brake and clutch

1. Vocabulary Term Definition
Actuation The energy and power source used to operate and engage a
mechanical device. Clutch and brake assemblies may be
actuated purely mechanically, or with some or all of their
power coming from hydraulic, pneumatic, or electric
sources.
Asbestos A fibrous, heat-resistant material once widely used in the
linings of friction clutches and brakes, along with many other
applications. Abestos is a known health risk, and OSHA has
established guidelines for installing, removing, and
maintaining clutches and brakes containing it.
Axial Force A force applied parallel to the centerline of a shaft
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
Band Clutch
A simple friction clutch consisting of a flexible, anti-friction
lined band wrapped around a rotating drum. Band clutches

2. Brake A specific type of clutch that slows and stops motion by
engaging a rotating shaft and a fixed component
Brake Fade
A reduction in braking effectiveness caused by excessive heat
and wearing of components.
Brake Fluid
Hydraulic fluid used in some brake designs. When disk brakes
are applied, the hydraulic fluid is sent through the brake lines to
the pressure plate or caliper to apply pressure to the rotor and
slow or stop motion.
Brake Pad
The anti-friction material that lines plates and calipers used in
disk brakes. Brake pads help to reduce heat and increase the life
span of braking elements.
Caliper
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.
Cam
A low-friction, circular lever consisting of a lobe and a shaft that
transforms circular motion into linear motion. Cams are
sometimes used in hydraulically actuated clutch and brake
systems.

3. Cantilever Brake
A friction brake featuring two separate arms located on each side of a
bicycle rim. The cantilever brake is actuated by pressing a hand lever
located on the handlebars.
Cast Iron
A metal consisting of iron, over 2.11% carbon, and 1 to 3% silicon
offering heat resistance and compressive strength. Cast iron is
often used in clutches and brakes.
Centrifugal Force
A force that attempts to pull an object traveling in a cylindrical path
away from the center of rotation.
Clutch
A device that controls the transfer of power between machine
components by engaging and disengaging two rotating shafts.
Clutch-Brake
Assembly
A unit that combines both clutching and braking capabilities. Disk
and drum styles may combine both functions and are used in
heavy machinery.
Coil Spring
A type of spring formed by winding strips of metal around a cylinder or cone
to create a helical or conical shape. Coil springs are used to assist in
various types of actuation for clutch and brake systems.
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.

4. Contaminant Damaging foreign material such as dirt or shop debris that causes
wear to machine components
Contamination Damage occurring when foreign materials such as dirt enter a clutch
or brake system and cause uneven wear.
Contracting
Drum Brake
A friction brake that slows or stops motion when shoes contract and
make contact with the outer surface of a rim or drum. Contracting
rim brakes are widely used in mining and marine applications
Contracting
Drum Clutch
A friction clutch that transfers torque when shoes contract and make
contact with the outer surface or a rim or drum. Contacting rim
clutches are widely used in mining and marine applications
Corrosion The gradual chemical attack on a material by atmosphere, moisture,
or other agents.
Cycling Rate 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.
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

5. Double Disk A friction clutch or brake assembly consisting of two drive and
driven disks. The double disk design produces more torque and
braking force than the single disk design.
Downtime Unproductive blocks of time during which machine operations cease,
often due to mechanical problems
Drive Disk The disk in a disk clutch or brake system that receives energy from a
power source, such as an electric motor. Drive disks are also called
input disks and transmit torque to a driven disk connected to an
output component, such as a transmission.
Driven Disk The disk that receives energy from the drive disk in a disk clutch or
brake system. Driven disks are connected to components such as
transmissions or other output devices.
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.
Eddy Current
Clutch And
Brake
An electromagnetic style of clutch and brake offering excellent control
in braking and clutching but greater heat generation than other
electromagnetic types.
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.

6. Electromagnet
ic Brake
A non-contact 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.
Electromagneti
c Clutch
A non-contact 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
Expanding
Drum Brake
A friction brake that slows or stops motion when shoes expand and
make contact with the inner surface of a rim or drum. Expanding drum
brakes are also called internal shoe brakes
Expanding
Drum Clutch
A friction clutch that transfers torque when shoes expand and make
contact with the inner surface or a rim or drum. Expanding rim
clutches are widely used in mining and marine applications.
Friction The resistance to motion between the contact surfaces of two objects.
Friction generates heat and increases the wear between components
but is the key to providing clutching and braking forces
Friction Clutch
And Brake
System
An assembly of components containing two surfaces that press
together and transfer energy through friction to provide torque or
prevent motion. Friction clutches and brakes are the most common
type available and include disk and drum styles.
Friction Lining A lining applied to friction clutches and brakes to reduce heat and
wear caused by contact between mating surfaces. Abestos was once

7. Friction Plate A stationary disk used in disk brakes to apply pressure to the rotor
and slow and stop motion.
Heat Cracks Visible damage to clutches and brakes caused by thermal fatigue.
High Efficiency
Particulate Air
Filter
A disposable dry filter encased in metal or cardboard, often
abbreviated as HEPA. The filter is normally paper and is regulated to
extract at least 99.97% of dangerous particles, such as asbestos, from
the air.
Hydraulic
Actuation
Actuation initiated by pressurized fluids. Hydraulic actuation is used
when a great deal of torque or braking force is required.
Hysteresis
Clutch And
Brake
An electromagnetic style of clutch and brake offering a very long
service life and precise control in applications requiring slip, such as
in coiling.
Inner Drum The cylindrical component nested inside the outer drum in a drum-
style friction clutch or brake. Depending on the style, shoes located
on the inner drum may expand and engage the outer drum, or
pressure may be applied from the outer drum to the outside surface
of the inner drum during actuation.

8. Input Shaft The shaft connecting the prime mover to the driving element, such
as a drive disk, in a clutch system.
Kinetic Energy Energy of an object that has been put in motion.
KPa Kilopascals. A metric unit used to measure pressure. 1 Kilopascal
equals 1000 pascals, and approximately 0.1450 psi.
Lever A simple machine consisting of a rigid bar that pivots about a fulcrum.
Levers are used to transmit motion and alter mechanical advantage.
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
Lockout
Device
A device that uses positive means such as a lock and key or
combination lock to hold an energy-isolating mechanism in a safe
position and prevent equipment or machinery from being energized

9. Lockout/Tagout A method of protecting employees from accidental machine
startup through proper locking and labeling of machines that are
undergoing maintenance
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 Force Force created by the movement of an object over a distance
Molded Lining A general purpose friction lining used in clutches and brakes.
Molded linings are inexpensive but cannot operate in high-friction
operations.
Multiple Disk A friction clutch or brake assembly consisting of multiple drive and
driven disks. The multiple disk design produces more torque and
braking force than single or double 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.

10. OSHA The Occupational Safety and Health Administration. A government
agency under the U.S. Dept. of Labor that helps employers reduce
injuries, illnesses, and deaths in the workplace.
Outer Drum The outer cylindrical component surrounding the inner drum in a
drum-style friction clutch or brake. Depending on the style, shoes
located on the outer drum may engage the inner drum, or pressure
may be applied from the inner drum to the inside surface of the outer
drum during actuation.
Output Shaft In a clutch system, the shaft connecting the driven element, such as a
disk, to the output component receiving torque, such as a
transmission
Personal
Protective
Equipment
Any example of various safety equipment that workers wear or use to
prevent injury in the workplace. Safety glasses are common personal
protective equipment (PPE).
Piston A cylindrical component that moves up and down inside a mating
hollow cylinder in response to a pressure change in pneumatic and
hydraulic systems. Pistons may be used to transfer motion to clutch
and brake components.
Pneumatic
Actuation
Actuation initiated by pressurized gas. Pneumatic actuation provides
greater force than mechanical actuation and produces very little heat.

11. 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
Power Assist A means of lessening the amount of human force needed to depress
brakes used in vehicles and other equipment. The assist can be
provided by hydraulic means or by an air vacuum created in the
piston
Prime Mover The device that introduces energy into a power transmission system
and converts the energy into the appropriate form.
Psi Pounds per Square Inch. A unit in the English measuring system used
to measure pressure. One psi equals approximately 6.8948 kilopascals.
Race A groove located on the inside of a sprag clutch that provides a
pathway for the rotating sprags.
Response Time The time needed for a clutch or brake to engage and perform the
needed clutching or braking action

12. Rotor The driven, rotating disk in a disk brake that is stopped when
pressure is applied by a stationary friction plate or by a caliper.
Shoe 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 A friction clutch or brake assembly consisting of a single drive and
driven disk. The single disk design is the least expensive option but
produces less torque and braking force than double and multi-disk
systems.
Sintered Metal
Lining
A friction lining made of metal powders heated, pressed, and
molded together. Sintered metal linings provide the best resistance
to heat and wear and are the most expensive choice
Slip Clutch A friction clutch that temporarily disengages if it reaches a higher
level of torque than it is designed to handle. The contracting drum
clutch can be used as a slip clutch
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

13. Spiral Claw
Clutch
A positive clutch design featuring curved mating surfaces. The
spiral claw clutch can operate in high speeds but in only one
direction
Spline A flexible connection featuring grooves cut in a shaft that mate with
corresponding grooves in a connecting member, such as a hub.
Sprag A small, tapered element used in a sprag clutch that is similar to the
roller in a roller bearing. Sprags rotate in races until motion in one
direction causes sprags to wedge together and permit motion
Sprag Clutch A one-directional positive clutch design that connects two shafts
when motion causes rotating elements located within races to wedge
together. Rotation in the opposite direction disconnects the input
and output shaft.
Square Jaw
Clutch
A positive clutch design featuring interlocking square teeth. The
square jaw clutch is the least expensive type available and can be
used only in low-speed applications.
Tension Brake A friction brake used in spooling and coiling that requires the brake
to control tension by stopping and holding after allowing a small
amount of material to advance

14. Thermal
Fatigue
Damage caused by excessive heat or heat fluctuations over time.
Thermal fatigue can cause heat cracks or brake fade in brakes or
clutches and is caused by inappropriately high operating
temperatures resulting from fast cycling rates or insufficient linings
or mating materials
Torque A force causing rotation. Clutches provide torque
Transmission A machine that uses a combination of gears and other mechanical
components to change the speed or torque of mechanical energy
Uniform Wear The wearing away of the contact surfaces of friction clutches and
brakes at the same rate across the entire surface. Disk, drum, and cone
clutches and brakes experience uniform wear, while band clutches
and brakes do not.
Wear The gradual removal of material on a surface caused by contact and
friction
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.
Woven Lining A friction lining providing greater flexibility than molded linings.
Woven linings are more expensive than molded linings, but they
provide better resistance to contamination and are widely used in
band clutches and brakes