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 discussion on the suitability of a sleeve-type magneto for the 20 HP chassis.
| Identifier | WestWitteringFiles\Q\February1927-March1927\ 83 | |
| Date | 8th March 1927 | |
| To R.{Sir Henry Royce} from EFC. c. BJ. E.{Mr Elliott - Chief Engineer} c. Wor.{Arthur Wormald - General Works Manager} Ey. c. Da.{Bernard Day - Chassis Design} Rg.{Mr Rowledge} c. Wd.{Mr Wood/Mr Whitehead} X.790 20 HP. CHASSIS MAGNETO. Is there good reason for departing from the sleeve type of magneto in the case of the 20 HP. chassis ? The very good reasons in the case of the 40/50 HP. and the fact that we have a battery ignition in simultaneous operation do not apply in this case. For the 20 HP. chassis we want a magneto which will start the engine easily and give a sufficiently good spark at moderate speeds, but it need not necessarily have a good high speed performance. The sleeve type of machine is or can be particularly suitable for this case as with the sleeve used in the correct way (which in our opinion it never has been on Watford magnetos. We refer to the fact that the sleeve is in the position for passing maximum flux through the armature in the central position of the lever and not in the position of nearly maximum retard as we think it should be. The maximum static flux which the sleeve passes through the armature for varying armature positions in relation to the sleeve, falls off considerably on either side of the central sleeve position), a better slow speed performance with a given total energy of the magneto at speed, or alternatively an equally good slow speed performance with a smaller total energy of the magneto at speed, can be obtained than with an ordinary rotating armature machine. A somewhat smaller total energy has the advantage that running at moderate and faster speeds Contd. | ||