 Getting Extra
Life from
Your Dozer Undercarriage
The Good and Bad News of Compact Dozer Undercarriage Maintenance
By Joseph Gimbel
When considering undercarriage maintenance on
your compact dozer, it’s a good news/bad news scenario. The bad news is that you can’t stop undercarriage wear on a dozer. The good news is you can, however, extend your undercarriage life by understanding the causes of wear.
A major portion of the owning and operating costs of a dozer or compact crawler tractor involves the undercarriage. As much as 25 percent of the original purchase price of your compact dozer was spent on the undercarriage. Nearly one-half of all the money you spend on maintaining your compact crawler during its lifetime is spent on
the undercarriage.
You will also give your engine and transmission a major portion of your time. Because of the dollar value of your undercarriage, it deserves at least an equal
measure of attention. The bad news is that the undercarriage does not run inside a case, in a continuous filtered oil bath as engine and transmission components do. The working components of the undercarriage are open to soil, sand, rock, water, chemicals and the elements.
The good news is that, unlike engine and transmission components, which provide only indirect indications of wear before teardown (for instance through oil analysis), undercarriage components are visible and available for inspection and evaluation without disassembly.
Operating Costs
The operating costs of undercarriage vary considerably due to the different types of worked materials and jobsite conditions. Increasing undercarriage life dramatically decreases your overall machine operating costs.
Undercarriage working life does not follow the familiar pattern of machine wear. It is independent from other machine costs because of the variability in underfoot
conditions, which do not necessarily relate to normal
tractor wear. Therefore, the operating costs of an undercarriage should be calculated as a separate wear item. Managing your undercarriage means managing wear.
You need to have knowledge of the causes of wear.
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Categories of Wear
Wear can be divided into two main categories —
environmental and human. Both affect undercarriage wear in different ways.
Environmental Factors
Environmental factors can include jobsite profile,
material abrasiveness, impact and moisture. You cannot alter the working conditions, but you can minimize
their effects on wear. You can also calculate a more accurate wear rate for your
job costing.
• Jobsite Profile
Any deviation from a flat surface — from hills and valleys to rocks and potholes
• Material Abrasiveness
Course sands and clays
• Impact
Rocks and compacted soils
• Moisture Content
Moisture aids in material adhesion to your undercarriage (packing)
Human Factors
Human factors include machine
configuration, operation, maintenance and repair. These factors can be controlled or at least influenced.
• Machine Configuration
Track length and width
Shoe width (the narrower the better)
• Operation
Adjust operation to keep your undercarriage running on its normal wear surfaces as often as possible or at least equalize wear right and left or front to back
Configuration Considerations
Some of the configuration decisions are fixed at the time of machine purchase and cannot be easily altered such as track gauge and pitch.
• Track Shoe Width
This is important! Use the narrowest shoe available that will still allow the shoe plates to stay above the ground (i.e., flotation).
• Rock Guards
Guards will protect the track from material getting between the undercarriage components. Guards will also retain
material between the undercarriage components once it does get in. Use guards in drier, rocky conditions. In situations with severe material packing, don’t use rock guards.
• Sprocket Types
Relieved sprockets wear best in severe packing conditions.
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Operational Considerations
Operator skill cannot always be guaranteed in advance. On a short-duration construction project, for example, it may not be practical to set up a training program.
Existing operator habits can have a bad effect on track wear. It’s true that depending on the demands of the job and the jobsite, some of these less-than-ideal situations may be unavoidable, but you can minimize their effects on wear.
• Tight Turning and Counter Rotation
Tight turns put torsional loads on the undercarriage.
If these turns are unavoidable, to minimize the impact, alternate turning left and right, trying to do each half of the time. Example: Your dozing cycle includes dozing
one way and then the other over the same area.
Alternate which way you turn at the end of each cycle.
• High-Speed Operation
Undercarriage wear increases dramatically for a given distance traveled as machine speed increases. Example: When traveling to a new area of the jobsite, avoid rushing. The savings in undercarriage life more than makes up for the added time it takes to arrive. If the trip is too far, have the unit hauled by truck.
• Reverse Operation
Avoid reverse operation, especially high-speed reverse operation. Conventional tracks will suffer three times the wear in reverse, as they will in forward. Example: Pushing scrapers — push a scraper forward then reposition for the next pass with the next scraper. This cycle provides a
50 percent improvement over reverse operation. You can further minimize wear by moving slowly back to your start position. Use all the time it takes the next scraper to arrive to reset your position.
• Track Spinning
Never spin the tracks. Wear increases and there is no productivity gain to offset the wear incurred. Eliminate track spinning entirely.
• Favored-Side Operation
Most people are either right- or left-handed. We all have “sided” tendencies. Minimize wear by alternating left and right turns within a production cycle.
• Side-Hill Operation
Alternate right and left sides downhill from cycle to cycle.
• Uphill and Downhill Operation
Uphill operation puts more stress on the rear of the dozer, on its driving mechanisms. Plus you have to push a load against gravity. Dozing downhill uses gravity to your advantage and lowers stress on the driving components.
Of course, you have to get up the hill again to doze
downward again. Don’t back up or down the hill. Use your time and wear to produce work. Take a smaller cut to remove stress and lower the chances of spinning the tracks.
• Ripping (Pulling)
Ripping puts stress on a machine in the opposite
direction from that of dozing. To minimize wear, alternate ripping and dozing within each cycle.
• Slot Operation
Working in a slot is like traveling in a U-shaped trench. Much more stress is put on the outside of each track
shoe where contact is with the rising side of the slot. Example: When skidding logs, the dragged logs create a rounded profile to the haul road. Minimize this wear by swapping chains from side to side during maintenance and spinning rollers 180 degrees to allow new wear
surfaces to come into use. As always, use the narrowest track shoes possible.
• Crown Operation
Crowns are the opposite of slots but the wear is similar. Working on a crown is like traveling along a small hilltop. Much more stress is put on the inside of each track shoe because contact is primarily with the falling sides of the crown. Minimize this wear by swapping chains from side to side during maintenance and spinning rollers 180 degree to allow new wear surfaces to come into use. Use the narrowest track shoe possible.
• Extended-Term Parking
Long-term parking puts stress on roller and chain seals. This may cause leaking. Minimize this stress by running and moving the unit periodically.
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Other Maintenance Considerations
Clearly, every machine owner considers his or her own maintenance procedures adequate, and it is not for this article to suggest otherwise. However, within a given contracting organization, for example, the standard of maintenance must in practice vary, depending on remoteness of the jobsite from workshops, availability of experienced mechanics and so on.
• Track Tension
Track tension is the primary curable cause of unnecessary track wear. Tight tracks put undo stress on all components. Check track tension at least once a shift — more often if the materials change or get wet and begin packing.
• Material Packing (Track Cleaning)
Materials that pack on and around undercarriage components cause unusual and unnecessary wear, especially if they are abrasive. Clean out the undercarriage as needed with a shovel. This is worth the effort.
• Track Alignment
Track frames, idlers, sprockets and carrier roller alignment need to be checked periodically. (Think of the front-end alignment for your car.) Unusual and unnecessary wear will occur when components are misaligned. See your machine’s operator and service manuals for proper alignment procedures.
• Mixing Old and New Parts
If possible, don’t mix new and old components. The new components will quickly wear to match the warn profile of the older components. Example: One track roller (bottom) is replaced with a new one. The new roller, with its new diameter, will touch the track chain before the warn rollers touch. The new roller will take most of the machine weight for that side of the machine until it wears to match the profile of the other track rollers.
Asset Management
Be sure to collect data. Measuring your undercarriage on a periodic basis gives you the information you need to help manage this asset. Periodic undercarriage measurement should not result in just a list of measured dimensions
but in asset management decisions.
Use the information generated by undercarriage
measurement to help decide on configuration, operational and maintenance changes. You can know what is really happening and take specific, corrective actions. Also, you can better decide between repair options and choose the optimum timing of needed repairs.
With some understanding of what causes undercarriage wear, you can maximize the hours of service
you will receive from your undercarriage, lowering
your operating costs. Besides being more economical to operate, your compact dozer will be more productive over its lifetime.
Joseph Gimbel is a product manager for Case Construction Equipment, Racine, Wis.
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