The excavator's undercarriage system plays a critical role in its overall performance, stability, and durability, particularly under harsh working conditions. This article examines the key components of an excavator’s undercarriage, providing practical tips on maintenance to help prevent costly damage and downtime.
1. Track Rollers
Track rollers, located beneath the X-frame, bear the weight of the excavator and allow it to move along the tracks. For a 20-ton excavator, each side generally has seven track rollers, with two protected by track guards. Track rollers should be kept free from mud, water, and ice as prolonged exposure can damage the floating seals between the roller shell and axle.
After each workday, lift one side of the track to clear off mud and debris by rotating the track with the travel motor. This maintenance is especially important during winter to prevent ice buildup on the rollers. When water freezes overnight, it can damage the seal, leading to oil leaks – a common issue in colder months. Damaged rollers can cause uneven travel and reduced driving power, so it’s essential to keep them in good condition.
2. Carrier Rollers
Positioned on top of the X-frame, carrier rollers maintain the straight line of the track chain. Damaged carrier rollers can cause the track to misalign, a condition often described as "throwing a track." Carrier rollers are pre-lubricated and cannot be refilled, so if a leak occurs, the entire roller must be replaced. To avoid excessive dirt accumulation that could restrict roller movement, keep the top surface of the X-frame clean and avoid allowing mud to build up.
3. Idlers
Idlers are located at the front of the X-frame and consist of the idler wheel and a tension spring mounted within the frame. Keeping the idler positioned forward during operation reduces abnormal track wear. The spring absorbs shocks from rough terrain, minimizing wear on other components.
The idler tensioning assembly comprises a spring and grease cylinder, allowing adjustments to the track’s tension via grease injection. Neglecting this detail may lead to serious consequences, as long periods of inactivity or exposure to moisture can cause the piston rod to rust, immobilizing the assembly. Regular greasing and bleeding are essential for maintaining correct track tension.
4. Drive Sprockets
Drive sprockets are located at the rear of the X-frame and consist of a travel motor, reduction mechanism, and drive ring gear, enabling track movement. The travel motor receives hydraulic power from the main pump and is slowed by the reduction mechanism to engage the drive gear, propelling the track.
The drive sprocket should always be positioned at the rear to prevent abnormal wear on the track gear and ring gear, as well as to avoid potential damage to the X-frame, which could lead to premature cracking. Mud and gravel accumulating in the travel motor guard can corrode the oil hose connectors and cause wear-related leaks, so it is crucial to regularly clean the guard’s interior.
5. Track Shoes and Chain Links
The track assembly consists of track shoes and chain links. Track shoes are available in reinforced, standard, and extended versions. Reinforced shoes are ideal for mining, while standard shoes are used in earthworks, and extended shoes are suited for wetland applications. Mining environments accelerate wear on track shoes, as gravel often becomes lodged between them, leading to deformation and cracking over time.
Chain links engage with the drive gear and rotate to propel the track. Excessive track tension accelerates wear on chain links, gears, and idlers. For effective operation, measure the track tension by either of these methods:
· Track Plate Tension: Place a straight rod on the track between the drive and idler sprocket and measure the vertical distance from the track to the rod, ideally 15-30 mm.
· Raised Track Tension: Lift one side of the track and measure the vertical gap between the track plate and the X-frame; this should measure 320-340 mm.
Adjust tension based on specific working conditions: for mining or wetland use, aim for 20-30 mm or 340-380 mm, and for sandy or icy conditions, consider slightly higher values.
