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 various electrical contact point configurations and materials.
| Identifier | ExFiles\Box 61b\1\ scan0122 | |
| Date | 9th October 1930 guessed | |
| -2- (1) Reversal of current supply. This test did not show any improvement as in this case the lever point surface was oxidized and the screw grey. Apparently the contact point with positive potential is the one susceptible to oxidation. (2) Stronger contact breaker spring exerting 50% more pressure on contact. The condition of the points did not indicate any improvement over standard. The points were worn and hammering due to excessive load on the points had occurred, whilst the rubbing block wear had been excessive. Oxidation was slightly less, however, than standard on the screw point. (3) Tungsten contact lever run with platinum screw. A 10,000 mile test was run but at the conclusion it was found that the bedding was very poor, only about 25% of the tungsten contact having made contact. Platinum from the screw point had been transferred to the tungsten contact and piled up making the ignition very uncertain. Apparently, once a thin film of platinum has welded itself to the surface of the tungsten point the contacts continue to function as platinum points, the bedding remaining on the platinum. (4) Tungsten contact screw running with platinum lever. A 10,000 mile bench test was carried out with this combination but the final result was not satisfactory. The condition of the points was better than the combination of tungsten lever and platinum screw. Both surfaces were pitted but fairly even and the surface of the screw point was also oxidized. | ||