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 redesigning a 28 slot armature for a 40/50 case, including coil turns and wire dimensions.
| Identifier | ExFiles\Box 68\4\ scan0267 | |
| Date | 9th May 1928 guessed | |
| -3- 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" .1875 On depth of slot we save 2 x .056 = .112 ✓ and spend 6 x .008 = .048 (Handwritten corrections above: .010 and .060) i.e. depth of slot is less by .064" .052 and will therefore be .536" .548 R.D's. correction. Present neck depth = .600 - 3/4 of .085 = .600 - .064 = .536" Dia. at neck = 3.500 - 1.072 = 2.428" Oce = 7.64" 1/29th of this = .2635, 1/28 of this = .273 But slot width = .170 Neck for 29 slots = .0935" and " " 28 slots = .103" New neck depth = .536 - 3/4 of .093 = .536 - .070 = .466 Dia. at neck = 3.500 - .932 = 2.568 Oce " " = 8.07" 1/28 of this = .288 Slot = .186" .. Neck = .102" This is O.K. | ||