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).
Preventing piston knock by improving lubrication and suggesting the use of Castrol oil.
| Identifier | ExFiles\Box 35\2\ scan 123 | |
| Date | 5th September 1919 | |
| Contd. -4- R3/G5.9.19. knock during the warming up period - surely this is not unreasonable ? You will see therefore that my impression is that it would be more harmful to go back to our dangerous practice of fitting tight cast iron pistons which have a considerable risk of seizing under exceptional circumstances of running, such as was found in starting up a cold engine and at once applying full load. In connection with the present arrangement, I have suggested that since we have made considerable progress in preventing the oil passing up the piston into the combustion chamber, we may be able to lubricate the pistons more thoroughly by keeping on the extra oil, even when running light (throttled). Mr. Hives has tested this idea, and finds that considerable increase can be given in the lubrication of the pistons even during their warming up. This causes the piston to cease knocking very much more quickly than with the old arrangement, in which case a new engine gets very little piston lubrication unless under full throttle. Another slight move which we have available for the present and past cars is to suggest the use of a lubricating oil which does not lose its viscosity as quickly as the mineral oil. We have now, however, a lubricant called "Castrol" which is castor oil with a small percentage of mineral oil. This has been used so successfully in aero engines and is exactly what is wanted for a car engine as far as we have been able to test. The cost of 4/- or 5/- per gallon for this oil (a gallon of which would certainly run the car 3,000 miles) amounts to an extra Contd. W.H.O. D-61-90 MS & S/L 600/1 919 H.N | ||