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).
Test report on diagnosing and rectifying a noise issue in a valve through various modifications.
| Identifier | Morton\M19\ img082 | |
| Date | 1st June 1931 guessed | |
| - 2 - When the hole in the valve was replugged the noise was again produced, also the diagrams remained "in the air". The hole was then re-opened and an additional hole .025" drilled in the L.P. section of the valve, but the noise remained, even after re-plugging the L.P. valve. After opening out the H.P. hole to .055" dia. the sound again vanished and after re-checking with a .025" hole when the noise again returned, the hole was re-opened to .055" dia. and found satisfactory. The Ball Pin loads obtainable with the valve spring issued were somewhere in the region of 300 lbs. and to bring the loads to more reasonable figures a spring giving 8 lbs. initial valve load (approximately 80/85 lb. ball pin loads) was fitted. A lighter balancing spring - 3 lb. initial - was also fitted but this spring does not affect the valve loading. With the fitting of the lighter springs the noise returned, more intensive than previously, and even re-opening the H.P. hole to .055" dia. failed to produce silence. During this test it was observed that the noise tended to decrease with increased temperature. Following this, two holes through the base of each piston leading into the spring well - .025" dia. each - plus a .025" H.P. valve hole, plus a .025" dia hole drilled right through the L.P. valve failed to procure silence. A small copper pipe leading from the L.P. valve passage sealing plug back to the reservoir via the filling hole in addition to the above arrangement provided too much leakage, and after deleting the piston holes the noise appeared on the L.P. stroke when the rig was started but disappeared quickly. On the H.P. side however, the noise re-appeared at approximately 70 RPM. and receded above 150 RPM. and this according to a diagram taken was due to lack of oil, we therefore removed the pipe. A masked valve having .002" radial clearance in the sylphon base was silent, but it was found that due to a slight eccentricity between the bore of the sylphon base and the valve mask, the valve was "sticking" badly. | ||