There are many different styles of undercarriage available in the market, each with unique design features that set them apart. Progress Mining supplies all undercarriage types giving us a unique insight into what works best in different situations. To illustrate how these undercarriage styles differ we are posting a series of articles, each a spotlight on a particular undercarriage style, outlining key features, advantages and disadvantages.
Above: Liebherr® R9800 hydraulics excavator with shared drive, single sunken drive lug and dual asymmetric roller undercarriage design.
The fourth article in this series focuses on the R9600 and R9800 range of Liebherr® hydraulic excavators. The features that define this style of undercarriage include:
- Shared drive type
- Single, sunken track shoe drive lug configuration
- Dual, asymmetric track shoe roller path configuration.
This undercarriage design is made to last with several features designed to extend undercarriage life through reduced wear related component changeouts. Progress Mining has supplied undercarriages for these platforms to customers operating in coal and copper mines across Australasia and Africa.
Above: Liebherr® undercarriage design illustrating the different design features.
This undercarriage design has proven its efficacy over time, the following advantages show why it is used in many mining fleets:
- The shared drive configuration minimizes drive lug contact pressure and wear rates by sharing the drive force between multiple lugs.
- The sunken drive lug configuration increases room for wear in the system. This extends the life of the drive lugs which often limits undercarriage life.
- The dual roller path design results in greater contact area between the rollers and the track shoes. This decreases the contact pressure and subsequent wear of both components.
- The asymmetric track shoe design allows for continuous roller engagement, helping decrease component wear.
As with any engineering design, there are certain aspects of the undercarriage configuration that may present disadvantages:
- The single drive lug design means contact pressure and resulting wear rates are higher than a dual drive lug system.
- The shared drive means that backlash it at a maximum from new, leading to higher roller path wear during direction changes in the early stages of life. Backlash is the distance between the non-driven shoe and sprocket drive lug flanks. The larger the distance the higher the sliding between the shoe and sprocket roller paths is during a change in sprocket rotation.
- Comparatively fewer bottom rollers are used in this design compared to other platforms in similar weight classes. This increases the load per roller and results in a less uniform load distribution, which can lead to increased roller path wear and roller bush/shaft wear.
The undercarriage design featured in this article does not apply to the R996B Liebherr® excavator platform. Like the R9600 and R9800, the R996B also uses a dual roller path asymmetric track shoe, though the drive lug is raised which is the same as the design style of the Hitachi® undercarriages featured in a previous article. Although there are still various R996B machines working in mine sites across the world, the R996B has been superseded by the R9600 in the same weight class. The most impactful improvement of the new design over the superseded one is the sunken drive lug design that increases room for wear in the system.
Progress Mining supply all undercarriage types to many different mine sites across the globe. The knowledge and insights gathered over the years puts our team in a position to understand the complexities of each undercarriage design. Using the data gathered from countless Condition Monitoring inspections in parallel with CAD engagement analysis, our team is well placed to analyse your fleet and provide recommendations based on your needs.
To find out how the team at progress Mining can help visit our Services page or email us at info@progressmining.com
Where ever mining is Progress Mining is there to help.
Read article 1 in the series: Undercarriage Design Series: Caterpillar®
Read article 2 in the series: Undercarriage Design Series: Komatsu®
Read article 3 in the series: Undercarriage Design Series: Hitachi®