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Presentation Topic :Gear & Gear Trains

GEAR

Types of Gear

Spur GearUsed to transmit rotary between parallel shafts.

Helical GearUsed to transmit rotary motion between parallel or nonparallel shaft.

Herringbone GearA Herringbone Gear consists basically of two rows of helical teeth cut into one gear. The axial thrust forces are cancelled by direct subtraction. Herringbone Gears are used for heavy and continuous load applications.

Bevel GearUsed to transmit rotary motion between intersecting shafts.

Worm GearUsed to transmit rotary motion between nonparallel nonintersecting shafts.

Gear Trains

IntroductionTwo or more gears are made to mesh with each other to transmit power from one shaft to another. Such a combination is called gear train or train of toothed wheels.

Types of Gear Trains

Simple Gear TrainWhen there is only one gear on each shaft it is known as simple gear train. The gears are represented by their pitch circles.

Compound gear trainWhen there are more than one gear on a shaft,it is called a compoundtrain of gear.

Reverted Gear TrainWhen the axes of the first gear (i.e. first driver) and the last gear (i.e. last driven or follower) are co-axial,then the gear train is known as reverted gear train.

Epicyclic Gear Trainthe axes of the shafts, over which the gears are mounted, may move relative to a fixed axis. If the motion is called epicyclic and the gear trains arranged in such a manner that one or more of their members move upon and around another member are known as epicyclic gear trains

Velocity Ratioz of Epicyclic Gear TrainThe following two methods may be used for finding out the velocity ratio of an epicyclic gear train.Tabular method, and Algebraic method.

Compound Epicyclic Gear TrainSun and Planet Gear

Gear Terminology Diametral pitch Module Circular pitch Gear ratio Pressure line Pressure angle Pitch angle Contact ratio Path of approach Path of recess Path of contact Arc of recess Arc of contact Angle of action Pitch circle Addendum circle Dedendum circle Clearance Backlash Full depth Face width

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