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).
Series of test procedures for a magneto, including endurance, circuit, and utility spark tests.
| Identifier | WestWitteringFiles\M\2October1924-December1924\ Scan83 | |
| Date | 20th October 1924 guessed | |
| -2- Contd. (a) A short endurance test in which the magneto shall be run for 7 hours at a speed of 2000 r.p.m. with timing lever fully advanced (hand range), sparking being caused to take place on a sequence of H.T. third point spark gaps in air set to 5.5 mm. (b) Immediately following (a) a short circuit test in which it is run at 1500 r.p.m. for half an hour with timing lever retarded (hand range) and primary and secondary windings short circuited, i.e. with the low tension and central high tension distributor terminals connected to the metal framework of the magneto. (c) Immediately following (b) an open circuit test at 1500 r.p.m. for quarter of an hour with timing lever fully advanced (hand range) and the H.T. terminals not connected to anything, so that the secondary discharges take place on the safety gap of the magneto. (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 700 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. Contd. | ||