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).
Notes on ignition timing settings, Packard clutch specifications, and engine performance from bench tests.
| Identifier | ExFiles\Box 37\1\ scan 220 | |
| Date | 25th August 1920 | |
| Contd. -4- Hs{Lord Ernest Hives - Chair}7/LG25.8.20. lever is fully advanced the spark takes place 8° B.T.D.C. We found on the Bench Test that this setting of the ignition gave us the best results. It was, however, necessary to run the ignition hand control fully advanced all the time. As long as we held the hand control fully advanced, we could not find any advantage at any speed from 300 to 2500 revs. if we altered the ignition by hand. We tried setting the ignition another tooth advanced and found no advantage at any speed. The 40° range on the automatic advance gave us all we required for full throttle condition of running but in order to obtain the best slow running it was necessary to retard the ignition by hand. We also find that when the engine is badly carboned up it is necessary then to retard by means of the Hand Control to avoid detonations. The Clutch on the Packard is the dry plate type. The six outer plates have the wire woven material rivetted on both sides. In all, there are twelve friction surfaces, the mean diameter of the plates is 7.050". The springs pressure is 380 lbs. when the clutch is engaged. The movement of the clutch shown by the marking on the sliding portion is .325". There is no clutch brake. This clutch has always works remarkably well and despite there being no clutch brake, there has never been any difficulty in engaging the gears. It never squeaks and the pick-up is smooth without any jaggers. The Packard engine runs very steadily on the Bench at High speeds there is a certain amount of noise coming from the Camshaft Drive. | ||