Gears :-
In order to transmit a definite power from one shaft to another shaft ,the projections on one disc and recesses on another disc can be made which can mesh with each other . this leads to the formation of teeth on both discs and the discs with teeth on their periphery are called "gears".
Advantage of Gear Drive
1. Gear drive is a positive drive . transmit exact velocity ratio from one shaft to another shaft.
2. It can transmit very large power.
3. Gear drive give high transmission efficiency.
4. Its required very less space.
5. It is very reliable.
Disadvantage of Gear Drive
1. Manufacturing cost of gear is high, special machine and tools are required to manufacturing the gear so very large cost are required to made gear.
2. Lubrication are required as maintenance so maintenance cost also very high.
3. Error are comes in the teeth of gear on overdrive then it produced noise and vibration.
Classification of Gears.
Gears are classified on the following basis.
1. According to position of shaft axes :-
According to position of shaft axes following position are required
a. Parallel shaft.
1. Spur gears :- spur gears are used when the axis of two shafts are parallel to each other. These gears have teeth parallel to the axis of the shaft.
2. Helical gears :- in helical gears teeth are made in some angle which are called helix angle.
3. Rack and pinion :- A rack and pinion is a special case of spur gear in which one gear is having indefinite diameter called rack.
b. Intersecting shaft.
1. Straight bevel gears
2. Spiral bevel gears
c. Non parallel and non intersecting shaft.
1. Spiral gears
2. Worm and worm wheel
2. According to the periphery velocity of the gears.
a. Low velocity gears:-
The gear having periphery velocity less than 3 m/sec.
b. Medium velocity gears :-
The gears having periphery velocity 3 to 15 m/sec.
c. High velocity gears :-
The gears having periphery velocity more than 15 m/sec.
3. According to types of meshing of gears.
a. Externally meshing gears or external gear.
b. Internally meshing gears or internal gears.
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