The Reasons for Excavator Track Derailment

Excavator track derailment refers to when the track disengages from the guide wheels, support wheels, drive wheel, and track rollers, a sight dreaded by both excavator operators and owners.

Avoiding track derailment requires careful attention from the operator, especially when making turns. If there are signs of initial derailment, the operator should lift the track and rotate it freely.

Frequent track derailment indicates underlying issues with the chassis that require repair. The causes of track derailment can generally be categorized into three types.

Firstly, if the four wheels are not on the same plane, it can lead to track derailment. The primary culprit is often the guide wheels, as they are the only ones among the four (guide wheels, support wheels, drive wheel, track rollers) capable of moving forward and backward. Wear and tear on the movable parts or the center shaft of the guide wheels can cause them to swing left and right, leading to track derailment. In such cases, replacing the guide wheels is necessary.

Secondly, loose tracks can also cause derailment. Track tension is regulated by the tension cylinder, which is controlled by a grease gun. However, sometimes, track tension cannot be adjusted due to various reasons:

1. Oil seal leakage in the tension cylinder leads to track looseness and prevents adjustment, necessitating replacement of the oil seal.

2. Leakage in the chain nozzle also prevents track adjustment, requiring replacement of the chain nozzle.

3. Breakage of the spring in the tension device also results in loose tracks, which can be challenging to replace and requires specialized tools.

4. Excessive wear or perforation of the track link sleeve increases the total length of the track, leading to loose tracks. If the track link sleeve is not perforated, a section of the track can be removed. However, if the sleeve is perforated, each section must be replaced.

5. Thirdly, worn-out guard plates that fail to function properly can cause track derailment. Unlike bulldozers, which rarely experience track derailment even with loose tracks, excavators have only two small guard plates—one at the position of the middle support wheel and the other at the guide wheel. Once the guard plates wear out, the track can slip beyond the guard plate, leading to derailment. Repairing or replacing the guard plates becomes necessary in such cases.

As for reattaching a derailed track, there is no fixed standard procedure. Generally, the track tension should be released by removing the chain nozzle and releasing the grease. Then, depending on the situation, the excavator's bucket and movement should be coordinated to reattach the track. Tracks that are prone to derailment are easier to reattach.

This process is similar to fixing a bicycle chain, except that excavator tracks are much heavier, requiring the use of the excavator's bucket. If the track slips outward, the bucket can be used to push part of the track onto the guide wheel or drive wheel. Then, rotating the drive wheel can reattach the track.

If the track slips inward, the bucket cannot reach the track. In such cases, a steel wire rope can be used to pull part of the track onto the guide wheel or drive wheel. However, attention should be paid to ensuring that the excess slack in the track is concentrated at the installation site to facilitate reattachment. Once the guide wheel and drive wheel are installed, most of the track is reattached. The track rollers can be directly installed using the bucket. If the bucket cannot reach, another method is to lift the track, place a suitable wooden stick between the track at the position of the track roller, and slowly lower the track. The track at the position of the track roller will be lifted by the wooden stick, thus reattaching the derailed track.

If the entire track is completely derailed, whether to install the drive wheel or guide wheel first depends on the situation. However, I prefer to install the drive wheel first and then the guide wheel.

If, after trying various methods, the track cannot be reattached, the last resort is to disassemble the track links. This makes reattaching the track much easier, although disassembling the track links can be challenging and may require heating with an oxyacetylene torch.

If the excavator is likened to a person, the tracks are its "feet." During movement, the four wheels interact directly with each other without any lubrication. Hence, this steel giant is not adept at walking. From another perspective, minimizing prolonged long-distance travel is also a way to take care of the excavator!

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