Undercarriage - 20/07/2021
In the previous articles we discussed how bad habits when driving tracked vehicles, loading, and the presence of external abrasive materials can affect wear on the undercarriage. Choosing the right chains, shoes, and guides for the type of work can also make a big difference.
The track guides help to keep the tracks on the track rollers. If a chain does not engage correctly with the track rollers under the various working conditions, it can come off during manoeuvres or when encountering large objects on the ground. This generates high loads on the chain components, with the risk of dry joints (in lubricated chains) or even structural damage and breakage. It is therefore necessary to follow the manufacturer's instructions to establish which guides are best for your specific application. It is also important to regularly check their degree of wear or damage, repairing or replacing them if excessively degraded.
There is a vast range of shoe profiles for medium-sized bulldozers. This wide choice ensures that you can find the ideal solution for adapting your machine to the ground conditions. There is no single shoe suited to all applications: the choice depends on the work environment, climate, and ground conditions. Moderate service shoes (MS), for example, are recommended for use in soft, non-abrasive conditions.
Under abrasive conditions, extreme service shoes (ES) are generally the best choice.
ES shoes are highly resistant thanks to increased plate thickness and higher, wider grousers. They certainly offer greater wear and structural resistance, but with a few compromises:
If unnecessary, they simply increase machine weight, speeding up wear on the undercarriage components and increasing the tendency to sink on soft ground.
They have more difficulty penetrating the ground since shoe grousers act much like blades: the thinner they are, the more easily they can penetrate the ground.
ES shoes influence terrain levelling capability because they can generate vibrations that are transferred to the blade.
They should therefore be used sparingly.
On medium-sized excavators, triple grouser shoes are standard. These machines can also be fitted with heavier or lighter profiles: the choice depends on the need for flex resistance, which depends on the consistency of the ground and the shoe length.
Many shoes offer options like mud relief to help keep material away from the chain links. This type of shoe is recommended for very sticky mud or clay. The drive sprockets expel mud from the chain links, helping to maintain correct track tension. However, in other contexts a mud relief shoe can cause damage: on soft ground, the material that is expelled from the relief hole can fall directly into the chain links, speeding up wear.
Another option, mainly used on bulldozers for levelling and finishing work, is shoes with clipped corners. The chamfers facilitate turning, reducing shear load on the shoe mounting bolts and the risk of link breakage.
Lubricated chains are recommended for machines that are constantly moving (like bulldozers or loaders) because the oil present between the pins and bushings forms a constant layer, greatly reducing internal wear for extended working life. This system is suitable for almost all applications, apart from very hot environments, like handling hot slag when the exposure of the tracks to high temperatures irreparably damages the sealing components.
There are some specific applications for dry chains. They offer more resistance to torsional loads, but the internal wear on the pins and bushings can become the main cause for extraordinary maintenance work.
Another chain type, today standard on almost all excavators, is the greased chains. These are similar to dry chains but are equipped with a sealing system that retains grease between the pins and bushings. This reduces internal wear and extends the life of the joints.
It is good practice to visually inspect the undercarriage every morning, or when changing work shifts. Check for loose or missing bolts, oil leaks, anomalous wear, loose or bent guides, jammed materials, etc.
Just a few minutes is enough to find and eliminate any problems, extending the life of the undercarriage and significantly reducing the need for more substantial maintenance work. Finally, for optimized management of undercarriage wear, it is fundamental to measure the parts subject to wear.
ITR have created Weartek+ for this purpose, an app for collecting the measurement data, forecasting residual working life, and selecting the optimum strategy to minimize the hourly cost of an undercarriage. The program can archive inspection data, monitor the stock of spare parts so that you always have replacements when required, schedule maintenance work, analyse the performance of each component, and lots of other things! Would you like to find out more? We will talk about this soon in another article, but in the meantime you can contact the author for more information.