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).
Performance issues and comparisons between the Phantom II and J.III petrol pumps.
| Identifier | ExFiles\Box 17\5\ Scan117 | |
| Date | 20th May 1932 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to R.{Sir Henry Royce} By.{R.W. Bailey - Chief Engineer} x7460 Ea/Rm.{William Robotham - Chief Engineer}1/KT.20.5.32. y5460 R.R. PETROL PUMP. There are one or two points which have come to light in connection with the R.R. petrol pump, two of these are peculiar to J.III. (1) The P.II. fuel pump with .250" stroke takes 1 min 45 secs to pump from the reserve on a dry pipe line, the engine turning at 100 R.P.M. on the starter motor. The A.C. pump takes almost exactly the same length of time. The J.III. fuel pump with .200" stroke takes 2 min. 45 secs under the same conditions. There does not appear to be any reason why J.III stroke should not be .250" (2) The push rod guide has a tendency to stick when the oil is cold and the engine turning slowly,in the J.III design of pump. This can be overcome by increased clearance, but this is limited by the permissible oil leak or reduced surface of the valve guide, both of which we are testing. The J.III. guide differs from the P.II. guide in that the former has a separate guide for the push rod. (See Sketch). (3) The pump delivery is very sensitive to the position of the ports. A drop in delivery of 40% occurs if the port is drilled 1/16" too high. J.III ports are .050" higher than P.II. relative to the valve seat. This we think undesirable. All three troubles happened to be present on the first J.III. petrol pump which caused it to be unsatisfactory. The one fundamental difficulty left seems to be the time taken to draw fuel from a dry pipe line, but when a .250" stroke is used, this is no worse than with the original P.II. suction pump and Autovac. The attached curve shows the actual delivery of a R.R. pump under running conditions with a two way tap filter etc. in the pipe line, and also the maximum pressure that the pump can exert on the Carb. needle valve. The second air bottle improved the delivery somewhat and we think that we have an adequate supply for high speeds. | ||