Class 2 (2nd Engineer) MEKG 📅 Apr 2025

Exam Question

With reference to keyless propellers explain: (16)

(a) How keys and keyways has been eliminated

(b) How angular slip is avoided

(c) Why mounting upon and removal of a propeller shaft requires a different technique than that employed for propeller with keys.

(d) State with reasons why use of wedges and jacks are not advisable when removing the propeller from its shaft.

Reference Answer

### (a) Elimination of Keys and Keyways
The elimination of traditional keys and keyways in propeller mounting is achieved through the principle of a high-integrity interference fit on a tapered shaft, secured using hydraulic methods. This design overcomes the significant stress concentrations and fretting corrosion issues associated with keyways.
**Mechanism:**
1. **Tapered Fit:** The propeller shaft tail end and the propeller boss bore are machined with a precise, shallow taper (e.g., 1:20 or 1:30).

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