Basic of Gears

8/2/2019 Basic of Gears

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Basic of Gear

K.P.Gowrishankar.

Gear

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Gear

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http://upload.wikimedia.org/wikipedia/commons/1/14/Gears_animation.gif


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-What is Gear?

-What is Gear box?

-Types of Gear

-Nomenclature of gears

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-A round or cylindrical mechanical component with teeth,used totransmit power.

-Gears are designed to mesh with one another and can alterthe speed, torque, or direction of mechanical energy.

What is the definition of gear ?

Gear

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Gear

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http://images.google.co.in/imgres?imgurl=http://static.howstuffworks.com/gif/gear-bevel2.jpg&imgrefurl=http://science.howstuffworks.com/gear4.htm&usg=__L0gMfxtwhFRwCIeMjkozEDDaS6Y=&h=368&w=400&sz=16&hl=en&start=13&um=1&tbnid=v5oc7KxTMfg_3M:&tbnh=114&tbnw=124&prev=/images%3Fq%3Dgear%2Bphotos%26hl%3Den%26rlz%3D1R2ADRA_enBE334%26sa%3DX%26um%3D1http://images.google.co.in/imgres?imgurl=http://static.howstuffworks.com/gif/gear-bevel.jpg&imgrefurl=http://science.howstuffworks.com/gear4.htm&usg=__rs4_W-lBc1YAJ_uqfCMLeI2uhAE=&h=343&w=400&sz=14&hl=en&start=3&um=1&tbnid=U6Glea_0nkbGaM:&tbnh=106&tbnw=124&prev=/images%3Fq%3Dgear%2Bphotos%26hl%3Den%26rlz%3D1R2ADRA_enBE334%26sa%3DX%26um%3D1


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What is the definition of gearbox?-A gearbox can also change the speed, direction, or torqueof mechanical energy.

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Gear types:-

-SPUR GEAR,

-RACK AND PINION,

-INTERNAL RING GEAR,

-HELICAL GEAR,

-DOUBLE HELICAL GEAR,

Gear

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Gear types:-

-FACE GEAR,

-WORM GEAR,

-HYPOID GEAR,

-STRAIGHT BEVEL GEAR &

-SPIRAL BEVEL GEAR,

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SPUR GEAR:-

Spur gears are the most common type used. Some noise isnormal.

Gear

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http://www.google.co.in/imgres?imgurl=http://www.precisiongears.com/images/spur_gear.jpg&imgrefurl=http://www.precisiongears.com/spur_gears.php&h=347&w=318&sz=56&tbnid=jMu21Vhy4eKCjM:&tbnh=120&tbnw=110&prev=/images%3Fq%3Dgears&hl=en&usg=__xxgDGgb6jzckAsDZP6c35cXN030=&ei=BqKXStmAFcft-AaFk_zCBA&sa=X&oi=image_result&resnum=1&ct=image


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RACK AND PINION:-Rack and pinion gears are essentially a linear shapedvariation of spur gear.
http://upload.wikimedia.org/wikipedia/commons/6/68/Rack_and_pinion_animation.gif


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Internal ring gear:-

Internal gear is a cylindrical shaped gear with the meshingteeth inside or outside a circular ring .Internal ring gearsmay be used within a planetary gear arrangement.

Gear

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http://upload.wikimedia.org/wikipedia/commons/0/06/Inside_gear.png


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Helical gear:-Helical gear is a cylindrical shaped gear with helicoidteeth.Helicalgears operate with less noise and vibrationthan spur gear.At any time,the load on helical gears isdistributed over several teeth,resulting in reduce wear.

They are widely used in industry.

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Gear

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http://upload.wikimedia.org/wikipedia/commons/d/d1/Helical_Gears.jpghttp://upload.wikimedia.org/wikipedia/commons/d/d1/Helical_Gears.jpghttp://upload.wikimedia.org/wikipedia/commons/d/d1/Helical_Gears.jpg


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Double Helical Gear:-

Double Helical gear may have both left-hand & Right handhelical teeth.

Gear

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http://en.wikipedia.org/wiki/File:Worm_hand.jpg


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Face Gear:-

Face gears are a circular disk with a ring of teeth cut on oneside.

Gear

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http://upload.wikimedia.org/wikipedia/commons/0/06/Inside_gear.png


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Straight bevel gear:-Straight bevel gears have tapered conical teeth which

intersect the same tooth geometry. Bevel gears are usedto transmit motion between shaft with intersecting centerlines.

Gear

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http://upload.wikimedia.org/wikipedia/commons/1/16/Bevel_gear.jpg


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Hypoid gear:-

Hypoid gears are typically found within the differential of

automobiles. Hypoid gears are similar to spiral bevel gears

expect that the shaft center lines do not intersect.

Gear

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Gear

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http://www.google.co.in/imgres?imgurl=http://school.mech.uwa.edu.au/~dwright/DANotes/gears/intro/hypoid.jpeg&imgrefurl=http://school.mech.uwa.edu.au/~dwright/DANotes/gears/intro/intro.html&h=201&w=180&sz=6&tbnid=Z0r1OE06_h0gVM:&tbnh=104&tbnw=93&prev=/images%3Fq%3DHypoid%2Bgears&hl=en&usg=__GxlCY_s63pNJQT5nCUKu_qQJ1yg=&ei=uqOXSry1G8L4-AaB2PXRBA&sa=X&oi=image_result&resnum=6&ct=imagehttp://www.google.co.in/imgres?imgurl=http://www.zakgear.com/Zak_hypoid_1.jpg&imgrefurl=http://www.zakgear.com/Hypoid_worm.html&h=602&w=800&sz=87&tbnid=wLfKIBkrJ-01UM:&tbnh=108&tbnw=143&prev=/images%3Fq%3DHypoid%2Bgears&hl=en&usg=__UghhQpxZKjVQKtrBIg9XR9xtEYk=&ei=uqOXSry1G8L4-AaB2PXRBA&sa=X&oi=image_result&resnum=4&ct=image


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Spiral Bevel gear:-Spiral bevel gears have a helical angle spiral teeth.

Gear

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Gear

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http://www.google.co.in/imgres?imgurl=http://static.howstuffworks.com/gif/gear-bevel2.jpg&imgrefurl=http://science.howstuffworks.com/gear4.htm&h=368&w=400&sz=16&tbnid=v5oc7KxTMfg_3M:&tbnh=114&tbnw=124&prev=/images%3Fq%3DSpiral%2BBevel%2Bgear&hl=en&usg=__xsSEcwLr6wcDHyoa3pcOb5RjhzU=&ei=PaSXSoz7KJGD-Qaj7ajjBA&sa=X&oi=image_result&resnum=2&ct=image


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Sun and planet gear

Gear

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http://upload.wikimedia.org/wikipedia/commons/d/d4/Sun_and_planet_gears.gif


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Epicyclic gearing

Gear

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Gear

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http://upload.wikimedia.org/wikipedia/commons/d/d5/Epicyclic_gear_ratios.png


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Nomenclature

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Gear or wheel.

Pinion.

Axis.

Pitch point (p).

Pitch circle.

Pitch diameter (D).

Module (m).

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Pressure angle ().Outside diameter (Do).

Root diameter.

Addendum (a).

Dedendum (b).

Whole depth (ht).

Clearance.

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Working depth.Circular pitch (p).

Base circle.

Interference.

Lead.

Linear pitch (p).

Lead angle ( ).

Pitch diameter (Dw).

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Gear or wheel.The larger of two interacting gears

Pinion. The smaller gear in a pair.

Axis. The axis of revolution of the gear; center line of the

shaft.

Pitch point (p). The point where the line of action crosses

a line joining the two gear axes.Pitch diameter (D). Diameter of a pitch circle. Equal totwice the perpendicular distance from the axis to the pitchpoint.

Module (m). The module of a gear is equal to the pitch

diameter divided by the number of teeth.

Outside diameter (Do). Diameter of the gear, measured

from the tops of the teeth.

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Root diameter. Diameter of the gear, measured from thebase of the tooth space.

Addendum (a). The radial distance from the pitch surface

to the outermost point of the tooth. a = (Do - D) / 2.

Dedendum (b). The radial distance from the depth of thetooth trough to the pitch surface.

b = (D - root diameter) / 2.Whole depth (ht). Whole depth (tooth depth) is the totaldepth of a tooth space, equal to addendum plusdedendum, also equal to working depth plus clearance

Clearance. Clearance is the distance between the rootcircle of a gear and the addendum circle of its mate

Working depth. Working depth is the depth ofengagement of two gears, that is, the sum of their

operating addendums.

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Lead. The distance from any point on a thread to thecorresponding point on the next turn of the same thread,measured parallel to the axis.

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Point of contact :-A point of contact is any pointat which two tooth profiles touch each other

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http://upload.wikimedia.org/wikipedia/commons/b/b1/Action_path.jpg


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Line ofcontact

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http://upload.wikimedia.org/wikipedia/en/d/d1/Contact_line.jpghttp://upload.wikimedia.org/wikipedia/en/d/d1/Contact_line.jpg


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Contact ratio:- it can be defined as a measure ofthe average number of teeth in contact during the period

in which a tooth comes and goes out of contact with themating gear.

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http://upload.wikimedia.org/wikipedia/commons/9/92/Action_arc.jpg


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Backlash :-clearance between mating components inreversible mechanical couplings

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http://upload.wikimedia.org/wikipedia/en/2/2e/Backlash.jpg


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Tooth profile :-A profile is one side of a tooth ina cross section between the outside circle and the root

circle.

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http://upload.wikimedia.org/wikipedia/en/7/75/Tooth_surface.jpg


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Pitch:-Pitch is the distance between a point on onetooth and the corresponding point on an adjacent tooth

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http://upload.wikimedia.org/wikipedia/en/1/1e/Pitches.jpg


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Circular pitch, p:-Circular pitch is the arc distancepitch circle or pitch line between corresponding profiles of adjacent

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http://upload.wikimedia.org/wikipedia/en/1/1e/Pitches.jpg


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Gear materials:-Numerous nonferrous alloys,cast irons, powder-metallurgy and even plastics are usedin themanufacture of gears.However steels are most

commonly used because of their high strength to weightratio and low cost.

Gear

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Gear

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http://www.google.co.in/imgres?imgurl=http://www.precisiongears.com/images/spur_gear.jpg&imgrefurl=http://www.precisiongears.com/spur_gears.php&h=347&w=318&sz=56&tbnid=jMu21Vhy4eKCjM:&tbnh=120&tbnw=110&prev=/images%3Fq%3Dgears&hl=en&usg=__xxgDGgb6jzckAsDZP6c35cXN030=&ei=BqKXStmAFcft-AaFk_zCBA&sa=X&oi=image_result&resnum=1&ct=image


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Measurement over pins:-Measurement over pins ismeasurement of the distance taken over a pinpositioned in a tooth space and a reference surface.

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http://upload.wikimedia.org/wikipedia/en/9/90/Pin_measurement.jpg


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Span measurement:-Span measurement is themeasurement of the distance across several teeth in a normal plan

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http://upload.wikimedia.org/wikipedia/en/7/7b/Span_measurement.jpg


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Basic of Gears

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