Rigging Mechanics 220

accelerate

To gain velocity or increase speed in a given direction.

acceleration

The rate of change of velocity.

applied force

The energy or effort provided to a machine to perform work. Applied force has many forms, from the power of an electric motor to the push from human hands.

axis

The center around which a wheel or component rotates.

belt

An endless loop of material used to transmit motion between two or more pulleys. Belts require friction to stay in contact with the pulleys.

brake

A device used to stop motion, usually through friction.

buckling

The bulging, bending, bowing, or kinking of an object as a result of compressive stress.

center of gravity

The point on a body at which the weight is distributed equally in every direction.

compressive stress

A force that attempts to flatten or "squeeze" a material.

corrosion fatigue

The disintegration of a material in the form of rust, pitting, or cracking. Corrosion fatigue typically is caused by environmental conditions.

creep

The slow deformation of a material over time. Also known as yielding.

decelerate

To lose velocity or reduce speed in a given direction.

deform

To change shape.

deformation

The change in an object's size or shape as a result of stress.

direction

The path that an object takes when it moves.

doorstop

A wedge used to hold open a door by placing it between the bottom of the door and the floor.

driven pulley

The pulley on a machine that receives power from the driver pulley via a belt.

driver pulley

The pulley on a machine that is attached to the power source, such as an electric motor.

ductile metal

A metal that can be drawn, stretched, or formed without breaking.

elastic deformation

The temporary change in the shape of an object as a result of stress. Once the stress is removed, the object returns to its original shape.

equilibrium

A state of balance. Objects that are in equilibrium are either completely still or moving at a consistent rate.

erosion

The wearing away of a material through processes such as abrasion, dissolution, or corrosion.

failure mode

A specific type of mechanical failure. Buckling, creep, fatigue, corrosion, and wear are examples of mechanical failure modes.

fatigue

Progressive structural damage to an object that is subjected to cumulative stress from repeated loads.

fatigue life

The number of times an object can carry a load before it fails. Fatigue life shortens as the stress on the object increases.

fixed pulley

A device consisting of a wheel rigidly fixed to a shaft that is used with a belt to transmit energy and motion to another fixed pulley.

force

An influence that produces a change in an object's motion or state of rest. A force has a specific direction and magnitude.

fracture

The breaking of an object into two or more pieces as a result of stress.

friction

A force that resists motion between two objects that are in contact with each other. Smoother surfaces exhibit less friction, while rougher surfaces exhibit more friction.

fulcrum

A pivot point of a lever, or the point around which an object turns.

inclined plane

A simple machine consisting of a flat angled surface used to raise objects. The mechanical advantage of an inclined plane increases with its length.

inertia

The tendency of an object at rest to stay at rest, and an object in motion to stay in motion, unless acted upon by an outside force.

jack

A tool used for lifting large or heavy objects. Jacks are used for items that cannot, or should not, be lifted with a crane or hoist.

lever

A type of simple machine consisting of a rigid bar that pivots on a fulcrum. Levers are used to transmit motion and alter mechanical advantage.

load

The opposition to applied force, such as a weight to be carried or moved.

lubrication

The use of a slippery substance, such as oil or graphite, placed between two moving surfaces that are in contact with each other. Lubrication minimizes friction, which aids movement and reduces heat.

magnitude

The measurement of the amount of an applied force.

mechanical advantage

The difference between the applied force and the work accomplished. Mechanical advantage allows machines to perform more work with less effort.

mechanical failure

A condition in which a device loses its capacity to carry a load. Mechanical failure is typically caused by overload.

mechanical law

The rules and principles applied to the branch of physics known as mechanics. Mechanics deals with different forces that cause or prevent motion.

mechanics

The branch of physics concerned with the motion of objects. Mechanics deals with different forces that cause or prevent motion.

moveable pulley

A circular lever that rotates around the fulcrum. A block and tackle is an example of a moveable pulley.

perpendicular

An intersection of two lines or objects at right angles. The delivered forces exerted by a wedge are perpendicular to its direction of travel.

plane

A flat or level surface.

plastic deformation

Deformation that is permanent. Plastic deformation occurs after excessive elastic deformation.

point of application

The place on the object where the force is applied. Point of application can affect forces such as torque and momentum.

ramp

A type of inclined plane. A ramp is often used to load materials onto a truck bed or to allow pedestrians to walk from one level to another.

resistance

The opposition to a force, such as the weight of a load or friction to movement.

rigging

The process of lifting and moving heavy loads with ropes, chains, and mechanical devices.

see saw

A long, narrow board equally balanced in the middle on a fulcrum.

shaft

A long cylindrical device such as a rod or pole. On a wheel, the shaft extends from the center of the wheel along its axis.

shear strain

The physical change resulting from two parallel planes sliding across each other. Shear strain is the result of shear stress.

shear stress

A force that attempts to cause the internal structure of a material to slide against itself.

shim

A thin wooden wedge used in woodworking to tighten and fill gaps in loose wooden parts.

shock

The jarring impact caused by sudden acceleration, deceleration, vibration, or collision. The effect of mechanical shock on an object depends on the object's structure and the materials from which it is made.

spreader beam

A rigging tool that keeps the legs of a sling at a 90° angle. Spreader beams reduce horizontal forces on slings.

strain

The ratio of change in a dimension that takes place with a material under stress.

stress

A force that attempts to deform an object.

tensile strength

The measure of a material's ability to stretch before deforming or breaking.

tensile stress

A force that attempts to pull apart or stretch a material.

torque

A force causing rotation.

vibration

The continued, repetitive, periodic motion in a machine or other structures.

wear

The erosion of material as a result of friction. Wear typically is caused by two or more objects rubbing or sliding against each other.

wedge

A friction-based inclined plane used to spread apart two opposing forces. A wedge is often used to split wooden logs.

wheel and axle

A wheel that is rigidly fixed to a central post that rotates with the wheel. A fixed pulley is an example of a wheel and axle.

yield strength

The point on the stress-strain curve where there is a sudden increase in strain, but no increase in stress. It is at this point that a metal is about to permanently deform.

yielding

The slow deformation of a material over time. Also known as creep.