Gears are widely used transmission devices and are available in different shapes and sizes. You may recognize some, but do you know about their advantages, limitations, and for what purpose they’re used?
This is The Mechanical post and today we are here to answer all these questions.
You can get your copy of the PDF on types of gear at the end of the article.
Types of Gear
The following are the different types of gear:
- Spur gear
- Helical gear
- Double helical
- Herringbone gear
- Bevel gear
- Rack and pinion
- Worm gear
- Hypoid gear
#1. Spur gear
The spur gear is one of the simplest and most popular type of gear. It is used when the shafts are parallel to each other. The teeth of the spur gear are parallel to the axis of rotation.
When 2 spur gears mesh with each other, there is point contact between the teeth.
Do check out the terminology used to describe and design a spur gear.
Whenever someone says the word “gear”, the spur gear would be the first one that comes to mind. Don’t believe it? try asking your family members or friends to describe a gear and see it yourself.
Advantages of spur gear
- Spur gears are economical to manufacture.
- They’re highly reliable.
- Spur gears are comparatively easy to design.
- Spur gears provide a constant velocity ratio.
- They are easy to maintain.
- Spur gears are mostly used to transmit large amounts of power.
Limitation of spur gears
- Spur gears cannot be used for non-parallel shafts.
- Over long distances, spur gears cannot be used to transmit power.
- At high speeds, spur gears are noisier.
Applications of the spur gear.
#2. Helical gear
The next type of gear is the helical gear. It is quite similar to the spur gear however its teeth are inclined to the axis of the rotation and the inclination is denoted by 𝞪 called the helix angle.
In the helical gear, the shaft axis is parallel to each other helical gears. The tooth engagement of it is very good and offers a good grip. There is sliding contact between the teeth.
The helix angle of single helical gears usually ranges from 20 to 35 degrees.
Advantages of helical gear
- Helical gears are highly durable and are used for high-load applications.
- Due to good tooth engagement, helical gears operate smoothly.
- Helical gears produced less noise.
Limitations of helical gear
- Due to sliding contact, there is a greater amount of friction as compared to spur gear.
- The sliding contact also results in heat generation and reduced efficiency.
- The helix angle of the gear teeth results in axial thrust on bearings.
- Helical gears are expensive than spur gears.
Application of Helical gears
#3. Double Helical gear
A double helical gear has two helical faces with opposite helix angles with a gap in between them. Double helical gears help reduce the axial thrust caused by helical gears.
The axial thrust caused by the right-hand teeth is canceled out by the left-hand teeth. Double helical gears are used in generators, fans, pumps, compressors, etc.
Advantages of Double helical gear
- Double helical gears offer smooth transmission.
- They are silent at all speeds.
- It can transmit more torque.
Limitations of Double helical gear
- Double helical gears are difficult to produce as compared to spur gears and thus are expensive.
- Due to sliding contact between the teeth, there is more friction and thus more heat is generated as compared to spur gear.
#4. Herringbone gear
Herringbone gears have teeth similar to the double-helical gear, however, they have don’t have a gap between the two faces and are cut in such a way, that the tooth structure looks like the letter “V”.
Advantages of Herringbone gear
- Herringbone gears operate quietly.
- Herringbone gears offer smooth power transmission.
- Due to the V shape, the axial thrust as produced in helical gears is canceled out.
Limitations of Herringbone gear
- Due to their design, manufacturing is difficult.
- Herringbone gears are expensive.
- Sliding contact between teeth results in friction and heat generation.
Applications of Herringbone gear
Applications of Herringbone gear include transmission of high torque, heavy machinery, gas turbines, heavy-duty vehicles, torque gearboxes, etc.
#5. Bevel gears
Also, the shaft axes can be said to be intersecting and non-parallel (As shown in the figure) The above picture shows a spiral bevel gear.
There are two types of bevel gears:
1. Straight bevel gear – The teeth are straight and do not have any helix angle.
2. Spiral bevel gear – The teeth are given a helix angle.
Advantages of Bevel gear
- A bevel gear is highly reliable.
- It can transmit the exact velocity ratio.
Limitations of Bevel gear
- Any error in the tooth may lead to vibrations and noise.
- Bevel gears are expensive when compared to spur gear.
Applications of Bevel gear
Bevel gears are used in the differential gearbox of the automobile, hand drills, agricultural machines, printing machines, mining, robotics, cement mills, etc.
#6. Worm Gear
A worm gear is a type of gear arrangement in which a screw meshes with a gear that is similar to a spur gear. The screw is called the worm and the gear it meshes with is known as the worm wheel.
In worm gears, the shaft axes are non intersecting as well as non-parallel.
Do you know?
In the worm gear, the worm can easily rotate the worm wheel, however, the worm wheel cannot rotate the worm.
Advantages of Worm gear
- A worm gear is capable of transmitting high torque.
- Worm gears have high reduction ratios.
- They are self-locking.
- They offer a smooth and silent operation.
- It occupies less space for the same speed reduction ratio as compared to other gears.
Disadvantages of Worm gear
Worm gear have are not efficient when it comes to transmitting power. Due to high friction between the surfaces, the worm gear is subjected to wear.
Applications of worm gear
Worm gear applications include Transportation machinery, machine tools, speed reducers, lifts, screw conveyors, etc.
#7. Rack and pinion
The rack and pinion is a type of gear arrangement where the rotary motion of a pinion is converted into linear movement of the rack.
The pinion is a small spur gear and the rack is made up of gear teeth cut in a straight row on a flat surface.
Advantages of Rack and pinion
- Rack pinion gears are cheap.
- They are compact.
- Rack and pinion are the simplest and easiest way to convert rotary motion into linear movement.
Limitation of Rack and pinion gear
- The mechanical advantage of rack and pinion is less when compared to a recirculating ball screw.
- It is sensitive to impacts.
Applications of Rack and pinion
The applications of Rack and pinion include steering mechanism of cars, lock gate control for canals, stairlifts, actuators to control the valves of pipelines, etc.
#8. Hypoid gear
A hypoid gear is similar to a spiral bevel gear except that the shaft axes do not intersect. The axis of the pinion is offset from the gear center.
In hypoid gears, the shaft axes are non-parallel as well as non intersecting.
The gear in the shape of a hyperboloid as compared to a spiral bevel gear which is usually conical.
Advantages of Hypoid gear
- Hypoid gears have a higher speed reduction ratio than bevel gears.
- Hypoid gears have a smooth and noiseless operation.
Applications of Hypoid gear
Hypoid gears are used for transmitting high torque at lower speeds and are mostly used in automobile differentials.
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