Gears

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Contents

Types of Gears

Spur Gears Rack and Pinion Bevel Gears Helical Gears Worm Drives
Spur gears.png
Rack and pinion.png
Bevel gears.png
Helical gears.png
Worm drive.png

Specialty Gears

Harmonic Drive Gear
Harmonic gears.jpg

Gear Geometry

For external spur gears (most common), the gear geometry is as shown in the figure below. The line of action is the line that passes through the intersection of the pitch circles and also tangent to the base circles.

Gear circle geometry.png

Gear Meshing and Forces

Gear meshing results in contacts with normals along the line of action, so the resultant force, W is along this line. This results in both tangential and radial forces, Wt and Wr, on the gear pair. When these gears are mounted on a shaft, the radial force causes a bending moment while the tangent force causes both a bending moment and a torque.

Gear triangles.png


References

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