Gear backlash, also known as gear play or gear clearance, is the amount of free movement between meshing gears in a gear system. It is the radial distance between the pitch circles of meshing gears.
When one gear is turned, the backlash allows the other gear to rotate a small amount in the opposite direction before the teeth make contact and transmit torque. This free movement can cause problems with the accuracy and smoothness of the transmission of power in a system. It can also contribute to noise and wear on the gears.
What is Gear Box Backlash ?
The amount of backlash in a gear system can be adjusted by tightening or loosening the fit between the gears. Too much backlash can cause the gears to slip and lose power, while too little backlash can cause the gears to bind and wear out prematurely. It is important to set the backlash to the manufacturer’s specifications in order to ensure proper operation of the gear system.
Gearbox Backlash Measurement
There are several methods for measuring gear backlash, but the most common method is to use a dial indicator. Here’s how to do it:
- Secure the gear system in a vice or other fixture to hold it in place.
- Attach a dial indicator to the gear housing or some other fixed reference point.
- Set the dial indicator to zero by rotating the gear and adjusting the indicator until it reads zero.
- Rotate the gear in the opposite direction and stop when the dial indicator begins to move. The amount of movement of the dial indicator is the backlash.
- Repeat the measurement at several points around the circumference of the gear to get an average value.
Other methods for measuring backlash include using a feeler gauge or a laser interferometer. It is important to follow the manufacturer’s specifications for the acceptable amount of backlash for the specific gear system.
How to Reduce Backlash in Gears
There are several ways to reduce backlash in a gear system:
- Use gears with a smaller amount of clearance between the teeth. This can be achieved by using gears with a higher quality or by using gears that are ground to closer tolerances.
- Tighten the fit between the gears. This can be done by using shims or by adjusting the spacing between the gears.
- Use a backlash eliminator or a preload device. These devices use springs or other means to apply a constant force to the gears, which reduces the amount of clearance between the teeth.
- Use a different type of gear system. Some types of gears, such as bevel gears or worm gears, have naturally low backlash due to their design.
- Use a different type of drive system. Systems that use belts or chains, such as belt drives or chain drives, have less backlash than systems that use gears.
It is important to consider the trade-offs involved in reducing backlash. Reducing backlash can improve the accuracy and smoothness of the transmission of power, but it can also increase the load on the gears and lead to increased wear and noise. It is important to set the backlash to the manufacturer’s specifications in order to ensure proper operation of the gear system.
Gear Backlash Calculation Formula
The formula for calculating backlash in a gear system depends on the type of gears being used. For example, the backlash in a spur gear system can be calculated using the following formula:
Backlash = (2 * C) – (2 * T)
where C is the center distance between the gears (the distance between the centers of the two gears), and T is the sum of the tooth thicknesses of both gears at the pitch line.
For other types of gears, such as bevel gears or worm gears, different formulas may be used. It is also important to consider the manufacturing tolerances and the specific operating conditions of the gear system when calculating backlash. In general, it is best to consult the manufacturer’s specifications or a reference manual for the specific formula and procedures for calculating backlash in a given gear system.
Too Much Backlash in Gears
Having too much backlash in a gear system can cause problems with the accuracy and smoothness of the transmission of power. It can also contribute to noise and wear on the gears. Here are some specific problems that can be caused by too much backlash:
- Slipping: When there is too much backlash, the gears can slip and lose power. This can cause the system to be less efficient and may result in a reduction in performance.
- Vibration: Too much backlash can cause the gears to vibrate, which can lead to noise and wear on the gears and other components of the system.
- Inaccuracy: When one gear is turned, the backlash allows the other gear to rotate a small amount in the opposite direction. This can cause the system to be less accurate and may result in positioning errors.
- Wear: Too much backlash can cause the gears to wear out prematurely due to the increased clearance between the teeth. This can lead to increased maintenance costs and downtime.
It is important to set the backlash to the manufacturer’s specifications in order to ensure proper operation of the gear system. If the backlash is too high, it may be necessary to tighten the fit between the gears or use a different type of gear system.
Gear Box Manufacturers
Here are the websites of some of the leading gearbox manufacturers:
Reasons for Gear Backlash Increase
There are several reasons why the backlash in a gear system may increase over time:
- Wear: As the gears wear, the clearance between the teeth may increase, leading to an increase in backlash.
- Loosening: The fit between the gears may loosen over time, due to factors such as temperature changes or vibration, which can cause an increase in backlash.
- Misalignment: If the gears are not properly aligned, the backlash may increase.
- Improper installation: If the gears are not installed correctly, the backlash may be too high.
- Changes in load: If the load on the gears changes, it can affect the amount of clearance between the teeth and cause an increase in backlash.
It is important to monitor the backlash in a gear system and make adjustments as needed to maintain the manufacturer’s specified level of backlash. This will help to ensure proper operation of the system and reduce wear and noise.