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 merits and drawbacks of an overhead camshaft engine design compared to existing push-rod engines.
| Identifier | ExFiles\Box 134\2\ scan0046 | |
| Date | 18th July 1935 | |
| -5- HS{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}15/KW.18.7.35. Overhead Camshaft Engine. Cont'd.{John DeLooze - Company Secretary} Some experiments we have done, the details of which are given in Hs{Lord Ernest Hives - Chair}/Smth.10/KW.4.7.35, show that there is no reason, apart from the drive, why the overhead camshaft should need more tappet clearance than the push rod engine of the 20/25 type. With modern sound insulation arrangements, it seems to us that it should matter little whether the camshaft is in the crankcase or on top of the cylinder head. The overhead camshaft seems to admit of the use of an aluminium cylinder head and cylinder block without the necessity for hydraulic tappets. In the head as suggested by Tsn., excellent volumetric efficiency is obtained. As we see it, the three doubtful points about this design could be adequately dealt with on a single cylinder unit; i.e. (1) Silence and reliability of the drive. (2) Silence of the valve gear. (3) Tendency of the head to detonate. We do not altogether share Tsn's enthusiasm for the square engine, though it has unquestionable merit where it is desired to get the maximum amount of horse power from a given number of c.c's capacity for the minimum weight. We do not think there is any very strong argument in favour of departing from the existing 20/25 stroke bore ratio, particularly on an 8-cylinder engine. In our opinion it would be well worth while going ahead at once with a single cylinder overhead valve unit of the Ramp Head type. | ||