Ignition devices for motors, with a chapter treating specially of structural details, choice, and management of automobiles - Softcover
Synopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1908 Excerpt: ...and completes its circuit at the " earthed" end of the armature. The lever, B L, is held by a spring against the cam, c; which cam rotates with the armature, causing the necessary " makes" and " breaks " at the platinum points. When the points, P, are separated, the earth circuit is broken, and the current can flow only down the wire, P w, through the coil, and thence through the frame to the armature: this can only happen when the switch, s (Fig. 33) is open, as in the diagram. When it is closed it conducts the current to earth without its passing through the coil. It will Fig. 34. BL, Bell-crank lever. AN, Adjusting nut. P, Platinum contact. R, Roller. S, Screw, carrying platinum. AR, Axle of roller. be noticed that even when the switch, s, is open, the armature itself is not on open circuit. On the other hand, the armature current flows along a path of very low resistance, namely, to earth; or, in other words, the armature is short-circuited. This is, in fact, its normal condition, and it is, as already explained, never advisable to run a magneto on open circuit. Under running conditions, with the switch open, there is a permanent connection through the coil, but no appreciable current passes this way until the points P are separated. This is due to the fact that the " earth" circuit presents far less resistance, so that practically the whole current takes the easier route. When, under the influence of the cam, c, the points, P, separate, there is consequently a sudden rush of current along the only path left open, namely, through the coil. It is Fig. 35. 1c, Insulated casting. sw, NuthoMing spring. CP, Carbon pencil. Ik, Insulating rings. at this instant that the spark occurs at the plug, S P (Fig. 33). In other w...
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