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 magnetic flux.
| Identifier | WestWitteringFiles\K\June1923\ Scan78 | |
| Date | 19th June 1923 guessed | |
| -6- AMPERE TURNS NECESSARY TO PRODUCE FLUX REQUIRED Part. Mstl. 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. .4375 7x.075 x 2.75 = 1.44 200,000 139,000 21,500 490 990 433 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 85700 13270 19 38 65 Total 728. | ||