tyres)
The use of modern synthethic rubber brings also risks: the softener used in these products have a tendency to dissolve in oil or petrol (ie. leaking diff oil!) and will loose the artificial softener over time. In 1-2 years (depending on circumstances) the rotoflex will be as hard as stone.