Variables That Affect
Undercarriage Life
The variables that determine complete
undercarriage system life and wear balance
between components can be divided into
three major groupings. The first are those
which, to a great extent, are controllable.
Controllable variables include track tension
adjustment (controlled by user operating
and/or maintenance personnel), shoe width
(controlled by user operating and purchas-
ing personnel) and on some models, align-
ment (controlled by user and/or dealer
service personnel).
The second major group, non-controllable
variables, discussed later in this major
section include those life determining
factors which are “givens.” They come
with the job. They are 100 percent deter-
mined by the underfoot conditions and
include impact, abrasiveness, packing,
moisture, terrain and even application,
meaning what the machine is doing.
The final major group is sometimes called
partially controllable variables and mainly
involve machine operator controllable
events such as “habits.”
A thorough knowledge of each of the
elements of all these three major groups is
essential if the CTS expert is going to be
able to not only explain “what has hap-
pened,” but also “what could be expected to
happen,” especially as any of these variables
were to change. Awareness of the relative
interplay between these variables on the
final wear or structural life of specific com-
ponents, and even on the system is so
important that their discussion has been
placed at the front of this book. To use the
rest of the book before understanding these
would be counterproductive.
Controllable Variables
Controllable variables that affect undercar-
riage life must be separated out for dis-
cussion because, in the case of at least the
first two, they can have major economic
effect on the operation of undercarriage
systems.
Track adjustment can have a very large
effect on external bushing life, even to the
extent of deciding whether a costly turn
will or will not be required to use up the
link-roller system. Track tension can also
affect track seal integrity. Track adjust-
ment is controllable because the user can
change it.
Shoe width, for which a detailed discus-
sion follows, is controllable because the
user, with your advice, chooses which
shoe to order on his new machine and/or
changes to when the machine changes
tracks or even jobs. Shoe width as you will
learn can effect such widely ranging items
as track seal and lubricant integrity to link
cracking to roller flange wear to bushing
wear rate.
Alignment, the third and least critical
controllable variable is discussed here
because, particularly on low sprocket
machines, it is wrongly blamed as a cause
for many symptoms. It is beneficial to
know how misalignment does and does
not affect wear patterns so you can better
identify the real cause, controllable or not.
A short discussion on track-excited
vibration is also placed in this area even
though it is only controllable at machine
design time.
Track Adjustment
Although the method of measuring the
reference sag and adjusting the track varies
by machine type, the importance for these
different machine types does not. As dis-
cussed earlier, track over-tightening can
drastically affect external bushing life
(increasing wear rate as much as three
times) and for this reason alone is listed fre-
quently as a “cause” or “accelerator” under
the wear and structural problems section for
many components. See separate machine
sections for complete instructions on track
adjustment.
11
General Information
UNDERCARRIAGE LIFE VARIABLES — CONTROLLABLE VARIABLES