Bevel Gears; Definition, Types, Calculations, Advantages

Bevel gears are one of the most important mechanical elements in machinery. Also, in the design phase of power transmission, there are lots of bevel gear mechanisms are used. So, there are very important and various kinds of applications for these gear types. Because of this, they are very important in the design of different machinery.

Here you will find the information about;

  • What is bevel gear?
  • Explanations of types of these gears,
  • Bevel gear geometry calculator.
  • General applications of these gears.
  • Advantages and disadvantages of these gears.

What is Bevel Gear?

A bevel gear is a type of mechanical application that they transmitting rotational energy. But the most important difference between bevel gears from other gear types in the direction of the axis of rotation changes.

Also, we use these gears where the power and torque must be transmitted between the non-parallel axes. Because of this reason, bevel gears find various kinds of applications themselves.

Furthermore, they are the gear pairs that have taper angles. These two taper angles complete each other to obtain the required amount of rotation of the axis. Also, the general teeth structures of these gear systems are different from other types of gears.

What are the Types of Bevel Gears?

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Moreover, these gears are used for the power transmission between non-parallel shafts. In general, shafts are in a 90-degree position. Cone-shaped gears are produced for the power transmission between these shafts.

Also, they can be also used for only changing the rotation direction of power transmission which are called miter gears. For miter gears, input and output bevel gears have the same number of teeth.

There are four types of these gears are available in general mechanical design; Hypoid type, spiral type, zero spiral types, and straight type them. In general, when the concept of ‘bevel gear’ is spoken, people generally think of the straight type of them. But the situation is not like that.

And also, the most general type of gear is the hypoid type. Other types of them are designed from hypoid type in terms of several parameters.

Hypoid Type

Firstly, the hypoid type of bevel gear is the most general form of them. Other types of them are obtained with these parameters: Offset of pinion from the centerline, spiral angle of gear teeth, and curving of teeth in spiral gear.

Hypoid type bevel gear.
Hypoid type bevel gear(Image Source https://grabcad.com/library/hypoid-gear-set-for-automotive-drive-axle-1).

Furthermore, in the hypoid type of them, all the geometrical features are available. The offset position of the pinion provides power transmission between perpendicular shafts that are not placed in planar positions. Other types of these gears must transmit power between planarly aligned shafts.

Also, the smooth working capability of hypoid gears is a very important thing.

Spiral Type Bevel Gears

And then, in this kind of bevel gear, there is no offset position teeth design like the hypoid type. But, teeth of the spiral type are tapered as a spiral line over the cone. This teeth geometry provides a more smooth power transition between gears.

Spiral type bevel gear.
Spiral-type bevel gear(Image Source:https://www.kggear.co.jp/en/kg-stock-gears/bevel-gears).

Spiral angles are generally between 20-45 degrees. But most generally used bevel gear spirals 35 degrees. The pressure angle of general spiral gears is 20 degrees. Also, the minimum number of teeth is generally 12.

Zero Spiral Type

In zero type of bevel gears, there is no offset teeth design and spiral geometry in teeth. But, the teeth of zero spiral gears are tapered in a curve shape. They are generally operating more smoothly compared with the straight type of them. Also, this is the most classical type of these gears type among others.

Zero sprial type
Zero bevel gear(Image Source: https://techminy.com/bevel-gear-types/).

Straight Type Bevel Gears

Above all, all the geometric features stated above for different kinds of bevel gears do not exist in straight-type gears. So, straight teeth are tapered on the cone. Anf also, typical pressure angles for straight-type gears are 20, 22,5, and 25 degrees. And the minimum number of teeth is used in pinion to avoid interference problems between mating gears.

Straight type
Straight type bevel gear(Image Source:https://link.springer.com/article/10.1007/s42452-019-1171-3).

Geometrical Calculator For Straight Bevel Gears

Mating bevel gears
Dimension of mating bevel gears(Image Source: Machine Elements in Mechanical Design-Book by Robert L. Mott).

Bevel Gear Geometric Calculations































































So, this is a very useful calculator that gives lots of kinds of information about the gear system that you want to design.

As you see above, there are lots of geometric variables available for calculation. You just need to enter the diameters of mating bevel gears and the number of teeth of them. Diameters must be entered in inches because the diametral pitch is used in calculations.

Variables in Calculator

Take a closer look at these variables;

  • Number of teeth on pinion: Pinion is the input gear of the bevel gear pairs. In general pinions have a lower number of teeth. So, before deciding the gear ratio, you need to decide the number of teeth of the pinion.
  • Number of teeth on the bigger gear: Bigger gear is the output gear of the these mechanism. So, you need to enter a bigger value for it. Also, this is a dimensionless value.
  • Diameter of Pinion: You need to enter the total diameter of the pinion. You can see the diameter of the pinion on the geometry above. The unit of diameter is m or ft in English units. 
  • Diameter of Bigger Gear: This is also a very important parameter. You can see the diameter value above. Also, the unit is the same as the diameter of the pinion.

After entering the required values inside brackets, click on the ‘Calculate!’ button to see all geometric results related to your bevel gear mates.

If you want to do another calculation, just click on the ‘Reset’ button, then re-enter new values.

Take a look at the article about the difference between diametral pitch value and metric module value for gears. 

Applications of Bevel Gears

Rear-wheel Drive Mechanisms

Rear wheel drive mechanisms are the most important applications of them. And also, in these applications, the shaft carries the power to the differential box. In this box, there is a very important bevel gear application. The gear system in this differential box provides the changing of the axis of rotation at 90 degrees. So, rotation of the wheels takes place.

You can use the calculator above to calculate the geometric features of a differential box.

Manufacturing Process Machines

Belt drive and machine drive mechanisms, use the bevel gear mechanisms generally. Because the rotation of the axis is a very useful feature of these mechanisms.

Bevel Gearboxes

In such power transmission applications, they use bevel gearboxes in general. Also because of the axis change of the power, these boxes are very useful in lots of machinery. According to the input power, the output can transmit to 90 degrees at different orientations with a very big efficiency. 

Advantages and Disadvantages of Bevel Gear Systems

Like other gear and power transmission systems, these systems have various kinds of advantages and disadvantages. Check them below.

Advantages

  • As we stated above, the biggest advantage of these systems is the ability to 90 degrees of change the rotation axis of the shaft. So, these different features of these systems make them very useful systems in lots of engineering applications. Around these applications, mill actuators, conveyor belts, excavators, etc.
  • They take up a little space if we compare them with other types of gear systems. We can design very useful gearboxes and gear systems with bevel gears. Also, different types of these mechanisms are available.
  • You can easily find the different types of them. It is not a hard thing to obtain all gear ratios with standard gears.

Disadvantages

  • One of the most important disadvantages of the bevel gear systems is the manufacturing. Manufacturing these complex shapes is very hard. In general conventional gear, manufacturing systems are not capable to produce these gear systems.
  • Because of the manufacturing costs, the general investment costs of these gears are high. If we compare it with other kinds of gear systems, bevel gears are costly.
  • Because of the change in the rotation direction, the efficiencies of these gears are low. In general, we can not obtain the same input power from the output in these mechanisms. So, around other gear mechanisms, these gears are one of the least efficient systems.

Conclusion

Bevel gear mechanisms are very important in most engineering applications. There are various kinds of advantages of these mechanisms. Because of these advantages, we are using these systems in various engineering applications.

Also, the downsides of the these gear mechanisms are very important. We need to consider these disadvantages in the design phase.

Furthermore, various applications use these systems. For example, in the differential boxes, we are using these mechanisms.

Moreover, there are various types of these gear mechanisms. Also, according to the application or requirements, we can select one of these types. The general difference between these types is the tooth geometry.

Above all, you can use the calculator to calculate the main geometric features of them mechanisms. You just need to enter only 4 values, and you will get tons of information about the geometric structure of your bevel gear mechanism.

Finally, do not forget to leave your comments and questions below about the them and types and calculator of it.

Furthermore, Mechanicalland does not accept any responsibility for the calculations done by users, in calculators. A good engineer must check the solutions again and again.

And also, check the other useful engineering calculators available in Mechanicalland!

Please inform us if there is any fault in the calculations done in calculators.

Your precious feedbacks are very important to us.

FAQs About Bevel Gears

Why bevel gear is used?

We use them in applications where we require to transmit the power in 90 degrees of different orientations. The most important example of it is the differential boxes of cars. So, in the differential box, the rotational energy of the shaft is transmitted to the wheels.

How does bevel gear work?

The working system is very basic. There are two mating 45-degree faced gears. These 45 degrees mate constitutes a 90-degree rotation of the axis of rotation. So, this is the main principle of the bevel gear.

Which bevel gear is commonly used?

One of the most used bevel gear types is the spiral type bevel gear. Because the spiral teeth of the bevel gear give an advantage for smoother working and much more strong.

Are bevel gears reversible?

Yes. You can turn the output gear to give rotation to the input pinion. But, it is not an efficient thing in the working mechanism of bevel gears.

What is the advantage of bevel gears?

he most important advantage of these systems, they can convert the axis of rotation of a shaft into 90 degrees of different orientation. This is the most important feature of these systems.

What is the biggest disadvantage of bevel gears? 

The most important disadvantage is the manufacturing costs. And also, we can not produce these systems with the conventional gear production methods. So, this is the additional cost of these systems.

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