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 and design specifications for a 40/50 Case armature, page 4.
| Identifier | ExFiles\Box 68\4\ scan0077 | |
| Date | 28th March 1928 guessed | |
| -4- Contd. 40/50 Case. Suggest first a 28 slot armature with three turns per coil instead of four. Since the area of C.S. of conductor is to be increased in the ratio of 4/3, the wire diameter will be increased in the ratio (4/3)½ = 1.15. Present dia. 18 S.W.G. is .048". New dia. = .055 ÷ say .056 or 17 S.W.G. Increased width of slot = .016" New " " = .186" On depth of slot we save 2 x .056 = .112 and spend 6 x .008 = .048 i.e. depth of slot is less by .064" and will therefore be .536". Present neck depth = .600 - ¾ of .085 = .600 - .064 = .536" Dia. at neck = 3.500 - 1.078 = 2.422" Oce = 7.62" 1/29th of this = .2625 1/18th of this = .272 But slot width = .170 Neck for 29 slots = .0925" and " " 28 " = .102" New neck depth = .600 - 3/4 of .093. = .600 - .070 = .530" Dia. at neck = 3.500 - 1.060" = 2.440" Oce " " = 7.67" 1/28 of this = .274" . Slot = .186" .. Neck = .088" | ||