From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Analysis of different clutch plate materials and driven plate designs.
| Identifier | ExFiles\Box 85\2\ scan0291 | |
| Date | 16th November 1936 | |
| Rm{William Robotham - Chief Engineer}/Smth.39/AP.16.11.36. Ferodo VM.20 (Moulded) is the material we hope to go over to. It is the most widely used material in this country. Is cheap, strong (requires fewer rivets) very durable, and can be ground parallel to within .002 (important for jaggers). We are using this on 25/30 and hope to do on Bentley. When first fitted this material is almost as good as No.6. for jaggers, but it rapidly assumes a polished dark brown surface which is distinctly inferior. No further deterioration in performance occurs after this condition is attained. Ferodo RAD.11 and Raybestos RR.1. are woven materials, the former having a brass interweave. Bentley has RR.1. It is said that owing to their more spongy nature, woven facings are better for jaggers than moulded. We have never been able to confirm this, in fact our evidence points the other way. Due to sponge cannot be ground so accurately as moulded, which is detrimental to jagger and in our experience more than offsets other advantage. We have a plate faced with "Mintex" which is a very spongy woven material, but have not tested this yet. VM.20 graphited is no improvement on VM.20. (b) Driven plate design.- We have tried the R.R. type of plate, B & B. long and B. & B. cross cushion, but have never had conclusive evidence that any type is superior to the others for jaggers. We have shown that the clutch improves as cushioning is increased. The B. & B. standard plate is undesirable because it is difficult to set the segments accurately and without "run out". No.6. flies off this plate when hot, and VM.20 cracks through the rivets. The Long plate will probably prove to be the best if we use more than .050 cushioning, because of the evenly distributed support given by spring plates to the cushioned facing. The snag is B. & B. do not make them and would take a long time to get them good. They will not allow us to make them, but we have made two experimental ones. The advantage claimed for the cross cushion plate is that the rating of the cushioning can be held constant instead of increasing rapidly under big loads. The R.R. plate is ground dead to size, can be accurately set without "run out", and is probably the only plate which will take No.6. without fear of bursting at speed. It is best to have the set towards the flywheel, not the pressure ring. Production cushioning is .030 but .040 at least is necessary with VM.20. (as in 35-MX.{John H Maddocks - Chief Proving Officer}) We shall probably get a Newton plate on test. So as to get some longitudinal flexibility in the plate as a precaution against seizure of the splines during engagement, we have tried a hub cut away and leaving only 4 thin spokes (Rm.{William Robotham - Chief Engineer}138) It is doubtful if this gives any improvement. continued | ||