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 production inspection and testing of a 20/25 HP Dynamo.
| Identifier | ExFiles\Box 163\6\ img257 | |
| Date | 2nd February 1933 | |
| 2.2.33. SPECIFICATION OF PRODUCTION INSPECTION AND TEST OF 20/25 HP. DYNAMO. Type D.Sch.529. For use with three-rate charge scheme. Armature :- 24 slot, 16 conductors, 17 S.W.G. Poles :- .015" air gap increasing to .055" Brush angles. 13° 123° (Nominal) INSPECTION. Upon receipt of the machine from the assembling benches :- (1) Inspect the brush mechanism and make sure that :- (a) The spring pressures on the brushes are suitable. The actual pressure exerted on each main brush by its spring should be 16 ozs. ± 3 ozs. and on each control brush 12 ozs. ± 2 ozs. (b) All brushes have the necessary freedom without being unduly slack, and that the connections of the pigtail conductors are not in any way damaged. Brush freedom and pigtail conductor connections should be tested by lifting the brush against the spring by means of the pigtail connection. (It sometimes happens that a brush may be jammed under the action of its spring and apparently free without spring pressure.) (c) The lower edges of the brush holders (near the commutator) are at the same distance of .075 + 15 / - 10 from the surface of the commutator. (d) Corresponding tips of the main brushes should on the average be exactly 12 commutator segments apart. (e) The brush springs are clear of the sides of the slots of the brush holders, so that the full tensions of the springs are exerted on their respective brushes. Also that these springs are long enough to reach and press on the centre of the brush, and not on the side. Test the springs for cracks by forcing these back as far as possible, when they should not become cracked. Note (1) It is possible that a spring which is noticeably weak is cracked and requires replacing. Note (2) It will usually be found that a spring which is good has a uniformly expanding spiral | ||