Introduction to Mechanical Systems 101

angular gear trains

A type of gear drive system that uses gears with slanted teeth and is designed to allow power transmission between gears of intersecting shafts. Angular gear trains can use a variety of gears, including bevel or miter gears.

applied force

The energy provided to a machine to perform work. Applied force is also known as effort.

axis

An imaginary straight line that passes through the center of an object. A cylindrical component typically rotates around its axis.

axle

The center post of a wheel. The axle is positioned on the wheel's axis.

bearing

A friction-reducing device that allows one moving part to glide past another moving part. Bearings operate using a sliding or rolling mechanism.

bearings

A friction-reducing device that allows one moving part to glide past another moving part. Bearings operate using a sliding or rolling mechanism.

belt

A band of flexible material that is looped around two or more fixed pulleys to transmit motion. Belts are made of various materials and come in different types, such as flat belts, round belts, and V-belts.

belt drive

A mechanical system consisting of a flexible belt and at least two fixed pulleys that is used to transmit motion. Belt drives are low maintenance and do not require lubrication.

bevel gear

A type of gear with conical teeth that are either straight or cut at an angle. Bevel gears are often used in angular gear trains.

block and tackle

A device consisting of a shell, movable wheel, and rope that is used to raise a load. Block and tackles are also known as movable pulleys.

brake

A device used to stop motion. Most brakes use friction in order to halt movement.

breech

The side opening on a movable pulley. The breech provides access to the sheave.

cam

A low-friction, circular lever consisting of a lobe and a shaft that transforms rotary motion into linear motion. Cams are often used in combustion engines.

cam follower

A specialized type of roller or needle bearing that works with a cam to transform circular motion into linear motion. The cam follower stays in contact with the lobe and moves the shaft up and down as the lobe rotates.

cam-action clamp

A clamp that uses a gradually curved surface to lock itself in place. Cam-action clamps can be used to securely hold or align a workpiece.

camshaft

A cam arrangement consisting of a cylindrical bar with lobes attached to it. Camshafts are often used in internal combustion engines.

clutch

A device that engages and disengages two rotating shafts. Clutches are used to control the transfer of power between machine components.

crankshaft

A rotating shaft with offset sections that transfers rotational motion into reciprocating linear motion. Crankshafts are used to power the pistons in an internal combustion engine.

cutting tool

A device with one or more edges that is designed to cut metal. Cutting tools are often designed to be used on a metal-cutting machine, such as a mill or lathe.

delivered force

The result of the effort applied to a machine. Delivered force is the resulting movement or work performed by a machine.

distance

The space between two points or objects. Distance is the amount of space through which the applied and delivered forces travel, which is a requirement for mechanical advantage.

drill presses

A machine tool that is used for a variety of holemaking operations. Drill presses commonly use fixed pulleys.

drive gear

The gear that receives energy from a power source, such as an electric motor. Drive gears transmit power to meshing driven gears in order to perform work.

driven gear

The gear that receives motion from the drive gear. Driven gears often transmit power to another meshing gear or an output shaft in order to perform work.

driven pulley

A fixed pulley in a belt drive system. The driven pulley receives energy from the driver pulley via a belt.

driver pulley

A fixed pulley in a belt drive system. The driver pulley receives energy from a power source and transfers it to the driven pulley via the belt.

efficiency

A measure of the work output of a system versus the total energy input. Efficiency determines the rate at which a mechanical system is able to convert a greater amount of the applied energy into the intended useful work.

effort

The energy provided to a machine to perform work. Effort is also known as applied force.

electric motor

A machine that converts electricity into mechanical energy or motion. Electric motors are common power sources for mechanical systems.

energy

The ability to do work. Energy, which is never created or destroyed, may be potential or kinetic and may appear as electrical, mechanical, thermal, or chemical.

fastener

A device that holds two or more objects together. Fasteners include bolts and screws.

first-class lever

A lever in which the fulcrum is positioned between the load and the effort. First-class levers include crowbars and balances.

fixed block pulley

A pulley arrangement in which a movable pulley is attached to a fixed point overhead, one end of rope is attached to the load, and the rope's free end is pulled to raise the load. Fixed block pulleys function as first-class levers.

fixed pulley

A circular device that is used in belt drive systems to transmit motion. Fixed pulleys are unable to be moved.

force

An influence, such as a push or a pull, which produces a change in an object's motion or state of rest. Forces have specific directions and magnitudes.

four-bar linkage

A multi-lever device used to convert rotary motion into reciprocating motion. Four-bar linkages are commonly used in robot arms.

friction

The resistance between the contact surfaces of two objects. Friction generates heat and increases the wear between components.

friction-based machines

A machine that requires some amount of friction to function. Friction-based machines, such as belt drives, require friction to keep from slipping or moving.

fulcrum

A central point on which a mechanism turns or swings. Fulcrums, or pivot points, may be physical objects or just points in space.

gear

A round or cylindrical mechanical component with teeth that is used to transmit power. Gears are designed to mesh with one another in order to alter the speed, torque, or direction of mechanical energy.

gear drive

A system consisting of gears that are designed to mesh with one another and can alter the speed, torque, or direction of mechanical energy. Gear drives transfer mechanical energy from one part of a mechanical system to another.

gear shafts

A cylindrical bar used to support rotating components or transmit rotation in a mechanical system. Gear shafts can be either parallel or at an angle to one another, as well as be either intersecting or non-intersecting.

gear train

A system of gears used to transmit rotary motion from one part of a mechanical system to another. Gear trains are a common method of power transmission.

helical gear

A type of gear with slanted teeth. Helical gears are quieter than spur gears, but they are more expensive and produce side loads.

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.

internal combustion engine

A type of engine in which heat energy and mechanical energy are produced inside the engine. Internal combustion engines include gas turbines and types of diesel motors.

joint

The point at which two materials join together. Loose joints can be tightened using a shim, or a wooden wedge.

lever

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

linear motion

Motion that takes place along a straight line. Mechanical energy can take the form of rotary or linear motion.

load

The overall force that is exerted onto a material or structure. Loads, such as weights that need to be carried or moved, are the opposition to applied forces.

lobe

The portion of a cam that intersects with the follower to transmit motion. Lobes have a variety of shapes but are most commonly oval.

low-friction machines

A machine that functions best when minimal friction is present. Low-friction machines, such as levers, maximize mechanical advantage.

lubrication

The act of applying lubricant, such as grease or oil, to machines. Lubrication reduces friction and wear between mechanical components.

machine

A device consisting of one or more parts that transform energy into motion. Machines are used to transmit or modify force and motion so as to accomplish some form of useful work.

mass

The amount of matter in an object. Mass gives an object weight when it is acted upon by gravity.

mechanical advantage

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

mechanical devices

A device that operates by reacting to and producing force and motion. Mechanical devices help machines perform work.

mechanical system

A collection of machines functioning together to perform useful work. All modern mechanical systems are based on simple machines.

meshes

The act of interlocking with another object. Gears are designed to mesh with one another in order to transmit mechanical energy.

metal-cutting machines

A general term for any powered machine that is used to manufacture parts by removing material from a metal workpiece. Metal-cutting machines include the saw, the drill press, the lathe, and the mill.

motion

A change in an object's original position as a result of a force applied to the object. Motion is typically described in terms of displacement, direction, velocity, acceleration, and time.

movable pulley

A device consisting of a shell, movable wheel, and rope that is used to raise a load. Movable pulleys are also known as block and tackles.

perimeter

The distance around the outside of an object. The perimeter of a circle is also known as its circumference.

perpendicular

Forming a 90° angle with another plane or object. The corner of a piece of paper is formed by perpendicular lines.

pin

A thin, often straight, cylindrical non-threaded fastener used to secure the position of two or more machine parts. A pin attaches the shell and sheave of a movable pulley.

pivot point

A central point on which a mechanism turns or swings. Pivot points, or fulcrums, may be physical objects or just points in space.

power source

A device that generates electricity. Power sources include batteries, electric motors, and generators.

rack

A flat bar with teeth used in a rack-and-pinion system to produce linear motion. Racks slide in a linear direction as circular pinions turn.

rack and pinion

A gear pair that is used to convert rotary motion into linear motion. Rack and pinions consist of a circular gear, or pinion, that meshes with a flat, toothed bar, or rack.

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.

reciprocating motion

Movement characterized by repeated back-and-forth action. Reciprocating motion is used in piston engines and pumps.

resistance

The opposition to a force. Resistance can include a variety of factors, such as the weight of a load or friction during movement.

rest

A lack of movement. Since rest is the opposite of motion, an object at rest is stationary and not in motion.

roller

A cylindrical device that rotates to move a load. Rollers are often attached to the end of valve stems in internal combustion engines.

rotary motion

Spinning or turning motion that takes place around an axis, without a change in linear position. Mechanical energy can take the form of rotary or linear motion.

runner pulley

A pulley arrangement in which a movable pulley is attached to the load, one end of rope is attached to a fixed point overhead, and the rope's free end is pulled to raise the load. Runner pulleys function as second-class levers.

screw

A type of inclined plane set around a cylinder. Screws are often used to fasten materials or transmit motion.

screw jack

A type of jack that consists of a threaded cylinder that is moved up or down when the handle of the jack is turned. Screw jacks are used to raise or lower heavy objects.

second-class lever

A lever in which the load lies between the fulcrum and the effort. Second-class levers include hinged doors and wheelbarrows.

shaft

A cylindrical bar used to support rotating components or transmit rotation in a mechanical system. On a wheel, the shaft extends from the center of the wheel along its axis.

sheave

The freely moving wheel that is part of a movable pulley. Sheaves are usually grooved in order to hold a rope or chain.

shell

The outer covering on a movable pulley. The shell surrounds the sheave.

shim

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

side load

A force that attempts to shift a component off its axis of rotation. Side loads occur when gear teeth mesh at an angle and can lead to increased wear.

simple machines

A basic mechanical device that uses mechanical advantage to multiply, transform, or change the direction of force. Simple machines include the lever, wheel, and inclined plane.

speed

The rate at which an object travels. Speed is calculated by dividing the distance traveled by the time elapsed.

spring

An elastic device used to dampen and apply force, control motion and vibration, and store energy. Springs are used in many mechanical systems to aid in the storage and transfer of energy.

spur gear

A type of gear that has straight, flat-topped teeth set parallel to the shaft. Spur gears are the most common type of gears used in industry.

tandem

Acting together or in conjunction with another object. Tandem components are usually arranged next to each other so that when one component moves, the other moves as well.

third-class lever

A lever in which the effort is placed between the fulcrum and the load. Third-class levers include brooms and hammers when they are used to drive a nail.

thread

The wedge-shaped spiral feature on a cylindrically shaped object that serves as the inclined plane. Threads are the raised, helical ribs or ridges found on screws, nuts, and bolts.

traction

The ability of a moving object to remain in contact with the surface over which it moves. Traction keeps a belt in contact with a rotating pulley.

valve stem

A moveable shaft within a camshaft that is commonly used with a follower. A valve stem is used by a camshaft to open and close holes in a device such as an engine.

wedge

A friction-based machine created by two inclined planes placed base to base. Wedges are often used to spread apart two opposing forces.

wheel

A circular machine that turns on a center axis. A wheel is a circular lever.

wheel and axle

A wheel that is rigidly fixed to a central post that rotates with the wheel. Wheel and axles include the fixed pulley.

work

The result of a force applied to an object and the distance through which the force is applied. In an equation, work is force multiplied by distance.

workpiece

Any part that is being machined, formed, or otherwise worked on. Workpieces are unfinished parts.