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).
Recommendation for high front engine mounts based on experiments with low and raised mounting systems.
| Identifier | ExFiles\Box 133\4\ scan0333 | |
| Date | 27th June 1939 | |
| 1127. By: from Rm.{William Robotham - Chief Engineer} ~~Da.{Bernard Day - Chassis Design}~~ ~~Da{Bernard Day - Chassis Design}/Ev.{Ivan Evernden - coachwork}~~ ~~Da{Bernard Day - Chassis Design}/Jnr.{Charles L. Jenner}~~ ~~e.{Mr Elliott - Chief Engineer} Rm{William Robotham - Chief Engineer}/Wym.{G. Harold Whyman - Experimental Manager}~~ FRONT ENGINE MOUNTINGS. We have for some time past been experimenting with a low engine mounting on cast iron 6-cylinder engines. We were encouraged to do so because this mounting appeared to be very successful on the straight 8. To begin with, the low engine mounting on the six gave such promise that we thought it would be good enough for production. It is desirable in other respects because it is lighter and simpler than the raised engine mounting. We have now concluded our experiments, however, and the results indicate that we must adhere to the raised mounting for six cylinder engines, and that this scheme will be even more imperative for the 4-cylinder units. The big advantage of the raised engine mounting is experienced at speeds below 10 m.p.h. The natural frequency of the low engine mounting occurs at the equivalent of about 8 m.p.h., at which speed, under full torque, the engine nearly jumps out of the frame. The same thing, of course, is likely to happen when the engine is started up and one cylinder misses fire. On the other hand, the raised engine mounting enables one to go down to 5 or 6 m.p.h. top gear full torque without any inconvenience. The raised engine mounting also is slightly better for preventing engine vibrations reaching the passengers under idling conditions. Under the circumstances, we recommend that all future designs for six and 4 cylinder engines should be produced with high front engine mounts. Rm.{William Robotham - Chief Engineer} | ||