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Choosing the Right Shoes for the Job

Field Fact: 50% of the cost of owning and operating a machine
are related to its undercarriage

C.N. Wood has developed guidelines to help you get the most out of your undercarriage with the lowest cost possible. There are three basic maintenance areas that can have a big impact in your cost—track tension, cleaning and service records.

Characteristics of Shoes

Shoes vary in two ways—width and type of shoe. Choosing the right shoe for the job will enable you to complete the job as quickly as possible without excess wear on your undercarriage system. Four factors affect shoe performance: flotation, penetration, maneuvering ability and robustness.

Flotation—the shoe's ability to keep the machine from sinking. Flotation depends on ground material, machine weight and shoe width. Ground Material—the type of ground material is the biggest factor affecting flotation. Machine Weight—the heavier the machine, the more difficult it is to keep it afloat. Shoe Width—determines the contact area between the tracks and the ground. Wider shoes provide more contact area and allow the weight of the machine to be distributed over a larger area, increasing flotation. This concept is called ground pressure. Ground Pressure—the relationship between shoe width and machine weight determines ground pressure, as shown in the following formula:

Ground Pressure = Machine Weight/Contact Area Contact Area = 2 x (Track on ground length x Shoe Width)

As a general rule of thumb, shoe width must be wide enough to keep the machine afloat, but not wider.

Penetration—describes how far that portion of the grouser that digs into the ground during operation actually penetrates into the ground. With good penetration the entire grouser is embedded into the ground. With poor penetration, very little of the grouser is embedded into the ground. Better penetration results in better traction.

Traction is the machine's ability to grip the ground and move in the desired direction. Traction is related to ground material, machine weight and shoe type. Shoe width does not affect traction.

Soil Conditions Determine Shoe Width and Type

Maneuvering Ability—is a function of ground material, machine weight, shoe type and shoe width. Wider shoes make it more difficult to maneuver the machine because they stick out farther and cause turning resistance.

Robustness—is the ability to withstand wear and impact. Shoes are subjected to a bending movement that increases proportionally with shoe width. A track shoe is like a lever—the longer the lever, the easier it is to break. Accordingly, wider shoes are more susceptible to wear and impact, and they increase the affects of impact on all the other undercarriage components. Problems related to wide shoes are: Increased wear on link sides, rollers and flanges External/internal bushing wear Pin loosening Premature seal failure Contribute to packing conditions, because they can scoop deeper and provide more room for soil accumulation.

Shoe type is also an important contributor to robustness. Matching the soil type and the shoes is critical to avoid premature wear in shoes. Examples include:

Type of shoe Intended soil type Problem if used on wrong soil
Rockbed shoesHard rocky terrainOn soft terrain, metal will not work-harden and grousers will quickly wear away and fail
Single grouser shoesSoft terrainOn hard rocky terrain, grousers will wear prematurely
Swamp shoesSwampOn hard ground, shoes will deform and wear prematurely
Flat shoesPaved surfacesOn soil, shoes will have no penetration and wear prematurely

Mud relief hole—A mud relief hole is drilled in the center of the shoe plate for certain types of shoes. It prevents packing accumulation by helping the material to escape. Every time the sprocket pushes on a bushing, it squeezes the material out.

Before using a shoe with a mud relief hole, check that the ground material is extrudable (e.g., clay, soil, snow and ice). Non-extrudable materials include rocks, gravel, branches and brush.

Roller Guards—prevent rocks from impacting and clogging track rollers and provide additional guidance for the track chain. One problem with roller guards is that they often trap material instead of letting it be thrown off naturally. For this reason, roller guards should not be used in high packing conditions.