How To Adjust The Tension of Chain Drive?

I. Basic Principles of Tension Adjustment

1. Proper Tension Level: The sag of the chain is an important indicator of tension. Generally, for horizontal drives or those with an inclination angle less than 45°, the chain sag should be 2%~3% of the center distance between the two sprockets; for drives with an inclination angle greater than 45° or vertical drives, the sag should be smaller (controllable within 1%~2%).

2. Avoid Over-Tensioning: Excessive tension will accelerate the wear of the chain, sprockets, and shafts, and increase power loss.

II. Common Tension Adjustment Methods

1. Center Distance Adjustment Method (Most Commonly Used)

• Specific Operation:

• Loosen the bolts fixing the driven (or driving) sprocket shaft, move the shaft away from the other sprocket to increase the center distance (tensioning the chain) or move it closer to reduce the center distance (loosening the chain).

• After adjustment, measure the chain sag. Once it meets the requirements, re-tighten the shaft bolts.

• Applicable Scenarios: Chain drives between gearboxes and working machines (such as motorcycle chains, conveyor chains) where the center distance is designed with adjustment margins.

2. Tensioner Pulley Method (When Center Distance Is Fixed)

• Design and Installation of Tensioner Pulley:

• Press Wheel Type: The tensioner pulley presses against the outer side of the chain, applying pressure via a spring or weight (e.g., bicycle chain tensioners).

• Guide Wheel Type: The tensioner pulley fits into the inner side of the chain, guiding the chain path and increasing the wrap angle (suitable for long-distance drives).

• Position: Usually installed on the slack side (non-loaded side) of the chain to avoid increasing the load on the tight side. For horizontal drives, the tensioner can be located below (to prevent the chain from dragging on the ground) or above the chain; for vertical drives, it is mostly located on the inner side.

• Types:

• Material and Size: Tensioner pulleys are usually made of steel or nylon, with a diameter not less than 60% of the minimum sprocket diameter to reduce chain wear.

3. Other Auxiliary Methods

• Chain Shortening Method: When the chain is severely worn or elongated (pitch elongation exceeds 3%), 1~2 links can be cut off (ensuring the chain can still mesh normally). However, this method is only suitable for small elongation; the chain must be replaced after multiple shortenings.

• Spring Automatic Tensioning Device: For drives with large vibrations and frequent load changes (such as agricultural machinery), a spring-driven automatic tensioner can be used. It automatically compensates for chain slack via spring force, eliminating the need for manual adjustment.

III. Notes

1. Regular Inspection: Chains elongate gradually due to wear during operation. The sag should be checked regularly, generally recommended every 100 operating hours or weekly.

2. Symmetric Adjustment: For double-row chains or multi-shaft drives, ensure the tension of chains on both sides is consistent to avoid uneven force and eccentric wear.

3. Coordination with Sprockets: During tension adjustment, ensure the chain fits well with the sprocket teeth without jamming or skewing, otherwise wear will be accelerated.

4. Running-in of New Chains: After installing a new chain, run it at low speed for running-in, then re-adjust the tension, as new chains elongate slightly during initial operation.

Summary