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 failures on Bentley pistons and proposing a modification.
| Identifier | ExFiles\Box 86\2\ scan0097 | |
| Date | 25th October 1933 | |
| x236. To [s]WOR{Arthur Wormald - General Works Manager}[/s]. from E.{Mr Elliott - Chief Engineer} c. Hs.{Lord Ernest Hives - Chair} [s]By.{R.W. Bailey - Chief Engineer} Sft.{Mr Swift}[/s] NHC. Bentley Pistons. Referring to pistons taken from the 10,000 mile car, Experimental Department have found a crack on the top side of one of the gudgeon pin bosses of No.[s]5.[/s] piston. Following this we have reconstructed the gudgeon pin bosses of No.6. piston [s]which was broken into fragments,[/s] and we find definitely two discoloured fractures on each side of one of the gudgeon pin bosses, and a rapid fatigue fracture between one of the diagonal webs and the bore of the other boss which is clean, and must have followed on after the fracture of the first boss. Our tests also on the bench have now produced a crack in the bottom of one of the gudgeon pin bosses. It is, therefore, clear that this boss is weak in section having failed at all four points of the compass and we have issued a modification - LeC.3675 increasing the diameter and also adding a little additional metal at the junction of the diagonal webs at the top. We think the dies should be immediately modified so that we can get some fresh pistons on test. The increase in weight of the piston as calculated will be .7 ozs. There is no doubt that our gudgeon pin diameter is on the small side for a modern engine and some increase on this dimension is overdue. We shall take the earliest opportunity of putting this up. E.{Mr Elliott - Chief Engineer} | ||