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).
Test results for an oil relay ignition advance system, focusing on piston clearances and oil leakage.
| Identifier | ExFiles\Box 65\1\ scan0056 | |
| Date | 3rd January 1925 | |
| +8685 Hs.{Lord Ernest Hives - Chair} from Rm.{William Robotham - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}2/LG3.1.25. OIL RELAY IGNITION ADVANCE. This is now a reasonable working proposition. The pistons we are fitting having a diameter of .618" or .007" clearance. We can detect a drop in oil pressure of [handwritten: rather] over 1 lb. per sq.in. due to leakage passed these pistons with any given relief valve setting. We have measured the actual amount of oil which passes the pistons at 1000 r.p.m - the oil pressure 30 lbs. per sq.in. We find it is 1.1 pts. per min. If we increase the piston diameter to .621" the leakage is reduced to .57 pts. per min. If we remove the piston altogether, we get a leakage of 8 1/2 pts. per min., and the oil pressure drops 4 lbs. per sq.in. It will therefore appear that there is a large reserve of oil passing the relief valve. The temperature of the oil in all these tests was 60° C. From the point of view of stiction due to grit, we do not [XXXX] want to run this small piston with less clearance than .005". We do not think that with the present oil pump, this will have any untoward effect on the main oil pressure. | ||