First presentation my class fellow

1. Gear
Talha Rehman
5520
Teacher
Adeel SB

2. Why should I be a mechanical
engineer
• I get the opportunity to create
something useful.
• My creations will be used by others.
• It gives me the greatest joy.
• Its the broadest branch of engineering…so my
career options are open even after my
graduate.

3. Questions of My topic
1. What is Gear
2. Function of Gear
3. Uses of Gear in different devices
4. History of Gear
5. How gear uses
6. Types of gears
7. Names of Applications of Gear

4. What is Gear?
• A gear or cogwheel is a rotating machine part
having cut teeth, or cogs, which mesh with
another toothed part to transmit torque.
Geared devices can change the speed, torque,
and direction of a power source. Gears almost
always produce a change in torque, creating a
mechanical advantage, through their gear
ratio, and thus may be considered a simple
machine.

5. Function of Gear
• When two gears mesh, if one gear is bigger
than the other, a mechanical advantage is
produced, with the rotational speeds, and the
torques, of the two gears differing in
proportion to their diameters.

6. Uses of Gear in different
devices
• In transmissions with multiple gear ratios such
as bicycles, motorcycles, and cars the term
"gear" as in "first gear" refers to a gear ratio
rather than an actual physical gear.

7. History of Gear
• Early examples of gears date from the 4th century BC in China (Zhan Guo times -
Late East Zhou dynasty), which have been preserved at the Luoyang Museum of
Henan Province, China. The earliest gears in Europe were circa AD 50 by Hero of
Alexandria, but they can be traced back to the Greek mechanics of the Alexandrian
school in the 3rd century BC and were greatly developed by the
Greek polymath Archimedes (287–212 BC).
• Examples of further development include:
• Ma Jun (c. 200–265 AD) used gears as part of a south-pointing chariot.
• The Antikythera mechanism is an example of a very early and intricate geared
device, designed to calculate astronomicalpositions. Its time of construction is now
estimated between 150 and 100 BC.
• The water-powered grain-mill, the water-powered saw mill, fulling mill, and other
applications of watermill often used gears.
• The first mechanical clocks were built in AD 725.
• The 1386 Salisbury cathedral clock may be the world's oldest working mechanical
clock.

8. How gear uses
• To reverse the direction of rotation
• To increase or decrease the speed of rotation
• To move rotational motion to a different axis
• To keep the rotation of two axis synchronized

9. Types of gears
• External vs internal gear
• Spur gear
• Helical gear
• Double helical gear
• Bevel gear

10. • Spiral bevels
• Hypoid
• Crown gear
• Worm gear
• 4-start worm and wheel
• Non-circular gears

11. • Rack and pinion gearing
• Epicyclic gearing
• Sun (yellow) and planet (red) gearing
• Harmonic gearing
• Cage gear in Pantigo Windmill, Long Island
(with the driving gearwheel disengaged)