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).
Technical discussion regarding spring poundage specifications for valve and clutch assemblies.
| Identifier | ExFiles\Box 129\4\ scan0056 | |
| Date | 8th November 1937 | |
| -2- Rm{William Robotham - Chief Engineer}/NRC.{N. R. Chandler}7/MH.{M. Huckerby}8.11.37. definitely drop a certain amount in poundage as compared to, for example, a valve spring which is continually worked through a considerable range of stress, and Messrs. Armitage and Barker said their experience confirmed this statement. The drawing of the Brown spring in question shows 147 to 155 lbs., and we had requested Borg & Beck in May 1936 to fit springs on the high limit, namely 151 - 155 lbs., which, it was said, leaves very little margin for error or settling. Rm.{William Robotham - Chief Engineer} then pointed out that if we cannot expect springs to be within certain specified limits, the limits are useless, and we do not know where we stand, and we had not been advised that some of the springs might have a working poundage considerably below the low limit. Mr. Thompson considered it would be better to select a spring having a required working poundage nearer the low limit instead of the high limit, to allow for the inevitable settling, and Rm.{William Robotham - Chief Engineer} stressed the point that we must know what the low limit will be. It was decided that Messrs. Borg and Beck and The Tempered Spring Co. should consider the design of a spring which would provide a minimum thrust of 150 lbs. under working conditions, but that the maximum should be kept as low as possible in order to avoid excessive pedal pressure, especially as it is not desirable to increase the pedal travel on the Bentley. With regard to fitting Thermoid faced plates to customer's cars at Derby and Depots, it was decided to establish a small stock of complete clutch assemblies with springs of required poundage, and Messrs. Armitage and Barker said that if we returned to them the assemblies removed, they would assemble them with new springs and rebalance them without charge. It was suggested that the design of a simple rig for testing the total thrust poundage of a clutch assembly without dismantling the springs might be considered, and we are investigating the possibilities of this. Rm{William Robotham - Chief Engineer}/NRC.{N. R. Chandler} | ||