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).
Advantages of using 14 MM sparking plugs over the standard 18 MM plugs.
| Identifier | ExFiles\Box 58\2\ Scan048 | |
| Date | 4th July 1932 | |
| 81812h To R.{Sir Henry Royce} from E.{Mr Elliott - Chief Engineer} E.1/HP.4.7.32. C. Sr. Wor.{Arthur Wormald - General Works Manager} Hs.{Lord Ernest Hives - Chair} By.{R.W. Bailey - Chief Engineer} FD.{Frank Dodd - Bodies} 14 MM. Sparking Plugs. The use of 14 MM. sparking plugs on any of our engines would enable us to improve the water cooling of the head, and would be an assistance to design in other ways, since the smaller plug does not demand such a bulky spanner. The plug will always require sufficient room around the terminal end to prevent the spark jumping to earth, but the lead terminals themselves are generally the offenders when this fault occurs, and could be modified with advantage as a rule. These smaller plugs would allow us to use larger valves in the Bensport if required at any time without offsetting the plug longitudinally. or two ignition plugs, giving double ignition, with still larger valves could be used disposed symmetrically around the centre. Wherever there is a standard 18 MM. plug in use the substitution of a miniature plug would improve the water cooling and coring. We should like to be able to make use of the advantages offered by the small plug without burning our boats, and we think this could be done by slight modifications to the cylinder castings to produce heads for both types. E.{Mr Elliott - Chief Engineer} | ||