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).
Calculation table for the Ampere-turns required to produce a specific magnetic flux.
| Identifier | WestWitteringFiles\Q\2April1927-June1927\ 147 | |
| Date | 2nd June 1927 guessed | |
| -6- AMPERE TURNS NECESSARY TO PRODUCE FLUX REQUIRED. Part. | Metl. | Length. (") | Virtual section (sq.ins) | Total Flux. | Flux density. inch units. | Flux density. Cm. units. | H.{Arthur M. Hanbury - Head Complaints} | A.T. per inch. | A.T. Armature teeth. | Lamin. iron. | .460 | 5 1/2 x .115 x 2.75 = 1.73. | 201000 | 116000 | 13000 | 200 | 400 | 184 Armature core. | " | .600 | 2 x .490 x 2.75 = 2.70. | 201000 | 74500 | 11540 | 7.5 | 15 | 9 Air gap. | Air. | .0125 | 1.80 x 2.750 = 4.95 | 201000 | 40600 | 6290 | 6290 | 12580 | 157 Pole core. | M.S. | .625 | .9x2.400 = 2.16. | 241000 | 111600 | 17300 | 130 | 260 | 162 Yoke. | M.S. | 1.700 | 2x.3125 x 4.000 = 2.50 | 241000 | 96500 | 14960 | 30 | 60 | 102 Total :- 614 EFC. | ||