Motor-cycle Principles and the Light Car by Roger Bradbury Whitman

Author:Roger Bradbury Whitman
Language: eng
Format: epub
Publisher: D. Appleton and company
Published: 1914-03-25T05:00:00+00:00

Fig. 35.— Abmature Cobb and Magnet Ends fob

V-Engines

When the core makes a half-revolution from the position shown in Figure 35, the narrow heads will be under the long pole-shoe edges, and the wide heads under the short

edges. As the core contiimes to revolve, its wide and narrow ends will pass from under their pole-shoe edges at the same instant. A sparking current will then be produced, but it will be seen that the core has made considerably less than half a revolution from the point at which the previous sparking current was produced. Following on, it will then be considerably more than half a revolution before the next spark it produced.

Afl all twin-cylinder engines do not have the same intervals between their firing points, the magneto must be made to suit any particular by a variation in the construction.

The circuit-breaker cams are so set that the contact points break at intervals corresponding with the production of sparking currents. This is shown in Figure 36, which illustrates the circuit breaker of the Splitdorf twin-cylinder magneto. The levers carrying the contact points are pivoted on a plate supported by the magneto frame, and it is the cam that

148 MOTOE-CYCLE PEINCIPLES

moves; its action is along different lines from the Bosch circnit breaker illnstrated in Fig-

Fio. 36.— SputdoefCircuitBrbakeb on Twin-Ctlindbb Magneto

The position of tiie two levers is such that after moving lever .2, the cam must turn further before moving lever 1 than

will be necessary in turning from lever 1 to lever 2.

In any magneto, the most complete change in magnetism occurs as the armature passes over position C, Figure 29, for then the center bar of the core loses its magnetism, but after having lost it, it is immediately regained as the core moves toward position D. The gain in magnetism does not occur with the rapidity with which magnetism is lost, and consequently the sparking current produced by the dying away of the magnetism will be more intense than the current produced by the gain in magnetism.

When the magneto circuit breaker is in the advance position, the contact points separate at the instant when th^ rear edge of the armature is just leaving the pole shoes, as shown in the first sketch. Figure 37. When in the retard position, the circuit breaker does not open until later in the revolution of the armature, or xmtil the armature is in the position

150 MOTOE-CYCLE PRINCIPLES

shown in the second sketch. By the time the armatnre has reached this position, the change in its magnetism is not very great,

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