[Physics Class Notes] on Types of Gears Pdf for Exam

To answer the question, what is a gear? We can say that a gear is a kind of machine element which has teeth cut around a cylindrical or cone-shaped surface with equal spacing? They are used to transmit rotations and forces from the driving shaft to the driven shaft when a pair of these elements have meshed. There are different types of gear. They have a different basis of classification. The history of gears is old and is mentioned by Archimedes to be in use in ancient Greece in B.C.

 

Classification of Gears and their Application

All types of gears are given in the classification chart below.

 

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Gears can be classified as parallel shaft gears, intersecting shaft gears and non-intersecting non-parallel shaft gears depending on the position of their axes. 

Some important gears are given in detail below.

1. Internal gear

2. Screw gear

3. Worm gear

4. Bevel gear

5. Spiral bevel gear

6. Spur gear

7. Mitre gear

8. Gear rack

9. Helical gear

Each type of gear is discussed in brief below:

1. Internal Gear

These gears have teeth cut on the inside part of cones and cylinders and are used to pair with external gears. These are used in shaft couplings which are of gear types and planetary gear drives. Due to trimming problems and interference such as trochoid and involute, there lies one disadvantage with this gear, which is an unequal number of internal and external gears.

2. Screw Gear

Screw gears or sometimes called crossed helical gears are helical gears used in motion transmission between non-intersecting shafts. In parallel shafts, the helical gears used have the same helix angle but in opposite directions. It consists of the same hand helical gears at an angle of 45 degrees on the non-intersecting and non-parallel shafts. It is used for small power transmission.

3. Worm Gear

It consists of two elements, a screw-shaped cut on the shaft called a worm and the other one is a mating gear called a worm wheel. These two together on a non-intersecting shaft form worm gear. material is used for worm and a soft one for worm wheels as it is necessary to reduce friction due to sliding contact of surfaces. They can have a cylindrical shape and also an hourglass type which increases the contact ratio but reduces the production.

4. Mitre Gear 

These are basic bevel gears with a speed ratio of 1. The direction of power transmission is changed by them without changing speed. They can be both straight and spiral. With spiral mitre gear thrust bearing is also used as it produces thrust force in the axial direction. Mitre gears with shaft angles other than 90° are called angular mitre gears.

5. Bevel Gear

These have a cone shape at their pitch surface and teeth are cut along the cone. They transmit force between two shafts that intersect at a point. Various kinds of bevel gears are helical bevel gears, spiral bevel gears, straight bevel gears, mitre gears, angular bevel gears, zero gears, hypoid gears and crowns bevel gears.

6. Spiral Bevel Gear

Bevel gears with curved tooth lines are called spiral bevel gears. They are superior to straight bevel gears in efficiency, strength, vibration and noise due to higher contact ratio but are difficult to produce. Since teeth are curved, it produces thrust force in the axial direction. These gears with zero twisting angles are called zerol bevel gears.

7. Spur Gear

Spur gears are included in the parallel shaft gear group. They are cylindrical gears having tooth lines straight and parallel to the shaft. Cylindrical gears are gears with cylindrical pitch surfaces. In meshing pairs, the larger one is called gear and the smaller one is pinion. They achieve high accuracy and are relatively easy to produce.

8. Gear Rack

A gear rack consists of same sized and shaped teeth cut at equal distances along a flat surface or a straight rod. It is a cylindrical gear having a radius of pitch infinity. It converts rotational motion into linear motion by meshing with a cylindrical gear pinion. Straight tooth racks and helical tooth racks are its broader classification.

9. Helical Gear 

These gears can transmit high loads. They are very quiet and are cylindrical gear with winding tooth lines. Its two subdivisions are left-hand twist and right-hand twist.

 

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Different Types and Applications of Gears

Since gears are an essential part of many devices, tools and vehicles they have a wide range of applications. Everywhere different types of gears are used as per the requirement. Thus applications of gears are given below as per the types of gears.

 

Fun Facts about Types of Gears and Their Applications:

Studying gear can become tiresome after a point in time. To get you out of this
boredom has brought some facts about gear:

• The first gear was made of wood. They were applied in watermills and windmills.

• Metal gears were used for the first time in the clocks.

• Gears used in cars are known as helical.

• Some gears are not circular in shape. Some of them are conical and square.

• The largest gear in the world weighs 73.5 tons and is 13.2 m in diameter.

• Roller coasters cannot work without gears

• An insect named Issus has gears in its hind legs which allows the legs to function together in synchronized motion when the insect jumps. This is an example of natural gear.

Conclusion:

The topic of gears forms an essential part of mechanics and a lot of questions are asked from this topic in various examinations including engineering exams in higher standards. The above write-up covers the topic of Types of Gears Their Applications in great detail. It starts with the definition of gear and goes on to cover topics like its types, classification, applications, etc. After reading this write-up you will be in a position to understand the basics of the chapter and also well prepared to grasp advanced concepts related to the topic.

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