6294 3940

Lignum Vitae
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Also known as BulnesiaSarmietoi, lignum vitae is the densest wood that sinks easily in water. Strength, durability, low cost and self lubricating are attributes that make lignum vitae a suitable candidate as propeller stern tube bearing. Changing of individual lignum vitae block is quite straight forward as compared to changing of rubber lining for stern tube bearing. The wearing down of lignum vitae stripe must be measured on a regular basis; a maximum allowance of 8 mm of wear off is the usual allowance before the wood stripe is replaced. The measurement is usually done by inserting a small wedge between the shaft liner and the outer end of the bearing at the top. Alternatively, a poker gauge with original markings can be inserted through a hole near the end of the stern tube until it touches the shaft.  If wearing down of the wooden block is too excessive, the consequent bending of the propeller shaft would cause alternating tensile and compression stress as the shaft rotates; this would cause fracture due to fatigue. Friction between the propeller shaft and stern tube bearing is the main factor that will greatly increase the fatigue level; hence a lubricating medium is necessary to resolve this problem. This lubricating medium needs to be “refilled” over time to minimize friction. Having natural oil impregnated in it, lignum vitae stern tube bearing can do without the lubricating medium. 

 

 

 

 

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