Spur Gear(Treb)

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    Prepared by:

    Roberto Reblora

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    Spur gear or straight- cut gears are thesimplest type of gear. They consist of acylinder or disk with the teeth projectingradially, and although they are not straight-sided in form (they are usually of special formto achieve constant drive ratio, mainlyinvolute, the edge of each tooth is straightand aligned parallel to the axis of rotation.

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    In general, spur gears are round metal disks

    with teeth cut around the circumference. In order

    for the gear to qualify as a spur gear, the teeth

    must be cut so that they run perpendicular to thegear's face. Spur gears are the simplest design

    of gear produced. They are usually used for the

    transmission of rotary force. For instance, if two

    shafts are parallel to one another, and one isspinning, a spur gear can help to transfer that

    force onto the other shaft. Spur gears usually

    have an operating efficiency of 98% to 99%.

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    Anti-Backlash Spur GearsAntibacklash spur gears, as their name suggests,

    have little to no backlash, and so are used in high-precision applications. Often, these spur gears are builtwith springs for proper tensoring. They are usually built

    from brass, aluminum or stainless steel. In order forantibacklash spur gears to work together, they musthave the same diametral pitch and pressure angle.

    Cluster Spur Gears

    Cluster spur gears come "clustered" together,usually on the same shaft, and have varying diameters.

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    Spur Gear Blanks

    Spur gear blanks are spur gears with no teeth cut into them. These

    types of spur gears can be useful if you do not yet know the precise number of

    teeth you will require for your spur gear's application.

    Pinion ShaftsPinion shafts are basically stretched-out spur gears, cylinders with

    teeth running for their entire length.

    Ratchets and Pawls

    Ratchets and pawls are two spur gears that work together. Ratchetsare gear wheels with teeth, while pawls are spring-loaded and pivot. Pawls are

    usually slanted. Together, these gears allow for unidirectional movement.

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    Clamp Hub Spur GearsClamp hub spur gears are named for the manner in which

    they connect to their shaft, that is, with a clamp at the spur gear'scenter.

    Hubless Spur GearsHubless spur gears have no hub and instead connect to

    their shafts through friction or with adhesive.

    Pin Hub Spur GearsPin hub spur gears connect to their shaft through the use of

    a removable pin as opposed to a clamp.

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    Pitch circle- theoretical circle on which allcalculations are based. The diameter of thepitch circle is the pitch diameter.

    Circular pitch- length of the arc of the pitchcircle between the centers or othercorresponding points of adjacent.

    p =

    The term above in the equation is thecircumference of pitch circle and N no. of teeth.

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    Pitch circle- theoretical circle on which allcalculations are based. The diameter of thepitch circle is the pitch diameter.

    Circular pitch- length of the arc of the pitchcircle between the centers or othercorresponding points of adjacent.

    p =

    The term above in the equation is thecircumference of pitch circle and N no. of teeth.

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    Diametral pitch (P)- the ratio of the numberof teeth to the number of millimeters of pitchdiameter.

    P=

    Clearance- the clearance prevents the teeth

    of one gear from riding into bottom part ofmating gear.

    Clearance circle- this circle is tangent to theaddendum circle of the mating gear.

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    Face width (b)- the face width should be thesame for all mating gears. Typically:

    9

    13

    Whole depth (h)- this can be defined in twoways:

    = d

    =

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    Tooth thickness (t)- the tooth thicknessmeasured at the pitch circle is equal to thewidth space.

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    Pinion- is the smaller of the two matinggears.

    T1N1 = T2N2

    D1N1= D2N2

    C =+2

    2

    Speed Ratio =

    2

    Gear Ratio = 2

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    where:T1 = no. of teeth of the driver (pinion)

    D1= diameter of driver (pinion)

    N1= speed of driver (pinion)T2 = no. of teeth of the driven gear

    D2= diameter of driven gear

    N2= speed of driven

    C = center distance

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    Advantages Spur gears have high power transmission efficiency.

    They are compact and easy to install.

    They offer constant velocity ratio.

    Unlike belt drives, spur geardrives have no slip. Spur gears are highly reliable.

    They can be used to transmit large amount ofpower (of the order of 50,000 kW).

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    Disadvantages Spur gear drives are costly when compared to belt

    drives.

    They have a limited center distance. This is because in aspur gear drive, the gears should be meshed and theyshould be in direct contact with each other.

    Spur gears produce a lot of noise when operating at highspeeds.

    They cannot be used for long distance power

    transmission. Gear teeth experience a large amount of stress.

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    ApplicationsSpur gears have a wide range of applications. They are used in:

    Metal cutting machines Power plants Marine engines Mechanical clocks and watches

    Fuel pumps Washing Machines Gear motors and gear pumps Rack and pinion mechanisms Material handling equipment Automobilegear boxes Steel mills Rolling mills

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