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).
The testing of SS. engine mountings, detailing road conditions and issues like radiator wobble and unsteadiness.
| Identifier | WestWitteringFiles\T\March1929-December1929\ Scan023 | |
| Date | 12th March 1929 | |
| R.{Sir Henry Royce} FROM E.{Mr Elliott - Chief Engineer} C. to SS.{S. Smith} WCR. HS.{Lord Ernest Hives - Chair} SECRET ORIGINAL E1/M12.3.29. SS.{S. Smith} ENGINE MOUNTING ETC. X7005 X7810 X7930 X7250 At the risk of repeating a little of what has already been reported the following notes are intended to shew the line of procedure adopted in connection with the above. CONDITIONS OF TESTING. The testing of the SS.{S. Smith} engine mounting has been greatly hampered by the difficulty of finding a suitable stretch of rough road on which it is possible to drive at 70 MPH., and also by unfortunate climatic conditions which rendered high speeds absolutely unsafe and out of the question - e.g. snow, ice, & fog. The early testing was done on more or less main roads and a set of values was established for different arrangements of mounting. Eventually however the Exp. Dept. found a long straight bye-road possessing a surface which did not appear to be very bad but brought up violent periodic wobbles of the radiator and front of frame at 65-75 MPH., the same cars behaving in a comparatively normal manner on ordinary main roads. These radiator wobbles were not associated with a steering wobble although the steering was affected directionally, and it was necessary to hold the wheel very tightly to keep the car on the road. This directional instability persisted also on the better roads in a minor degree. This test which proved to be the ultimate one was by no means abnormal as we found that 12-EX, an open touring Phantom, would traverse the course at full speed with the radiator remaining perfectly steady, and there is no doubt that in France this condition would be frequently met. In passing it should be mentioned that the road in question had to be used with caution and economy to avoid giving objection to the local road users before the tests were brought to a successful conclusion. It was noticed that the behaviour of a car on good and ordinary roads is not necessarily a criterion of what it will do on bad. One of the examples tested on the main road gave the impression of incipient unsteadiness, but in the ultimate test behaved very much better than expected, and went through with comparatively little periodic bouncing. This peculiarity necessitated a revaluation of the earlier tried systems, in particular the first strip rubber mounting which was found to be appreciably below the required standard, and was "written down" from 80% to 60%. It was also said that once a car has been vigorously wobbled it is more prone to wobble afterwards. The policy therefore adopted was to apply the ultimate cure to the chassis known to be the worst for this defect. (1) | ||