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).
Technical description and performance analysis of an annular spark gap.
| Identifier | ExFiles\Box 37\1\ scan 132 | |
| Date | 26th January 1922 | |
| X3199 26th Jan. 1922. EFC. AB.37. X.3199 X.2065. ANNULAR SPARK GAP. This consists of a steel cone forming one electrode, arranged concentrically in a brass ring forming the other. The object is to obtain a spark length to indicate a definite voltage, by avoiding corona discharge before the spark passes. The spark lengths obtainable with the annular gap are considerably less than those obtainable with the third point type of gap, both on magneto and battery ignition. The spark length is, however, very indefinite and the difference between possible and regular sparking is considerable. An R.{Sir Henry Royce} Bosch magneto, when set to give a 10.0 mm spark on a third point gap, gives about 5.0 mm on the annular gap. On the standard battery ignition a reduction from 10.0 mm to about 3.0 or 4.0 mm, is observed. With the magneto on the annular gap some added capacity on the secondary increases the maximum regular spark length, but in all other cases, the tendency is to reduce the gap. Best sparking is obtained on the battery ignition with the central cone positive when the gap is about 4.0 mm. irrespective of which terminal is earthed. When the cone is negative, the gap obtainable is about | ||