Question

With reference to Keyless Propellers:

(a) Sketch a section through a keyless sleeved propeller. (4)

(b) State the advantages of using a keyless sleeved propeller. (4)

(c) State with reasons, which metal sleeve, should be made for contact with the forged mild steel tail shaft. (4)

(d) State the material used to bond the sleeve to the propeller and the general thickness of the bonding material. (4)

Answer 1

Part (a)

Part (b)

Keyless design avoids stress concentration caused by keys and keyways.
Stresses are evenly distributed across the internal surface of the propeller boss
The absence of a keyway increases the friction available for torque transmission.
The design prevents overstressing or permanent damage to the propeller hub during operation.
The keyless arrangement simplifies the propeller and shaft interface, making it easier to manufacture and maintain.

Part (c)

With a coefficient of friction of 0.28, it minimizes the likelihood of propeller slippage.
Its expansion rates are similar to those of steel, reducing the risk of misalignment or loosening during temperature variations.
Pearlitic cast iron exhibits excellent resistance to fretting, which is important for prolonged and reliable operation.

Part (d)

High-strength epoxy Araldite filling is used to bond the sleeve to the propeller securely.
The bonding material is applied with a thickness of approximately 1 mm, ensuring adequate adhesion and durability.

✓ Verified Model Answer (Text Solution)