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).
Analysis of piston seizure causes, including engine boiling and rich fuel mixtures.
| Identifier | ExFiles\Box 87\2\ scan0055 | |
| Date | 17th April 1935 guessed | |
| -4- In each case of piston seizure it has been noticeable that the eng seizure has been on the pressure faces and not on an axis through the gudgeon pin. Allowing for the water temperature to rise when boiling to 105 or 106°C. due to the pressure in the system and a normal working temperature of 80-85°C., this would only tend to decrease the working clearance approx. .0006 which is hardly enough to offset the increase in clearance previously mentioned. One customer has complained that his piston seized when his engine was boiling, but we are inclined to think that the boiling was due to the piston seizing and not the piston seizing due to boiling. It is noticeable when stopping an engine after running for some time at high speed that the thermometer is at boiling due to the heat from the cylinders and cylinder head being transferred to the water which is stagnant of course when the engine is stopped. The amount of heat thus transferred to the water is sufficient to increase the temperature to boiling point in the cylinder head, where of course the thermometer is connected. In fact, from our experien ce it is much more likely for the exhaust valves to seize before the pistons when running with the engine boiling, but even in this case it is necessary for the water to be boiling at the ijlet to the pump, a condition not likely to be met with on the road, as the radiator will probably keep the inlet temperature down to 90-92°C, even if the water is boiling in the cylinder head. Rich Mixture. Our conclusions are that running and starting under normal atmospheric temperature conditions on a well "run-in" engine, a rich mixture will not produce a seizure. Our tests, which were all carried out on the test bed, where normal atmospheric xx temperatures were prevalent, i.e. we were not running these tests either for running or starting under freezing conditions, were sufficiently drastic to have caused seizing had rich mixture been the cause, particularly in the case of running and starting with rich mixtures with one cylinder not firing. We would say that a fast "getaway" was not the cause of the piston seizure unless the atmospheric temperature was around freezing point, and the car had been left for some time in the open. | ||