First of all, when the lubrication is bad.
In the diesel lubrication failure system, the connection of the semi-friction state between the journal and the gasket is weakened, that is, the bearing force at the cutting part will lead to the failure of the bearing bush combustion and the frequent axial and radial runout. In addition, the stress changes after the root is removed, which will lead to the fracture between the root of the crankshaft and the crank arm.
Secondly, the bearings do not work very well.
For diesel engines, when the pivot rolls the main bearing, or when the clearance is too large and the main bearing has a different shaft, too large, that is, the frequent crankshaft, flywheel and radial deflection of the diesel itself has a specific weight and an uneven force on the crankshaft, plus the impact of the operation of each cylinder.
In addition, when the connecting rod bearing assembly clearance is too large, or when the alloy falls, the impact load will cause the crankshaft to occur for the first time, leading to an increase in the cause of fracture
Third, looseness of the main bearing cap nut is one of the important causes of early fatigue fracture of the crankshaft, because its crankshaft is lost or loosened in the support or each coaxial bearing hole is offset coaxially.
If the channel after the loose main bearing nut loosens the track axis and the bearing clearance affects the channel, the diesel engine must exceed the tolerance, i.e. the loss of the spindle neck.
If the concentric deviation causes the crankshaft to rotate to the end of the shell hole, then the crankshaft load is different, resulting in the crankshaft fracture accident.
Fourth, the axial disturbance of the crankshaft is too great.
If the clearance in the direction of the crankshaft is too large, the main reason is due to the axial movement of the crankshaft.
A connector thrust bearing, the crankshaft located on the fourth side of the main track, one (also known as a general synthetic flange shingle) as an example, when it reaches 0.5-0.6 mm or more, the directional clearance.
In order to ensure some degree of deflection, the result is that the workload of diesel engines and crank arms with crank counterforces on the receiving end face will be more severe.