Structure and Application of Track pads

- Feb 18, 2019-

The common track shoes can be divided into three types according to the grounding shape: single bar, three bars and flat bottom, and some of them adopt triangular track shoes. Single-ribbed track pad is mainly used for bulldozers and tractors, because the track shoe is required to have high traction capacity when such machinery works. However, it is seldom used on excavators, only when the excavator is equipped with a drill rack or requires a large horizontal thrust. High traction force is needed when turning from sub-track, so high crawler tendons (i.e. crawler tendons) will squeeze the soil (or land) between the crawlers, thus affecting the maneuverability of excavators.

Steel track pads can be divided into excavator track shoes and bulldozer track shoes. These two track pads are the most commonly used, using section steel as raw materials. Another is the wetland plate used by bulldozers, commonly known as "triangular plate", which is cast plate. Another kind of casting track pad is used on crawler crane & hyundraulic excavators. The weight of this track pad is tens of kilograms less and hundreds of kilograms more.

Most excavators adopt three-ribbed crawler board, while a few adopt flat-bottom crawler board. When designing the three-barred track board, first of all, the grounding specific pressure and the meshing soil capacity between the track bar and the ground are calculated to ensure the necessary adhesion; secondly, the track board should have higher flexural strength and wear resistance. The three-ribbed track board usually has two mud holes. When the track plate rotates around the driving wheel, the sludge on the chain rail joint can be removed automatically by means of the gear teeth, so the sludge clearing hole should be located between the two screw holes which fix the track plate on the chain rail joint.

In order to protect the surface of the ground and reduce the turning resistance, it is more appropriate to adopt extended track and flat track in the tracked walking device used in marshes or farmland [1]. In order to ensure that stones are not clamped between two adjacent track boards at any position of the caterpillar chain (including grounding, rotating around the driving wheel and the guide wheel, as well as the upper suspension position), the pitch of the Caterpillar board should be adjusted accurately, and the lap lip with appropriate shape should be designed. The function of lapping lip is to make the track board close to each other and form a band with the head and tail connected. Track panels should be installed in the same direction in sequence. The smaller the pitch of the track, the smaller the rise of the track chain between the driving wheel and the guide wheel. In this way, the running uniformity is good, the wear of the caterpillar chain is low, and the driving efficiency is high when walking. However, the minimum pitch value should be determined according to the weight of the machine and the rank of the caterpillar chain. The hole spacing on the two rows of chain rails with caterpillar plates should be larger in order to replace caterpillar plates with different grounding specific pressures. Walking devices used in marshes need wide track boards and rail surfaces, which sometimes have high bending stress. For example, when the excavator works on the ground with residual tree roots, because a large part of the excavator falls on a trackboard supported by the tree roots, it causes very high bending stress on the trackboard, thus affecting the life of the trackboard. In order to prevent the damage and bending of caterpillar board, the section coefficient and bending strength should be improved. Increasing the cross-section coefficient will increase the height of the crawler, but this will obviously increase the turning resistance and affect the maneuverability of the excavator. Therefore, steel rolled hollow crawler plates are suitable for walking devices with widths exceeding 700 mm for use in marshes. Most of the two ends of the track board used in marshes are made of slope angle, which is convenient to protect the surface of the ground, reduce turning resistance and subsidence. Moreover, when walking on hard ground, the supporting arm is shortened, and the bending moment of the edge load can be reduced.

The excavator whose crawler board width exceeds 800 mm is mainly used in marshes. It is not suitable for general occasions. The excavator with widened and lengthened crawler walking device is especially suitable for pipeline engineering.