Choosing the Right Shoes for the Job

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

Shanahan Equipment 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:

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.