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).
Bench tests conducted on a Scintilla shunt-wound dynamo and regulator.
| Identifier | ExFiles\Box 179\2\ img161 | |
| Date | 9th January 1932 | |
| To R.{Sir Henry Royce} from Hs{Lord Ernest Hives - Chair}/Pgt. C. Sg.{Arthur F. Sidgreaves - MD} C. WCR. E.{Mr Elliott - Chief Engineer} C. Da.{Bernard Day - Chassis Design} EV.{Ivan Evernden - coachwork} ORIGINAL. Hs{Lord Ernest Hives - Chair}/Pgt.1/AWR.9.1.32. X6133 SCINTILLA SHUNT-WOUND REGULATED DYNAMO. We have now carried out some bench tests on a Scintilla shunt-wound dynamo and regulator, obtained by us for the purpose of investigating this type of machine. In size, this machine is very close to our 20/25 dynamo, the length and diameter of the carcase being practically the same. It is rated at 105 watts, so that at a terminal voltage of 13.0, corresponding to a load on the battery of about 14.0 amperes, it should give an output of a little over 8 amperes continuously without overheating. This output seems hardly high enough although the makers state that this size of machine is suitable for large cars. The regulator is of the vibrating contact type and, with the cutout, comprises a separate unit to be mounted apart from the dynamo in any convenient place. Dynamo. The chief feature of the dynamo is the use of four single brushes spaced 90° apart round the commutator. The brushes are small and the commutator narrow - brushes of the same polarity being connected together by aluminium rings encircling the commutator, which support the brush holders. The reason for this design appears to be (without dismantling) that it is desired to use twin brushes, but at the same time, in order to get as long a core as possible the space allowed for the commutator has been reduced to a minimum. Like the Bosch, the negative brushes are earthed. The brushes were found to be noisy. Regulator and Cutout. In this unit, although it is built up on one cylindrical core, the magnetic circuit is so divided and arranged that the regulator and cut-out are virtually two separate units - one operating at each end of the core. It operates on a slightly different principle from that of the Bosch. Whereas the Bosch operates in two stages, the first inserting resistance in the field circuit and the second short circuiting the field winding, in the Scintilla case the field circuit is definitely broken by the separation of the contacts. In order to bring the contacts together again | ||