What is GEAR ?

        A Gear is a wheel with teeth that meshes together with other gears and is usually made of metal or plastic. Gears are used in various areas from the Bicycle till the Bulldozers.

        Gears are used to change the speed, torque and direction of a power source.

        Gears are available in various sizes and types. Depending on the usage, the gears are chosen to work where one gear may work better than another.

        Mechanical engineers use gears when designing machines such as bicycles, elevators and automobiles in order to increase the speed of a device, or its ability to pull or lift heavy objects.

Types of Gears

        Gears are found in various types and size but the important number is how many teeth are in gears.

        Simplest and widely used gear type is Spur Gear.

        There are other type of Gears also used for different purposes around us, they are

Worm Gear

Bevel Gear

Rack and Pinion Gear

What is Pulley ?

        Pulley is a wheel with a grave carved around its circumference in which a rope or belt is placed to drive the wheel.

Pulleys are used for various applications including

• Elevator
• Cranes
• Automobiles

GEAR RATIO

        A Gear Ratio is the ratio between the Driver gear ( the one being connected with motor ) and Driven gear (the one connected with the driver gear ).

Gear ratios are expressed as fractions and can be written in different ways.

Eg. 1 to 3 (or) 1/3 (or) 1:3

Always remember that the driven gear will turn in the opposite direction of the driver gear.

· Number of Teeth on Driven Gear / Number of Teeth on Driver Gear.

· Size of the Driver Pulley / Size of the Driven Pulley.

VELOCITY RATIO (VR)

    Velocity is a measure of how fast something moves in a particular direction. When calculating for velocity or speed, it is best to have a ratio in which the driver gear is larger than the driven gear.

For maximum we should always have a larger driver gear/pulley paired with a smaller driven pulley.

Eg. Bicycle

TORQUE OF GEAR

        Torque is a measure of how much a force acting on an object causes that object to rotate. The gear ratio expresses the ratio of the output torque to the input torque.

        Thus, we can multiply the torque supplied at the motor shaft (the input) by the gear ratio to find the torque at the wheel axle (the output). Transmitting power through a series of gears can also affect rotational speed.

If we take gear image as an example, the Gear Ratio is 3:1 or 3/1. If the driver turns at 60 RPM then the driven gear must turn at

6 Nm x 3

Torque = 18 Nm

Note : Small Gears driving large gears increase torque.

 

Hope this article make you to understand the gear concept better. Please checkout our other posts too. Thank You.