iglidur bearings in the mini-excavator undercarriage greatly extend service life

Susceptible grooved ball bearings for supporting the skate wheels have been replaced by maintenance-free plain bearings.

This mini excavator from Yanmar (with a Hinowa chassis) uses skate wheels to distribute weight evenly over the entire base. But harsh operating conditions make the skate wheel structure very susceptible to dirt, moisture, and damage. Plastic plain bearing bushings from the iglidur G series were to remedy this, replacing expensive and vulnerable deep groove ball bearings. In addition to the cost reduction because there are no regularly purchased parts, the new design promises a greatly extended bearing service life. The result is an excavator has been in use for several years without maintenance.

Profile

What was needed: iglidur G plain bearings
Requirements: low moisture absorption, dirt resistance, load capacity, and freedom from maintenance
Industry: construction machinery, excavators
Success for the customer: The bearing change has extended the machine's service life and greatly increased availability. The new solution also enables the customer to completely eliminate short maintenance intervals. Overall, the mini-excavator's stability and load capacity increases.

Skate wheel on the excavator undercarriage: Dirt particles and moisture penetrated into the ball bearings previously used and repeatedly led to the failure of one or more skate wheels despite regular maintenance at short intervals.

Problem

Since the deep groove ball bearings in the skate wheels of a Yanmar mini-excavator were failing increasingly often, the excavator company was looking for an alternative.
The mini-excavator moves with a rubber track roller unit powered by one oil engine on each roller. The excavator's weight is distributed evenly on the undercarriage skate wheels on both sides, which also laterally guide the rubber track. But the internal skate wheel structure is susceptible to damage because of the harsh operating conditions to which excavator undercarriage is exposed. Dirt particles and moisture penetrating into the ball bearings repeatedly cause one or more skate wheels to fail despite regular maintenance at short intervals. Such failure means a great deal of repair work and associated high costs for spare parts and downtime.

Solution

To solve the problem, the expensive and error-prone grooved ball bearings were to be replaced with plain bearings made of the iglidur G material. All that was needed for this was a modified axis and two placeholders to fill in the cavity created when the ball bearings were eliminated. The smaller circlips used for the axial spacing between the bearings are no longer needed thanks to the change in the axis. The low cost of the changes required makes this solution a very cost-effective one. Since the iglidur plain bearings are lubrication-free, dirt is unable to adhere. The bearings' low moisture absorption means that they are suitable for wet environmental conditions. This extends machine service life and greatly increases availability. The new solution also enables the customer to completely eliminate short maintenance intervals. The mini-excavator's stability and load capacity are greatly improved by the bearings' increased load capacity.

View of the original skate wheels

Economical all-rounder bearings made of plastic

The iglidur G material is a good idea whenever an economical all-rounder bearing that can withstand extremely high loads and operate at low to medium surface speeds is necessary. The coefficient of friction in the iglidur G series changes with load much as wear resistance does: it decreases as load increases. The maximum permissible short-term temperature for this plain bearing is +220 °C, and the minimum application temperature is -40 °C. Although the compressive strength decreases with increasing temperatures, the permissible surface pressure at a possible long-term +130 °C is still more than 40 MPa. Significant bearing wear occurs only starting at +120 °C. iglidur G plain bearings resist chemicals well. Most weak organic and inorganic acids cannot harm the material. The bearings are also resistant to many lubricants.