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).
Specification for the inspection and readjustment of faulty dynamos.
| Identifier | ExFiles\Box 50\5\ Scan210 | |
| Date | 25th July 1923 | |
| 25.7.23. SPECIFICATION OF INSPECTION & READJUSTMENT OF FAULTY DYNAMOS. The faults experienced on dynamos of the nature here to be considered may perhaps be divided into two categories:- (1) Excessive output. (2) Bad commutation and brush sparking, with consequent overheating. Excessive output appears to be due to imperfect brush bedding which in its turn may be due either to (a) Imperfect bedding in the first instance, or to (b) Brush holders having been subjected to some disturbance which may be the result of temperature effects on the insulation, or actual mechanical dislocation. (i) In this case it is first necessary to examine and if necessary correct the following brush system points :- (a) ALIGNMENT & FIXING. The radial and axial alignment of the brush holders. The examination of this is best carried out with the brushes removed. At the same time it should be noted that the nuts fixing the brush holders are tight. If the alignment is not correct, this may require slackening off and re-tightening in the process of adjustment. (b) BRUSH SPACING. Corresponding tips of the main brushes should be exactly 7 1/2 commutator segments apart. (c) FREEDOM. Freedom of brushes in holders without undue slack, particularly circumferentially. (d) SPRING PRESSURE. The actual pressures exerted by the springs on the main brushes should be between 3/4 and 1 lb; and for the control brush about 3/4 of this. (e) BEDDING. The working surface of the brush should show evidence of making contact over at least 80% of the whole surface, otherwise the brush bedding must be | ||