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).
Issues and potential solutions for fabric couplings on 40/50 and E.A.C. models.
| Identifier | Morton\M3.5\ img038 | |
| Date | 4th April 1925 | |
| TO HS.{Lord Ernest Hives - Chair} FROM R.{Sir Henry Royce} S E C R E T Copy to - OJ. " - BM. 40/50 AND E.A.C. FABRIC COUPLINGS. The coupling problem is not confined to EAC, but is a 40/50 proposition, and the reason for requiring a fabric coupling is the same as the cause of its destruction, namely, the rise and fall of the back axle controlled by the torque tube. We cannot get rid of this source of trouble until we come to 'X' series, when we hope to have ready the modified EAC. 1, which consists of 'V' and 'W' series, but with the new axle already made but not tested, and a new frame. The situation is not confined to RR cars alone, but exists in about 90% of our Competitors cars, that is, all those who employ torque tubes, and it is worse in those where the torque tube is often very much shorter, as in the case of Hispano. We cannot hope to produce any new apparatus immediately that will cater for the fault, and must make the best of what is known. It appears that the fabric coupling does help in many ways, in addition to this particular trouble, and we estimate that if it can be made to bear a reverse torque equal to three times the engine torque, say 10,000 in. lbs., that it ought to have reasonable life on our cars. Will you kindly make careful calculations in your reverse testing apparatus and run it at a speed that will give as nearly as possible exactly this 10,000 in. lbs. reverse torque. This will be useful, as it will not only tell us whether we can hope the coupling will last, but will enable us to pick out any improvements in design, or manufacture. So far as we know there is little hope of the steel spring coupling bearing such a test, and the only alternative would be to fit a plain metal coupling, which evidently does stand, but does not annihilate a certain amount of vibration. To make the situation as easy as possible we recommend that the rear springs should not be over flexible, the rear shock dampers should be kept fairly tight, and above all, we should use low pressure tyres on the back wheels. This latter will considerably ease this, and many other troubles. The conclusion we come to is that the fabric coupling is so desirable that if it can be made to stand generally under favourable conditions of roads and tyres, it is a pity for us to fit the metal coupling. R.{Sir Henry Royce} Handwritten Note: X SERIES - MODIFIED EAC1 = V & W WITH NEW REAR AXLE & FRAME | ||