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).
The running of car 27.G.VI and a detailed investigation into exhaust valve sinkage.
Identifier | ExFiles\Box 131\3\ scan0106 | |
Date | 18th July 1939 | |
2. Mx.{John H Maddocks - Chief Proving Officer}1/MG.18.7.39 (continued) By cyanide hardening followed by cloudburst hardening we can produce a surface hardness comparable with that of Chromium, without the known evils of chromium plating. RUNNING OF 27.G.VI. This car has now been handed over to LA{L. A. Archer} to be made suitable for sale as a second-hand car after a total mileage of 54,176. A separate report is being made on the development work carried out. It is being replaced by 8.B.V which Rm{William Robotham - Chief Engineer} has now handed over. EXHAUST VALVE SINKAGE. The coolant jets referred to in Mx.{John H Maddocks - Chief Proving Officer}1/MG.22.6.39 have been run 3,000 miles on 27.G.VI, as this car had suddenly developed sinkage on Nos. 1 and 2 exhaust valves at the rate of .004" per 1,000 miles. Before doing any further running the seats were measured for depth by making a suitable gauge so that any subsequent sinkage could be accurately measured. During the first 1000 miles of subsequent running, No.1 exhaust valve lost clearance at the same rate as formerly, i.e., .004" per 1000 miles, but as there was some uncertainty as to whether this might be due to other reasons, such as the cylinder head gasket settling, or the valve itself bedding in after having been disturbed, the head was removed to measure the actual sinkage of the seat. Measurement by the gauge confirmed a further sinkage of .004" on No.1, but as the valve was not ground in on the previous occasion, it was felt that it might have been replaced with imperfect bedding which caused some settling down. It was therefore decided to grind the valves in and run the car further. At the same time, some of the core plugs were removed to examine for silting up. This did not seem abnormal, but in one point between Nos. 1 and 2 heads we removed some silt to enlarge the passage. During subsequent running, the tappet clearances were checked every 250 miles, but no signs of sinkage were apparent. The car has since run a further 2,000 miles without the least variation in tappet clearances. We must assume from this that the coolant jets serve a useful purpose, and there is no apparent disadvantage. It is open to question whether the reduction in sinkage was due to direct water cooling or to the effect of the jets in removing or preventing silting up. The scheme will be tried on a Customer's car as soon as we find a suitable complaint case. (continued) | ||