De Dion Type of Ignition.—We will now describe the ignition fitted to some of the best known types of engines.
De Dion et Bouton.—This well-known firm may be said to have set the fashion of electric ignition in the smaller engines. The system they employ belongs to Class I.
The most notable feature is the commutator. This device consists of a cam or disc c, fastened to the half-speed shaft of the motor, and provided with a wedge-shaped notch. Around the cam is attached a pear-shaped plate f constructed of good insulating material, such as ebonite, to which are attached a
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spring vibrator or 'trembler' t, and a brass pillar in which is fastened a platinum-pointed screw k. The trembler is provided with a platinum stud or 'contact' about the middle.
The Action of the Trembler.—The action of this trembler is very simple. Normally the end of the trembler t presses on the cam c, the platinum contacts on t and k being a little apart. If the engine be now turned round until the time for firing the charge arrives, the trembler will be seen to fall into the notch in the cam, allowing the two platinum points to come
