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 for PI and PII type dynamos with 56 coils and thinner armature stampings.
| Identifier | ExFiles\Box 60\1\ Scan142 | |
| Date | 1st April 1927 | |
| X7660 40/50 J.B. MACHINES. 56 Coils and Thinner Armature Stampings PI and PII X.7660. PERFORMANCE COMPARISON OF DYNAMOS. (on routine procedure of 1.4.27) | Date. | Dynamo. | Particulars and remarks | (1) | (2) Brush angles. | Temperatures. | Peak | |---|---|---|---|---|---|---| | | | | | Main. | Control. | Amb. | Rise | Machine. | Amps. | Speed. | | 5-4-29 | YH.15. S.28 | First of PI machines with thinner stampings & 28 slots with B=9° C=122° nominally. | O.K. | 9.5° | 121.5° | 16 | 64 | 80 | 13.8 | 1350 | | 10-4-29 | YH.35 S.28 | Borrowed from prod.n for purpose of making observations. | O.K. | 9° | 121.5° | 17 | 63 | 80 | 13.5 | 1330 | PII Type Machines. | 10-5-29 | X1.15.SS{S. Smith} | First machine a complete inversion of the Phantom I type. | OK | 10° | 122.5° | 20 | 68 | 88 | 13.4 | 1420 | | 30-5-29 | X1.35.SS{S. Smith} | * Still rising. Reading observations only made. | — | — | 121° | 25 | 65 | 90 | 13.5 | 1440 | | 9-7-29 | VK.55 SS.{S. Smith}X | Reading and output observations only made. | — | — | 122° | 21.5 | 68 | 89.5 | 13.0 | 1330 | | 10-1-30 | XK.35 SS.{S. Smith} | " | — | — | 121.5° | 17 | 71.5 | 88.5 | 12.6 | 1430 | | ||