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).
The EAC dynamo of the Narrower Brush (N.B.) type, comparing its performance with the standard 20 HP dynamo.
| Identifier | WestWitteringFiles\O\2April1926-June1926\ Scan085 | |
| Date | 3rd May 1926 | |
| Expl. Report. To R.{Sir Henry Royce} from EFC. C. to BJ. PN.{Mr Northey} C. to Da.{Bernard Day - Chassis Design} E.{Mr Elliott - Chief Engineer} C. to Wor.{Arthur Wormald - General Works Manager} Ey. C. to HP. X.8660. EAC. DYNAMO OF THE N.B. (NARROWER BRUSH) TYPE. We have got considerably further with the EAC. machine with brushes of narrower circumferential widths, and increased air gap, (.022" in place of .015"), and the results so far are universally promising, though we anticipate that the wear of the brushes, though still small (i.e. smaller ever since the change to 57 segment commutator) may be a little increased. The wear, however, on 57 seg. commutator machines generally is so small in any case that the difference is of little consequence. The attached diagram shows the comparison of the main and control brushes of the three dynamos, 20 HP., present standard EAC., and the EAC. with narrower brushes. The present standard EAC. brushes as compared with the 20 HP. brushes are considerably larger, both circumferentially, and, taking the two of each pair together, axially, whereas the peak ampere output is not materially different. The total area of the EAC. brushes is actually 67% larger, and in spite of the EAC. commutator being somewhat larger than the 20 HP. commutator, the brushes at present subtend a larger angle at the centre, namely, 19.5°, as against 16.4°. Contd. | ||