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).
Modifications and tests performed on a No 2 Double Piston Damper to resolve a noise issue.
| Identifier | ExFiles\Box 16\5\ Scan001 | |
| Date | 7th July 1931 | |
| Copy for files. N.Sch.3190/2/5 X7520 7.7.31. X235 X7520 NO 2 DOUBLE PISTON DAMPER. After having successfully cured the valve "squawk" on the first damper tested, the modifications necessary to accomplish this were made to a second damper, after ensuring first of all, that the latter suffered from the same complaint as the former. The modifications were as follows:- (a) Masked valve, .010" diametral clearance. (b) .025" diam high pressure valve leak. (c) Valve spring 200LB/IN rating, 8LB initial load. (d) Balancing spring 7lb initial load. Even with these modifications the damper was still noisy, and it was also discovered that when the external pressure scheme was brought into action the noise increased. Further investigation showed that the maximum sound was produced at approx: 10lb/sq ins, and that if the pressure was increased to 25 or 30 lb/sqins, the noise diminished, and sometimes ceased altogether. The intensity of the noise was generally much greater, when, after the application of 30lb/sq ins, the pressure was reduced to 10-15lb/sq ins. The attempts made to cure this fault were many and varied, the following tests show only the main lines followed. In addition to the above modifications the initial load of the 200 LB/IN spring was increased by adding washers, the poundage of the piston retaining springs was increased to 50 LB, a very light valve spring 18 LB/IN rating, and a very heavy spring- 330 LB/IN rating-both set to give an initial load of 8 LB, were tried. The latter in conjunction with a .025" valve leak proved successful in abolishing the noise, but the temperature rise under these conditions was extremely rapid. A valve having only .005" diametral clearance, with an .025" diam HP leak, was also successful, but the ball-pin loads were increased enormously when using the 200 LB/IN valve spring. In view of this, the HP leak was reduced to .015" diam. At this setting, the noise returned in a small degree, but when the light 18 LB/IN, or the heavy (1) | ||