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ACTUATION

1. Manual. The operator provides the force, usually through a lever arrangement.

2. Spring applied. The force is applied automatically by springs. Thus, if power fails, the springs apply the

brake and stop the load.

3. Centrifugal. employed to permit the driving system to accelerate without a connected load. At a

preselected speed, centrifugal force moves the clutch elements into contact to connect the load and as

the system slows, the load will be automatically disconnected.

4. Pneumatic. Compressed air is introduced into a cylinder or other chamber.

5. Hydraulic. This type used oil hydraulic fluids instead of air.

6. Electromagnetic. An electric current is applied to a coil, creating a magnetic flux.

PARAMETERS INVOLVED IN THE RATING OF CLUTCHES AND BRAKES

1. Torque required accelerating or decelerating the system.

2. Time required accomplishing the speed change.

3. The cycling rate: number of on/off cycles per unit time.

4. The inertia of the rotating or translating parts.

5. The environment of the system: temperature, cooling effects.

6. Energy-dissipation

7. Physical size and configuration

8. Actuation means

9. Life and reliability of the system

10. Cost and availability

VALUE OF THE K FACTOR

K=1.0 under average conditions

T=CPK/n

Where: C-conversion factor for units

K-service factor based on the application

P- Power of the motor

n- Speed of the motor

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K=1.5 f or light duty 

K=3.0 f or heavy duty 

K=2.75 typical industrial motor 

K= 4.0 f or high starting torque motor 

K=5.0 f or systems driven by gasoline, diesel or other prime mover engines

n/t =

k = I/m or k2

= I/m

where: m = mass

m = W/g

I = mk2

= Wk2/g

Wk2

is called the inertia of the load.

Example:

Compute the value of Wk2 for the steel flat-belt pulley.

T=5252 (P/n)

Where: T = ft-lb

P = hp

n = rpm

Time, t required to accelerate the load

t = I = Wk2/g ((n)/t)

where: I  moment of inertia of the components being accelerated

 angular acceleration, rate of change of angular velocity