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).
Causes and potential solutions for the pitting of platinum points on a 20 HP chassis.
| Identifier | ExFiles\Box 47\4\ Scan091 | |
| Date | 22th September 1925 | |
| To Hm.{Capt. W. Hallam - Head Repairs} from EFC. c. D/L. c. By.{R.W. Bailey - Chief Engineer} X4118 EFC6/T22.9.25. 20 HP. CHASSIS GRK-30 - WATSON. X4117 PITTING OF PLATINUM POINTS With reference to Hm{Capt. W. Hallam - Head Repairs}/NRC{N. R. Chandler}18/D18.9.25. and BY15/H.21.9.25. we agree with BY.{R.W. Bailey - Chief Engineer} that under present standard conditions this is not really a bad case of pitting, and that it would give considerable further length of life without any further touching up. At the same time we are not inclined to think that it is principally due to oil, as the effect of the presence of oil vapour is more uniform pitting right across the surface of the points. We agree that pitting of this description frequently occurs to this extent, after which it does not materially increase. It should be ascertained that the pressure connections of the condenser are metallically clean, if so, the presence of oil vapour in the condenser housing should have no primary effect. Also it is important that all the electrical pressure connections between the contacts and the condenser be clean and securely tight. Pitting of this kind does occur on our experimental rig. It is the pitting of the kind that we consider is due to the presence of oil vapour which does not occur on our rig. We are tackling the question of this pitting in a more fundamental direction, namely, by reducing the amount of current which has to be carried by the contact breaker, by the use of more highly efficient ignition coils, of which we have a number on experimental test at the moment. We are also further experimenting on the use of tungsten contacts, and we have an experimental modification to the ignition tower by which the crank chamber gases are more effectively excluded from the contact breaker and distributor chamber. EFC. | ||