Clutches and brakes

Clutches and brakes couple, decouple, accelerate, and decelerate rotating machine components and maintain them at proper speed. The functions of each are so similar that their rolls are often interchangeable. Whether the clutch/brakes are mechanically, electrically, or fluid power actuated, they are considered mechanical devices because they transmit mechanical power.

06/12/2003


Key Concepts
 
  • Types

  • Selection

Sections:
Selection
Oil-shear clutches and brakes
Sidebars:
Selection criteria
Application notes
Troublemakers

Clutches and brakes couple, decouple, accelerate, and decelerate rotating machine components and maintain them at proper speed. The functions of each are so similar that their rolls are often interchangeable. Whether the clutch/brakes are mechanically, electrically, or fluid power actuated, they are considered mechanical devices because they transmit mechanical power.


Clutches and brakes are generally used in rotary motion applications. The clutch or brake must be designed to convert mechanical energy absorbed during relative motion or slippage into heat energy. It must survive both mechanical and thermal steady-state and shock loads imposed by the system during the operational cycle without damage.




Selection

The first step in selecting a clutch or brake is to determine the configuration required, depending on performance characteristics.

After selecting a type to use, the required size must be determined. Selection charts are available for this purpose.

A typical chart is based on the horsepower and speed of the system, which should be the shaft speed at the clutch or brake, not motor speed.














For example, the clutch needed to drive a shaft powered by a 1-hp
motor rotating at 1750 rpm is Model A. If the shaft speed at the clutch is a 2:1 reduction, clutch speed would be 875 rpm, and Model B would be selected.

The relationship between system horsepower and speed is given by the following equation for determining the dynamic torque capability required from the clutch or brake:

D = 5252 x hp x SF

_____________

N

where:

D = dynamic torque, lb-ft

hp = horsepower

SF = service factor (ranges from 1-10)

N = speed of clutch/brake, rpm

As rpm decreases, torque increases. For this reason, the best location for a clutch or brake is on the high-speed shaft of a machine.

Speed should not be too low; below 300 rpm is not recommended for friction-driven units. At low speeds, burnishing or mating wear of the friction faces does not occur, and torque capacity may be reduced dramatically.













When a clutch or brake must be operated at very low speeds, it might be necessary to oversize the unit. In these cases, it is normally sufficient to use a unit with a static torque rating two times the calculated dynamic torque requirement.



Oil-shear clutches and brakes

In a basic oil-shear drive, torque is transmitted through shearing of an oil film between two disks. As the rotating input disk moves toward the stationary output disk, the oil shearing action forces the output disk to begin rotating. There is no friction material-to-metal contact until input and output disk speeds are nearly equal. Then the oil film breaks down, allowing full static engagement. Wear is greatly reduced by the oil film, which lubricates while transmitting most of the dynamic torque of engagement.



Selection criteria

Maximum operating torque

Maximum torque

Type of actuation

Type of engagement

Response time

Cycle rate

Thermal capacity

Space or weight restrictions

Environmental conditions

Acceptable service life

Amount of routine maintenance

Application notes

Pneumatic and hydraulic-powered clutches and brakes have higher torque ratings than electric-powered units.

Electromagnetic tooth clutches have higher torque ratings than electromagnetic disk clutches and don't slip.

Self-actuating clutches work best where motor speed is an adequate control, soft starts are acceptable, and energy savings are important.

Magnetic particle clutches and brakes are useful in tensioning and positioning when there are continuous speed changes.

Eddy current clutches are useful for providing drag loads needed in tensioning.

Multicaliper clutches, with ventilated disks, are designed for continuous duty.

Square jaw clutches are limited to running engagements under 10 rpm.

Spiral jaw clutches allow engagement speeds up to 150 rpm.

Multitooth clutches can have running engagement speeds up to 300 rpm.

Disk clutches and brakes are preferred over drum-style units for frequent start-stop applications.

Eddy current clutches are used primarily in adjustable speed drives.

Troublemakers

Environmental and service conditions that can cause trouble for clutches and brakes include:

Exposure to gritty dust

Poor ventilation

Operation in wet or damp environments

Exposure to:
— oil vapor
— salt air
— chemical fumes



The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Women in engineering; Engineering Leaders Under 40; PID benefits and drawbacks; Ladder logic; Cloud computing
Robotic integration and cloud connections; SCADA and cybersecurity; Motor efficiency standards; Open- and closed-loop control; Augmented reality
Controller programming; Safety networks; Enclosure design; Power quality; Safety integrity levels; Increasing process efficiency
This article collection contains several articles on how advancements in vision system designs, computing power, algorithms, optics, and communications are making machine vision more cost effective than ever before.
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Women in engineering; Engineering Leaders Under 40; PID benefits and drawbacks; Ladder logic; Cloud computing
Robotic integration and cloud connections; SCADA and cybersecurity; Motor efficiency standards; Open- and closed-loop control; Augmented reality
Controller programming; Safety networks; Enclosure design; Power quality; Safety integrity levels; Increasing process efficiency
This article collection contains several articles on how advancements in vision system designs, computing power, algorithms, optics, and communications are making machine vision more cost effective than ever before.
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
Each year, a panel of Control Engineering and Plant Engineering editors and industry expert judges select the System Integrator of the Year Award winners in three categories.
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Women in engineering; Engineering Leaders Under 40; PID benefits and drawbacks; Ladder logic; Cloud computing
Robotic integration and cloud connections; SCADA and cybersecurity; Motor efficiency standards; Open- and closed-loop control; Augmented reality
Controller programming; Safety networks; Enclosure design; Power quality; Safety integrity levels; Increasing process efficiency
This article collection contains several articles on how advancements in vision system designs, computing power, algorithms, optics, and communications are making machine vision more cost effective than ever before.
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Cloud, mobility, and remote operations; SCADA and contextual mobility; Custom UPS empowering a secure pipeline
Infrastructure for natural gas expansion; Artificial lift methods; Disruptive technology and fugitive gas emissions
Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me