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).
Test report on sample tungsten contacts from Messrs. Blackwell.
| Identifier | ExFiles\Box 35\6\ scan 038 | |
| Date | 13th April 1921 | |
| EFC. 91303. April 13th 1921. P.A. 75. X. 2694 - TEST OF SAMPLE TUNGSTEN CONTACTS FROM MESSRS. BLACKWELL. These contacts have now run for 103 hours, with the following results. The spark points were set at 4.5 mm. to ensure regular sparking. There was practically no sparking at the contacts at the commencement of the run, but after six hours running, a slight sparking started, but sparks on the gaps were quite good. After 40 hours running, the contacts were examined, and found to be wearing on one side, and the surfaces pitted. After 70 hours missing occurred on the spark gaps, which was remedied by adjusting the third point, also there was missing when starting up, but improved after a time. Towards the end of the run, although the sparking on starting up was bad, it improved after a few minutes running. But it appeared that the machine would be of little use at low speeds. Finally, the contacts were examined and it was found that one side of the lever contact was very much worn while the corresponding side on the stationary contact appeared to be hardly touched. Both surfaces were pitted, but not badly, and covered with a light grey oxide. C&A.P. | ||