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).
Testing procedures for a magneto's spark-producing capability under various adverse conditions and speeds.
| Identifier | WestWitteringFiles\N\2October1925-December1925\ Scan274 | |
| Date | 25th February 1925 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 six test gaps sparked by the magneto in (4a) above, the remaining five 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 500 r.p.m. to 2100 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 six 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 six 5.5 mm. third point spark gaps in air at a speed of 3500 r.p.m. in the fully advanced position. (7) The magneto shall similarly be capable of firing regularly in sequence six 5.5 mm. third point spark gaps in air at speeds of :- A.{Mr Adams} 280 r.p.m. for the fully advanced position of the timing lever. B. 210 r.p.m. for the central position. C. 190 r.p.m. for the fully retarded position. Contd. | ||