CHAPTER VII
CLUTCHES
Clutches are essential in all gasoline cars, for the reason that the driving power of the motor must be frequently disconnected from the running gear.
These devices are designed to transmit motion from the engine to the transmission shaft, so that when the clutch is engaged the transmission shaft will turn with the engine shaft.
Clutch Requirements.—The first requisite of a clutch is its ability to firmly hold the two shafts together; the second is, that it may be engaged gradually, and not suddenly; third, that it must disconnect instantaneously; and, fourth, that the force required to hold the two parts of the clutch together must not produce an end thrust on either shaft.
These requirements must be met by a condition that the act of engaging the clutch will not necessitate a long movement of the foot pedal which sets the clutch. Other considerations must be taken into account, also, and that is facility for examining and repairing, easy removal of worn or broken parts, and capability of adjustment as the contact surfaces wear.
Fig. 40. Cone Clutch.
It will be seen, therefore, that there are many elements necessary to provide a satisfactory clutch, well adapted for all purposes, and all these factors must be considered and understood by the boy who would be well informed.
Frictional Contact.—In any form of automobile clutches, there must be a frictional contact, which means wear, whatever may be the character of the material employed for the surfaces which are in engagement. As a result, clutches are now made which will permit the use of oil. Others dispense with it entirely.
Each type has its advantages. The cone clutches usually do not use a lubricant. This is described in the diagram, Fig. 40.