In more ways than one, there's a lot riding on an excavator's undercarriage, so diligent maintenance is key.
"Good routine maintenance keeps the overall cost of ownership down," says Chris Giorgianni, general manager of product marketing for JCB. "It extends the life of the wearing parts of the machine, such as sprocket, idler, chain and pads. It also stops vibration in the machine and damaging movement if these wear items are looked after well."
Scott Emmans, district service manager at New Holland Construction and Kobelco Construction Machinery America, explains, "The moving components of the undercarriage are wear-items, meaning they are expected to wear over time in the process of doing their job. The bottom rollers carry the weight of the machine while it is traveling and digging. The front idler holds the track chain in proper alignment while the machine is traveling and acts as a shock absorber and chain tensioner."
He adds, "The upper rollers carry the chain in alignment and are high enough to allow debris to fall from the chain, so it is kept relatively clean. The drive sprocket engages the track chain and propels the machine by pulling the chain over the sprocket.
"These components wear out over time," he continues. "With proper maintenance and normal use, their life should be reasonably long. With poor maintenance and rough operation, their life expectancy will be less. This becomes a significant issue because these
components are expensive to replace and time-consuming to install. Taking the time to do proper maintenance can go a long way to reducing operating costs."
Amy Van Hook, product manager, customer support, for John Deere, points out, "The undercarriage can represent a significant portion of the operating costs for an excavator. Proper maintenance will help extend undercarriage life and lower operating costs by keeping the excavator on the jobsite moving material and generating rental fees, not in the shop for repairs."
Are you doing enough?
There are signs that a rental center has forgotten or neglected undercarriage maintenance. They include loose tracks (which adds wear to pins, bushings and sprockets), chipped or broken sprockets, and loose or missing sprocket bolts - plus an increase in repairs.
"If you notice tracks are packed with dry dirt or clay, or in winter, snow and ice, you have situations that block the rollers from turning and cause accelerated wear," says Dave Pooley of Hyundai's service department. "Clean the tracks when they return to the rental yard and urge your customers to keep them clean, too."
Training your customers in other operational techniques can also help decrease undercarriage wear. For example, Giorgianni notes, "tracking backwards all the time can wear the tracks and undercarriage. Remind your customers that excavators should always be tracked in the correct direction over long distances. Also they should know to dig over the idler, not the sprocket, to reduce wear."
John Deere recommends the narrowest shoe possible to achieve required flotation. "If a machine is equipped with wider shoes than necessary for the application, you can expect to see shortened undercarriage life," Van Hook explains. "Wide shoes are necessary in soft underfoot conditions, but take that wide shoe into harder ground conditions, stumps or rocks, and you can expect to see reduced life. Wide shoes have an impact on track chain wear in general and can increase the load on the complete undercarriage system and components."
Hyundai's Pooley and Tom Novak point out that track tension must be checked daily for jobsite conditions. "You want to slacken tension for soft and muddy conditions and tighten for rock and general hard ground conditions. Slack measurement depends on size of machine, and manufacturers specify that in their operators manual," they say.