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8/6/2019 Gear Design and Optimization
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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