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).
Investigation into a charred coil on a Goshawk dynamo armature due to carbon lodging between commutator segments.
| Identifier | ExFiles\Box 51\1\ Scan291 | |
| Date | 31th October 1923 | |
| X4383 To EY. from EFC. {E. Fowler Clarke - Electrical Engineer} EFC {E. Fowler Clarke - Electrical Engineer} 1/T31.10.23. X.4333 - GOSHAWKAero EngineCodename for 20HP Car / Aero Engine after KestrelAero Engine DYNAMO - COMMUTATION. With reference to the dynamo armature in which one coil had been charred, an effect suggested to be due to a piece of carbon being lodged between two adjacent commutator segments, we have made experiments on this armature to discover the magnitude of a piece of carbon which would be necessary to cause such a phenomenon to occur. We have purposely placed in a small piece of carbon and have found that in every case, where the carbon has only been of such magnitude as might be lodged there accidentally, the running of the machine raises this to incandescence and clears it, the output simultaneously jumping up to normal from the reduced value due to the short. It is possible, of course, by jamming in a sufficiently large piece of carbon sufficiently tightly, to cause the phenomenon to occur, but it is considered extremely unlikely from our experiments that a piece of carbon of such a size as might accidentally become lodged between the segments would produce the effect. We return the armature herewith. You will note that a second coil has been charred. This was done by jamming in quite a large piece of carbon rather tightly and represents the very extreme case which we do not consider would occur naturally. EFC. {E. Fowler Clarke - Electrical Engineer} | ||