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).
Summary of an investigation into gear noise on Bentley & 20/25 engines, focusing on the wheelcase, crankcase, and engine gears.
| Identifier | ExFiles\Box 136\1\ scan0174 | |
| Date | 15th January 1936 | |
| COPY. To E.{Mr Elliott - Chief Engineer} from RHC.{R. H. Coverley - Production Engineer} c. By.{R.W. Bailey - Chief Engineer} c. Wor.{Arthur Wormald - General Works Manager} c. Sft.{Mr Swift} Bentley & 20/25 Engine Gears. Referring to the investigation which has been proceeding in connection with the above, we give below a summary of the various points which appear to have some bearing on the question of gear noise. WHEELCASE. The construction of the wheelcase is such as to cause resonance with gear noises of certain frequencies and at certain engine speeds sympathetic vibration in the front face and walls of the casting has the effectof amplifying gear noises. This can be demonstrated by the fact that the application of a screwdriver or similar metal object to the face of the wheelcase will damp out the vibration and gear noises are not then apparent. It is suggested that the casting should be ribbed in order to cut out the diaphragm effect and eliminate drumming. CRANKCASE. The overhanging section of the crankcase housing the dynamo drive is too weak and deflection of the casting during facing operations interferes with alignment of the pinion housing. The crankcase has to be supported at the back of the housing, otherwise the face can be thrown as much as .005" out of alignment and it is the usual practice to allow for this when lapping the gears, so that when the engine is revved up the misalignment is catered for. Again it is suggested that the casting might be ribbed in order to ensure the desired rigidity. ENGINE GEARS. The bronze cam wheels on 20/25 are causing more trouble than Bentley, and the fault lies in the method of pressing on the cam balancer. This cam is supposed to be shrunk on, but owing to the use of unsatisfactory tackle, which chills the cam before there is time to assemble, shearing takes place and the wheel is distorted due to the excessive pressure required to force the cam into position. | ||