Clutch and Brake Applications 271

"Clutch and Brake Applications" covers the functionality of various clutch and brake types. Many industrial machines use clutches and brakes to cause or prevent the transfer of motion through mechanical systems. Understanding how different clutches and brakes function and how to choose appropriate components for a particular system is essential to regulating the safe and efficient transfer of energy. Clutches and brakes also work in conjunction with other power transmission components and must be properly maintained to prevent machine damage.

Machine operators must determine which clutches and brakes are most suitable for an application based on machine loads, operating speeds, and the general type of machine application. They must also recognize signs of wear and determine when clutching and braking components should be repaired or replaced. After taking, this course, users will understand clutch and brake function, and appropriate procedures for safe clutch and brake operation



Class Details

Class Name:
Clutch and Brake Applications 271
Version:
2.0
Difficulty:
Intermediate
Number of Lessons:
21
Related 1.0 Class:
Clutch and Brake Applications 250

Class Outline

  • Clutches and Brakes
  • Clutch and Brake Actuation
  • Friction Systems
  • Disk Clutches
  • Disk Brakes
  • Review: Types, Friction Systems, and Disk Clutches and Brakes
  • Cone Clutches and Brakes
  • Drum Clutches and Brakes
  • Band Brakes
  • Review: Types of Friction Clutches and Brakes
  • Spring-Applied Clutches and Brakes
  • Positive Clutches
  • Overrunning Clutches
  • Contact-Style Electromagnetic Clutches and Brakes
  • Noncontact-Style Electromagnetic Clutches and Brakes
  • Review: Specialty Clutches and Brakes
  • Clutch and Brake Selection
  • Clutch and Brake Installation and Repair
  • Clutch and Brake Inspection and Maintenance
  • Clutch and Brake Safety
  • Review: Clutch and Brake Selection and Maintenance

Objectives

  • Describe clutches and brakes.
  • Distinguish between different types of clutch and brake actuation.
  • Describe friction clutch and brake systems.
  • Describe disk clutches.
  • Describe disk brakes.
  • Describe cone clutches and brakes.
  • Distinguish between types of drum clutches and brakes.
  • Describe band brakes and their common uses.
  • Describe spring-applied clutches and brakes.
  • Distinguish between different types of positive clutches.
  • Describe overrunning clutches.
  • Describe contact-style electromagnetic clutches and brakes.
  • Describe noncontact-style electromagnetic clutches and brakes.
  • Describe factors affecting clutch and brake selection.
  • Explain important considerations for installing and replacing clutches and brakes.
  • Explain important considerations for regular clutch and brake inspection and maintenance.
  • Explain important safety considerations for clutches and brakes.

Job Roles

Certifications

Glossary

Vocabulary Term Definition
actuation The process required to engage or disengage a clutch, brake, or other component. Actuation methods for clutches and brakes include mechanical, hydraulic, pneumatic, and electric energy.
air compressors A component that pressurizes air and delivers the compressed air into a pneumatic system. Air compressors are required for pneumatic clutch and brake operation.
armature A rotating component attached to the output shaft of an electromagnetic clutch. The armature is pulled against the rotor when the clutch is engaged.
asbestos A fibrous, heat-resistant material once widely used in the linings of friction clutches and brakes, along with many other applications. Asbestos is a known health risk, and The Occupational Safety and Health Administration has established guidelines for installing, maintaining, and removing clutches and brakes containing it.
axial force A force applied parallel to the centerline of a shaft. Axial force is required for clutching and braking applications.
backing plate A stationary component on a drum clutch or brake that supports the shoes or pads and other actuating devices. The backing plate on a drum clutch is attached to the driving shaft.
backstopping A method used in safety applications that prevents a load from travelling backwards once the load has stopped moving. Backstopping is accomplished with an overrunning clutch by attaching the outer race to a stationary component.
band A circular component made of flexible steel component and lined with friction material. Bands are used in friction-style clutches and brakes.
band brake A simple friction brake consisting of a flexible, anti-friction lined band wrapped around a rotating drum. Band brakes are used in hoists.
bearings A friction-reducing device that allows one moving part to glide past or rotate within another moving part. Bearings operate using a sliding or rolling mechanism.
bleed To safely remove liquid or gas from a closed system. Bleeding air from hydraulic brakes helps ensure braking power is not lost.
brake A device that slows and stops power transmission. Brakes engage a rotating shaft and and a fixed component to produce friction and halt movement.
brake drum A cylindrical steel component used to slow or stop rotary motion. The brake drum usually rotates in unison with a wheel hub which slows or stops when braking force is applied.
brake fade A reduction in braking effectiveness caused by excessive heat and wearing of components. Brake fade occurs in all friction-style brakes.
brake pads The anti-friction material that lines friction plates and calipers used in disk brakes. Brake pads help to reduce heat and increase the life span of braking elements.
braking The process of engaging the components in a brake in order to slow or stop power transmission. Braking is accomplished in most mechanical systems through friction.
braking force The amount of force braking components can apply in order to bring a moving component to a full stop. Braking force varies depending on the type of actuation and the design features of brake components.
calipers A component in disk brakes that holds brake pads and straddles the rotor, pressing against it when the brake is applied to slow and stop motion. Disk brakes with calipers do not create as much heat as brakes with a friction plate.
cast iron A type of steel, formed from a molten state, that contains at least two percent carbon as well as percentages of silicon and sulfur. Cast iron is often used in clutches and brakes.
catastrophic damage Damage that causes the sudden and complete loss of machine functionality or performance. Catastrophic damage can occur if operators do not ensure that clutches and brakes are properly maintained.
catastrophic damage The sudden and inadvertent loss of functionality in one component due to the failure of another component. Catastrophic damage to fully functional components is costly but can often be avoided by closely monitoring component service life.
centrifugal brake A type of expanding drum brake that is automatically engaged by centrifugal force. Centrifugal brakes can be designed to engage and disengage at predetermined speeds.
centrifugal clutch A type of expanding drum clutch that is automatically engaged by centrifugal force. Centrifugal clutches can be designed to engage and disengage at predetermined speeds.
centrifugal force A force directed outward and away from the center of a rotating object. Centrifugal force engages centrifugal clutches and brakes automatically and also allows expanding drum brakes to engage or contracting drum brakes to disengage more easily.
claw clutch A positive clutch design featuring interlocking square teeth. The claw clutch is also known as the square jaw clutch.
clutch A device that engages and disengages two rotating shafts. Clutches are used to control the transfer of power between machine components.
clutch band Bands often used in clutches to hold clutching components. Clutch bands help transmissions achieve different gear ratios.
clutch disk The rotating component in a disk clutch that is attached to the driven shaft. The clutch disk receives energy from the clutch plate when the clutch is engaged.
clutch drum A cylindrical steel component used to transfer rotary motion. The clutch drum is attached to hub on a driven shaft.
clutch hub The component on a clutch attached a driving component, such as a flywheel or driving shaft. The clutch hub on an expanding drum clutch supports the shoes that engage the clutch drum.
clutch plate The disk-shaped device that receives energy from the driving shaft in a disk clutch. The clutch plate transfers energy to the clutch disk on the driven shaft when the clutch is engaged.
clutch slip The process of a clutch disengaging when it exceeds maximum torque or operating speed. Clutch slip occurs in overrunning clutches when the output component rotates faster than the input component.
clutch-brake assembly A unit that combines both clutching and braking capabilities. Clutch-brake assemblies are often used in press brakes and other industrial machines.
clutching The process of engaging the components in a clutch to allow for power transmission. Clutching allows for the transfer of torque from a driving shaft to a driven shaft.
clutching force The amount of force clutching components can apply in order to transfer motion from a driving shaft to a driven shaft. Clutching force varies depending on the type of actuation and the design features of clutch components.
CNC mill A machine tool that uses computer numerical data to control cutting operations on flat, square, or rectangular workpieces. On a CNC mill, the cutting tool rotates against a workpiece that is fixed to a worktable.
compressed air Air that has been forced into a small space at high pressure. Compressed air is often used to power clutches and brakes.
cone A tapered, driven component in a cone clutch that attaches to the driven shaft. The cone receives energy from the prime mover via the cup.
cone brake A friction brake consisting of a cone that fits inside a cup when engaged. Cone brakes are less expensive than disk styles but can be difficult to disengage.
cone clutch A friction clutch consisting of a cone that fits inside a cup when engaged. Cone clutches are less expensive than disk styles but can be difficult to disengage.
contaminants Any foreign substance, such as dirt, that can reduce efficiency of machines and damage components. Contaminants can cause machines to wear prematurely and reduce service life.
contaminants Damaging foreign material, such as dirt or debris, that causes wear to machine components. Contaminants can reduce machine efficiency and potentially create safety hazards.
contamination The presence of foreign materials such as dirt or shop debris in a lubricant. Contamination in lubricants can damage machinery.
contracting drum brake A friction brake that slows or stops motion when shoes contract against the outer surface of a brake drum. Contracting drum brakes are widely used in mining and marine applications.
contracting drum clutch A friction clutch that transfers torque when shoes contract against the outer surface of a clutch drum. Contracting drum clutches are widely used in mining and marine applications.
conveyors A moving strip of material that carries parts or other components from one area of a manufacturing facility to another. Conveyors are commonly used to transport parts from production to packaging.
corrosion The disintegration of a material in the form of rust, pitting, or cracking. Corrosion is typically caused by environmental conditions.
cup The driving component in a cone clutch that attaches to the driving shaft. The cup transfers energy to the cone when the clutch is engaged.
current The flow of electricity. Current is used to actuate electrically powered clutches and brakes.
cycling rates The amount of time needed for a clutch or brake to go through a cycle of engagement and disengagement, and how quickly it can begin a new cycle. Cycling rates vary depending on the type of actuation and the type of clutching or braking application.
cylinders A linear actuator that houses a piston attached to a movable piston rod. Cylinders are used on some clutches and brakes to transfer hydraulic or pneumatic force.
disk brake A friction brake that stops motion when a stationary element is pressed against a rotating disk. Disk brakes are commonly used in automobiles and in some industrial machinery, especially in older machines.
disk clutch A friction clutch that transmits torque when rotating disks are pressed together. Disk clutches are commonly used in automobiles with manual transmissions.
downtime The period of time when a machine or system is not operating and is not producing or performing work. Downtime due to unscheduled service or maintenance can have a negative impact on overall production efficiency.
driven component A power transmission component connected to a driven shaft in a mechanical system. The driven component receives energy from the prime mover via the driving component.
driven shaft A rotating shaft that receives power from a driving shaft in a mechanical system. A driven shaft transports power to a machine's components when connected to the driving shaft by a clutch or other device.
driving component A power transmission component connected to the driving shaft attached to a prime mover in a mechanical system. A driving component engages a driven component to transfer energy to the driven shaft.
driving shaft A rotating shaft that receives power directly from a prime mover. A driven shaft introduces power into a mechanical system.
drum A cylindrical steel component used in drum-style friction clutches and brakes. A drum rotates with the driven shaft and either transfers rotary motion in a clutch or stops rotary motion in a brake.
drum brakes A friction brake that stops motion when a stationary component is pressed against a rotating drum. Drum brakes are commonly used in cranes and other industrial equipment.
drum clutches A friction clutch that transmits torque when shoes or pads make contact with a drum. Drum clutches are widely used in heavy machinery and industrial equipment.
dry operation Operation that occurs without lubrication. Dry operation provides the greatest amount of torque or braking force but also generates heat and increases wear.
dual disk brake A friction brake assembly consisting of two rotors and two stationary friction plates. The dual disk brake design produces more braking force than the single disk design and may also use calipers.
dual disk clutch A friction clutch assembly consisting of two clutch plates. The dual disk clutch design produces more clutching force than the single disk design.
eddy current An electromagnetic current generated when a metal object enters an electromagnetic field. Eddy currents rotate an outer ring or drum connected to an output shaft in eddy current clutches or to stop rotation in eddy current brakes.
electric actuation Actuation initiated by electric currents from an electric motor. Electric actuation offers fast cycle rates, quick response times, and remote operation but provides less force than hydraulic actuation and produces considerable heat.
electromagnetic brakes A brake design actuated when an electric current charges a coil that acts as an electromagnet. Electromagnetic brakes are widely used in automated machinery and provide a high cycling rate.
electromagnetic clutches A clutch design actuated when an electric current charges a coil that acts as an electromagnet. Electromagnetic clutches are used in some automated machinery and provide a high cycling rate.
electromagnetic coil The component of an inductive proximity sensor that consists of an electrically conductive material wrapped around a ferrite core. The electromagnetic coil is responsible for generating and shaping the electromagnetic field.
electromagnetic tooth clutches An electromagnetic clutch that uses interlocking teeth to transfer rotary motion. Electromagnetic tooth clutches can transfer high levels of torque and do not slip like friction clutches but cannot be engaged at high speeds.
emergency brakes A standard device on automobiles and industrial vehicles that prevents the wheels from rolling when parked or stops the vehicle when necessary. Emergency brakes are commonly referred to as parking brakes.
emergency stops A button or switch that brings a machine to a safe, rapid stop. Emergency stop buttons or switches may also be called E-stops.
expanding drum brake A friction brake that slows or stops motion when shoes expand and make contact with the inner surface of a brake drum. Expanding drum brakes are typically used on automobiles but are also found in heavy machinery.
expanding drum clutch A friction clutch that transfers torque when shoes expand and make contact with the inner surface of a rim or drum. Expanding drum clutches are widely used in mining and marine applications.
failure The complete loss of performance in a component or a system. Failure of a clutch or brake can result from using the wrong friction materials or lubricants, or from neglected machine maintenance.
flanges A projecting rim or edge for fastening. Flanges on the input and output shafts of a positive clutch transfer energy through interlocking teeth.
friction A force that resists motion between two objects that are in contact with each other. Friction is a type of contact force used in mechanical systems.
friction lining A lining applied to friction clutches and brakes to reduce heat and wear caused by contact between mating surfaces. Abestos was once commonly used, but today other materials are being used, such as cotton and rubber.
friction lining A material applied to friction clutches and brakes to reduce heat and wear caused by contact between surfaces. Friction linings may be made of cotton, rubber, or other materials.
friction plate A stationary disk used in disk brakes to apply pressure to the rotor and slow and stop motion. Friction plates are lined with friction material to reduce heat generation.
friction systems A clutch or brake system in which the surfaces of components, usually lined with friction material, slide against one another to transfer or stop motion. Most clutch and brake applications use friction systems.
high efficiency particulate air filter HEPA. A disposable dry filter encased in metal or cardboard. The high efficiency particulate air filter is normally paper and is regulated to extract at least 99.97% of dangerous particles, such as asbestos, from the air.
hoisting Lifting and lowering loads by means of a drum or lift-wheel around which rope or chain wraps. Hoisting devices are often installed on cranes and other heavy industrial equipment.
holding Maintaining the position of a component and preventing its motion. Holding components in place is often necessary in clutch applications to control the flow of power transmission.
holding brake A brake that is typically used to hold a component in place rather than slow its movement. Holding brakes, such as parking brakes, often use bands to apply holding force.
hydraulic actuation Actuation initiated by pressurized fluids. Hydraulic actuation is used when a great deal of torque or braking force is required.
hysteresis The delay between the action and reaction of interacting objects. Magnetic hysteresis is used to transfer motion from an input to an output component in hysteresis clutches or to stop motion in hysteresis brakes.
indexing The act of moving a machine component in fixed increments along a circular or linear path. Indexing is accomplished with an overrunning clutch by attaching the outer race to a stationary component.
inflating tubes A type of pneumatic fluid conductor used in some contracting drum clutches that expand when compressed air is forced into it. Inflating tubes may also be used in some expanding drum brake designs.
inner diameter The interior surface of a circular or spherical component. The inner diameter of the drum on an expanding drum clutch or brake is the contact point for transferring or stopping motion.
kilopascals kPa. A metric system unit used to measure pressure. Kilopascals may be used to measure the pressure requirements for a hydraulic system.
lever A simple machine consisting of a rigid bar that pivots upon a fulcrum. Levers are used to transfer the energy required to actuate clutches and brakes.
linkage system A system of cables or rods that transmits power or motion from an input to an output component. Disk clutch and brakes require a linkage system.
load The amount of force or pressure placed on a component or system. The load that a positive clutch can withstand depends on a number of factors, including the number and shape of its teeth.
lockout device A device, such as a lock and key or combination lock, used to hold an energy-isolating mechanism in a safe position and prevent equipment or machinery from being energized. A lockout device can also be used to lock moving components of a mechanical system in place.
lockout/tagout A method of protecting employees from accidental machine startup through proper locking and labeling of machines that are hazardous to nearby employees. Lockout/tagout is an essential practice for safe repair of machines.
lubricant A substance that reduces or prevents friction, resistance, heat, and wear during a variety of manufacturing processes. Lubricants include oil, grease, and graphite.
lubrication The act of applying lubricant to machine components to reduce friction and wear between contacting surfaces. Lubrication must be monitored for some friction systems that require wet operation.
magnetic force A force of attraction that surrounds magnets and current-carrying conductors. Magnetic force can be used to physically engage friction or positive clutches, or to transfer rotary motion without contact.
mechanical actuation Actuation caused by the physical movement of components when an operator applies force using levers, pedals, and other devices. Mechanical actuation is inexpensive but offers limited force and slower cycling rates and response times.
mechanical lockup clutch A clutch that consists of two mating surfaces with interconnecting elements, such as teeth, that lock together during engagement to prevent slipping. Mechanical lockup clutches are also known as positive clutches.
molded Formed by into a particular shape by manipulating material in a flexible state. Molded friction linings are inexpensive but cannot operate in high-friction operations.
multiple disk brake A friction brake assembly consisting of three or more rotors and three or more stationary friction plates. The multiple disk brake design produces more braking force than single or dual disk designs and may also use calipers.
multiple disk clutch A friction clutch assembly consisting of three or more clutch plates. The multiple disk clutch design produces more clutching force than single or dual disk designs.
multiple tooth clutch A cylindrical clutch containing a series of small tooth-like projections around a perimeter. The multiple-tooth clutch is used in some slow-speed industrial equipment requiring a large torque-carrying capacity.
Occupational Safety and Health Administration OSHA. A government agency that sets the standards for working conditions in the United States and ensures that employees work in safe and healthy environments.
OSHA The Occupational Safety and Health Administration. A government agency that sets the standards for working conditions in the United States and ensures that employees work in safe and healthy environments.
outer diameter The exterior surface of a circular or spherical component. The outer diameter of the drum on an contracting drum clutch or brake is the contact point for transferring or stopping motion.
overrunning clutch A clutch containing an output component that disengages from the input component and runs freely in one direction when it exceeds a maximum speed. An overrunning clutch can be useful for managing the speed output of mechanical systems.
pedal A device similar to a lever that activates or deactivates a valve or actuator. Pedals are usually located on the floor and are operated by foot.
personal protective equipment PPE. Articles of clothing or safeguarding devices that employees use to prevent injury or exposure to health hazards in the workplace. Personal protective equipment such as safety glasses, face shields, insulated gloves, face masks, or respirators may be when servicing certain clutches and brakes.
pistons A disk or short cylinder fitting closely within a tube. Pistons move up and down against a liquid or gas.
pneumatic actuation Actuation initiated by pressurized gas. Pneumatic actuation provides greater force than mechanical actuation and produces very little heat.
positive clutch A clutch that consists of two mating surfaces with interconnecting elements, such as teeth, that lock together during engagement to prevent slipping. Positive clutches are also known as mechanical lockup clutches.
positive engagement Engagement of a clutch using interlocking teeth rather than friction. Some contact-style electromagnetic clutches use positive engagement
pounds per square inch psi. A unit of English measurement used to measure pressure. Pounds per square inch units are used to measure pressure requirements for the hydraulic system and for system components.
power excavation Using power equipment, such as cranes, loaders, or other devices to demolish structures, or to dig up earth, rock, and minerals prior construction. Power excavation often requires band brakes or other brake and clutch devices.
predetermined speed A specific speed, determined by the manufacturer, at which a component may be design to produce a certain action. A predetermined speed directs the design of centrifugal clutch and brake components.
premature wear The erosion of material as a result of inadequate lubrication or improper operation. Wear is typically caused by two or more objects rubbing or sliding against each other.
press brakes A machine with a stationary base and an upper ram that moves along a vertical axis to shear, bend, or form sheet metal. Press brakes often use disk clutches and brakes.
pressure plate A metal plate in a clutch that forces the clutch disk against the clutch plate when the clutch is engaged. The pressure plate is usually bolted to the clutch plate.
pressurized fluid A fluid under high pressure. Pressurized fluids can supply high levels of clutching and braking force in clutch and brake systems that use hydraulic actuation.
prime mover The device that introduces energy into a system and converts energy into the appropriate form. Prime movers include electric motors and diesel engines.
race A groove located on the inside of a clutch or bearing that provides a pathway for rotating components. Both an inner and an outer race are used in sprag and roller ramp clutch designs.
ratchet clutch A positive clutch design featuring curved mating surfaces. The ratchet clutch is also known as the spiral claw clutch.
reservoirs The main storage container for fluid in a hydraulic system. Reservoirs are required for hydraulic clutch and brake actuation.
response times The time needed for a clutch or brake to engage and perform the needed clutching or braking action. Response time for clutches and brakes vary depending on design features, actuation type, and other factors.
revolutions per minute Rpm. A unit of measurement that indicates the number of rotations a cylindrical component completes in one minute. Revolutions per minute is a measurement of rotary speed.
rim The round, exterior component on a contracting drum clutch. The rim contains shoes or pads that contract against the outer diameter of the clutch drum during clutch engagement.
roller ramp clutch An overrunning clutch that uses rollers to engage input and output shafts by pressing against inner and outer races. A roller ramp clutch typically engages in one direction and disengages to rotate freely in the opposite direction.
rotary motion Spinning action that takes place around an axis without a change in linear position. Mechanical energy can take the form of rotary or linear motion.
rotor A rotating part of an electrical or mechanical device. The rotor on a disk brake is connected to a rotating component, such as a wheel hub, that requires braking to slow or stop its rotation.
safety brakes A brake that remains mechanically engaged, or engages automatically under certain conditions, until disengaged by actuating force. Safety brakes often use a spring-applied brake design.
seals A device used to close an opening or form a closed joint between objects. Seals are used with bearings and other components to retain lubricant and prevent contamination.
service life The length of time a machine or machine component is expected to be operational before it must be replaced. The service life of clutches and brakes can be reduced if components are not serviced properly.
shoes Anti-friction material that lines metal plates in drum clutches and brakes. Shoes help to reduce heat and increase the life span of clutching and braking elements.
single disk brake A friction brake assembly consisting of one rotor and either a stationary friction plate or brake pads housed in a caliper. The single disk brake design is the least expensive option but produces less braking force than dual and multiple disk designs.
single disk clutch A friction clutch assembly consisting of a single clutch plate. The single disk clutch design is the least expensive option but produces less clutching force than dual and multiple disk designs.
sintered Heated and pressed together below melting temperature to improve hardness and durability. Sintered metals are very uniform in composition.
slipping A condition that occurs when the drive disk of a clutch fails to make complete contact with the driven disk, causing the driven disk to rotate at a different speed. In many operations, continuous slipping causes excessive wear and premature failure in the clutch system.
spiral claw clutch A positive clutch design featuring curved mating surfaces. The spiral claw clutch is sometimes called a ratchet clutch.
spline Teeth added to shafts and interconnecting components that ensure they move together. Splines fit loosely and provide flexible movement for many devices.
sprag clutch An overrunning clutch that engages input and output shafts by wedging sprags between inner and outer races. A sprag clutch typically engages in one direction and disengages to rotate freely in the opposite direction.
sprags A small, tapered element used in a sprag clutch that is similar to the roller in a roller ramp clutch. Sprags rotate in races until motion in one direction causes them to wedge together at an angle, transferring motion between input and output shafts.
spring-applied brakes A brake that remains mechanically engaged by springs until disengaged by actuating force. Spring-applied brakes are used in applications in which safety is a high priority, such as heavy load operations.
spring-applied clutches A clutch that remains mechanically engaged by springs during normal operation. Spring-applied clutches are used in applications in which safety is a high priority, such as heavy load operations.
square jaw clutch A positive clutch design featuring interlocking square teeth. The square jaw clutch is sometimes called a claw clutch.
tagout device A warning device, such as a tag, that can be securely attached to a machine or power source to alert employees that equipment is not to be operated until the tag is removed. Tagout devices should only be removed by authorized personnel.
technical support Assistance provided by those with product and system knowledge to solve customer problems, identify optimal solutions, or provide information about product use. Technical support is usually available by phone or through online channels for some manufacturers.
tensile springs A type of spring designed to support tensile, or pulling, loads. Tensile springs in centrifugal brakes expand under increasing centrifugal force.
thermal fatigue Damage caused by excessive heat or heat fluctuations over time. Thermal fatigue can cause heat cracks or brake fade in clutches or brakes and is caused by high operating temperatures resulting from fast cycling rates or insufficient friction linings.
thermal fatigue Damage caused over time by excessive heat or heat fluctuations from fast cycling rates or insufficient friction linings. Thermal fatigue often causes heat cracks or brake fade in clutches or brakes.
torque A force that produces rotary motion. Torque is measured in foot-pounds in the English system and newton-meters in the metric system.
valves A mechanical device that regulates the flow of gases or fluids by opening to let gas or fluid through or closing to obstruct the flow of gas or fluid. Valves help pneumatically actuated clutch and brake systems apply the appropriate clutching or braking force.
wear The erosion of material as a result of friction. Wear occurs over time in almost all clutch and brake application due to friction between components in contact.
wear indicators A device or design feature on a clutch, brake, or other component that helps operators determine when to replace the component. Some wear indicators are designed to make noise when significant wear occurs, while others indicate wear visually.
wet operation Operation that occurs with components submerged in oil or similar substances. Wet operation reduces heat and wear but also reduces the amount of torque and braking force available.
wheel hub The central part of a wheel or other type of rotary component. The wheel hub is typically connected to an output shaft in a mechanical system.
woven Stitched tightly to join fabrics or other material together. Woven friction linings are more expensive than molded linings, but they provide better resistance to contamination and are widely used in band clutches and brakes.