fitted at the back of the cone by which it is forced into its socket. In a great many of the most popular types of car the hollowed socket for the cone is formed in the centre of the fly-wheel of the engine, which thus drives the mechanism through the clutch. The spring has a certain tension, and the friction between the two surfaces when pressed together by the spring is sufficient to drive the car without slip under all ordinary circumstances; but at starting, when the power is applied suddenly to an inert mass, a much greater amount of friction is engendered, and the cone slips slightly in
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Fig. 9
its socket, thus saving the gearing and the machinery from jar and shock, and enabling the power to be applied gently. The construction of a clutch of this character is shown at fig. 9.
Occasionally also two friction clutches acting in opposite directions are used to connect or disconnect alternately some portion of the gear, in which case they are not spring held, but are moved from side to side by a lever—thus, in fig. 10 we have two gear wheels, which may be of different sizes, running on one shaft with a double clutch between them. By moving the clutch over to the left, wheel a is held fast to and driven by the shaft upon which the clutch slides, whilst by moving it
