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).
Technical analysis of sleeve valve engine design, covering engine length, sleeve balance, and drive torque.
| Identifier | ExFiles\Box 127\3\ scan0240 | |
| Date | 20th June 1935 | |
| -3- Hs{Lord Ernest Hives - Chair}/Smth.6/KW.20.6.35. Length of Engine. The width of the induction passage which should be provided between the cylinders appears to be purely a matter of opinion. We think that a conservative estimate of this would be obtained by dividing the maximum area of one port opening by the depth of the port. This gives a value of .625 for a 3½" bore and .560 for a 3¼" bore engine. Assuming a sleeve thickness of .100 and a cylinder wall thickness of .150, the length of a sleeve valve engine would compare with that of poppet valve engines as shown in Figs 2 & 3. Sleeve Balance. If all the sleeve drives are uniformly handed the inertia forces balance, but there is a considerable out of balance couple acting in a vertical plane parallel to the axis of the engine. The magnitude of the couple oscillates between its maximum + and - values at half crankshaft speed. The effect is to make the engine pitch about a horizontal axis though its centre of gravity. Taking the R.R. standard firing order on the 6-cylinder engine, the maximum value of the couple is 490 lbs ft. at 5,000 r.p.m. The value for the 8-cylinder engine is 300 lbs.ft @5000 r.p.m. adopting the Wraith firing order with a 2 - 4 - 2 crankshaft. Neither of these values can be reduced to any extent by choosing a different firing order. The couples can be balanced by attaching weights to the two end sleeve cranks. For the 6-cylinder engine 2.8 lb.ins. of balance is required on each crank, located 210° in advance of the pins. The 8-cylinder engine requires 2.5 lb. ins. 159° in advance of the pins. It may not be a simple matter to fit these weights in the room available. Sleeve Drive Torque. The friction torque is indeterminate, but the sleeve should be made about .100" thick to avoid excessive peaks at the instant of firing. Owing to the combined reciprocation and rotation of the sleeve there is an oscillating inertia torque on the sleeve drive which completes a cycle every revolution of the engine. The maximum magnitude of this in a 3½" bore engine is + or - 5 lbs.ft. per cylinder at 5,000 r.p.m. This will be much greater than the average friction torque, so that at high speeds there will be torque reversals in the individual sleeve drives which may give rise to rattles in the worm gears. Rm{William Robotham - Chief Engineer}/Smth. | ||