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).
Page 2 of a magneto utility test procedure, detailing spark gap testing under various conditions.
| Identifier | ExFiles\Box 43\4\ Scan036 | |
| Date | 13th December 1926 guessed | |
| -2- Contd. (5) The magneto shall now be subjected to a utility test, i.e. a test to find out its capability of producing sparks under adverse (i.e. leaky ) plug conditions. For this purpose a 3.0 mm. annular spark gap ( dia. of central electrode .087", inside dia. of earthed electrode .325") in air, shunted by a constant non-inductive chemical leak of value 3 micromhos, shall be arranged to replace one of the twelve test gaps sparked by the magneto in (4a) above, the remaining eleven gaps being set as before to 5.5 mm. The magneto shall be capable of firing this special test gap with shunted leak regularly for any position of the hand range lever, and at the same time over a speed range of from 700 r.p.m. to 2800 r.p.m. Note:- It will generally be found that the capability of regular sparking depends to some extent on the polarity of the spark. Therefore in the above, it is to be understood that the one of the twelve test gaps which is replaced by the annular gap with shunted leak is the one of that polarity which is the less easy to spark regularly. (6) The magneto shall be capable of firing regularly in sequence the twelve 5.5 mm. third point spark gaps in air at a speed of 400 r.p.m. in the fully advanced position. (7) The magneto shall similarly be capable of firing regularly in sequence twelve 5.5 mm. third point spark gaps in air at speeds of :- Contd. | ||