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).
Page 2 of a document describing a pressure-operated mechanism for engine ignition control.
| Identifier | WestWitteringFiles\N\2October1925-December1925\ Scan104 | |
| Date | 28th October 1925 | |
| Contd. -2- EFC2/T28.10.25. Instantaneous pressure from the main cylinder will then in principle be conducted to either side of the piston in the operating cylinder at pre-determined times, and the small piston will tend to move so long as the pressures on the two sides are not equal. The movement of the piston can be made to operate the ignition advance and retard (on the principal suggestion) but it can also be used, if desired, to operate mixture strength control for altitude or otherwise. It was tentatively suggested that the instants of opening of the two valves should be (1) Exact top centre. (2) 1/10 of the way down the stroke. If we consider an indicator diagram of the main cylinder, there must be two instants for any condition of the working stroke, on either side of the instant at which the maximum pressure obtains, at which the pressures are equal. If the little valves open at these two respective instants and engine conditions are unvarying, there will be no movement of the small piston. If now the engine conditions vary so that in the ordinary way the maximum pressure peak will be rendered earlier or later in the stroke, the pressures conveyed to the small piston will become unbalanced and a motion of the piston will occur which, on the principal idea of the application of the principle, will readjust the timing of the [struck through: maximum] ignition until equalisation of the pressures at these two Contd. | ||