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).
Description of the timing and operation of an engine's inlet and exhaust valve mechanism, comparing its efficiency to poppet-valves.
| Identifier | ExFiles\Box 147\4\ scan0177 | |
| Date | 13th August 1940 guessed | |
| The exhaust-port opens at 246° of rotation of the wheel 15 and remains open while this wheel turns through 117°. During this period, the arm 14 turns through 111° and its average speed is reduced in the ratio 111/117 or 0.95/1. The exhaust port opens at 132° of crankshaft rotation in the firing stroke of the piston and closes at 6° in the next suction stroke so that it is open for 234° of crankshaft rotation. With this arrangement, the inlet-port and the port 23 (Figure 1) in the valve each subtends one half of 134°, or 67°, at the axis of the valve, and the exhaust-port subtends 111°-67° or 44°, at the axis of the valve. The inlet-port is being opened during 67° of valve-movement up to its fullest extent, and is then closed during the next 67° of valve-movement. The exhaust-port opens during 44° of valve-movement which occurs at less than the mean speed, remains fully open for 23° and then closes during 44° of valve-movement which occurs at about mean speed. There is a loss in the opening of this port due partly to its slower opening and partly to its smaller area. The effect of the smaller area is, how-ever, reduced by the fact that the port is fully open for a substantial period so that the total loss is small compared with the gain in the inlet-valve opening and the exhaust-port opening is better, despite the loss, than could be obtained by using poppet-valves. It will also be clear that the maximum increase in port area will be obtained by arranging that the valve-port and its co-operating inlet port are in full register with one another at the time when the valve is moving with its maximum velocity as is the case in the 6. | ||