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).
Investigation into the sources of noise, or 'knocks', in rear dampers and proposed solutions.
| Identifier | ExFiles\Box 151\2\ scan0374 | |
| Date | 22th December 1938 | |
| 1292 To Ry. from RM {William Robotham - Chief Engineer} /AFR. c. Da. {Bernard Day - Chassis Design} c. RHC. {R. H. Coverley - Production Engineer} c. Hd. {Mr Hayward / Mr Huddy} c. GWH. {George W. Hancock - Head Chateauroux} RM {William Robotham - Chief Engineer} /AFR.1/MH. {M. Huckerby} 22.12.38. DAMPER KNOCKS - R.H. REAR DAMPERS. In view of the various notes that have been circulated about damper knocks, we decided to find out the origin of the noise in our dampers. The tests were made by HPS {Horace Percy Smith - Experimental Factory Mgr} /WB. {Mr Brazier / Mr Bell} There are three main sources of the noise, and their order of importance appears to be as follows:- (1). Replenishing valve knocks. (2) Knocks due to poor fit of bolt through the two pistons. (3) Bearing knocks. To cure (1) the spring pressure on the replenishing ball valve must be as small as possible, but it must not be quite free. Knocking can occur if the load on the ball is zero or too high. This is of prime importance, so will RHC. {R. H. Coverley - Production Engineer} and Hd. {Mr Hayward / Mr Huddy} see that the dampers they handle are correct. The spring is held in position by a pin. The spring when free should reach the centre of the pin hole, i.e. it should be compressed half the pin diameter. To cure (2) the bolts must be maintained a good fit. We have seen dampers in the Repair Dept. where this bolt is not a good fit in the hole. No attempt should be made to facilitate production by instructing loose fitting bolts. (The new S.V. type dampers do not have this bolt). Complaint (3) does not seem very common. The present procedure of rebushing all knocking dampers, which should certainly be continued if the damper has to be disturbed and the bushes are found slack, probably cures the knock by accident. The knock complained of by GWH. {George W. Hancock - Head Chateauroux} appears to be a replenishing valve knock. | ||