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).
Detailed description and weight comparison of a sparking plug.
Identifier | ExFiles\Box 58\2\ Scan147 | |
Date | 1st September 1934 guessed | |
Report No.R.A.E./E.{Mr Elliott - Chief Engineer} and I.856. -2- The sparking tip consists of a short length of nickel rod approximately No.11 gauge, one end of which is pressed into the upper part of the central electrode shoulder. the edge of the latter being swaged to the nickel to secure greater reliability. The earth electrode is a short length of nickel wire No.14 gauge pressed into the mouth of the plug. The terminal end of the central electrode is screwed No.0.B.A. thread and the upper mica washers are secured in position by a brass No.0.B.A. lock nut as shown. The length of the internal leakage path is 6.5 mm. and the volume of the gas space within the plug is 1.6 cu. cm. On account of the large gas space volume this plug should be satisfactory under oily conditions. In order to minimise the risk of preignition both the earth electrode and central electrode sparking tips are within the plug mouth/are of comparatively large diameter and finished square. No adjustment of the electrode gap is possible. 3. Weights. Table I. - Comparison of weights. | Type of plug | Weight of a single plug. | Weight of plugs for 9 cylinder engine | |----------------------|--------------------------|---------------------------------------| | Bologna plug | 3 oz. 7 drams. | 3 lb. 13¾ oz. | | Standard British plug| 3 oz. 5 drams. | 3 lb. 11½ oz. | | ||