Function and requirements of supporting wheels

The supporting wheel is often immersed in mud, water, dust, and subjected to strong impacts, therefore it is required to have reliable sealing and wear-resistant wheel rims.
The function of the supporting wheels is to transfer the weight of the locomotive group to the ground and roll on the tracks. To prevent derailment, the supporting wheels should also be able to prevent the tracks from causing lateral relative movement to them.
Supporting wheels often work in mud, water, ash, and sand, and withstand strong impacts. The working conditions are extremely harsh, and the wheel rim is easily worn.
The requirements for the supporting wheel are: wear-resistant rim, reliable bearing sealing, and low rolling resistance.
Having more supporting wheels can make the ground pressure of the tracks more uniform, which can reduce sinking when walking on wet and soft soil. However, on the other hand, because the length of the tracks is certain, having more supporting wheels will inevitably result in a smaller diameter for each, which increases rolling resistance. Generally speaking, as a walking mechanism for combine harvesters, the number of supporting wheels is usually 3-4, with a few using 6.
Sliding bearings are commonly used for supporting wheels (such as iron-based powder metallurgy oil containing bearings), but rolling bearings are also useful. Regardless of the type of bearing used, it is essential to prevent mud and water from entering.
The rim of the supporting wheel should be wear-resistant and generally made of 45 steel. The surface of the rim should have a hardness of not less than HRC53 after quenching.