What is an undercarriage overhaul all about? Part 1: machine survey

Proper maintenance of the undercarriage is an essential aspect when it comes to preserving the service life of an excavator or bulldozer. Depending on how intensively it is used, the undercarriage must undergo an undercarriage overhaul about every five years. As a rule, it is recommended to have an undercarriage inspection carried out on site beforehand to determine if a partial or complete overhaul is required. Not all undercarriage components wear at the same rate. Practical experience shows that a complete undercarriage overhaul is the most cost effective option in the long term. But what does it all involve? And why? This blog gives you an extensive answer to these questions in three parts.

When the top and bottom rollers are still in good condition, a partial undercarriage overhaul could be a cost-saving option. A partial undercarriage overhaul consists of replacing the sprockets, chains, bolts and nuts, as these components are inextricably linked. Fact is that the chain, and therefore also the sprockets, wear out significantly faster if they run over rollers that have been in service for some time and have worn away by more than 50 percent. For that reason (unnecessary early wear and tear) it is often the smarter choice to immediately renew the top and bottom rollers. This will ultimately result in the lowest cost per operating hour.

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Machine survey

For tailor-made advice, the machine can be surveyed on site. A number of facets associated with the chain, i.e. the pitch elongation, link width and bushing diameter, will be inspected. This is because the pitch elongation shows the play between the pin and bushing. If this play becomes too big, the bushing is worn internally into an oval shape and the pin becomes thinner because of the constant friction against the wall of the bushing. This wear can create too much space, resulting in a longer chain with less tension on it. If this problem is not fixed, there is an increased risk of chain breakage and downtime.

The link width shows the width of the link, which together with the bottom rollers create the height of the clearance of the undercarriage. This clearance height ensures that the front wheels and drives do not have to bear any machine weight.
Exact specifications are listed in tables that show to what extent a chain’s bushing has been worn. The external diameter of the bushing wears in the sprocket tooth curvature when it is powered. The undercarriage is set in motion when the sprockets run over the bushings, powered by the drive train.

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Appropriate advice

This measurement report with any wear values will be used to provide the most appropriate advice for the undercarriage overhaul. For the purpose of this report, the quality of the top and bottom rollers and front wheels will naturally also be inspected. The condition of the sprocket also forms part of the chain inspection. These two components cannot be separated, because a new chain and new sprocket interplay seamlessly and must therefore always be replaced at the same time during an undercarriage overhaul.

In part 2, you can read more about the process in the workshop and the undercarriage components that must be replaced during an undercarriage overhaul.

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Rubber tracks

Rubber pads

Idlers

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Bolts & Nuts

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