# Gear and its types

Gear is a toothed wheel to transmit power from one shaft to another shaft with exact velocity ratio without slip and power loss.

Gear Train:

if the two or more number of gears are used to transmit power, then the arrangement is called as gear train.

Types of Gears:

1.Parallel shaft gears

In this type, the axis of meshing gears are parallel.

• Spur gear: Teeth are parallel to the axis of shaft. It is used in high speed and high load application.
• Helical gear: Teeth are inclined at an angle to the axis of shaft. It is used in smooth high speed applications.
• Rack and pinion:Teeth are parallel to the axis of shaft but one gear has infinite diameter i.e rack. It is used to convert the rotary motion into reciprocating motion and vice versa.

2.Intersecting shaft gears

Bevel gear: In this type, axis of meshing gears are right angle to each other i.e the angle between two axis is 90 degree, hence both gears are intersecting to each other.

• Straight bevel: Teeth are formed on the cones parallel to axis of gear.
• Spiral bevel: Teeth are formed on the cones at an angle to axis of gear.
• Hypoid bevel: Axis are at an angle of 90 degree but they don’t intersect each other.

3.Non parallel non intersecting shaft gears

In  this type, the shafts are not parallel and also don’t intersect each other.

• Spiral gear: The helical gear with high helix angle.
• Worm gear: The axis of gears are non intersecting  and non parallel, i.e there is a gear with tooth meshing with thread on cylindrical bar. It is used for getting high and less speed ratio, in this type even 200:1 0r 1:200 is possible. It means that we can convert 1 revolution of one large diameter gear into 200 revolution of one small diameter gear and vice versa.