What is Gear: Define, Types, Formulas, Process & Facts

Gears are another important invention. Gears are wheels with teeth. They are simple machines that harness force. Bicycles, non-digital clocks, wind-up toys, and many other machines work with gears. Gear devices can change the speed, torque, and direction of a power source. There are types of gear like a spur, helical, worm gear, rack, and opinion. It observes the gears used almost in all mechanical devices to obtain different torque and speed ratio. The engine is the main power source which produces power from combustion of chemicals like diesel, petrol, CNG, and LPG this power transmitted to driven objects such as wheels, motors, pumps.

Types of gear:

Types of gear

  1. Gear rack: It consists of rectangular or circular rod-shaped gear with mating small gear which changes rotary motion to linear motion.
  2. Screw gear: They are used in offset shaft application. Shape-wise, they are the same as helical gears.
  3. Helical Gear: Quiet and able to transmit larger torque than spur gears. Cylindrical gears with spiral-shaped tooth trace.
  4. Bevel gear: these cone-shaped gears are used in intersecting shaft application there are also bevel gears with spiral-shaped tooth trace called spiral bevel gears.
  5. Internal gear: Gear teeth help in cutting on the inside surface of hollow cylindrical forms and used in planetary gear systems. The gear teeth are cut using gear shaper machines.

The gear module:

The gear module

The module is the unit of size that shows how big or small gear is. It is the reference diameter ratio of the gear divided by the number of teeth. Example: assume that there are two friction pulleys in contact whose diameters are equal to the reference diameters.

The formula for gear module:

The formula for gear module

To obtain the module you need to know the formula:

Module  Circular Pitch MOD = CP 3.1416

Module  Diametral Pitch-MOD = 25.4 DP

Module  Outside Diameter and the Number of Teeth MOD = OD N+2

Pitch Diameter -Module and the Number of Teeth- PD = MOD x N

Gear teeth formula:

Gear teeth formula

Dedendum (d)-Whole Depth and Addendum-d = how – a

Tooth Thickness (t) at the Pitch Diameter- Diametral Pitch (P)  t = 1.5708/P

Working Depth (WD).- Addendum-WD = 2(a)

Center Distance (C)-Normal Diametral Pitch (P) and the Number of Teeth in Both Gears-C = (N1+N2)/2P

The process of forming gear:

The process of forming gear

Gear cutting is any machining process for creating a gear. The most common gear cutting process includes hobbing, broaching, milling and grinding. Gears can be manufactured by a variety of processes such as forging, extrusion, powder, metallurgy, and blanking.

Gear facts:

Gear facts

gears concept

  • Machines typically use two or more gears of different sizes; one gear is often larger than the other.
  • The smaller gear usually rotates faster than the larger one. The larger gear typically has more teeth than the smaller one.
  • Beveled gears include one gear that sits at an angle to another gear.
  • The first gears were wooden and had wooden teeth they were used in water mills, windmills etc.
  • When one gear turns, it also turns the other gear.
  • The gears used in the car are helical.
  • Metals gears are used in clocks.
  • Gears are used to generate more speed or power or transmit power from one part of a machine to another part.

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