Clutches

Driveline components transmit and control power and motion. As simple as this sounds, it is necessary on every machine. Brakes are basically a clutch with one member held stationary. The objective with both classes of hardware is to take two shafts rotating independently at different speeds and bring them into partial or total engagement. Connecting shafts can be by direct mechanical lockup, mechanical friction, electromagnetic action, or hydraulic forces. Among the electromagnetic types, actual engagement may be mechanical, with electrical components used only for actuation. Mechanical clutches generally are the simplest and normally used where an operator can actuate the clutch manually. Vehicles, for example, typically use mechanical clutches. Electric clutches are generally used where remote actuation is required (as on automatic machinery) or where special slip characteristics are required. Hydraulic or fluid couplings are used in place of mechanical clutches where exceptionally smooth engagement is required or where it is desired to have the clutch automatically pick up a load with an increase in input speed. They are also used where constant engagement and disengagement would result in too much wear and maintenance. Clutches rely on mechanical or electromagnetic action for torque transmission. However, they are usually identified by their mode of actuation: mechanical, electrical, pneumatic, or hydraulic. Although the four operating modes are considered highly competitive, each mode actually is restricted to a fairly well-defined area of application. Within each area, one method provides definite advantages in terms of cost, response time, and torque transmission. is the simplest mode, and mechanically actuated clutches generally are the least expensive. Mechanical clutches can be actuated through hand or foot-operated linkages or cables, which provide a "feel" for the amount of engagement. Small mechanical clutches are actuated directly with cams or levers, while larger clutches are operated through compound linkages. Usually, mechanical