Undercarriage - 11/05/2021
As noted in the previous article, over the life of a tracked vehicle undercarriage maintenance costs can represent as much as 50% of total expenses. Wear on these components is inevitable due to dynamic loading and external agents. However, good machine management can offer considerable reductions in maintenance costs while improving productivity.
In the last issue we introduced the theme of reducing wear on the undercarriage and specifically discussed bad habits when using the machine, like excessive speed. There are 2 more factors influencing wear that we can control in order to extend duration and improve efficiency:
Excessive chain tension
This is the controllable factor that most influences wear on the undercarriage. Keeping the track chains excessively tensioned for the conditions of work increases wear on the external diameter of the bushings. This wear is estimated to be between 50% and 75% faster compared to use with correct chain adjustment.
Excessive shoe width
Using wider shoes than necessary for the machine flotation can seriously reduce the life of the undercarriage. The stress on the chain elements is proportional to shoe width. For example, a 36’’ shoe generates up to 50% more stress compared to a 24’’ shoe and excessive stress can cause breakage. Unnecessarily wide shoes also:
However, LGP machines can be equipped operate with wide shoes. This fact because the weight of the vehicle, if only operating in soft terrains, is distributed more evenly across a wider shoe.
Excessive machine weight
Excessive machine weight, for example due to unnecessary equipment being fitted, increases the load on the undercarriage, encouraging premature wear. This can be avoided by not overloading the machine and not fitting any elements that are not strictly necessary for the activity.
Misalignment of components
Misalignment of undercarriage components that are in contact with each other as effect of improper maintenance or excessive load produces uneven and accelerated wear. Differences in wear between the right and left sides, front and back, inside or outside of tracks, if not a consequence of the type of work or the way the machine is being used, is often the result of incorrect alignment between frame, idler wheel, and drive sprocket. The bigger and heavier the machine, the greater the risk of misalignment of components.
One of the factors that further accentuates misalignment is excessive track chain tension, already mentioned above, because it increases loading between interacting parts.
It is therefore important to eliminate any misalignments before installing a new undercarriage. How can this problem be recognized? As a rule of thumb, the presence of misalignments can be checked visually by closely observing any abnormal wear pattern on the bottom rollers.
Pivoting on the drive sprocket wheel when digging (among the most common bad habits when using excavators)
This bad habit generates excessive dynamic loading on the drive sprocket (also giving the machine a tendency to judder), which in turn bears on the bushings causing accelerated structural damage to them and the other undercarriage components involved.
Cleaning the machine
At the end of each work day the operators should take time to clean any dirt and debris that has accumulated on a tracked undercarriage. If the tracks are clogged with dirt the machine will have greater difficulty operating, wasting energy and generating additional loads that shorten the useful life of the undercarriage. This phenomenon is especially critical in geographic areas with cold climates, where mud, dirt, and debris tend to freeze up.
Another negative effect of dirt on the machine is accelerated wear on the drive sprocket teeth and the outside of the chain bushings caused by incorrect contact between these elements. The rollers, both bottom and carrier, are also affected by this problem to the point of complete seizure. This is indicated by the appearance of flat areas on the tread surface.
Finally, over time the presence of mud creates additional layers of material on the undercarriage components, generating excessive tension in the chains and so further increasing the rate of wear. Shovels and pressure water cleaning systems can be used. However, care must be taken with the latter! Never direct water jets towards the lubricated chain plugs! This could cause them to move and come out of their seatings, resulting in loss of joints lubrication.
Along with management of controllable factors like speed, bad machine user habits, loading, and external abrasive materials, there are other forms of good practice that can help avoid premature wear on the undercarriage, and we will talk about these soon in another post.