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 engine testing methodologies, comparing Rudge and Bentley engines, and investigating anomalies like vibration and friction losses.
| Identifier | ExFiles\Box 133\1\ scan0112 | |
| Date | 17th September 1936 | |
| -8- Another, and possibly even more serious source of error, is that it is extremely difficult to obtain consistent readings because, if readings are taken as the speed increases, and then repeated as the speed drops, a difference in the two readings at the same speed is observed, and this difference increases as the speed falls. In the accompanying curves a mean value is taken, but there is no means of telling whether or not this is accurate. Results are, however, given in Figs. XXX to XXXII. In Fig. XXX an investigation was carried out to try and find the most accurate and simple method of carrying out the tests and, as stated earlier on in this report, it was finally decided to motor the engine without previously running it, with both petrol and fan off, and the petrol pump uncoupled. The reasons for selecting this method were that it gave results almost identical to those obtained when the engine was run, and then motored over, it was simple, and it would line up with future tests run without pumping losses etc. Curves were now drawn in Fig. XXXI showing comparative figures between Rudge & Bentley, stripping each unit by degrees, by removing first the valves, then piston rings and finally the piston and conn. rod. This latter curve was attempted on the Rudge but was abandoned due to excessive vibration. A rather peculiar effect noticeable in this latter engine is that the curves have a reasonably steady slope up to about 4,500 R.P.M., and they then abruptly begin to rise, this persisting even when no piston or conn. rod is fitted, it being very marked indeed in this case, the rise beginning at 4,000 R.P.M. as soon as vibration becomes excessive. It is thought therefore that the increase in power required to motor the engine is due to the energy absorbed in promoting the vibrations in addition to the friction losses inherent in the engine. Assuming, however, that the results are accurate, we see that the friction losses in the Rudge are considerably less than the Bentley, and this is put down to the following :- | ||