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).
Noise tests conducted on Goshawk dynamos to analyze the effect of different armature configurations.
| Identifier | ExFiles\Box 51\1\ Scan342 | |
| Date | 20th February 1924 | |
| EFC. {E. Fowler Clarke - Electrical Engineer} AB.104. 20.2.24. X.4610 NOISE TEST OF GOSHAWKAero EngineCodename for 20HP Car / Aero Engine after KestrelAero Engine DYNAMOS. Some tests have been made on the bench to find the effect of the armature with two coils per slot, on the noise made by the machines. Two standard armatures were tried in machine 604; also the armature with two coils per slot from machine B, and one of the standard armatures with B rear-end plate, which has an easy fitting and running bearing. In all cases there was a moderate drag, perceptible on the armature teeth when the brushes were lifted and the field separately excited, and there was slight humming at a fairly high pitch, and humming at a lower pitch which started at 1400 r.p.m. and became loud at 1850 r.p.m. and 2300 r.p.m. As a check, the straight slot armature was fitted to the machine, when it was found that the low-pitched hum remained about the same, while the high pitched hum became loud. The magnetic drag on the teeth of this armature is no worse than on the others. The B machine, complete with its own two coil per slot armature was also tested. With this, the tooth drag was much sharper, but the humming effects were the same as those first mentioned. The characteristic low pitched hum is found to occur on machine 604 as standard, with all brushes lifted and the machine unexcited. EFC {E. Fowler Clarke - Electrical Engineer} /RJA. | ||