Piston knocking in cold temperatures, comparing cast iron and aluminium pistons and potential remedies.
| Identifier | ExFiles\Box 18\6\ Scan034 | |
| Date | 11th September 1919 guessed | |
| -2- Winter Temperature. Piston knocking is a question very much wrapped up in radiator temperature. We are going to fit a thermostat which will allow for quicker warming up of the water. This will result in the radiator not being used in traffic, this will reduce piston knockings, help lubrication and improve petrol consumption. Mr. Royce stated that he would not agree to using cast iron pistons with a fine clearance in future. The result of this will be that if cast iron pistons are used with a proper clearance, knocking will result. The reason why some aluminium pistons do not knock while others do was found to be that the non-knocking pistons are mounted a little our of true with the connecting rod. Mr. Royce will not recommend mounting pistons "out of true", but if Works care to try this, no trouble will result. Mr. Northey considered Sales could persuade customers to accept the peculiar characteristics of aluminium pistons which includes a slight knocking when starting from cold, providing the full advantage of aluminium pistons are explained at the same time. This of course is an alteration to past policy of Rolls-Royce, when it was the practice to cure any engine knocking which became evident in a customer's car. He suggested that a standard of knocks, such as that on the Salamanca chassis, on which the slight knocking disappeared when the car was driven as far as Marble Arch from Conduit Street. It was the general opinion of the Technical Dept., that the knocking became impossible to distinguish from other engine noises as soon as the temperature reached 50° centigrade. Mr. Royce considered if ignition is retarded while engine is heated up the knocking will not appear. HSC. (C) 1011 F91 52S. 16.10.(?) I. coll Y Sec. (?) | ||
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).