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).
Continued discussion on the issues and relative merits of cast iron versus aluminium pistons.
| Identifier | ExFiles\Box 35\2\ scan 222 | |
| Date | 12th April 1920 | |
| W. H.{Arthur M. Hanbury - Head Complaints} S. (100 T) (S.F. 846 8-19) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2489 Contd. -2- Hsl/LG12.4.20. miles, has worn .007". As the wear is generally consistent on all six cylinders the most porbable cause for the variation one would think, is the different qualities of lubricating oil. It has not been found that the strength of the rings makes very much difference. Four or five months ago we should have welcomed the idea of returning to cast iron pistons but we are now, however, in favour of persevering with the aluminium. We feel that we know the worst about them and are well on the way to making them a success. Before we think of returning to cast iron pistons it is necessary to analyse the piston position as it was in 1914. We were then using the light cast iron pistons and were working to extremely fine limits on both cylinders and pistons. A considerable amount of time was also spent fitting them by hand. In spite of all the care that was taken on the pistons at that time, 20% of them on the average, were scrapped when cars were on test due to either piston knocks or seizure. The cars that come in the Repair Shop with these pistons most frequently have to have a proportion if not all of them changed after 10,000 miles running because of piston knocks. When the cars are sent out from the Repair Shop with the new pistons it sometimes happen that they seize up after the car is delivered. The other point against the cast iron piston is the fact that it is necessary to decarbonise the engine at least twice as often as with aluminium pistons. This is a big disadvantage when Contd. | ||