Mechanical Components: Belts, Pulleys, and Gears

Belts

may be used for long center distances

Belts

the angular-velocity ratio between driving and driven shafts is neither constant nor equal to ratio of pulley diameters because of slip and creep (except for timing belts)

Belts

idler or tension pulleys can be used to avoid adjustments in center distance are necessitated by age or installation of new belts

Pulleys

used to transmit power from one shaft to another by flat belts, V-belts or ropes

Pulleys

must be in perfect alignment to allow the belt to travel in a line normal to the pulley faces

Pulleys

may be made of cast iron, cast or pressed steel, wood and paper

Chains

made up of number of rigid links which are hinged together by pin joints to provide the necessary flexibility for wrapping around wheels

Wheels

have a projecting teeth of special profile and fit into the corresponding recesses in the links of the chain

Angle of Articulation

function of the number of teeth. Rotation of the link through this causes impact between the rollers and the sprocket teeth and wear in the chain joint

Clutches

machine member used to connect shafts so that the driveshaft will rotate with the driving shaft, and to disconnect them at will

Jaw/Tooth Clutches

clutches wherein Jaws/Teeth are used to interlock

Hydraulic Clutches

clutches utilizing fluid friction

Friction Clutches

clutches which driving force is transmitted by friction

Electromagnetic Clutches

clutches utilizing electromagnetic fields

Axial Clutch

mating frictional members are moved in a direction parallel to the shaft

Disk clutch

employs one or more disks as operating members

Advantages of disk clutch

freedom from centrifugal effects, large frictional area in a small space, more effective heat-dissipation surfaces, and favorable pressure distribution

Brake

machine element used to regulate or stop the motion of a body

Mechanical Brakes

brakes are band, block, shoe, disc and spot

Hydrodynamic Brakes

brakes utilizing fluid friction

Electrical Brakes

brakes utilizing electromagnetic fields

Band Brakes

consists of a band friction material that tightens concentrically around a drum

Flywheel

machine element used to store energy and distribute it when needed

Flywheel

used to smoothen the operation of a machine where energy input or output is varying

Radius of Gyration (k)

distance from the rotation axis where a concentrated point mass equals the moment of inertia

Gears

provide positive means of transmitting power thru parallel shafts at a constant angular velocity

Gears

they do not have slippage between contacting surface similar to rotating cylinders

Spur Gear

gears that have teeth parallel to the axis of rotation

Spur Gear

gears that transmit motion from one shaft to another parallel shaft

Helical gear

gears that have teeth inclined to the axis of rotation

Helical gear

can be substituted to spur gears because they are less noisy

Herringbone Gear

also known as a double helical gear

Herringbone Gear

equivalent to two helical gears of opposite hang, mounted side by side on the same shaft

Herringbone Gear

gears that develop opposite thrust reactions and cancel out the thrust load

Bevel Gear

teeth formed on conical surfaces used for transmitting motion between intersecting shafts

Miter Gear

shaft intersection angle is 90 degrees and both gears are equal size

Spiral Bevel

cut so the tooth forms a circular arc (not straight)

Zerol Bevel

patented gear having curved teeth with a zero spiral angle

Zerol Bevel

generated by the same tool used for regular spiral bevel gears

Hypoid Gear

similar to spiral bevel gears except the shafts are offset and non-intersecting

Worm Gear

gear that resembles a screw

Worm Gear

gear wherein the teeth of one or both wrap partly around the other

Rack and Pinion

spur gear having an infinitely large pitch diameter

Rack and Pinion

the sides of involute teeth makes an angle to the line of centers equal to the pressure angle

Internal Gear

gear wherein the teeth is formed on the inner surface of a cylinder or cone (do not cause direction reversal)

External Gear

gear wherein the teeth is formed on the outer surface of a cylinder or cone

Face gears

transmit power at right angles in a circular motion (not very common in industrial application)

Pitch Circle

theoretical circle which all calculations are usually based

Pitch Circle

pair of mating gears that are tangent to each other

Addendum

radial distance between top land to pitch circle

Dedendum

radial distance between bottom land to pitch circle

Whole Depth

sum of the addendum and dedendum

Circular Pitch

distance from a point on one tooth to another point on an adjacent tooth

Circular Pitch

sum of tooth thickness and width of space

Module

ratio of pitch diameter to number of teeth

Diametral Pitch

ratio of number of teeth to pitch diameter (reciprocal of the module)

Clearance Circle

circle tangent to the addendum circle of the mating gear

Clearance

amount by which the dedendum exceeds the addendum of its mating gear

Backlash

amount by which the width of a tooth space exceeds the thickness of the engaging tooth measured on the pitch circles

Pinion

smaller of two mating gears

Gear

larger of two mating gears

Base Circle

circle tangent to the pressure line

Pitch Angle

defined by the pitch cones meeting at the apex