

How to Select
a Brake or Clutch 

To properly size a brake or clutch, the operating parameters
of MAXIMUM TORQUE (T), SLIP SPEED (rpm), and KINETIC POWER (watts)
will have to be determined. Once calculated, these parameters
can be used to select the proper size brake or clutch from the
technical data provided in the Hysteresis Product Data Sheets. These parameters are easily calculated from system operating
requirements such as: total web or strand tension (F); the radius
of the full reel, roller, pulley, etc. (d/2); and linear velocity/feed
rate (v). The following example is given to show the relationship
of these system requirements to the calculation of the brake
operating parameters. Since this example is not meant to cover
all possible applications, the application
data sheet is provided in the product catalogs. If additional assistance is needed,
simply complete a copy of the data sheet and fax it to Magtrol.
Our Application Engineering staff will be pleased to assist
you. 

Sample Problem  English 
Select a
brake to tension a 7inch diameter payoff reel in a system
requiring total (web or strand) tension of 2 lb and a
process speed of 600 ft/min. 
Solution: 


Brake Torque (T) = 
Force (F)
x Radius (d/2) 

T = 
2 lb ×
3.5 in = 7 lb·in 
or T = 
32 oz ×
3.5 in = 112 oz·in 
Slip Speed (rpm) = 
linear velocity
(v) (in/min) / circumference (in) 
rpm = 
(600 ft/min
× 12) / (pi × 7 in) 
rpm = 
327 
Kinetic Power (W) = 
Kinetic Power
requirement is calculated using basic horsepower formula
x 746 watts /hp 
W = 
(T (lb·in)
x rpm/63025) x 746 
W = 
(7 lb·in
x 327 rpm/63025) x 746 = 27 watts 




Quick Check:
The curves to the left can be used as a quick
check to verify the kinetic power calculation. Simply
locate the required torque on the vertical axis, move
horizontally until you intersect the appropriate speed
line, and then read vertically (up or down) to obtain
the resulting watts or horsepower.
Selection:
From the Hysteresis
Brake ratings it can be seen that an HB140 Hysteresis
Brake which has a rated torque of 140 oz·in, a maximum
speed capability of 12,000 rpm, and a kinetic power
capability of 75 watts continuous, would be the proper
selection for this application. 



Sample Problem  Metric 


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