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 comparison table of dynamos for single modification 20 HP machines.
| Identifier | ExFiles\Box 165\6\ img156 | |
| Date | 1st April 1927 | |
| -2- PERFORMANCE COMPARISON OF DYNAMOS. (On routine procedure of D.A.27). SINGLE MODIFICATION 20 H.P. MACHINES. Table Headers: Dynamo (4) Speed for 10V. 14V. 17V. (5) Speed for 0 amperes (5) Peak Speed. amperes, 2500 RPM amperes superch. (6) Speed for 10V. 13.6V. 17V. (7) Speed for 0 amperes 8 & 15 Table Data: Row 1: P2KM | 440 700 945 | 840 | 2150 | 11.0, 9.8 at 3000 | - - - | - - Row 2: P6KM | 805 905 975 | 905 | 2250 | 11.2, 10.5 at 3000 | - - - | - - Row 3: I2RM{William Robotham - Chief Engineer} | 825 910 990 | 710 | 2100 | 10.7, 10.4, 9.8 at 3000 | - - - | - - Row 4: C70-M | 720 815 905 | 815 | 1940 | 11.65, 10.8, 9.8 at 3000 | - - - | - - Footer: 4.27 | ||