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).
Investigations into armature hum, comparing 57 coil, 29 coil, and 28 slot armatures.
| Identifier | ExFiles\Box 165\6\ img128 | |
| Date | 29th June 1920 | |
| RR 236 (150 BKS.) (SH 57. 29-6-20.) MP 224358 ROLLS-ROYCE LTD. INSTRUCTIONS. To __________ 19__ Order No. __________ Customer's No. 2 Spacing between pole-tips show irregularities up to about .050". Winding found to be rubbing the poles. Knocked in but no improvement in silence. 57 coil armature hums in this carcase, similarly to the 29 coil machine originally sent to Mr. Brock. No 665 Tooth frequency hum at about 1000 to 1700 rpm. Armature tooth-drag slight. Slight radial play in both bearings. Air gaps fairly equal. Pole tip opening somewhat irregular. [Text below is struck through in the original document] 57 coil armature hums in this carcase. [End of struck-through text] Side pressure on armature shaft slightly improves quietness. 28 slot armature much quieter in this carcase although tooth-drag with it is (Cont'd) Signed __________ This Sheet must be filed on completion of the work. | ||