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).
American Chassis Parts, specifically B-G and Herz sparking plugs.
| Identifier | WestWitteringFiles\D\March1920\ Scan57 | |
| Date | 17th March 1920 | |
| To R.{Sir Henry Royce} from HE. c. to C.L. c. to BN.{W.O. Bentley / Mr Barrington} c. to Da.{Bernard Day - Chassis Design} c. to OY. c. to NA.{Mr Nadin} ORIGINAL. C-K.{Mr Kilner} Hs{Lord Ernest Hives - Chair}4/LG17.3.20. X.3905 REPORT ON AMERICAN CHASSIS PARTS. X.3403 B-G SPARKING PLUGS. These plugs have mica insulation and the centre portion is made detachable so that it can be taken out and cleaned. The novelty about these plugs is the small brass spinning which fits into the earthed portion of the plug and acts as a baffle to protect the insulation from oil. These plugs are quite unsuitable for car work because there is no means of adjusting the gap. The spark gap is an annular gap formed by the centre electrode and the earthed portion of the plug. We have tested these plugs for 50 hours and they have been very reliable. We intend, at the next opportunity, to try them in an aero engine; they appear to be more suitable for that class of work. The points we have against the plugs are as follows:- 1. The centre electrode is made of chromium steel. All the successful car plugs we have had have used practically pure nickel for that purpose. 2. The leakage length on the insulation is only .25" - we like to have at least .375". 3. Where the centre electrode passes through the brass spinning (which acts as an oil baffle) it leaves an annular gap of .060". If the points became oxidized we should anticipate the plug would jump across at that point. X.3722. HERZ PLUGS. These plugs have mica insulation. There is no novelty about them. They have two sparking points. We have run a set of these for 10 hours and during that time we had two fail owing to the centre stem breaking. Contd. | ||