Ignoring undercarriage management can be costly. However, the con to not servicing and managing your equipment properly, can be extremely costly when something catastrophic happens on a job site. Equipment failure of this nature can lead to even more lost money besides the repair. Trying to recover the excavator out of the mud and wasted company time and employee hours are just a few additional losses a company can take when equipment malfunctions. Making good business decisions, such as being proactive in maintenance at the due time, measuring wear and periodically following a few basic recommendations can stop the costly repairs and expenditures in its tracks. A good place to spot with this type of maintenance is pin and bushing turning.
Pins and bushings wearing internally due to lack of lubrications, primarily wear on one side of the pin. The side that takes the burden of the wear is the mating surface of the bushing’s inner diameter. Due to a lack of lubrication, wear changes the geometry of the track by allowing the pitch of the track (distance between pin centers) to lengthen. The lengthening of the distance between the pin centers causes the chain to ‘stretch’ and run loose.
Industry standard wear occurs on the outside of the bushing, mainly on the one side, the reverse-drive side. The rotation of the bushing is burdened with a load on the top of the sprocket when the machine is in reverse, although when engaged in forward travel, the load is minimal.
The one-sided wear of pins and bushings allows these parts to be ‘turned’. The basic practice of a pin and bushing turning entails a 180-degree rotation where the pins are flipped end-for-end. The rotation of the pins brings new surfaces to working areas, allowing the wear for the difference in load to be distributed. The pin and bushing turning provides new surfaces to working areas both internally and externally. Turning restores pitch on the track between pins, and can prolong undercarriage life by enabling the chain to last until links and rollers need attention.
A pin and bushing turning and sprocket segment replacement at the time of the turn can help with the longevity of your complete undercarriage on dozers and track loaders. This is significant in that the bushings become completely worn out, which helps you with wearing the life of your track link assembly completely out.
“Turns” on today’s machines with lubricated tracks can be either in the form of “wet” or “greased.” A wet turn entails the work of the pins being refilled with oil, a process that involves pulling a vacuum in the pin’s oil reservoir (through a self-sealing plug in the end of the pin) and drawing in clean oil. If the assembly won’t pull a vacuum, chances are that the seals are not proper and will cause leaks. With a grease turn, pins and bushings are simply reassembled with heavy grease as lubrication.
Although a pin and bushing turning has been a known and used maintenance staple in the past, the economic value of the practice is getting a second glance today because of all the benefits a simple maintenance step can bring in cost savings to business owners.