GEAR
Gear is the positive drive which transmits exact velocity ratio from one shaft to another shaft.
1.PARALLEL GEARS
In this, axis of both gears are parallel.
i) Spur Gear
ii) Helical Gear
iii) Rack and Pinion Gear
i) Spur Gear
*For this gears, teeth are parallel to the axis of the shaft.
*These are used in high speed and high load application.
ii) Helical Gear
*In these gears, teeth are at some angle (called helix angle α) with respect to the axis of the shaft.
*In helical gears contact between teeth gradual which produce less noise. It is preferred for high speed transmission.
iii) Rack and Pinion Gear
*In these gears, teeth are parallel to axis of the shaft but one gear has infinite diameter called rack.
*It is used to transmit the rotary motion into reciprocating motion.
2. BEVEL GEARS
*When axis of both gears are intersecting to each other and angle between them is 90° then these gears are called "Bevel Gears".
i) Straight Bevel Gear
ii) Spiral Bevel Gear
iii) Hypoid Bevel Gear
i) Straight Bevel Gear
In these gears teeth are formed straight on the cones and they are parallel to axis of the gear.
ii) Spiral Bevel Gear
In these gears, teeth are formed at an angle with respect to its axis
iii) Hypoid Bevel Gear
Axis of these gears are at 90° but they do not intersect with each other.
3. SPIRAL GEAR
It has high helix angle, these are used for light load and low speed applications.
4. Worm and Worm Wheel Gear
*Their axes are non-intersecting and normally at right angles to each other.
*It provides large speed reduction. Ex: Speed reduces 100:1.
