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).
Letter from the Springfield plant to Derby discussing piston pin performance and knocking issues.
| Identifier | ExFiles\Box 81\2\ scan0084 | |
| Date | 10th December 1923 | |
| ROLLS-ROYCE OF AMERICA, INC. SPRINGFIELD, MASS. x416 Oy2-E-121023 December 10, 1923. Mr. E.{Mr Elliott - Chief Engineer} W. Hives, % Rolls-Royce, Ltd., Derby, England. Hs.{Lord Ernest Hives - Chair} from Oy. Re: Piston Pins Proposal Sheet No. 25. We do not quite agree with you in this matter. We know that while a few of the old type piston pins E-17765 worked loose in the piston and caused knocks, many have run over 20,000 miles and one in an English post war car came in from Canada the other day having run 60,000 miles in 3 years, and the piston pins are perfect and do not knock. In 102 CE we ran 25,000 miles with these piston pins without any knock and practically no measurable wear, whereas the new type pins knocked badly after 10,000 miles because they wore out the little end bushes. Our explanation would be as follows:- Any pin in any aluminum piston will be slightly slack in bosses when piston is hot, the new type not less than the old because of the difference in coefficients of expansion. Theoretically for 150°F rise of temperature on the skirt which probably represents ordinary road-running of a car the slack should be about .001. We do not think this causes a knock or otherwise every engine we ever turned out would knock at once on its first run, and every other car with aluminum pistons would do the same. This is not so. The elusive knock appears in our experience after 10,000 miles at the very least. | ||