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).
Suitable metal alloys for primary current circuit contact points.
| Identifier | ExFiles\Box 35\5\ scan 074 | |
| Date | 6th November 1919 | |
| H.H. 235A (500 T) (S.D. 408. 26-4-17.) Bm. 2/158/13. X.2894 X.1818 COPY. Gr{George Ratcliffe}2-E61119. November 6, 1919. Cy from Gr.{George Ratcliffe} Subject: CONTACT POINTS FOR PRIMARY CURRENT CIRCUITS. Regarding your letter of November 4th re contact points for primary current circuits, the following information I trust will be of interest: For open arc purposes such as make and break ignition apparatus used on stationary gas engines where the number of movements per day of the contact breaker is small, Monell metal is much the best material. For damped arc circuits such as primer-distributors where the points are protected with a condenser, any of the alloys of tungsten, such as Cretium made by Fansteel of North Chicago and that made by the General Electric Company, is the best alloy to be used. For high duty on alternating impulse currents most makers in this country use genuine Iridium and Platinum; Iridium 20% and Platinum 80% is the proportion of the alloy. The metal is usually silver soldered or electrically welded to the breaker arrangement. Iridium alone is sometimes used but is generally considered much too hard. The percentage given of Iridium-Platinum alloy is much preferred, having a better conductivity and stands up to very hard service. There is another metal being put out called the Meteor alloy, constituents of which are nickel 90% with iron and manganese. I have been unable to get any service or other particulars on this alloy and I do not know any firm who is using it. Iridium and Platinum is also used on high grade work for primary current circuits. Gr.{George Ratcliffe} | ||