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).
Design, performance and mechanical limitations of the Aspin rotary valve.
| Identifier | ExFiles\Box 134\1\ scan0217 | |
| Date | 6th July 1940 | |
| 1129 To Rm.{William Robotham - Chief Engineer} Jnr.{Charles L. Jenner}1/JH.6.7.40. Aspin Valve. The further drawings I have made I think answers all your questions in memo. Rm.{William Robotham - Chief Engineer}14/ML.21.6.40. PL.275 shows the largest valve possible for a given cylinder centres, there being a .250 gasket joint between the valves. There are 2 Aspin curves shown both with the same amount of overlap, namely 12°, 1 with a long duration and the other a conventional timing. On PL.276 is a summary of various 2 stroke valve port opening areas. These I obtained from Mr. Wood's assistant Bradbeer, and I have brought them to a common basis the same as the G.M. which I know is actual. From this study the point arises why does Aspin run his 2 stroke valve at half engine speed using 2 inlet ports and 2 plugs per cylinder alternately. Kadenacy does not suggest the rate for the opening, but it is clear that any port design which is controlled by the piston or sleeve of the cylinder gives rapid opening areas. PL.278. The device for speeding up the rotary valve and using the best part of the curve for the inlet port does show a gain over the whole of the duration. In doing this investigation I got absorbed in the quantities and lost sight of the mechanical limitations until near completion, it is the driving wheel must be no bigger in diameter than the distance between the cylinder. This means a reduction in the length of the crank arm and less eccentricity between the driver and driven. I am annoyed with myself. Herewith blue prints No. PL.275, 276, 278. Jnr.{Charles L. Jenner} | ||