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).
Tests on various valve and spring configurations to reduce noise and rationalize pressure diagrams.
| Identifier | ExFiles\Box 182\M19\ img083 | |
| Date | 1st June 1931 guessed | |
| - 3 - By increasing the radial clearance to .010" and utilising the .025" dia. H.P. valve hole, the damper was silent, and the diagrams were more rational. The high pressure diagram showed a distinct step in the middle of the stroke due to a sudden drop in pressure whilst the low pressure showed a slight "kick" at the beginning of the stroke before settling down to a fairly uniform pressure during the remainder of the stroke. Lightening the masked valve by drilling out as much metal as possible had no effect upon the results. All the diagrams returned to the original fine. The stroke was reduced to 1"; still no noise - no diagrams taken. Tests were then taken with masked, and standard valves, having additional slight masking below the H.P. valve seat similar to "Delco" design - HS.{Lord Ernest Hives - Chair}345. Undrilled these were almost as noisy in operation as the standard valves and drilled the H.P. hole in these cases also effected a cure. Diagrams were taken at 1" stroke, and from these it was found that the max. pressures were increased at 450 RPM. after drilling the H.P. holes, possibly due to pressure being retained behind the valve. This tendency was also marked during 4" stroke, and also with the original valves. Tests followed at 300 RPM, 4" stroke to find out whether or not the dampers replenished quickly enough. The diagrams taken were of peculiar shape, but the evidence was sufficient to shew that the damper was not suffering from lack of oil to any great extent. Since the noise was apparently due to the valve tests were taken to find out the effect of valve lift on the sound. The 8 lb. initial load spring previously referred to had a very low rating - approximately 16 lb/in. - and with no apparatus erected for these valve tests the valve could be seen "shuddering" when operating. The lift with this spring was very high, roughly .200" at 150 RPM. 4" stroke, with a "Delco" valve, but by using a 300 lb/in rating spring, thus reducing the lift to .045", the noise was reduced. However, when diagrams were taken the H.P. was found to be "in the air". This spring was also set at 8 lb. initial load but had to be used without the syphon, being too large on the outer diameter. Tests with the standard valve gave approximately the same results as the "Delco" except that the valve lifts were not as high. | ||