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Program: The Installation of Bevel Gears

Part 1 - Introduction and the reason why proper installation is so important

Welcome to Arrow Gear’s program on the Installation of bevel gears.

For bevel gears to perform properly in a gearbox, certain procedures must be followed during installation. Failing to follow these procedures can result in poor performance or gear failure.

The purpose of this program is to provide you with the information you need to successfully install bevel gears. Here’s what we’re going to cover.

First we’ll talk about the specific reasons why proper installation is so important. We’ll then talk about Mounting Distance, Marked Teeth, Backlash, and Contact Pattern.

The Importance of Proper Installation

In this section, we’ll be talking about the specific reasons why proper installation of bevel gears is so important.

Installing bevel gears is much more involved than installing spur gears. For example, bevel gears must be oriented to each other so that they run smoothly without binding or interference. They must also maintain the correct amount of tooth clearance at all operating conditions.

For spur and helical gears, the best orientation normally requires only that the center distance and shaft alignment be correct - no further adjustment is needed. This is seldom the case with bevel gears, because the mounting arrangements allow for wide variations in position.

All types of bevel gears have an optimum position for best performance. This holds true for straight, zerol, spiral and hypoid bevel gears. The manufacturer determines this optimum position by running tests on each individual gearset.
Several parameters contribute to proper assembly so that the gearbox operates smoothly and efficiently. The most important are mounting distance, matched teeth, and backlash. These parameters will be covered in more detail in subsequent sections.

Here’s another point to keep in mind. Bevel gears with a quality level of ANSI AGMA Q8 or better are normally manufactured and tested in sets. During manufacturing, the preferred values for each of the three key parameters are marked on the individual gears.

Also, it is common for the manufacturer to mark a gearset number on each of the two gears in a set. Gears manufactured in sets should only be assembled with their mates. This is one reason why, if one gear in a set fails, the entire set should be replaced.