The "rail biting" phenomenon of the traveling device of crawler construction machinery

"Rail biting" is a typical fault phenomenon of crawler construction machinery, which is manifested as the service life of the guide rails, idler wheels, drive wheels, support wheels and tracks when the entire machine is moving. There is side clearance between the tracks and the above-mentioned "four wheels", among which the side clearance with the guide wheels is the smallest and that with the idler wheels is the largest. Under normal circumstances, there will be normal friction between the tracks and the "four wheels", but there will be no "rail biting". The fundamental cause of "rail biting" is that the tracks cannot be wound correctly. The center planes of the "four wheels" do not coincide.

"Rail biting" caused by guide wheels

The guide wheel is an important component of the walking system, and the correctness of its installation position has a significant impact on the service life of the walking system. Under normal circumstances, the tracks should be wound in the middle of the guide wheels. Except for a brief lateral shift when turning, the tracks generally do not slip sideways. However, if the guide wheels are skewed, the tracks will be subjected to a component force in the non-skewed direction, causing them to move axially and thus resulting in the "rail biting" phenomenon. The direction of the guide wheel's inclination varies, and so does the position where the guide wheel "bites". If the guide wheel tilts in the horizontal plane, "rail biting" will occur in front of the guide wheel. If tilting occurs in the vertical plane, it usually happens as "rail biting" above and below the guide wheels. In severe cases, it can cause the front support wheels to drop off the edge. When both types of tilting exist simultaneously, the "eight-shaped rail biting" phenomenon will occur. It can be seen from this that whether the installation position of the guide wheel is correct or not has a great impact on whether the track "bites the rail".

The main factors influencing the installation position of the guide wheel are:

The coaxiality of the circle formed by the centers of the 8 screw holes on the end face of the spring box hole and the spring box hole is out of tolerance. After assembly, the longitudinal centerline of the guide wheel does not coincide with the longitudinal centerline of the trolley frame.

(2) The perpendicularity between the end face of the front hole of the spring box and the longitudinal centerline of the trolley frame exceeds the tolerance. Moreover, the verticality of the installation with the support wheels of the trolley frame is also out of tolerance.

(3) The parallelism between the base of the spring box and the centerline of the spring box hole exceeds the tolerance.

(4) The centerlines of the semi-circular holes for installing eccentric pins at both ends of the guide wheel shaft are not parallel, resulting in asymmetry of the left and right brackets after assembly and causing the guide wheel to tilt.

(5) There is an error in the mutual position of the four holes connecting the left and right brackets to the guide wheel brackets.

(6) The clearance adjustment between the guide wheel, the bracket and the anti-friction plate is improper.

In addition, if there are processing defects in the guide wheels, it can also cause "rail biting", such as: axial offset occurs during the processing of the middle shoulder of the guide wheels; The diameters of the raceways on both sides are different, which causes the tension forces of the tracks on both sides to be different. The tracks are prone to migration, and the generatrix of the raceways is not parallel to the axis of the track pins, thus causing local side sliding of the tracks.

2. "Rail biting" caused by idler wheels

The function of the idler wheels is to transfer the weight of the machine to the tracks. During the operation of the machine, in addition to rolling along the track surface of the tracks, it also needs to hold the tracks to prevent them from sliding out laterally. When the machine turns, it also needs to make the tracks slide laterally on the ground. The idler wheels are divided into single-sided and double-sided types. Taking the TY220 crawler bulldozer as an example, there are a total of 12 idler wheels, among which 4 are double-sided and 8 are single-sided. The single-sided and double-sided idler wheels together form a raceway, and the tracks roll on the track. When the rail busbar does not coincide with the centerline of the idler gear block and the centerline of the guide wheel, it will cause the idler wheel to "bite the rail".

The main reasons for the idler wheel "biting the rail" are:

(1) The fixing bolts of the idler wheels are loose, causing the axial position of the idler wheels to change or skew.

(2) The positioning grooves of the idler wheels are severely worn.

(3) The centerlines of a set of holes for the fixed idler wheels of the trolley frame are not perpendicular to the straight lines formed by the half shaft installation holes and the inclined support installation holes (not perpendicular in space).

(4) The middle flange of the idler wheel was offset during processing.

(5) When the raceway generatrix is not aligned with the axis of the track pin, the track slides sideways.

(6) The diameters of the raceways on both sides of the idler wheels are different.

(7) When processing the idler wheels, the axial dimension of the raceway is too small, causing the gap between it and the track to be smaller than that between the guide wheels and the track, resulting in "rail biting".

3. "Rail biting" caused by drive wheels

The side clearance between the drive wheel and the track is the largest, and "rail biting" generally does not occur. However, if the centerline of the tooth block does not coincide with the centerlines of the guide wheel and the idler wheel, "rail biting" can also occur.

The main reasons for the drive wheel "biting the rail" are:

(1) When pressing the supporting rollers, the centerline of the supporting roller tooth block was not pressed in place or exceeded the position of the inner shell end face.

(2) The coaxiality of the inclined support holes on the trolley frame and the bearing holes on the half shaft supports is poor, resulting in the centerline of the tooth blocks not being perpendicular to the longitudinal centerline of the trolley frame.

(3) During the processing of the half shaft bracket or the axial dimension of the half shaft, the deviation occurred, resulting in the improper installation of the drive wheels.

(4) Due to improper use, the half shaft was bent, causing the drive cycle to flatten and become skewed.

4. Rail biting caused by deformation of the trolley frame

The trolley frame is a rectangular frame structure composed of U-shaped and L-shaped connections. The "four wheels" and buffer devices are all installed on it. Deformation of the trolley frame will disrupt the positional relationship between the "three wheels" and the driving wheels, thereby causing "rail biting".

The main reason for the "rail biting" caused by the deformation of the trolley frame is:

(1) The trolley beam is bent. The bending of the trolley beam includes the bending in both the horizontal and vertical planes. From the perspective of the impact on the overall machine usage, the bending within the uneven plane has the greatest effect on "rail biting", and it can also cause the entire machine to deviate.

(2) Deformation of the front opening crotch of the trolley frame. One is to separate outward, and the other is to tilt the crotch.

(3) Deformation of the inclined support of the trolley frame. This will disrupt the installation position of the trolley frame.

5. "Rail biting" caused by wear and other reasons

The working environment of the trolley frame is harsh and it is subject to considerable external forces, so it is prone to wear and tear. The main causes of "rail biting" are:

(1) The installation surface and mating surface of the trolley frame are worn significantly, which damages the perpendicularity between the trolley beam and the half shaft.

(2) The loosening of the installation bolts on the trolley frame causes "rail biting".

(3) During the operation of the entire machine, foreign objects got stuck between the guide wheels and the trolley frame, preventing the guide wheels from being adjusted.

In conclusion, the causes of "rail biting" are very complex. Not only should problems during processing and assembly be taken seriously, but also regular and irregular inspections and adjustments of the traveling components should be carried out during use to prevent the occurrence of "rail biting". That is: Check the gap between the outer cover of the guide wheel and the trolley beam. If it does not meet the requirements, make corresponding adjustments. Adjust the axial position of the idler wheels; Check whether the bolts fixing the rear frame are tightened. Check whether there are any foreign objects or the like between the guide wheels and the trolley frame.