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).
Experiments using different diameter pipes to investigate and eliminate a 'squawk' noise from a valve damper.
| Identifier | ExFiles\Box 151\2\ scan0254 | |
| Date | 19th June 1934 | |
| -4- Later, instead of scrolls, copper pipes of various diameters, each 9" in length (the approximate total length of the transfer passages) were fixed in the valve chambers, so that one end of the pipe was open to the L.P. pressure, whilst the other end covered the L.P. valve port as shown in Hs. {Lord Ernest Hives - Chair} 1406F, thus the oil had to traverse the length of the pipe before reaching the L.P. valve. Commencing with a .250" diam. pipe, when the "squawk" was definitely on the H.P. stroke, and continuously increasing the diam. it was eventually found that with a .375" diam. pipe, the damper was noisy at first, but when the temperature had been raised (by running on the rig) it was necessary to increase the load considerably in order to produce the "squawk", then it was still a H.P. noise. The bore of this .375" diam. pipe was .304" diam., whereas the transfer passage bore was .324" diam., therefore there seemed to be something in the theory of "balanced" passages. However, using a .437" pipe (.365" bore), the damper was noisy on the L.P. stroke when operated by hand, but when run on the rig was equally noisy on both strokes. This valve chamber was also tried with the L.P. valve taper reduced to .025" in length, with no effect. Finally, a 1/2" diam. pipe (.464" bore) was used, and this definitely brought the "squawk" back to the L.P. stroke. Conclusions. Although the main objective of these experiments was not fully achieved, they have proved useful in demonstrating that neither the valve nor its position is the direct cause of the squawk, and that although the noise can be avoided by the adoption of valve damping devices, the effect and not the cause is attacked. | ||