Crankcase and flywheel case air pressure, detailing tests and modifications to manage it.
| Identifier | ExFiles\Box 103\2\ scan0209 | |
| Date | 2nd October 1929 guessed | |
| -3- and flywheel acting as a pump, drives air out of the two large drain holes situated under the flywheel and gearbox. There is no positive inlet for air to enter, other than the annulus round the rear bearing of the crankcase, and a depression is caused. When the car is driven on the road, the inrush of air through the radiator causes a higher compression under the bonnet, with a consequent higher crankcase pressure. The air under these conditions entering by the annulus round the fan pulley. The increased volume of air in the crankcase is forced and drawn through the annulus round the rear bearing and makes a compression, although of a lower value in the flywheel case. Tests taken show the compression to be, crankcase pressure .125" of water, flywheel case pressure .05" of water. To defect the higher compression in the crankcase, we made the action of the flywheel create a definite pressure in the flywheel case. To obtain this, we fitted plates over the large drain holes leaving a .187" hole for drainage. Then we drilled the top cover of the flywheel case at the off side (this is important) approx. 1" in dia. With this arrangement we then get a higher compression in the flywheel case than what is obtained under any conditions in the crankcase, the results being at maximum speed with radiator shutters full open, crankcase compression .187" water, flywheel pressure .275" of water. It is then impossible for any oil to be drawn into the flywheel case as a definite stream of air is being forced | ||
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).