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 report discussing engine length and sleeve balance considerations for 6 and 8-cylinder engines.
| Identifier | ExFiles\Box 133\2\ scan0157 | |
| 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 3¼" bore and .560 for a 3½" 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 through its centre of gravity. Taking the standard R.R. 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 500 lbs.ft. at 5,000 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 210º in advance of the pins. The 8-cylinder engine requires 2.5 lb.ins. 159º in advance of the pins. It may not be a simple matter to fit these weights in the room available. | ||