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).
Proposed piston design with an oil ram to prevent knocking in the 40/50 HP chassis.
| Identifier | WestWitteringFiles\D\October1919\ Scan11 | |
| Date | 16th October 1919 | |
| To B.N. from E.{Mr Elliott - Chief Engineer} Copy to C.J. " " W.H. " " D.A. " " E.F.C. ORIGINAL E.{Mr Elliott - Chief Engineer} PONTIFICATES 2 BN{W.O. Bentley / Mr Barrington} E1/G16/10/19. RE 40/50 H.P; CHASSIS PISTON. Referring to the proposed type of piston in which a small oil ram at right angles to the piston pin is incorporated for taking up clearance and preventing knocks, would you kindly note that Mr. Royce has already suggested that the oil should be shut off by the swing of the connecting rod, and be thus hydraulically confined behind the ram. Mr. Royce wishes me to tell you that we have the scheme of this piston in hand. An investigation has been made to determine the value of the forces controlling the piston sideways in the cylinder, and since it is found that at 400 R.P.M. the side pressure of the piston due to inertia is in the neighbourhood of 5 lbs., whereas the side pressure due to the compression is about 85 lbs., Mr. Royce thinks that it is quite evident what is the cause of the piston knocking, and that if we can succeed in holding the piston on to the power side, or only permitting it to come off the power side by a few thous, we shall make the whole engine even quieter than we had been used to before the War. Mr. Royce would like you to take out patents for both split and ram pistons. The ram should be placed slightly above the centre of the piston pin. The combination of spring and oil should be tried for operating the ram, and the opening of the oil pressure should be experimented with at different timings. (Contd.) | ||