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).
Comparing the Aspin engine's valve timing and performance against the B.60 and Merlin engines.
Identifier | ExFiles\Box 134\1\ scan0226 | |
Date | 18th June 1940 | |
To Rm.{William Robotham - Chief Engineer} Aspin Engine. Your reference Rm.{William Robotham - Chief Engineer}14/ML.10.6.40. On PL.249 herewith I have shown the inlet valve opening areas for the Aspin compared with B.60 In order to be accurate I have assumed that we have a valve clearance of .009 when hot; as will be seen the Aspin compares very unfavourably with the large poppet valve we are able to use on the power head engine. Mr. Aspin for some reason obscure to me makes the duration of the exhaust valve longer than the inlet. This has also been plotted just for the purpose of recording. On PL.252 I have striven to make the Aspin inlet port as good as the B.60. This has been achieved by making the height of the valve .125 longer and increasing the opening duration from 240 to 248°. The result of this is that we have to accept the valve timing which savours of a racing engine, the overlap will give poor slow speed torque. Herewith the originals of PL.249 and PL.252. Jnr.{Charles L. Jenner} P.S. A print No.C.144 just to hand for the 5.5 bore engine shows a big improvement over that which was shown on Fletchers diagram; however, when it is corrected to 5.4 which is the size of the Merlin engine, the curve is not so good as the Merlin Poppets taking it step by step through the duration period. | ||