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).
Endurance test report for a main switch, comparing the DCD.123 model with two others.
| Identifier | ExFiles\Box 168a\2\ img378 | |
| Date | 11th April 1938 | |
| To By o.{Mr Oldham} to Hs.{Lord Ernest Hives - Chair} o.{Mr Oldham} to By/RD. 6139. Rm{William Robotham - Chief Engineer}/RC.{R. Childs}3/JH.11.4.38. re Endurance test of main switch to DCD.123. The above is a hinged armature type of switch built on the same lines as the existing standard switch except that the carbon contacts have been deleted and the construction greatly simplified. It has also been designed for mounting on the motor carcase. The test consisted of operating the switch 'on' for 3.5 seconds and off for 12 seconds, a current of 200 amperes, passed through the windings of a stalled Bentley starter motor, for 17,000 consecutive operations. The switch then failed to make contact due to oxidation of the main contacts. Volt-drop figures were taken at the commencement and at the end of 15,000 operations. We have compared the results with those obtained on a switch made by HPC/TT. and the Lucas ST.900. TYPE. WEIGHT. Coil consumption at 6 volts. Copper contact pressure at 6 volts. Volt drop. across contacts initial. Volt-drop across contacts after 15,000 ops. DCD.123. 12 oz. 2.6 2 lb. 3 oz. 300 amps : .270V .600 V.{VIENNA} 200 " : .190V .270 V.{VIENNA} 100 " : .090V .210 V.{VIENNA} HPC/TT. 12 oz. 3.0 1 lb. - oz. 300 amps : .156V .220 V.{VIENNA} 200 " : .105V .170 V.{VIENNA} 100 " : .050V .110 V.{VIENNA} Lucas. 1 lb. 4 ozs. 2.55 9 lb. 2 oz. 300 amps : .123 V .095 V.{VIENNA} 200 " : .095 V .050 V.{VIENNA} 100 " : .042 V .027 V.{VIENNA} It will be seen from the result that the Lucas ST.900 switch is much more efficient than the other two: this is to a large extent due to the construction of the Lucas unit which is of the enclosed solenoid and plunger type. We consider that if we are to avoid intermittent failures due to oxidation of the contacts, we must have a good contact pressure on this type of switch in which there is no carbon contact to take the flash. | ||