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).
Clarifying the specification for measuring the spacing of dynamo commutator brushes for 40/50 and 20 HP models.
| Identifier | ExFiles\Box 70\4\ scan0064 | |
| Date | 3rd March 1926 | |
| X6781 do To Sft{Mr Swift}/Mr. Brock. EFC5/T31.3.26. RE DYNAMOS. X2604 do With reference to the Specification of production inspection and test of both the 40/50 and 20 HP. dynamos, par. (1). item (c). It has been pointed out that owing to irregularities in commutator production the spacing of the brushes is not consistently represented in terms of commutator segments taken at random on the commutator. It is, therefore, to be understood that in specifying that corresponding tips of the main brushes should be 14¼ segments apart, this implies 14¼ segments apart on the average, and the words "on the average" might be twice added to the paragraph concerned to make it read, in the case of the 40/50 :- (c) "That corresponding tips of the main brushes are, on the average, exactly 14¼ commutator segments apart, and at the same time, the distance of the trailing edge of the control brush from the leading edge of the main positive brush should be, on the average, 162⅔ segments." the latter figure in the case of the 20 HP. being 16¼ segments. We allow that it is not essential electrically for the commutator to be a dead accurate job, and that therefore the spacing of brushes by angular measurement is better when reckoned on the commutator. Our paragraph may therefore be taken, from your point of view, as giving the angles in degrees by proportion, which angles | ||