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 10,000-mile test for the Phantom III piston development to address piston knock.
| Identifier | ExFiles\Box 94\5\ scan0113 | |
| Date | 3rd February 1936 | |
| X336 COPY. E.{Mr Elliott - Chief Engineer} Hs.{Lord Ernest Hives - Chair} Hy.{Tom Haldenby - Plant Engineer} SFT.{Mr Swift} Copy to Wcr. EXG/T3.2.36. PHANTOM III PISTON DEVELOPMENT. We have completed a 10,000 miles test on the unit bed without any sign of piston knocks. To obtain this result we had to deal with two problems. (1) Cylinder distortion, mainly due to the swelling of the rubber sealing rings, (2) Condition of piston projecting .1.6" out of the bore at bottom of the stroke. With regard to the cylinder distortion, we have succeeded in reducing this to a negligible amount by using two types of ring per cylinder. The upper or water seal to be specification DTY.10 which is a rubber ring coloured pink for identification. The lower or oil seal to be a "D" type ring which is a synthetic production and will be black. With regard to the piston, the final result was obtained by grinding the skirt of the piston parallel to a dimension of 3.250 dia. for a length of 1 inch. The remainder of the bearing area being taper to standard dimensions. The 10,000 miles was run at varying speeds and loads, we tried to simulate as far as possible road conditions. The engine was stopped frequently and allowed to become quite cold, in order to test for piston knocks, starting up under those conditions. The average speed was 43 1/2 m.p.h. " " oil temperature 73°C. " " water temperature 65°C. An oil consumption test was taken during the last 4500 miles of the run. The amount used being 3 1/4 gallons which is an average of 1400 miles per gallon. On dismantling the engine, the pistons were found to be in very good condition. | ||