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).
Test report comparing the performance of two different machines, Lucas and Watford, including utility and speed tests.
| Identifier | ExFiles\Box 40\2\ Scan207 | |
| Date | 13th June 1927 guessed | |
| -6- Contd. (9) & (10). The open circuit volt-speed curve and the short circuit ampere-speed curve of the primary windings of these two machines have been observed, making use of suitable A.C. instruments, and comparative curves of the two machines are given on the blueprint attached, from which it will be noted that the armature volt-amperes capacity for the Lucas is very much bigger than that of the Watford. There appears little to choose between the ohmic resistance and the eddy current effects of the armature in the two cases, though the armature capacity of the Watford at 2000 r.p.m. is 21.4, and of the Lucas at 2000 r.p.m. 36.2. (11) Utility Test. For the purpose of this test a 3.0 mm. annular spark gap (dia. of central electrode .087", inside dia. of earthed electrode .325") in air shunted by a non-inductive chemical leak of value 3 micromohs is arranged to replace one of the six test gaps sparked by the magneto, the remaining five gaps set as before to 5.5 mm. The speed range over which the magneto was capable, for all positions of the hand range lever, of firing this special test gap with shunted leak regularly is determined. In the case of the Watford magneto we found it capable of sparking this shunted gap between speeds of 700 to 4000 r.p.m. in the retarded position only, and to be incapable of sparking at any speeds in other positions except those quite close to full retard. In the case of the Lucas in the retarded position, the magneto was capable of firing this gap over a speed range of from 500 to 4000 rpm. and in the central position from 900 | ||