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 endurance testing of Aerolite pistons for 3½ and 4¼ litre Bentley engines.
| Identifier | ExFiles\Box 87\2\ scan0134 | |
| Date | 10th February 1936 | |
| -4- Hs{Lord Ernest Hives - Chair}/Mths.{Reg Matthews}1/KW.10.2.36. The standard Aerolite piston as fitted to the 3½ litre Bentley would complete about 30-35 hours of this test, and we now have a set of Aerolite pistons for the 4¼ litre engine having the heat break sawcut in the scraper ring groove, and these completed 78 hours before showing signs of cracking. This is rather important as 10,000 miles represents only a few months under quite an average amount of running in a customer's hand. It is quite true, however, that we have not had a case of piston failure reported with a car in a customer's hand, but we should have a very large safety margin with the pistons that completed 78 hours. Incidentally, these pistons have considerably more taper on the skirt than the standard 3½ litre piston, and it is hoped that this will give us a piston that has less tendency to knock and is less likely to seize due to the large clearance at the top of the skirt. The clearance at the lower end of the skirt is about .001. B-19, the next 10,000 miles unit, is fitted with this type of piston, and it will be interesting to see what the results of this will be as the only pistons we have had for test have been used for endurance, and on these pistons we do not get a true indication of the bedding due to the excessive heat the pistons are subjected to. Hs{Lord Ernest Hives - Chair}/R.Matthews. | ||