**Anatomy of the Sliding (Plain) Bearing of the Starter (1)**
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Source: China Bearing Network | Time: 2014-05-14
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Sliding bearings play a crucial role in the operation of starter motors. These include bushings and bearing bushes, which are all classified as sliding bearings. Ensuring the accuracy and efficiency of the starter motor requires strict control over the clearance of these bearings. The failure of sliding bearings can be attributed to several factors, such as poor lubrication conditions, foreign contaminants, or improper maintenance.
According to an analysis by Cummins in the United States, the primary causes of sliding bearing damage are as follows:
1. **Contamination due to poor hygiene** – 45%
2. **Wear from smooth surface damage** – 25%
3. **Damage caused by improper application or equipment issues** – 15%
4. **External reactions and other factors** – 15%
From this breakdown, it's clear that maintaining cleanliness is the most critical factor in preventing bearing damage. This includes not only ensuring that parts are clean during assembly but also following proper procedures during operation and maintenance.
The outer bearing alloy layer on the crankshaft and connecting rod is particularly vulnerable due to its softness and high load. Damage to these areas often leads to early failure. Therefore, it’s essential to monitor and address any signs of wear promptly.
### Common Issues Caused by Poor Hygiene
#### 1. Wear from Small Particle Contaminants
Small particles entering the bearing area can cause gradual wear. For example, when oil is drained, small alloy particles may be visible, indicating potential bearing wear. If left unchecked, this can lead to severe damage to both the bearing and the shaft. Timely inspection and removal of contaminants are crucial to prevent further harm. Once removed, the bearing life is significantly reduced, equivalent to normal wear over 2,500 hours.
**Causes of small particle contamination:**
- Poor air filter performance or leaks in the intake system.
- Long-term use of contaminated oil or clogged filters.
- Fuel leakage leading to oil contamination.
- Improper cleaning during engine assembly.
After removing the fault, it's important to replace the oil and filter, run the machine for two hours, and then inspect again. If no more debris is found, continue monitoring for 60–120 hours before replacing the oil and resuming normal operation.
#### 2. Damage from Larger Particles and Residual Oil
If large pieces of metal or residue are found in the oil filter or oil sump, it indicates serious damage. Immediate inspection and repair are necessary to avoid further destruction. Large particles can come from uncleaned parts during installation or leftover machining debris.
Residual oil with impurities can reduce the lubrication effect, leading to increased wear and potential melting of the bearing material. Always ensure that new oil meets quality standards and is properly filtered before use.
#### 3. Damage from Foreign Objects Moving Between Surfaces
Large foreign objects between the bearing and the shaft can cause uneven contact, leading to localized wear. These objects can embed themselves in the bearing surface, causing permanent damage. It’s essential to thoroughly clean all components before installation and avoid re-contamination.
Before installation, carefully inspect the oil passages and internal surfaces. Use clean tools and avoid touching metal parts unnecessarily. Proper preparation and attention to detail can significantly extend the life of the bearing.
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