Understanding Mini Excavator Undercarriages

Tracks, Sprockets, Idlers and Everything in Between

It may not seem like much, but in more ways than one, there’s a lot weighing on a compact excavator’s undercarriage. And when it comes to lowering the cost of equipment ownership, proper operation and maintenance are the difference between money saved and costly repairs. Normally, a compact excavator doesn’t put in a lot of travel time. On a jobsite, its main responsibility may be to sit and spin on its housing, digging holes and trenches. Because of its lack of motion, there’s less fatigue and wear on the undercarriage compared to other machines. However, as the most costly part of the tracked machine, it’s important for operators to understand the parts and components that make up the undercarriage and frequently inspect them to make sure everything is working properly.

Keeping Track of the Tracks

The most important component of a compact excavator’s undercarriage is its tracks. Most compact excavators come with rubber tracks, which allow for greater versatility on the jobsite, high floatation, low ground pressure, machine stability and a smoother ride. Rubber tracks come in a variety of widths, depending on the machine size and manufacturer. Some are more narrow to help the machine squeeze through gates and doorways on jobsites, while a wider width provides added stability even on uneven ground.

Properly caring for the tracks is essential for operators, as they are expensive to replace. As the most obvious wear item on the undercarriage, the rubber tracks are susceptible to increased damage based on the operating environment and the amount of usage. Because of this, rubber tracks should be used primarily on flat surfaces, avoiding rocky or debris-heavy areas. To track the wear on the undercarriage, operators should perform a daily visual inspection to look for any cuts, tears or distress. It’s also important to take note of any spots on the tracks where the steel imbeds are showing. Any of these problems could lead to machine failure and unexpected downtime.

Operators should also monitor track tensioning. An improperly tensioned track can cause uneven or accelerated wear on the machine and its other components, including the sprocket. If a track is too loose, it can de-track, while a track that is too tight could cause damage to the undercarriage and wear other components at an excessive rate. Operators should reference the machine’s operator’s manual, which will diagram the correct track tension ranges for that specific machine.

Drive Sprockets

A sprocket is a profiled wheel with teeth that meshes with the compact excavator’s tracks. It aids in the motion of the machine as a whole, propelling it forward by pulling the chain over itself. Not only do the drive sprockets move the tracks, but they also handle the brunt of everyday operations. Accelerated wear of the drive sprockets can be common. Because of this, they should be checked periodically during a machine walk-around. Operators should pay attention to the shape of the drive sprocket teeth: A tooth in good shape has a rounded end, while a worn tooth is more pointed. A worn sprocket could potentially lead to damage on the lugs of the rubber track, so operators should check the condition of the sprockets before changing the excavator’s tracks.

Idlers

Another component of the compact excavator’s undercarriage are the idler wheels. The idler is a large, metal wheel at the front of the track frame that guides the rubber track. It’s also responsible for tensioning the track around the front of the undercarriage frame, decreasing the risk of de-tracking. Worn idlers should be replaced to prevent damage to the undercarriage due to increased drag, which can result in severe damage to the tracks and undercarriage.

Rollers

The undercarriage of a compact excavator includes small parts called rollers. Rollers are metal wheels that are mounted to the top and bottom of the track frame, which support and guide the rubber track between the sprocket and the front idler. The track roller is responsible for guiding the track over the frame, while the primary function of the bottom rollers is to bear the weight of the machine. Any worn, seized or loose rollers can cause damage to tracks due to increased drag and may cause premature failure of rubber tracks as a result of frequent de-tracking. Inspections of these parts could save operators a significant amount of time and money in repairs.

Final Notes

The components of the compact excavator’s undercarriage are designed to wear evenly over time. Premature wearing can affect the wear of other components as well, affecting the machine’s overall productivity. If some components wear more quickly than others, it could be a sign of improper operation or lack of maintenance. Each operator should be taught the correct way to operate their compact excavator and have an understanding of how they can keep it running as productively as possible. Actions such as operating at high speeds, excessive time in reverse and driving over curbs can cause accelerated wear on the undercarriage.

Operators should change their turning direction, or limit turning if possible, to balance wear on each side of the undercarriage. Constantly turning to one side will greatly reduce the life of the machine’s tracks. In order to get the most from the machine’s undercarriage, operators should clean all of the undercarriage components, including rollers and tracks, after every use. The accumulation of jobsite debris, like mud and dirt, around the undercarriage can interfere with proper operation, which leads to faster wear. Special attention should be paid to the cleanup of rubber tracks since buildup can cause them to stretch.

Usage conditions and maintenance greatly influence the life and longevity of a compact excavator’s undercarriage. But understanding and taking care of each component that makes up the undercarriage will lead to a more productive machine and money saved.

Kevin Lock is a parts marketing manager with Case Construction Equipment, based in Racine, Wis.