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).
20 HP Dynamo, specifically investigating a 19 slot, 57 coil armature.
| Identifier | WestWitteringFiles\N\July1925-September1925\ Scan135 | |
| Date | 26th August 1925 | |
| R.R. 493A (50H) (D.B. 175 25-9-24) J.H.D. EXPERIMENTAL REPORT. Expl. No. 4121. X4610 REF H701/T26.8.25 To R.{Sir Henry Royce} & E.{Mr Elliott - Chief Engineer} from EFC. c. CJ. & PM. c. EY. Da.{Bernard Day - Chassis Design} 20 HP. DYNAMO- 19 SLOT 57 COIL ARMATURE. Experiments have been made on a 19 slot 57 coil, (and 57 com. segs.), three coil per slot armature. This provides a symmetrical armature, i.e. not complicated by a dummy, but utilising the same number of commutator steps as our standard. Attached please find photostat copy of curves of performance of this armature with the standard 57 segment commutator in comparison with that of the standard armature which has 20 slots (two coils per slot and one dummy). When investigating the performance of any machine, the no load neutral axes of commutation are taken as the basis of reference for the brush positions. For each of one or two main brush positions (in relation to this datum) a test is made in which the control brush is moved relatively until the final temperature rise is within a certain limit. An output curve of the machine on an external circuit of definite volt-ampere characteristic is then taken, and thus the around position of the brushes, giving the best performance (output curve) for a given degree of heating, is arrived at. Contd. | ||