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).
Transmission vibration issues in a 10.B.V Coupé and the series of tests conducted to find a cure.
| Identifier | ExFiles\Box 156\4\ scan0106 | |
| Date | 9th August 1939 | |
| 1330 RSH Rm{William Robotham - Chief Engineer} from Mx{John H Maddocks - Chief Proving Officer} c. By c. Da{Bernard Day - Chassis Design} TRANSMISSION VIBRATION 10.B.V Coupé suffered from a transmission period in a very marked form on forward drive at 38 to 45 m.p.h. and we carried out a series of tests to find a cure. It is believed that the vibration originates in the universal joints, and is due to variations in the angular velocity which are known to exist if the transmission is not absolutely in line. It is not a new vibration, since this variation in the angular velocity must exist in all similar universal joints. All that is new is the degree to which the vibration is made apparent to the occupants of the car, the important factors in this respect being the shorter propeller shafts on B.V and the easy transmission of vibration from the centre joint to the cruciform member. Attempts to improve the alignment of the transmission by tilting the axle only made the vibration worse, and we had to revert to the standard position. When running at the critical speed, it was found by feel that the vibration was at a maximum where the mounting for the centre joint of the divided propeller shafts was attached to the cruciform member. There was no apparent sign of the vibration being transmitted via the axle tubes and road springs to the frame. By temporarily disconnecting the fixing bolts of the centre joint mounting, the vibration almost entirely disappeared, and could be reproduced in varying intensity depending on the degree of tightness of the fixing bolts. Experiments were then made with various schemes for isolating the centre joint mounting. The best result was finally obtained with a semi-flexible mounting supported by thick felt on the bottom flange of the cruciform member, as shown in the sketch herewith. This scheme was 100% effective, but could be criticised on the score of durability. Tests were then made using rubber as an insulating medium, and this was found to be less effective than felt by say 10%, providing (continued) | ||