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).
Investigation into an engine knock, detailing tests on a slipper wheel and identifying the cause.
| Identifier | WestWitteringFiles\R\2December1927-February1928\ Scan131 | |
| Date | 23th January 1928 guessed | |
| contd :- -2- considerably reduced and was sufficient to prevent crankshaft periods being objectionable. We then tried a heavier slipper wheel by bolting an extra rim on to the existing wheels. This had the effect of entirely overcoming the knock with a friction load of 190 in.lbs. and was very good in damping the crankshaft periods. It also brough the period of the knock down to 16/20 m.p.h. when tightened up to produce them. Although these tests had eliminated the knock, they had not proved the source of it. To obtain this end we again brought the slipper wheel load up to produce the knock. We then dismantled the engine piecemeal, testing after each part was taken off, and we were still able to obtain the knock with only the front cylinder working, the other piston, rods etc. being dismantled. We found during this operation that No.3. cyl. gave the maximum knock and No.1 the minimum. It was noticed that when the load on the engine was such to produce the knock the slipper wheels moved on the hub whereas when the load was insufficient to produce knocks the slipper wheel did not function. With the knowledge from our tests with various settings of the slipper wheels, the results led us to the knock being caused by the torsional stress set up in the crankshaft. Further investigations proved that the knock was caused by the connecting rod, the actual knock being a concussion between the crankshaft journal and the gudgeon pin. We presume that when the slipper wheels are setat a heavy load before slipping, they act as a solid flywheel, contd :- | ||