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GEAR DESIGN AND

OPTIMIZATION

Mayank Mangal

Abhishek Parmar

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INTRODUCTION:

o A gear is a Mechanical component used

to transmit power and motion

o

Key operations: Reversing the direction of rotation

Altering angular orientation of rotary

motion

Convert rotary motion into linear

motion & vice versa

Altering speed ratios

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INTRODUCTION:

o In geometry gears are:

Toothed wheels

Transmit motion & power from one shaftto another when they are not too far

apart

Constant velocity ratio is desired

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INTRODUCTION:

o In comparison with belt, chain & friction

devices

More compact Operate at high speeds

Precise timing

Large power Costly

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CLASSIFICATION OF GEARS:

According to the position of axis of the shafts:

Parallel- Spur gear, helical gear

Intersecting- bevel gear

Non-intersecting andnon-parallel- skew bevel gear

o According to peripheral velocity of the gears:

Low velocity

Medium velocity

High velocity

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CONTINUED

According to the type of gearing:

External gearing

Internal gearing

Rack andpinion

According to the position of the teeth on the gearsurface:

Straight

Inclined

Curved

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Spur Gear

Rack & Pinion

Bevel GearWormGear

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GEAR TERMINOLOGY:

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GEAR TERMINOLOGY:

Pitch Circle: It is an imaginary circle which bypure rolling action, would give the same motionas actual gear.

Pitch Circle diameter: It is the diameter ofthe

pitch circle.

Circular pitch: The arc length between a pointonone tooth, andthe corresponding pointonthenexttooth, measured along the Pitch Circle.

Diametral pitch: Ratioofthe number ofteethon a gear tothe diameter ofthe Pitch Circle.

Pressure angle: Angle betweenthe Line ofAction, and a line tangenttothe line connectingthe centers oftwomeshed gears.

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GEAR TERMINOLOGY:

Circular tooth thickness: The arc length

betweenpoints on either side ofa tooth,

measured along the Pitch Circle.

Addendum: Radial distance betweenthe PitchCircle andthe top edge ofa tooth.

Dedendum: Radial distance betweenthe Pitch

Circle and bottom edge ofa valley

Root Diameter: The diameter ofthe circle thatcontains the bottom (or "roots") ofthe valleys

Base Diameter: The diameter ofthe circle from

which the involute curve ofthe teeth is generated

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GEAR TERMINOLOGY:

Backlash: The distance betweenthe trailing edge ofa meshing tooth onone gear andthe leading edge ofthe meshing tooth onthe other gear. Backlashmeasures the tolerance ofa gear.

Module:It is the ratioofthe pitch circle diameter tothe noofteeth.

Tooth depth: It is the radial distance betweentheaddendum circle anddedendum circle ofa gear. It isthe sumofaddendum anddedendum.

Length of the path of contact: It is the length ofthe commonnormal cut-offbythe addendum circles ofthe wheel andthe pinion.

Centre distance: It is the distance between centresoftwomeshing gears

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INVOLUTE PROFILE:

Involute Profile

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INVOLUTE PROFILE:

o In an involute gear the profiles ofthe teeth areinvolutes ofa circle where involute ofacircle is the spiralling curve traced bythe endofan imaginarytaut string

unwinding itselffromthat stationarycircle

o In involute gear design all contactbetweentwo gears occur inthe same

fixedflatplane (the plane ofaction)even as their teeth mesh in andout