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).
Valve timing tests for high power single-cylinder units and proposals for future development, including a new cylinder head.
| Identifier | ExFiles\Box 134\2\ scan0174 | |
| Date | 20th December 1937 | |
| File 1129a HIGH POWER UNITS. 20.12.37. A considerable amount of work on valve timing etc. has been carried out on the above unit, and it has been found that best all round performance is given by I.O TDC; I.C.30°L; E.O.51°E; E.C. T.D.C. with valve sizes - inlet 1.750" dia. and exhaust 1.500" dia. Work has yet to be carried out on a 1.600" dia. inlet valve, and in addition tests are to be run on the venturi type of valve seat which seems to promise quite well. Jobs in hand are, therefore, the tests on venturi seats on high power units with 1.750" inlet valve and 1.600" inlet valve, and on the standard Bentley. In addition, tests are to be run showing the effect of exhaust valve lift on power output. Beyond this point, there is no work outstanding of importance and it would seem that the future programme on the high Power single cylinder unit would resolve itself into two parts, viz:- (a) Endurance testing on main engine parts. (b) Investigation of the effect on performance of detail changes made necessary by the main engine layout. The present single cylinder unit has a rather complicated mechanism for modifications to valve timing, which, now that a fairly rational timing has been decided upon is not particularly essential. In addition, due to the design of the valve gear mechanism between the camshaft and the rocker it is impossible to modify the existing design of the unit to adapt it to the design of camshaft, bottom tappets, valves etc. in the main engine, since the position of the various centres is entirely wrong. It would appear, therefore, that before any reliable information can be obtained from this unit, which would be directly applicable to the main engine, several drastic alterations would have to be made, and roughly these appear to be as under. (1) New cylinder head (A/C). This should be an exact copy of the main engine head in every respect, including stud positions, water passages, valve and plug positions and inclinations, port shapes, | ||