Unit 1 Spur gear Gear Gear can be
![Unit 1 Spur gear Unit 1 Spur gear](https://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-1.jpg)
Unit 1 Spur gear
![Gear • Gear can be defined as mechanical element used for transmitting power & Gear • Gear can be defined as mechanical element used for transmitting power &](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-2.jpg)
Gear • Gear can be defined as mechanical element used for transmitting power & rotary motion from one shaft to another by means of progressive engagement of projection called teeth. • Small pair is called pinion & larger is called gear.
![Classification of gear Gear Parallel axis gear Spur gear Intersecting axis gear Helical gear Classification of gear Gear Parallel axis gear Spur gear Intersecting axis gear Helical gear](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-3.jpg)
Classification of gear Gear Parallel axis gear Spur gear Intersecting axis gear Helical gear Non-intersecting & perpendicular axes gear Non-intersecting & non parallel axes gear Herringbone gear Bevel Gear Worm Gear Crossed helical Gear
![Spur Gear Teeth are cut parallel to the axis of gear Helical Gear Teeth Spur Gear Teeth are cut parallel to the axis of gear Helical Gear Teeth](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-4.jpg)
Spur Gear Teeth are cut parallel to the axis of gear Helical Gear Teeth are cut at an angle known as helix angle with the axis of the gear
![Double helical gear (herringbone gear) • herringbone gear consist of identical helical gear but Double helical gear (herringbone gear) • herringbone gear consist of identical helical gear but](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-5.jpg)
Double helical gear (herringbone gear) • herringbone gear consist of identical helical gear but at opposite hand cut on the same blank with small groove between the two to facilitate the gear generation. • For axial thrust on shaft & bearing this gear is used.
![Intersecting Axes Gear Bevel Gear • Two intersecting axes shaft are connected by gears Intersecting Axes Gear Bevel Gear • Two intersecting axes shaft are connected by gears](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-6.jpg)
Intersecting Axes Gear Bevel Gear • Two intersecting axes shaft are connected by gears known as bevel gear • Bevel gear are made up of shaft angle 900.
![Non intersecting & perpendicular axes gear • Worm gear- two Non intersecting & perpendicular Non intersecting & perpendicular axes gear • Worm gear- two Non intersecting & perpendicular](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-7.jpg)
Non intersecting & perpendicular axes gear • Worm gear- two Non intersecting & perpendicular axes shafts are connected by worm gears. it consist of worm & worm wheel.
![Non intersecting & non parallel axes gear (crossed helical gears) • Non intersecting & Non intersecting & non parallel axes gear (crossed helical gears) • Non intersecting &](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-8.jpg)
Non intersecting & non parallel axes gear (crossed helical gears) • Non intersecting & non parallel axes shaft are connected by spiral or crossed helical gear
![Spur gear terminology Spur gear terminology](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-9.jpg)
Spur gear terminology
![• Pitch surface : The surface of the imaginary rolling cylinder (cone, etc. • Pitch surface : The surface of the imaginary rolling cylinder (cone, etc.](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-10.jpg)
• Pitch surface : The surface of the imaginary rolling cylinder (cone, etc. ) that the toothed gear may be considered to replace. • Pitch circle: A right section of the pitch surface. • Addendum circle: A circle bounding the ends of the teeth, in a right section of the gear. • Root (or dedendum) circle: The circle bounding the spaces between the teeth, in a right section of the gear. • Addendum (ha): The radial distance between the pitch circle and the addendum circle. • Dedendum(hf): The radial distance between the pitch circle and the root circle. • Clearance: The difference between the dedendum of one gear and the addendum of the mating gear • CL = h f - h a
![• Face of a tooth: That part of the tooth surface lying outside • Face of a tooth: That part of the tooth surface lying outside](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-11.jpg)
• Face of a tooth: That part of the tooth surface lying outside the pitch surface. • Flank of a tooth: The part of the tooth surface lying inside the pitch surface. • Circular thickness (also called the tooth thickness) : The thickness of the tooth measured on the pitch circle. It is the length of an arc and not the length of a straight line. • Tooth space: The distance between adjacent teeth measured on the pitch circle. • Backlash: The difference between the circle thickness of one gear and the tooth space of the mating gear. • Backlash = Space width – Tooth thickness
![](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-12.jpg)
![• Velocity ratio: The ratio of the number of revolutions of the driving • Velocity ratio: The ratio of the number of revolutions of the driving](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-13.jpg)
• Velocity ratio: The ratio of the number of revolutions of the driving (or input) gear to the number of revolutions of the driven (or output) gear, in a unit of time. • Pitch point: The point of tangency of the pitch circles of a pair of mating gears. • Common tangent: The line tangent to the pitch circle at the pitch point. • Base circle : An imaginary circle used in involute gearing to generate the involutes that form the tooth profiles.
![](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-14.jpg)
![Forces analysis of spur gear Forces analysis of spur gear](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-15.jpg)
Forces analysis of spur gear
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![Types of gear tooth failure Gear tooth failure Bending failure Wear failure Pitting failure Types of gear tooth failure Gear tooth failure Bending failure Wear failure Pitting failure](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-20.jpg)
Types of gear tooth failure Gear tooth failure Bending failure Wear failure Pitting failure Initial pitting Destructive pitting Scoring failure Abrasive Wear Corrosive Wear
![Gear material • • • Cast iron Steels Non ferrous metal Sintered metal Non Gear material • • • Cast iron Steels Non ferrous metal Sintered metal Non](http://slidetodoc.com/presentation_image_h2/18e7fac38ce6e9ce357c0d463dafd4ab/image-21.jpg)
Gear material • • • Cast iron Steels Non ferrous metal Sintered metal Non metals
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