Experiments to eliminate a 'squawk' noise from a damper by modifying springs, valves, and leaks.
| Identifier | ExFiles\Box 56\1\ Scan160 | |
| Date | 7th July 1931 guessed | |
| (2) 330 LB/IN springswere used the damper was quiet. Having arrived at this possible solution, the Hp. leak was again blocked up to ensure that the cessation of the "squawk" was not due to some other unknown factor; the noise returned in full force. The leak was redrilled .085" diam, and the 200 lb/sq ins, fitted, to find whether or not the noise could be cured by means other than varying the springs, also other means then varying the clearance, of releasing the increased pressure behind the valve. Holes were first drilled through the masking flange, but since the spring partly covered them, these tests, which showed good promise were abandoned, and instead of drilling straight through the masking flange, the centre bore of the valve was countersunk, and holes drilled inclined as shown in sketch, thus avoiding any obstruction. Two holes .055" diam were first drilled, and were immediately successful in eliminating the noise, but the initial load (no external pressure) was still slightly above the static load. Opening out the two holes to .062" diam caused the noise to reappear intermittently. The quietening experiments carried out on No1 damper were made without any externally applied pressure therefore in view of our experiences with No2, the first damper was retested with .010" masked valve, the .025"HP valve leak, and the 200 lb/in spring. This was still OK without external pressure, but between 5 and 10 lb/sq ins, there was just a faint intermittent "squawk" which disappeared entirely above 10 lb/sq in. The only radical difference between No1 and No2 damper was that the L.P. valve guide of No1 was bored out to DA {Bernard Day - Chassis Design} 's scheme. We are of opinion that this difference does not account for the fact that with the modifications found satisfactory for No1, No2 was noisy. To clear up this matter however, we hope later to apply Da {Bernard Day - Chassis Design} 's scheme to No2, and retest. At the present time the "Swan" dampers are occupying the rig. If masked valves with .005" diametral clearance (.0025" radial) are used, it will certainly be necessary to ensure that the sylphon, cover, and valve are in absolutely correct alignment to avoid sticking valve. | ||
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).