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 ampere-turns required to produce a specific magnetic flux in various motor/generator parts.
| Identifier | ExFiles\Box 64\1\ scan0150 | |
| Date | 19th June 1923 guessed | |
| -6- AMPERE TURNS NECESSARY TO PRODUCE FLUX REQUIRED Part. | Matl. | Length (") | Virtual section (sq.ins) | Total flux. | Flux density Inch Units. | Cm. Units. | H.{Arthur M. Hanbury - Head Complaints} | A.T. per inch. | A.T. Armature teeth. | Lamin. iron. | .4375 | 7x.075 x 2.75 = 1.44 | 200,000 | 139,000 | 21500 | 490 | 990 | 433 Armature core. | " | .55 | 2x.50x2.75 = 2.75 | 200,000 | 72,700 | 11260 | 9 | 18 | 10 Air gap. | Air | .015 | 1.85x2.75 = 5.08 | 200,000 | 37,400 | 5,790 | 5790 | 11700 | 175 Pole core. | M.S. | .625 | .94x2.45 = 2.30 | 240,000 | 104,000 | 16100 | 35 | 70 | 45 Yoke. | M.S. | 1.7 | 2x.312x 4.50. = 2.8 | 240,000 | X85700 | 13270 | 19 | 38 | 65 Total | 728. | ||