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).
The tests of tungsten contact points with double capacity and on 6 volts to suppress sparking.
| Identifier | WestWitteringFiles\H\November1921\ Scan13 | |
| Date | 7th November 1921 | |
| R.R. 235A (50 T) (S H 986, 19-2-21) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 3008. COPY. 7th Nov. 1921. EFC. AB.29. X.2894. TESTS OF TUNGSTEN POINTS WITH DOUBLE X.2512. CAPACITY AND ON 6 VOLTS. In order to see if sparking could be completely suppressed and so enable tungsten contact points to operate satisfactorily, two condensers were connected in parallel by short stout copper wires and used in conjunction with a set of Fansteel contacts (A.B.) and run for 160 hours. The points have, however, developed in a slightly less degreee the same faults as with the standard capacity, viz. pitting and discolouring, though very little sparking occurred whilst running. Towards the end of the run, bad misfiring at the spark gaps set in and the contacts showed a slight resistance of about .05 ohm. An attempt has been made to reproduce the conditions of the American distributors in running a set of tungsten points. In this test, a set of points by the Fansteel Co. (A.F.) was used, with the vlade insulated from the rocker-arm roller by a small piece of sheet fibre. A standard R.R. coil was used, without a ballast on 6 volts, and a Liberty paper condenser of .35 mf. capacity was connected across the points. A preliminary test under otherwise standard conditions, indicated that merely insulating the roller from the vlade would not appreciably affect the performance of the points. But with the above, arrangement the points ran very well for 200 hours, the average current being .9 amp. Some missing took place at the end of the run, but there was no perceptible contact resistance. The condition of the points is considerably better than most sets in tungsten, there being only a slight transfer of metal and formation of scale, though the result is not yet up to requirements. The roller was insulated from the blade, for the purpose of finding out whether the rusting that takes place is due to electrical surges. In this case the distributor *-372 mf. total Contd. | ||