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).
Performance analysis and comparison of Scintilla and Bosch dynamo regulators against a standard 20/25 machine.
| Identifier | ExFiles\Box 179\2\ img162 | |
| Date | 9th January 1932 | |
| -2- quickly, and so close the field circuit as soon after it is broken as possible, an additional winding is put on which is excited by the discharge of the field at break. This winding speeds up the demagnetisation of the core, which allows the contacts to spring together. In addition there is a lamp-current winding and a battery-current winding, both of which assist the regulator to operate in order to prevent either of these currents becoming excessive. Finally, there are the cutout shunt and series windings so that, in all, this unit has six windings, making it rather complicated. In operation, the regulator is, on the whole, very smooth. For a short period after it commences to operate, visible sparking takes place at the contacts, but at all higher speeds of the dynamo there is no visible sparking. Of the two principles involved in obtaining regulation, we think that the Bosch, although perhaps not so smooth in operation, would prove to be the more reliable. Output Performance. As before stated, the dynamo is designed to give about 8 amperes at 13 volts, but actually it gave, as a plain shunt machine, 10.7 amperes at 13.0 volts for a carcass temperature rise of 58CO, while the regulator permitted the output to rise as high as 11.5 amperes at 4000 R.P.M. We think that the output should be at least 11.5 amperes, i.e. as high as the peak of our present 20/25 machine. Attached is a sheet of curves showing the output performance of the Scintilla dynamo compared with that of the 20/25 standard dynamo. These curves are for conditions of night running with a battery load of 14 amperes, and the dynamo hot. In addition a curve is given for a standard 20/25 machine (similar to 1) modified for shunt operation. In this latter case we have not a regulator, but have assumed that the regulator would commence operating at 11.5 amperes, and keep the curve level. We have already ascertained that this output can be obtained from the R.R. shunt-wound machine, without overheating. As will be seen, the R.R. shunt-wound machine shows a big improvement on the present standard machine. The cutting in speed is just over 10 M.P.H. as compared with about 13 M.P.H. for the standard, while the same peak is reached at about 14 M.P.H. as compared with about 29 M.P.H. Further, the output would be over 2½ amperes more than the standard at high speeds. We hope to improve this machine, details of which will be reported later. The Scintilla shows a still earlier cutting in, about 7 M.P.H., but it is at the expense of some loss of output at the low speeds. We propose putting the Scintilla on a car for further test, particularly of the regulator. Hs{Lord Ernest Hives - Chair}/C.A.Piggott. | ||