Spiral bevel gear
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A spiral bevel gear is a bevel gear with helical teeth. The main application of this is in a motor vehicle differential, where the direction of the drive carried by the propeller shaft (drive shaft) has to be turned through 90 degrees in order to power the driven wheels. The helical design produces less vibration and noise than conventional straight-cut or spur-cut gear with straight teeth.
A right hand spiral bevel gear is one in which the outer half of a tooth is inclined in the clockwise direction from the axial plane through the midpoint of the tooth as viewed by an observer looking at the face of the gear.
A left hand spiral bevel gear is one in which the outer half of a tooth is inclined in the counterclockwise direction from the axial plane through the midpoint of the tooth as viewed by an observer looking at the face of the gear.
A spiral bevel gear and pinion are always of opposite hand, including the case when the gear is internal.
The designations right hand and left hand are applied similarly to spiral bevel gears, zero bevel gears, skew bevel gears, hypoid gears, and oblique tooth face gears.
In hypoid gear design, the pinion and gear are practically always of opposite hand, and the spiral angle of the pinion is usually larger than that of the gear. The hypoid pinion is then larger in diameter than an equivalent bevel pinion.1
[edit] Notes
1. ANSI/AGMA 1012-G05, "Gear Nomenclature, Definition of Terms with Symbols".
