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).
Insufficient dynamo output at high speeds and proposed modifications to the armatures.
| Identifier | WestWitteringFiles\S\March1928-May1928\ Scan083 | |
| Date | 30th March 1928 | |
| To R.{Sir Henry Royce} from EFC. c. BJ. E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} c. BY.{R.W. Bailey - Chief Engineer} PN.{Mr Northey} Wor.{Arthur Wormald - General Works Manager} ORIGINAL EFCA/T30.3.28. INSUFFICIENT DYNAMO OUTPUT AT HIGH SPEEDS. (Refs. EFC3/T27.2.28 and R5/M9.3.28). Handwritten notes: + X8780 X8664 X5663 It appears difficult to prevent customers using fairly large capacity side lamp bulbs. Also we should imagine that only a few customers do or would accept the expense and inconvenience of garage charging. Our preliminary experiment with an armature with coils half paralleled went further, as anticipated, in the required direction than was necessary or desirable, but was a useful indication of the required alteration to the armature for moderately higher cutting in and greater current at the higher speeds. We are now arranging for armatures with three turns per coil instead of four, with one gauge coarser conductors, and 28 slots in place of 23, thus retaining an even number of slots and utilising the type of winding which has been so successful with the 28 slots. We expect such armatures to give a cutting-in speed about 35% higher and an output of perhaps nearly 50% higher. In the case of the 20 H.P. we judge that the brush contact area is not sufficient for the higher output, therefore the armatures which we are having instructed are to be suitable for the experimental 20 H.P. machines which we made some time ago with the EAC. type of brush gear, which gear provides 33% greater contact surface area. The matter has been very carefully considered and we think that the armatures which we have now asked to be instructed should turn out at once, or with slight alteration to the control brush position, to be suitable for the purpose in hand. EFC. | ||