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).
Observations on the performance of Mercury and Lodge ignition plugs under different test conditions and positions.
| Identifier | ExFiles\Box 50\2\ Scan071 | |
| Date | 28th October 1921 | |
| Hs.{Lord Ernest Hives - Chair} from EP.{G. Eric Platford - Chief Quality Engineer} X4295 EP{G. Eric Platford - Chief Quality Engineer}6/H28.10.21. RE. IGNITION PLUGS. X.4295 X.601. We have been noticing the behaviour of Ignition Plugs on cars on test, and our observations are as follows:- 1. On all engines in which cylinder lubrication, i.e. oil in the compression chamber, is below normal, the Mercury Plugs in the pocket position show distinct signs of pre-ignition. 2. This pre-ignition is hardly perceptible on the same engine when the lubrication of the cylinders is increased. 3. There does not seem to be the same tendency for the Mercury plugs to pre-ignite in the intermediate position under the same conditions as described in No.1. 4. The Mercury plugs do not fail due to oiling up in either the intermediate or the pocket position, even though cylinder lubrication is inclined to be excessive. 5. The Lodge Plugs do not pre-ignite either in the pocket or intermediate position, even though the cylinder lubrication is scanty. 6. The present Lodge Plugs do fail owing to over-oiling in the intermediate position if the cylinder lubrication is normal. 7. The new type Lodge Plugs supplied function similarly as the above present standard Lodge Plugs. I feel that more than ever we must consider a different characteristic plug for the pocket position from the type we consider suitable for the intermediate position, as it would appear that the plugs inclined to pre-ignite are not inclined to over-oil. Such a plug can be used for the intermediate position, which is a cool position, but a position which fairly easily oils up. On the contrary the pocket position does not suffer from over-oiling but from over-heating, and therefore a different characteristic plug is required. Unless therefore you have some better plugs than these, or a plug which is more universal in its characteristics as required for both positions as explained, I still recommend that we should standardise the MERCURY PLUGS for the intermediate position and the Lodge Plugs for the pocket position. contd:- | ||