Gears, If you are a Mechanical Engineer then you should aware about this word GEARS. Gears is very large topic in Mechanical engineering. You may study it in Design of Machine Element, Kinematics of Machines, Dynamics of Machinery and Theory of Machines Here we will discuss about definition and types of gears with their uses. There are mainly 5 types of gears we will descuss here however some sub types of gears are there you may check in your books
What is Gear ?
Gear is a cylinder, wheel, or disk on the surface of which are cut parallel teeth. The larger gear is called the gear the smaller, the pinion. Usually when two gears in mesh and one is larger than the other is, the names gear pinion is are replied. Spur gear is used to transmit power from one shaft to another in cases where those shafts have their axis parallel.
Types of Gears
There are five types of Gears. They are use in different different applications. so just check out
- Spur gear
- Helical gear
- Bevel gear
- Worm & Worm gear
- Rack and Pinion
Spur gears are the most common type used. Tooth contact is primarily rolling, with sliding occurring during engagement and disengagement. Some noise is normal, but it may become objectionable at high speeds.
This types of Gears are used in series for large gear reductions. The teeth on spur gears are straight and are mounted in parallel on different shafts. Spur gears are used in washing machines, screwdrivers, windup alarm clocks, and other devices. These are particularly loud, due to the gear tooth engaging and colliding. Each impact makes loud noises and causes vibration, which is why spur gears are not used in machinery like cars. A normal gear ratio range is 1:1 to 6:1.
Helical gears operate more smoothly and quietly compared to spur gears due to the way the teeth interact. The teeth on a helical gear cut at an angle to the face of the gear. When two of the teeth start to engage, the contact is gradual–starting at one end of the tooth and maintaining contact as the gear rotates into full engagement. The typical range of the helix angle is about 15 to 30 deg. The thrust load varies directly with the magnitude of tangent of helix angle. Helical is the most commonly used gear in transmissions. They also generate large amounts of thrust and use bearings to help support the thrust load. Helical gears can be used to adjust the rotation angle by 90 deg. when mounted on perpendicular shafts. Its normal gear ratio range is 3:2 to 10:1.
Bevel gears are used to change the direction of a shaft’s rotation. Bevel gears have teeth that are available in straight, spiral, or hypoid shape. Straight teeth have similar characteristics to spur gears and also have a large impact when engaged. Like spur gears, the normal gear ratio range for straight bevel gears is 3:2 to 5:1.
Spiral teeth operate the same as helical gears. They produce less vibration and noise when compared to straight teeth. The right hand of the spiral bevel is the outer half of the tooth, inclined to travel in the clockwise direction from the axial plane. The left hand of the spiral bevel travels in the counterclockwise direction. The normal gear ratio range is 3:2 to 4:1.
Worm & Worm Gears
Worm gears are used in large gear reductions. Gear ratio ranges of 5:1 to 300:1 are typical. The setup is designed so that the worm can turn the gear, but the gear cannot turn the worm. The angle of the worm is shallow and as a result the gear is held in place due to the friction between the two. The gear is found in applications such as conveyor systems in which the locking feature can act as a brake or an emergency stop.
Rack and Pinion Gears
A rack and pinion mechanism is used to transform rotary motion in to linear motion and vice versa. A round a spur gear, the pinion, meshes with a spur gear which has teeth set in a straight line, the rack. The rack and pinion can transform rotary motion into linear motion and vice versa in three ways.
- Rotation of the pinion about a fixed center causes the rack to move in a straight line.
- Movement of the rack in a straight line causes the pinion to rotate about a fixed center.
- If the rack is fixed and the pinion rotates, then the pinion’s center moves in a straight line taking the pinion with it.
These are the Major types of Gears however they have some sub-types in gears you will study in your subject. you can also checkout some Mechanical Objective Questions for Theory of Machine MCQ and Machine design MCQ which covers Gears topic