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).
The design and testing of silent dynamos with various armature configurations.
| Identifier | ExFiles\Box 180\M1\3\ img023 | |
| Date | 10th October 1921 | |
| To EFC. from R.{Sir Henry Royce} WW LIGHTING SET (handwritten) R1/G10/10/21. 3 (handwritten) Copy to CH. " " FN. " " H.S. " " Mr. Bentley " " Mr. Hulley X.294 RE DYNAMOS. (handwritten) [STAMPED: ORIG... RECEIVED ... 1921] WW LIGHTING SET (handwritten and underlined) 273 (handwritten) Regarding the silent dynamos, you will remember that some time ago we obtained some sort of proof that, at my suggestion, an even number of sections in the armature might do much towards making the dynamo silent, owing to the fact that with an even distribution of poles the armature would always be in magnetic balance. *Royce Limited of Manchester are making me a dynamo for the house and office lighting here.* I am having three armatures made for this dynamo, one of which will be one coil per slot, the second one being two coils per slot, an even number of slots and a dummy. The third one will have an uneven number of slots, coils grouped in three, and naturally no dummy. These three armatures will be run for the same purpose in the same carcase, and should shew definitely - (1) if there is any advantage in fine slotting. (2) if there is any advantage in even numbers, as regards silence. (3) and whether an equally good dynamo could be made with the most practical arrangement of coil which is three per slot for four poles. As regards the number of teeth on the armature, and the number of sections in the commutator for the three grooving, we calculated that there are certain numbers distinctly advantageous, and supposing these numbers of sections fulfil the ordinary conditions of the calculations, the number of slots in the armature for a four-pole machine should be four times x plus 1, this giving the least amount of copper on the armature and the best commutation owing to the winding being in the neutral position, i.e. pitch of coil just the minimum less than pitch of poles. R.{Sir Henry Royce} | ||