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\T\November1928\ Scan060 | |
| Date | 27th November 1928 guessed | |
| 4a- AMPERE TURNS NECESSARY TO PRODUCE FLUX REQUIRED | Part. | Mat'l. | 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. | .360 | 6.5x.089 x3.50 =2.00 | 240000 | 120000 | 18600 | 110 | 220 | 79 | | Arm: core. | " | .650 | 2 x .540 x 3.500 =3.78 | 240000 | 63500 | 9850 | 7.5 | 15 | 10 | | Air gap. | Air | .0115 | 1.80x3.50 =6.30 | 240000 | 38100 | 5900 | 5900 | 11800 | 136 | | Pole core. | M.S. | .650 | .90x3.350 =3.00 | 288000 | 96000 | 14900 | 25 | 50 | 33 | | Yoke. | M.S. | 1.700 | 2x.3125 x4.750 = 2.96 | 288000 | 97500 | 15100 | 28 | 56 | 95 | | | | | | | | | | Total = | 353 | | ||