Answer EKG Question 7

Q7. With reference to Keyless Propeller:
A. Sketch a section through a keyless sleeved propeller. B. State the advantages of using a keyless sleeved propeller.
C. State with reason, Which metal sleeve should be made for contact with the forged mild steel tail shaft?
D. State the material uses to bond the sleeve to the propeller and the general thickness of the bonding material.
Answer:

A. Sketch a section through a key-less sleeved propeller.

B. State the advantages of using a keyless sleeved propeller. 

The propeller torque is taken only by friction between the propeller and propeller shaft. It has the following advantages surpassing the keyed propeller:

-simple construction, no key slot and consequently no concentration of stresses at the edge of key slot unlike the ordinary keyed propeller, and uniform distribution of stresses over the internal surface of the propeller boss.

-The keyless propeller therefore aroused a great interest among the maritime communities and that demand for it is on the steady increase.

C. State with reason, Which metal sleeve should be made for contact with the forged mild steel tail shaft? 

A cast iron sleeve is fitted between Bronze propeller and mild steel tail shaft.

-coefficient of friction between mild steel and Bronze is less. which is required to be high, the cast iron sleeve is providing the same.

-also bedding and gripping enhanced.

-chances of slippage reduced.

D. State the material uses to bond the sleeve to the propeller and the general thickness of the bonding material..

see first figure: material is Araldite. maximum thickness is 1mm (commonly ranges from 0.3 to 0.7mm)