3. Mud and snow sprockets and segments
should only be used in the constant
presence of soft extrudable packing
materials. In any other material they
will result in much accelerated external
bushing wear due to reduced contact
area in the sprocket root where the slots
are located. This is particularly true of
Sealed and Lubricated Track because
the bushing spends a greater period of
time exposed to the root area of the
sprocket tooth.
Other Environment Variables
There are other conditions that may or
may not be associated with the soil and
underfoot conditions.
Moisture
The effects of moisture as contributing to
abrasiveness and packing have been
explained in the previous section. Moisture
or water in itself can corrode (rust) steel
resulting in the loss of wear material.
Moderate amounts of moisture increase
the corrosive effects of many other chemi-
cals and compounds; both those found in
nature and man made, such as sulfur, salt
and fertilizers.
Water in liberal amounts has the beneficial
effect of washing abrasive particles away,
softening many packing materials to ease
their extrusion and finally, diluting some
chemical corrosion agents to lessen their
effect.
Chemicals
Corrosive chemicals found in nature plus
man-made compounds may have the effect
of either eating away at wear material or
increase the rate of certain types of cracks.
Ironically, most hardened steels are more
susceptible to corrosion and corrosion
cracking than softer, unhardened steels.
Highly acidic and saline soils can con-
tribute to these effects.
Organic chemicals such as petroleum
products can attach rubber load rings and
toric rings in rollers and idlers causing
these to swell and fail.
Temperature
The effect of higher temperatures is to
increase the rate of chemical action.
Extremely high temperatures like those
found in slag removal in steel mills can
damage seals and soften hardened steels
found in undercarriage parts reducing their
strength and wear resistance.
The effect of temperatures below 32°F
(0°C) is to freeze soils and water, creating
all previously discussed packing effects
from normally non-packing materials.
Very low temperatures at -40°F (-40°C)
can result in increased steel brittleness,
(loss of cracking resistance) loss of rubber
type seal resiliency and reduction in the
lubricant flow necessary in Sealed and
Lubricated Track and Lifetime Lubricated
roller and idlers.
23
General Information
UNDERFOOT CONDITIONS