1. UNIT III GEARS AND GEAR TRAINS

2. 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

3. DEFINE GEAR
A circular body of cylindrical shape or that of the shape of frustum of a cone and of uniform small width, having teeth of uniform formation, provided on its outer circumferential surface is called a gear or Toothed gear or Toothed wheel.

4. Advantages
It transmits exact velocity ratio.
It may be used to transmit large power.
It has high efficiency.
It has reliable service.
It has compact layout.
Disadvantages
The manufacture of gears require special tools and equipment.
The error in cutting teeth may cause vibrations and noise during operation.

5. SPUR GEAR
External and Internal spur Gear…

6. (c) Bevel gear (d) Spiral gear
(a) Single helical gear. (b) Double helical gear.
(c) Bevel gear
(d) Spiral gear

7. 2.According to the peripheral velocity of the gears
Low velocity
Medium velocity and
High velocity
3.According to the type of gearing
External gearing
Internal gearing and
Rack and pinion
4. According to position of teeth on the gear surface
Straight
Inclined and
curved.

8. External gearing
Internal gearing
Rack and pinion
Internal gears
Rack and pinion

9. SPUR GEAR

10. NOMENCLATURE OF SPUR GEARS