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).
The EAC ignition oil relay, testing the performance of the inner piston diameter under varying conditions.
| Identifier | ExFiles\Box 65\1\ scan0034 | |
| Date | 23th December 1924 | |
| R.R. 493A (50H) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. Expl. No. REF: Hs{Lord Ernest Hives - Chair}/Rm{William Robotham - Chief Engineer}/LG23.12.24. EAC. IGNITION OIL RELAY. (1) Inner piston diameter. From the point of view of stiction when the viscosity of the oil is high, and also foreign matter in the oil causing destruction, we wish to run this piston with the maximum permissible clearance. The limiting factor in this case is the point when the oil pressure is lowest and its temperature highest. We have heated up the relay cylinder by means of steam until the oil attained a temperature of 80°C and reduced the oil pressure from its normal 20 - 30 lbs. per sq. in. to 6 - 18 lbs per sq. in. (the oil pressure on all EAC. engines appears to vary 10 lbs. between max. and min. r.p.m.) We did not consider it necessary to go below 6 lbs. per sq.in. as it would certainly be unwise to run the engine in this condition, and the fact that the automatic advance was not in action might draw the drivers' attention to the oil gauge by reason of the consequent loss of power. We find that under these conditions we can obtain a satisfactory ignition advance curve with .005" clearance. If we cool the oil to 5°C, the whole relay movement becomes very sluggish but still functions, the only material difference being a slight variation in the zero point due to the return spring being unable to overcome the stiction when fully extended. This only amounts to 4° ignition advance on the flywheel however, and in addition the relay casing does not take long to warm up by conduction from the crankcase. contd :- | ||