## Introduction to gears

 A gear can be thought of in a couple of ways. First, it is a specialised wheel with teeth around it that can mesh with another similar gear.Second, it can be seen as a lever, providing either a speed or force advantage. Here are three ways a load, force and fulcrum can be arranged to amplify force or amplify the speed of rotation. Torque is the strength of of the force over the length it operates in a rotation.. It is it can be thought of as the twist of a force.

## Classification of Gears

 Classification of gears can be done according to the relative position of the axes of revolution into three types. They are: Gears for Parallel shafts 1.1 Spur Gears1.2 Helical Gears1.3 Herringbone Gears1.4 Rack and Pinion Gears for Intersecting Shafts 2.1 Straight Bevel Gears2.2 Spiral Bevel Gears Gears for Skew Shafts 3.1 Hypoid Gears3.2 Worm Gears Linkages 4.1 Cams

## Parallel gears : the spur gear

 The motion between parallel shafts is same as to the rolling of two cylinders. Straight Spur gears are the simplest form of gears having teeth parallel to the gear axis. The contact of two teeth takes place over the entire width along a line parallel to the axes of rotation. As gear rotate , the line of contact goes on shifting parallel to the shaft.

## Parallel gears : helical gears

 In helical gear teeth are part of helix instead of straight across the gear parallel to the axis. The mating gears will have same helix angle but in opposite direction for proper mating. As the gear rotates, the contact shifts along the line of contact in in volute helicoid across the teeth.

## Herringbone gears

 Herringbone gears are also known as Double Helical Gears. Herringbone gears are made of two helical gears with opposite helix angles, which can be up to 45 degrees.

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