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 report on the operation of Watford magnetos, discussing flux, armatures, and sleeve positioning for high-speed operation.
| Identifier | ExFiles\Box 48\2\ Scan482 | |
| Date | 29th March 1926 | |
| Contd. -4- EFCl/T29.3.26. energy at high speeds by breaking the current very early with the result of keeping the current broken and the platinum point spark at break down to a minimum. But in this case they are adding to the excess energy which has to be dissipated in the secondary circuit after break due to the mere fact of the rotation of the armature in the field maintaining the arc which has been started by the initial spark. It would appear better to make the break later and adopt other means of keeping down the excess energy. Our further suggestion is that in this magneto they are not making the fullest use of the sleeves. According to our investi- gations (on two standard Watford magnetos) the sleeves as at present arranged gave the maximum flux through the armature in the former machine No.73972 in almost exactly the half advanced position of the advance and retard lever, and this flux (measured by open circuit voltage) fell away symmetrically on either side. In another machine No.85285 the flux was a maximum for a position of advance and retard lever a little more than half advanced, and the flux fell away on either side according to a curve, copy of which we attach. In the sleeves, we have a method of reducing the effective strength of the magnets, and as we always want to reduce the effective strength of the magnets for high speed operation, it would appear desirable to make use of this fact, and keep the sleeves central in the fully retarded position, where every bit of flux is required. In this way it would appear that we can still Contd. | ||