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).
Investigation into crankcase and flywheel case pressures and modifications to the breather system.
| Identifier | ExFiles\Box 103\2\ scan0208 | |
| Date | 2nd October 1929 guessed | |
| -2- even whilst the car is stationary. We find that instead of there being a depression in the crankcase we have a compression which is increased or lowered by the opening or closing of the radiator shutters, the mean pressure being .125". The flywheel case still remains with a depression. We have now a condition whilst standing of a greater pressure in the crankcase than in the flywheel case which the pumping action of the screw has to overcome to prevent oil being drawn into the flywheel case. The pressure in the crankcase is produced by the fan causing a pressure under the bonnet, which we have proved enters the crankcase via the breathers on the rocker cover, the fan pulley, and the crankcase breather which is attached to the carburetter intake. To overcome this we stopped up the holes on the rocker cover, and made the crankcase breather more efficient by carrying the pipe into the inner intake of the carburetter. To make this clear, we found that with a pressure of approx. .300" of water under the bonnet, the same pressure was found to exist at the mouth of the breather pipe whilst / the inner intake of the carburetter there was a depression of approx. .300" of water. This proved that instead of the pipe acting as a breather to the crankcase, it was actually conveying air pressure to the crankcase. With these alterations we have got practically no compression in the crankcase whilst the car is stationary. We then turned to the cause of the depression in the flywheel case. This was obvious. The clutch case | ||