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).
Sourcing, testing, and performance characteristics of tungsten points.
| Identifier | ExFiles\Box 35\6\ scan 146 | |
| Date | 8th July 1925 | |
| To R.{Sir Henry Royce} from EFC. c. CJ. c. BY.{R.W. Bailey - Chief Engineer} X2894 EFC9/T8.7.25. X.2894. TUNGSTEN POINTS. Reference your note R2/M3.7.25. A further dozen sets of tungsten points are being obtained and these will be of rather larger diameter than the platinum points (.175" as against .150"). We will arrange for these to run on as many experimental and test cars as possible. Regarding tungsten points generally, the following points may be noted :- (a) Points must be made of pure tungsten for reliability. (b) The performance of tungsten points improves with the increase of the size of the point, i.e. with area of contact. Apparently they will not comfortably take the same current density as platinum. (c) With too high current density, oxidation occurs rather rapidly, causing undue resistance on contact. This oxidation is not so bad if the contact faces are carefully trued up initially, and bed together properly. (d) The best results we have had are from tungsten obtained from Messrs. Melin, and designated "Eska". (e) It is probable that the moister climate of the British Isles has something to do with the less reliable performance of tungsten points here than in America. This idea is held not only over here but in America. EFC. | ||