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 experimental testing of a Phantom dynamo with a coarser gauge armature for higher output.
| Identifier | WestWitteringFiles\S\June1928-August1928\ Scan150 | |
| Date | 31th August 1928 | |
| To R.{Sir Henry Royce} from EFC. c. BJ. E.{Mr Elliott - Chief Engineer} c. De. By.{R.W. Bailey - Chief Engineer} c. Wor.{Arthur Wormald - General Works Manager} PN.{Mr Northey} PHANTOM DYNAMO WITH COARSER GAUGE ARMATURE FOR HIGHER OUTPUT. We have now experimentally tested this higher output armature in our expl. N.B. dynamo carcass. The armature has three turns per coil of 17 S.W.G., instead of four turns per coil of 18 S.W.G. as in the case of the standard. The main brushes are, as in the standard case, 8º retarded from the no-load neutral position. A suitable setting of the control brush for this higher output armature was found to result in a control brush angle (i.e. main positive brush to control brush) of 127º (present standard 121º). This corresponds to a smaller field span than the standard. In the normally hot condition the balancing speed for 14.0 volts was found to be 790 r.p.m., as against 555 r.p.m. for the standard machine. It will thus be seen that the retardation of the cutting-in point in this Phantom case is somewhat more than in the case of the 20 H.P. reported in EFC5/T11.7.28, but as against that it should be stated that the standard Phantom cutting-in point is more nearly down to our desired figure of 540 r.p.m. than the 20 H.P. cutting-in point of 710 r.p.m. is down to our required figure of 640 r.p.m. The peak ampere output on the approved setting was 15.1 amperes (at the schedule voltage of 18.3) at a speed of 1780 r.p.m., as against the present standard peak output of 12.0 amperes (at a schedule voltage of 17.7) at 1300 r.p.m., and at 3000 rpm. Contd. | ||