Excavator undercarriage parts are key components of the excavator's travel system, mainly including the track frame, drive wheel, idler, support roller, track roller, track shoe, tensioning device, travel hydraulic motor and reducer, etc. The following is a detailed introduction:

Track Frame
Structure: Travel structures can be divided into two types: combined and integral. The base frame of the combined track frame is a frame structure, the crossbeam is an I-beam or a welded box beam, inserted into the track frame hole. The track frame usually adopts an open "∏" shaped cross-section at the bottom, with forked ends for installing the drive wheel, idler, and support roller. The integral track frame has a simple structure, light weight, high rigidity, and low manufacturing cost.
Function: Acts as a support structure, bearing the weight of other excavator components and providing an installation base for the travel system.
Drive Wheel
Function: It is an important component of the crawler travel device. The torque output by the motor or electric motor is transmitted to the drive wheel, and through the meshing of the drive wheel and the track shoe, the power is transmitted to the track shoe, thereby obtaining the traction force required for crawler travel.
Characteristics: During track operation, it is subjected to cyclic load excitation and is prone to fatigue failure. Its shape, structure, and material have a great impact on the life of the drive wheel.
Idler
Function: Changes the direction of the track and plays a guiding role. The closer the distance between the idler and the nearest support roller, the better the guidance.
Structural Characteristics: The wheel surface is smooth, with a shoulder ring in the middle for guiding, and the annular surfaces on both sides support the track chain. It is usually cast and quenched from 40, 45 steel or 35Mn steel, with a hardness of HB230-270.
Support Roller
Function: Transmits the weight of the excavator to the ground. When the excavator travels on different ground surfaces, the support roller often bears the impact of the ground, so the load on the support roller is relatively large.
Characteristics: The working conditions are harsh, often in dust, and sometimes immersed in mud, so good sealing is required. It is usually cast from 35Mn or 50Mn steel, and the wheel surface has a quenching hardness of HRC48-57 to obtain good wear resistance. Sliding bearings are mostly used for support, and floating oil seals are used for dust prevention.
Track Roller
Function: Supports the track, prevents the track from sagging, and ensures smooth rotation of the track wheel. Its structure is basically the same as the support roller.
Track Shoe
Types:
Integral Track: The track shoe has engaging teeth that directly mesh with the drive wheel. The track shoe itself becomes the rolling track for the support rollers, etc. Integral manufacturing is convenient, and the pins connecting the track shoes are easy to disassemble, but wear is faster.
Combined Track: Composed of track shoes, track links, track pins, and bushings. The left and right track links are tightly connected with the bushings. The track pins inserted into the bushings have a certain clearance for flexible rotation, and their two ends cooperate with the holes of two other track links. The locking track pin and the track link hole are a dynamic fit, facilitating the disassembly of the entire track. The combined track has a small pitch, good winding performance, making the excavator travel faster, the pins have higher hardness, are wear-resistant, and have a long service life.
Rubber Track: More commonly used on small agricultural excavators or micro-excavators and other agricultural machinery. Rubber tracks are non-detachable annular continuous tracks made of rubber by segmented molding or integral vulcanization, consisting of rubber, fabric, metal transmission parts, and steel wire ropes.
Form: Track shoes have several types: single rib, double rib, and triple rib. Single rib track shoes have higher ribs, easily insert into the ground to generate greater traction, mainly used for bulldozers; double rib track shoes have slightly shorter ribs, are easy to turn, and have better track shoe rigidity, and can be used for excavators or heavy mining excavators; triple rib track shoes also have short ribs, and because of the multiple ribs, the strength and rigidity of the track shoe are improved, with high load-bearing capacity, used for excavators.
Tensioning Device
Function: After a period of use, the crawler travel device of a hydraulic excavator will have increased pitch due to wear of the track pins, causing the entire track to lengthen, leading to friction against the track frame, track derailment, and increased noise in the travel device, thus affecting the travel performance of the excavator. Therefore, each track must be equipped with a tensioning device to maintain a certain tension in the track.
Structure: The oil cylinder and the support and shaft of the idler frame are bolted together to push the idler to extend and retract. The piston is installed in the oil cylinder, and the oil seal seals the piston and the grease in the oil cylinder cavity. When pressure grease is injected from the injection nozzle, the piston is pushed to the right, the piston pushes the push rod, and the push rod pushes the spring front seat. The spring front seat compresses the large and small springs, thus forming an elastic body between the idler and the spring, buffering the impact force applied to the track, eliminating impact load, reducing impact stress, and improving service life. The screw plug is used for releasing grease. When the track tension is too large, slowly rotate the screw plug to slowly squeeze out the grease.
Travel Hydraulic Motor and Reducer
Function: The travel hydraulic motor converts hydraulic energy into mechanical energy to provide power for travel; the reducer reduces the speed of the motor and increases the output torque to meet the needs of the travel system.