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).
Tungsten contact point trouble and oxide formation on a 20 HP chassis.
| Identifier | ExFiles\Box 61b\1\ scan0110 | |
| Date | 9th June 1930 | |
| X2894 W/N. To A.{Mr Adams} from EFC. EFCl/ADl9.6.30. X.2894. TUNGSTEN CONTACT POINTS. May we refer you to our EFC6/AD20.5.30 as the information therein asked for would be of great assistance to us in analysing the real cause of the tungsten contact point trouble. To illustrate more exactly the nature of the information we would like, we give below one typical case of what we imagine might be observed. It will be appreciated that the trouble is only complained of in connection with 20 HP. chassis where there is only the one (battery) ignition. The report on our imaginary case might be as follows :- "On 20 HP. Chassis - the owner has observed either when the car is new or after overhaul in which the condition of the ignition equipment can be considered as new, that the engine fires beautifully at low speed partly throttled giving the impression that it is almost impossible to know that the engine is running, i.e. it gives the impression of ignition carburation etc. being all in perfect condition. After, however about 200 miles running the owner noted that this beautiful condition disappeared and the engine became lumpy directly it was throttled downslowly either light or with a light load. Upon the contact points being inspected it was noted that the screw contact point gave a bluish appearance on the surface as in the formation of oxide, whilst the lever contact point remained with a greyish appearance. Upon cleaning away the very fine layer of oxide, without however removing sufficient material appreciably to upset the bedding of the points, the good condition of the engine was restored and persisted for another few hundred miles when there re-appeared a tendency to misfire with consequent lumpiness. | ||