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Undercarriage wear and maintenance tips.

Undercarriage wear and maintenance tips

The modern crawler undercarriage is a precision component that requires attention to ensure efficient performance and economical operation. This fact, however, is easily overlooked when a dozer is continually slogging through deep mire or being repeatedly jolted as it pulls a ripper.

Even though undercarriage maintenance accounts for an estimated 40-70% of total crawler repair costs, routine undercarriage maintenance and signs of abnormal wear are very often overlooked, not so much through neglect as from a lack of undercarriage knowledge. The service engineers at KDC Parts have prepared a few tips on undercarriage maintenance how to extend undercarriage life.

Undercarriage wear. The rate of wear depends primarily on the crawler's operation and application. Wear will accelerate when the undercarriage is subjected to conditions which continually pack the undercarriage with dirt or debris. These conditions are often found in reclamation operations, or when running in ice and snow. High abrasiveness also contributes to accelerated wear. Reverse-sprocket tip wear and accelerating bushing outside-diameter (OD) wear are two of the most significant types of wear resulting from packing of the undercarriage.

Even though packing conditions cannot be totally eliminated, a few changes such as using track shoes with clearing holes, removal of rock guards and periodic cleaning will help relieve the packing conditions.

Track chain wear. Two of the most critical wear areas of an undercarriage are internal-pin and -bushing wear and bushing outer-surface wear.

Internal-pin and -bushing wear results as a track chain revolves around the sprocket and front idler. As the crawler works, this wear causes the track chain to increase in length, thus the dimension between pin centers becomes greater. Internal-pin and -bushing wear is virtually eliminated with a lubricated-track system. Lubrication between pins and bushings virtually eliminates pitch extension and the familiar snaky-track.

Bushing-OD wear results as the sprocket teeth engage the track-chain bushing to move the crawler. Speed, direction of travel, abrasive material, and working in a packing condition contribute to both the wearing of the bushing OD and the sprocket teeth.

Since both bushing-OD wear and internal-pin and -bushing wear are simultaneous, their wear limits must be closely monitored so they do not exceed the maximum allowable limits. Turning pins and bushings within the allowable limits is a common and practical maintenance operation that extends track life considerably. Both internal-pin and -bushing and bushing-OD wear occur only on one side, thus a 180 [degrees] rotation allows the unused portion of the pins and bushings to be used. This procedure restores track pitch to new dimensions and allows a new bushing surface to work against the sprocket tooth. Whenever pins or bushings are turned, or when new track chains are installed, new sprockets should be considered to match the new pitch and the new bushing-OD dimensions. Lubricated track bushings can also be turned. Because internal wear is virtually eliminated, wear limits of the bushing OD is extended.

Pin-boss damage. Pin-boss damage is a combination of worn rollers and worn track links. In most cases, pin-boss damage is the result of a seized or broken roller.

When pin-boss damage is observed, rollers should be checked and replaced immediately. Severe pin-boss damage weakens the link and pin connection, resulting in shortened track life. The damage will also prohibit turning pins and bushings.

Rolling diamater. Rolling-diameter wear applies to the track rollers, front idlers, and top idlers. Each of these components has a hardened surface that continually rolls across the track chain. Wear of these parts cause the rolling diameter to decrease. In addition, the track rollers must bear the entire weight of the crawler as it moves across the track chain. In some operations, the weight of the crawler is concentrated on just a few rollers. Along with abrasive materials, this will contribute to roller and track chain wear.

Maintenance. Undercarriage wear is inevitable and progressive. However, there are a few simple maintenance items that can definitely help to control wear. First, periodically remove material that might be packed around the idlers, rollers, sprockets, and the top of the track frame. A top idler that cannot turn because of packed material, for example, will quickly wear a flat spot on the rolling diameter as the chain drags across it.

Next, watch for leaks around the rollers, top idlers, and the front idlers. A leaking component means that lubrication is being lost. If ignored, the component could seize with the quick result of excessive wear in the track chains.

Also keep the chain at proper tension, and watch for loose or missing hardware, such as track-shoe bolts. Missing hardware can cause premature failure.

Above all, check for signs of abnormal wear. If excessive, unexplainable wear is occurring, call an undercarriage expert. He has the means to keep tabs on undercarriage wear and can recommend corrective maintenance before wear becomes excessive. For instance, constant evaluation of bushing-OD wear and internal-pin and -bushing wear will allow turning of pins and bushings at the optimum time. If chain-pitch or bushing-OD wear are not monitored, they could wear beyond turnable limits.

Crawler operator techniques greatly affect undercarriage life. Spinning tracks, cutting too deep, and lifting the machine's front end cause excessive undercarriage wear. Fast reversing, pivot turns, and hillside work are very abusive and should be avoided if possible. Alternating directions and varying work patterns will equalize wear and extend undercarriage life.

Proper track and track-drive components matched to the job will maximize he time between rebuilding or replacement of parts. In sand or abrasive soil, use wide shoes for high flotation, enabling the crawler to stay "on top" and out of the abrasive particles. In wet, clay-based soils, use center-punched shoes to reduce clogging.

Prolonging undercarriage life is the responsibility of both operator and service personnel. Proper maintenance practices will help you obtain the maximum useful life from your crawler undercarriage.

Recognizing the need for undercarriage advice, KDC Parts conducts ongoing undercarriage seminars. These intensive programs enable distributors to train their personnel as undercarriage specialists who are knowledgeable in undercarriage evaluation and can offer maintenance options.

When undercarriage replacement is necessary, a genuine OEM undercarriage may be more affordable than you think. Also, many distributors can offer rebuilding alternatives that can result in additional savings.

PHOTO : The modern crawler-tractor undercarriage is a precision component that requires proper attention for efficient and long life.
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Title Annotation:crawler maintenance
Publication:E&MJ - Engineering & Mining Journal
Date:Apr 1, 1991
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