- The internal passages in the crankshaft are made in such a manner, in case of small diesel engines where crankshaft size is comparatively small, that oil is supplied to the main bearing. From there to the passage in the crankshaft it is feed to the crank pin bearing. Thus avoiding the complicated piping to supply oil to the crankpin bearing and gudgeon pin bearing.
- This is applicable only in case of small crankshafts. Bigger crankshafts may fail under fatigue if the holes are drilled out for the passage of the oil. Hence in case of the bigger crankshafts, no drilling of the holes is done on the crankshaft and hence this method of lubricating the bottom end bearing and gudgeon pin bearing is not applicable.
- In that case, there is a separate supply of lubricating oil to main bearing and as well as to the crosshead bearing, which will be further bifurcated into two: the crosshead bearing and piston cooling, and the bottom end bearing, for lubricating.
1. High cost: Manganese bronze is a costly alloy, making it less economical for large propellers. 2. Low strength-to-weight ratio: Compared to other propeller materials like nickel-aluminum bronze or stainless steel, manganese bronze has a lower strength-to-weight ratio. 3. Susceptible to corrosion: Manganese bronze can corrode in seawater, especially when exposed to high velocities and turbulence. 4. Poor cavitation resistance: Manganese bronze is more prone to cavitation damage than other materials. 5. Difficult to cast and machine: Manganese bronze is challenging to cast and machine, making it less desirable for complex propeller geometries. 6. Limited weldability: Manganese bronze has poor weldability, making repairs and modifications difficult. Nickel-aluminum bronze or stainless steel are commonly used for propellers due to their: - High strength and durability - Excellent corrosion resistance - Good cavitation resistance - Ease of casting and machining - Weldability
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