Fault Diagnosis and Removal of Engine Crankshaft Fracture

To prevent the crankshaft from breaking, the following measures can be taken during maintenance:

First of all, before repairing the crankshaft, it is necessary to carefully check whether there are cracks in the crankshaft, paying special attention to the fillet transition area. If there are cracks, the shaft should be scrapped. When polishing the journal, it is necessary to maintain a certain radius of the fillet between the journal and the crank arm. It is not allowed to arbitrarily reduce the size of the radius of the fillet. Attention should be paid to the surface finish of the fillet, otherwise stress concentration will be caused and the crankshaft will break.

Secondly, when the dimensional wear of the journal exceeds the limit, it is necessary to choose methods that have a small impact on the fatigue strength of the journal to recover. For example, using spray plating to reduce the fatigue strength of the journal is less, while using surfacing to recover the fatigue strength is significantly reduced.

Then, the fit clearance and end clearance between each journal and bearing should be in accordance with standards. Excessive clearance can easily damage the crankshaft due to impact, while too small clearance may break the crankshaft due to holding the shaft. In assembly, the ignition time should be calibrated accurately, not too early or too late, and attention should be paid to the balance of the crankshaft, flywheel, and clutch.