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).
Summary of test results concerning engine valve issues, particularly lead attack, and notes on bearings.
| Identifier | ExFiles\Box 173\1\ img072 | |
| Date | 15th January 1934 guessed | |
| - 2 - HS{Lord Ernest Hives - Chair} cooled) type. Latter have not been standardized on all engines although a certain number of Cyclone engines have been fitted with same. This type of valve is not entirely satisfactory owing to variation of material section which has been proved at Works, cannot be controlled effectively to the necessary fine limits, and also difficulty of inspecting same making it impossible to guarantee that material section is up to drawing requirements. The cylinders on the Conqueror are of butt-ended type with seats cut in roof of liners (see sketch) Therefore, no alternative seat materials have been tried, but various valve material including stellite valves have been tried on both types of engines. Results, however, are so conflicting that while some consider stellite reduces lead attack, others think there is little improvement. The following is a summary of test results to date: 1. Sodium cooling apart from pre-ignition does not necessarily reduce lead attack. Hollow head valves have been used as already mentioned but not fully cooled. 2. They are not certain that hot valves are more immune from lead attack. 3. It is thought that lead attack is more pronounced under high power output conditions, but under lower powers corrosion causes valve sticking on stems. 4. Air cooled engines are considered to be slightly better than water cooled with regard to lead attack, but it is thought that if design would permit the introduction of two exhaust valves instead of one, tremendous improvement would result. 5. The period of running to produce failure using 3½ c.c.'s is about 70 hrs, then rate of attack is rapid, but trouble commences after 30 hrs. running with 6 c.c. lead. 6. Oily cylinders reduce trouble particularly if applied through super-charger. 7. Fighting grade fuel is 87 octane. With regard to lead bronze bearings, these are used on air-cooled as well as water cooled engines and give very satisfactory results. Bearings from 2 suppliers are used viz., Allisons and Bohn's, in both cases bearings are made from solid and not from bent strip. Allison's bearings, however give best results. All bearings are supplied finished, allowance being made for final reaming in position, adopted clearances are in line with R.R. practice being .001 - .00125 per inch dia., oil pressure 60-70 lbs. sq.in., inlet temperature 90 C, the bearing experience on | ||