Selecting the best bevel gear

A Bevel gearbox has advantages over say, a worm gear because of efficiency, which is considerably higher. Another vital advantage is that bevel gears offer the flexibility of 90 degree solution at ratio that is lower.

Some of the important factors to be noted in the selection process of a bevel gear are given here. It must be remembered that all the points need not apply in tandem but depending on the application, they must be looked out for:

1. Power transmission requirements
2. Design life
3. Corrosive elements
4. Noise and heat generation.

All of these factors determine the success of the gear in a particular application. Four bevel gears in a square make a differential gear, which can transmit power to two axles spinning at different speeds, such as in an automobile.

Why use Bevel Gear Box?
A Bevel gearbox has advantages over say, a worm gear because of efficiency, which is considerably higher. Another vital advantage is that bevel gears offer the flexibility of 90 degree solution at ratio that is lower.

Other advantages include:

1. Good performance under high speeds and loads.
2. Works particularly well for right-angle drives.

Basic Limitation of a Bevel Gear

• Bevel Gears have been observed to suffer from a basic limitation making it sometimes not a preferred choice for application. This limitation is because of the fact that in Bevel Gears often there is no room or leverage provided for supporting it at both the ends while the shafts intersects. This creates the problem of one or both the gears displaying a tendency to overhang their supporting shafts. This problem is referred to as the overhung load (OHL). It causes further problems like deflecting the shaft, misaligning of gears leading to poor tooth contact and consequently accelerating wear.
• The complicated tooth form of Bevel Gears is a limiting factor in precision.

Accuracy of the Bevel Gears
According to the international standards there is generally four types of error. They are the following:

Single Pitch Error -
This type of error is reported as the deviation found in the actual measured pitch value between any of the tooth placed adjacently and the circular pitch(theoretical) at mean cone distance.

Pitch Variation Error -
 Error of the Pitch Variation type is referred to the absolute pitch variation taking place between any two of the tooth placed side by side at the mean cone distance.

Accumulated Pitch Error -
Accumulated Pitch Error is referred to as the difference found between the pitch sum (theoretical) of a teeth interval and the total summation of measured pitches(actual) for the same teeth interval taken at the mean cone distance.

Runout Error of Teeth -
Runout Error of Teeth is defined as the tooth runout, maximum taking place in the radial direction. It is often measured by placing a ball or pin placed between any two teeth at central cone distance.

Manufacturing Bevel Gears
There are different ways available now for the manufacturing of Bevel gears. But unlike the spur gears, Bevel gears can be made to have cones that are shaped differently, depending on the type of manufacturing process.

Highlights of the Manufacturing Process

1. As shown in the image, these gear mates with a virtual generating gear.
2. The cutting blades copies the teeth of a virtual generating gear.
3. The virtual generating gear is rotated around its axis (called the cradle). Please see the image.

Application of Bevel Gears
The bevel gear find suitable application in a variety of industries. Prominent among them are the locomotives, printing press, power plants marine applications, cooling towers, steel plants etc