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).
The disadvantages of a side valve exhaust engine design and considerations for future valve configurations.
| Identifier | ExFiles\Box 148\5\ scan0117 | |
| Date | 1st September 1936 | |
| -4- The disadvantages of the construction are :- (1) The side valve exhaust valve may tend to cause cylinder distortion. This should not be appreciably worse than the ordinary side valve engine which is extensively used, however. (2) The unit is wider than the conventional overhead valve job. (3) It may not be easy to get a satisfactory top joint to the liner with all aluminium cylinder block construction. (4) If the overhead inlet continues to demand a very short duration camshaft, it may mean high stresses to get the valve open and closed in the time available. From the information so far obtained we think it is well worth considering the design of a C-cylinder overhead inlet, side valve exhaust engine to see whether there is any inherent difficulty in making such an engine that can easily be produced. At one time we thought it essential that two inlet valves should be used. Since then, however, we have run the standard Bentley unit with a 1.7 inlet valve up to 4600 R.P.M. without the slightest difficulty, and therefore we think possibly the complication of two inlet valves can hardly be justified at the present moment, particularly in view of the fact that the crankshaft prevents engine speeds much in excess of 4750 R.P.M. Looking into the future, however, there is no doubt that peak speeds up to 6,000 R.P.M. are likely to be approached in five years' time. If this is the case, a very large single inlet valve will throw almost intolerable stresses on the valve gear. Therefore we believe that, with any new type of engine under consideration to-day, a basic consideration should be that the design does permit of two inlet valves being employed, if and when such a move is found desirable. It would therefore be interesting if the Design Dept. could tell us whether these can be incorporated on the high power type head without spoiling the layout. The full scale overhead camshaft engine now on test has of course two inlet valves as a basic feature of its design. | ||