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).
Five performance improvements for the 20 HP car, focusing on engine and exhaust modifications.
| Identifier | ExFiles\Box 5a\5\ 05-page206 | |
| Date | 11th October 1929 | |
| HS.{Lord Ernest Hives - Chair} From R.{Sir Henry Royce} c. to Ss.{S. Smith} Nor. c. to Ey. RHO. 1577 R.3/M11.10.29. X.5770 X.5090 X.5771 20 HP. CARS (CONTINUED.) The third item - i.e. to improve the performance of the 20 HP. - is as follows, (agreed by Hs.{Lord Ernest Hives - Chair} Rm.{William Robotham - Chief Engineer} E.{Mr Elliott - Chief Engineer} & R.{Sir Henry Royce} at Ww. 9.10.29.) It will be understood that the alteration to the crankpins is independent of this argument, and will probably be done at some time convenient to the works. The engines of the three experimental chassis, that is, 16-G4, 12-G4, and the chassis for which we are producing a new body, should be fitted with the following items: (1) The lightest possible pistons. (2) Long duration camshafts, which will also help the valve springs so that the engine speed can be increased to 3500 RPM. at least. The duration (rapid acceleration) of the cams for inlet being 60 divisions = 240° of the crankshaft, and for exhaust 64 divisions = 256° of crankshaft, so that the changeover point can be something after the top dead centre, with the object of preventing the engine roar (see E's sketch of our latest efforts.) (3) The size of the light(inlet) valves will be either 1.35 or 1.4, the head will be of the 6 ported type with increased passages either in aluminium or cast iron, as experience indicates. The exhaust valves will be of the cooler type in the non-stretching steel. (4) The cyl. block will have a substantial hole for the passage of the exhaust gas to the carburetter jacket. (There will be a fairly large pipe insulated with asbestos) It is intended to try a valve on either the swan neck pipe or on the exhaust pipe just before it enters the main silencer, to force the flow through the throttle jacket during the starting operations, ( i.e. control with the extra oil.) (5) An efficient exhaust system will be fitted probably with the addition of the cast boxes at present, similar to those promises that promise so well on Phantom II, with exhaust cut-out. It is understood in this memo. that the long frame is at present available for anybody particularly wishing for it as an alternative to the short one at present in course of | ||