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).
Report page detailing tests on sodium-cooled valves, cylinder head joint issues, and engine expansion characteristics.
| Identifier | ExFiles\Box 113\5\ scan0213 | |
| Date | 13th February 1939 guessed | |
| -5- rometer maintaining a consistent contact with the top spring washer every time the valve closes. This indicates the time at which the maximum expansion is reached. The throttle is then closed to give a light running of 1000 RPM, and the mike reading taken every 15 seconds, giving a contraction reading against time. This test was carried out on the sodium cooled valve on No. 5 cylinder, and on completion, the sodium was removed from the valve and the test immediately repeated. The result showed that the particular valve expanded half as much with the sodium removed. The expansion of a similar valve in No. 6 cylinder was checked in the same way, and the result showed a maximum expansion less than the valve in No. 5 whilst the maximum temperatures, measured optically appeared the same. Due to the difficulty of measuring temperatures below 700°C with the instrument, it is possible that an appreciable difference exists between the exhaust valves, which would account to a certain extent for slight expansion differences. Temperatures were in the order of 740°C for an uncooled valve, and 630°C for the cooled valve. The difference in expansion between cooled and uncooled valves is almost certainly the increased heat-flow to the valve stem from the sodium giving higher stem temperatures with a lower head temperature. On the solid valve heat to the guide is regulated purely by the conductivity of the valve material. Cylinder Head Joint Considerable trouble was experienced due to internal and external water leaks, the former leak giving rise to a siezed big end with consequent fracture of the connecting rod. The idea of increased unit pressure by virtue of narrow bedding surfaces does not appear practical in view of existing gasket materials, and whilst a reasonably satisfactory joint was ultimately obtained by employing a form of klingerite packing, the studding of the head, especially on the inlet side, appears inadequate. Several alternative gaskets were tried including solid copper cortu-joint & C and A, but none proved satisfactory, the best compromise being the soft jointing. Expansion. Expressed in terms of tappet clearance variation between hot and cold engine conditions. The maximum variation is .004". It is interesting to note, however, that this maximum figure is obtained as soon as the circulating water temperature rises above 75°C irrespective of oil temperature, or combustion chamber temperature. | ||