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).
Calculations for static torque, polar flux density, and armature design.
| Identifier | ExFiles\Box 64\1\ scan0130 | |
| Date | 30th May 1923 guessed | |
| -2- Contd. The static torque at this current must be 10% greater (say) then the running torque, i.e. it must be 60.4 lb-inches. Take a useful polar flux density of 6750 lines per cm² reckoned on minimum pole face Armature diameter = 3.100" Armature circumference corresponding to 69% polar embrace = 69/100 x π x 3.100 = 1.68" = 4.27 cm. Useful length of armature = 2.75" = 6.99 cm. Useful flux per pole = 6750 x 6.99 x 4.27 = 201,000 lines Number of conductors = (Tb x 10⁸) / (1.41 P Ø C) = (60.4 x 2 x 10⁸) / (1.41 x 4 x 201,000 x 145) = 73.5 i.e. 74 nearly. Number of slots or sections = 37 (This conforming to the 4n+1 rule) Contd. | ||