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A gear is a mechanical system composed of two or more toothed wheels for the transmission of the rotational movement.

A gear is composed of a pinion (so called the only wheel or the smallest wheel) and a wheel, a rack or a crown. When there are more than two toothed wheels, it is called a gear train.


Gear with parallel axes

Gear whose axes are parallel.


Concurrent gear

Gear whose axes have a point of intersection, the conical pinions


Left Gear

Gear whose axes are neither parallel nor concurrent, the gears wheels and worms.

Pressure angle

(Α) It is generally 20 ° but it also exists at 14 ° 30, 30 ° ...

Propeller angle

(ß) Angle of inclination of a helical gear. It may be right or left.

The helix angle will vary the Ø d and the diameters Ø da and df.



Ø primitive: d = m * z

Head Ø: da = d + 2 * m

Ø of foot df = d-2.5 * m

Pitch of the teeth: p = π * m.   



Name of the smallest wheel or wheel.


Gear Train

We speak of a gear train when there



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