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 log sheet for PI and PII type dynamos.
| Identifier | ExFiles\Box 60\1\ Scan198 | |
| Date | 19th February 1930 | |
| X.8664. 40/50 B. MACHINES. PI and PII 56 Coil Higher Output Machines PERFORMANCE COMPARISON OF DYNAMOS. (on routine procedure of 1.4.27) Table Headers: Date. | Dynamo. | Particulars and remarks. | (1) Brush angles. | | (2) | (3) Temperatures. | | | Peak | | | | Main. | Control. | | Amb. | Rise. | Machine. | Amps. | Speed. P I Type 24-9-28 | H O I. | Exptl dynamo. First of higher-output machines. | O.K | 10° | 127° | 17 | 58 | 75 | 15.9 | 1660 13-11-28 | 2. NB. HO | First of higher-output machines received from production. | O.K. | 8.5° | 126° | 16 | 68 | 84 | 14.7 | 1700 22-11-28 | 3. NB. HO | Received from production. | O.K. | 9° | 125.5° | 18 | 61 | 79 | 14.9 | 1850 3-12-28 | 4. NB. HO | Received from production. | O.K | 10° | 128.5° | 13 | 64.5 | 77.5 | 16.3 | 1820 P II Type 19-2-30 | 18. HO. SS.{S. Smith} | Recd from Prodtn for the P-of-W's car. First of its type. *C angle afterwards reduced to 127.5° to increase output. | O.K. | 8.5° | 128° * | 16 | 58 | 74 | 14.6 | 1750 | ||