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).
Page of calculations for armature design, including resistance, slot dimensions, and tooth width.
| Identifier | ExFiles\Box 64\1\ scan0132 | |
| Date | 30th May 1923 guessed | |
| -4- Contd. Resistance per 1000' = 12000 / 11 x .000757 = .826 ohm. But ohms per 1000' at 20°C = .00815 ÷ cross sectional area (a) Whence a = .00815 / .826 = .00986 sq.ins. Take copper space efficiency of 50% (say) Then slot area = 4 x .00986 = .03944 sq.inches. Total area of all slots = 1.46 sq.inches. Suggested slot depth not to exceed = √(1.46 / 2π) = √.232 = .482 Corresponding width .0818" Suggested slot depth and width = .4375 deep by .090 wide. Armature diameter at root of tooth = 3.100 - .875 = 2.225 Circumference = 7.00" For one tooth and slot = .139" Hence width of tooth at root = .099" (here see table p.5) Contd | ||