2. GEAR
• A gear or cogwheel is a rotating machine element
having toothed wheel which mesh with another
toothed wheel to transmit torque.
3. HISTORY OF GEAR
• Gears were already in use in 350 B.C. (about
2,300 years ago. One of Greek philosopher
Aristotle's writings includes a description about
a gear.
• An Italian mathematician, Leonardo da Vinci
is credited with developing the idea of the
chain and cog in the 15th century.
4.
5. TYPES OF GEARS
1. According to the position of axes of the shafts.
a. Parallel
1.Spur Gear
2.Helical Gear
3.Rack and Pinion
b. Intersecting
Bevel Gear
c. Non-intersecting and Non-parallel
worm and worm gears
7. EXTERNAL SPUR GEAR
Toothed profile on the outer surface mating
cylindrical wheels,is parallel to the axis of rotation,
transmits motion or torque between parallel shafts.
8. INTERNAL SPUR GEAR
• Internal gear is a gear with its teeth cut in
the internal surface of a cylinder and transmits motion
or torque between parallel shafts.
9. ADVANTAGES AND DISADVANTAGES
ADVANTAGES
• High power transmission efficiency.
• Constant velocity ratio.
• Reliability.
DISADVANTAGES
• Limited centre distance.
• Noise
• stress
10. APPLICATION
• Metal cutting machines
• Power plants
• Marine engines
• Mechanical clocks and watches
• Fuel pumps
• Washing Machines
• Gear motors and gear pumps
• Rack and pinion mechanisms
11. HELICAL GEAR
• Teeth are inclined to the axis of rotation, the angle
provides more gradual engagement of the teeth
during meshing
• Are used in transmitting torques between parallel or
non parallel shafts, they are not as noisy as spur
gears.
12. ADVANTAGES AND
DISADVANTAGES
• Helical gears are preferred for heavy load
applications and noise produced is less.
• power transmission between two parallel shafts
and also between two non parallel shafts.
• The helical gear efficiency is lower due to the
contact between its teeth, which produces axial
thrust and generates heat. A greater loss of energy
reduces efficiency.
• Higher manufacturing cost than spur gears.
13. APPLICATION
• Helical gears find application in transmitting high
load or power in case of necessary.
• Lathe machine.
• Automobile.
• Aerospace industries.
14. RACK AND PINION
• The rack and pinion that comprises a pair of gears
which convert rotational motion into linear motion.
15. ADVANTAGES,DISADVANTAGES
AND APPLICATION
• Cheap.
• Easiest way to convert rotation motion into linear
motion.
• Rack and pinion gives easier and more compact
control over the vehicle.
• Find application power steering , tie rod etc.
16. BEVEL GEAR
• Shafts of the gear and pinion can intersect at 90°or
any desired angle and Changes the direction of
rotation.
17. ADVANTAGES AND
DISADVANTAGES
• Bevel gear efficiency is quite enough; bevel
gear may provide efficiency up to 90 % .
• Manufacturing costing will be less.
• Sliding friction will also be lower in bevel
gearing mechanism.
• Bevel gears should be assembled with respective
shaft precisely.
• At high speed, such gearing mechanism will
produce noise.
19. WORM AND WORM GEARS
• Worm gear is one type of gear device in which the
two shafts are at a right angle to each other and non-
intersecting.
• worm and worm gear used for Large speed reduction
in a small space.
20. ADVANTAGES AND
DISADVANTAGES
• Higher speed reduction could be secured; speed
reduction could be secured up to 300: 1
• Worm and worm gears operate silently.
• Manufacturing cost is heavy as compared with
manufacturing cost of bevel gear.
• Cost of raw material to manufacture the worm and
worm gear set will be quite high.
• Worm and worm gear set will have heavy power
losses.
• Efficiency will be low.
22. BASIC FORMULAS
• gear ratio = rotations of driver/ gear rotations of
driven gear
(Or) teeth of driven gear/ teeth of driver gear.
• Work Done = Force x Distance moved in the
direction of the force.
• Power = total work done /total time taken.
• efficiency = power output/power input*100.
