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 mileage testing of improved split pistons and their effectiveness in overcoming piston knock.
| Identifier | ExFiles\Box 77\3\ scan0121 | |
| Date | 20th February 1920 | |
| X.3757 To R.{Sir Henry Royce} from Ms. c. to CJ. c. to Bn.{W.O. Bentley / Mr Barrington} c. to Da.{Bernard Day - Chassis Design} c. to E.{Mr Elliott - Chief Engineer} c. to EP.{G. Eric Platford - Chief Quality Engineer} Hs{Lord Ernest Hives - Chair}5/LG20.2.20. _______ X.3751. RE PISTONS. X.3429. ------- ------- We have been running several sets of the improved split pistons. We have run one set of pistons 6200 miles. This car has run every day and at night it has been on the dynamometer running undervarying loads and throttle positions. We have run another set of these pistons 2100 miles. Another set of these piston have run 3000 miles, and another set has run 3500 miles. The results of the tests as far as they have gone is that we appear to have practically overcome the piston knocks which we had when starting up cold. These four sets of pistons will now all start up from dead cold with no knock which is manifest. One anticipates that if immediately the car is started up, one applied the load, there may be found a slight knock but under ordinary conditions on these four cars, there have been no complaints of piston knocks when cold. We do, however, find with these pistons a slight knock when the engine is hot. It has none of the characteristics of the ordinary piston knock. The knock we refer to is only there when the engine is running free. If any definite load is put on, it disappears. It cannot be cured by any excess of oil. We have tried pouring about half-a-syrings full of oil into Contd. | ||