How to prevent crankshaft breakage

To prevent crankshaft breakage, the following measures can be taken during maintenance.

First, before repairing the crankshaft, carefully check the crankshaft for cracks, paying special attention to the transition part of the rounded corners. When polishing the journals, the journals and crank arms should maintain a certain radius of rounded corners. The size of the rounded corner should not be reduced arbitrarily. Pay attention to the surface finish of the rounded corners, otherwise it will cause stress concentration and lead to crankshaft fracture.

Second, when the journal size wear exceeds the limit, choose a method that has less impact on the fatigue strength of the journal for recovery. For example, the reduction of fatigue strength of crankshaft journals by spraying method is small, while the reduction of fatigue strength is larger when recovery is done by overlay welding method.

Then, the mating clearance and end play of each journal and bearing should meet the standard. If the clearance is too large, the crankshaft is easily damaged by impact. If the clearance is too small, the crankshaft may break due to the shaft. In terms of assembly, the ignition time should be accurately calibrated, not too early or too late, and attention should be paid to the balance of the crankshaft, flywheel and clutch.