Bevel Gears

Presented By:

Shahid Mehmood UW-12-ME-BE-007

GEAR…..

Power transmission is the movement of energy from its place of generation to a location where it is applied to performing useful work

A gear is a component within a transmission device that transmits rotational force to another gear or device

Involute tooth profile

TYPES OF GEARS

1. According to the position of axes of the shafts.a. Parallel

1.Spur Gear2.Helical Gear3.Rack and Pinion

b. IntersectingBevel Gear

c. Non-intersecting and Non-parallelworm and worm gears

Bevel Gears

A bevel gear is shaped like a right circular cone with most of its tip cut off.

When two bevel gears mesh, their imaginary vertices must occupy the same point.

Their shaft axes also intersect at this point, forming an arbitrary non-straight angle between the shafts.

Bevel Gears

Bevel gears are primarily used to transfer power between intersecting shafts, where the axis of rotation of two shafts are at 90 degrees to each other.

The teeth of these gears are formed on a conical surface.

Bevel Gears Nomenclature

Driving and driven gear

The driving gear is attached to the source of power, usually a motor

The driven gear is being rotated by the driving gear

Speed vs. Torque

Speed is the magnitude of an objects velocity, or the rate of change of its position

Torque is the tendency of a force to rotate an object about an axis Just as a force is a push or a pull, a torque

can be thought of as a twist

The gear ratio can be thought as a multiplier on torque and a divider on speed or vise versa

To gain torque you must give up speed To gain speed you must give up torque

Gear ratio

Gear Ratio

The gear ratio is the relationship between the number of teeth on two gears that are meshed

To calculate the gear ratio, you count the number of teeth on the driven gear, divide that number by the number of teeth on the driving gear

Number of teeth on driven gearNumber of teeth on driving gearGear ratio =

Gear Ratio

The gear ratio of a bevel gear system is calculated in the same way as for a simple gear train.

Gear ratio = Number of Driver Gear Teeth

Number of Driven Gear Teeth

Ratio =100

60= 1.6:1˙

Big or small ratio?

If a motor needs to lift a heavy object you will need to increase torque Increase the torque with a large gear ratio

Small gear driving a larger gear

If you need to increase the speed of a motor Increase the speed with a small gear ratio

Big gear driving a smaller gear

Bevel Gears cutting

METHODS:form milling – using a cutter and creating first one, than the opposite face flank of the toothinvolute-generating milling– using two cutters representing one tooth of a rack and a generating process for creating a tooth profileshaping – using a shaping rack tool and a generating process for creating a tooth profilebroaching – using rotational broach

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Straight bevel gears involute-generating milling

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Straight bevel gears - shaping

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Straight bevel gears - broaching

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Curved bevel gears - Oerlikon

Types of BEVEL GEARS

Types of Bevel Gears

There are THREE types of bevel gears.

Straight Cut

Curved (spiral)

Hypoid

Straight Cut Bevel Gears

Standard bevel gears have teeth that are cut straight. The teeth point toward the apex of the cone on which they are machined.

Apex of the cone

Spiral Bevel Gears

Spiral bevel gears have teeth that have been cut on a curve.

Hypoid Bevel Gears

Hypoid bevel gears are a special type of spiral gear that will allow non-intersecting, non-parallel shafts to mesh.

Intersecting shafts Parallel shafts

Hypoid gears are stronger, operate more quietly, and can be used for higher reduction ratios than spiral bevel gears.

Application

Standard bevel gears are mainly used in low speed (less than 500 rpm) applications. At high speeds they become noisy. They are typically used in applications such as hand drills.

Applications

Spiral bevel gears are typically used for high speed (greater than 500 rpm) and performance applications, where low noise and vibration levels are important. They are typically used in transmission systems.

Applications

Hypoid bevel gears are also used in high performance applications, but are more expensive to produce. They are typically used in transmission systems.

Applications

Moreover Bevel Gears are used for locomotives, marine applications, automobiles, printing presses, cooling towers, power plants, steel plants, railway track inspection machines, etc.

Bevel Gears used in car Differential