INTERMEDIATE SHAFTING :

These shafts are mae by forging carbon or carbon manganese steel where minimum tensile strength is within the range of 400 - 600 N/mm². Alloy steels can also be used depending on the mechanical properties of the material and their chemical composition. If they are to be used their maximum tensile strength should not exceed 800 N/mm². The forgings used should be subjected to ultrasonic examination.

The shaft is subject to torsion, based on the required horse power, the diameter of the shaft is worked out by an empirical formula relating the power developed by the prime mover, various constants and the minimum tensite strength of the material to be used, as laid down by the classification societies.

End thrust, from the propeller, is small in comparison with other stresses. A thrust ahead of about 500 x 10³ N would only induce a compressive stress of about 1.73 Kn/m², this can normally be ignored except where such thrust is transmitted to the hull i.e. at the base of thrust collar.

Bending stresses could really arise only from the ship movements and alignment variation and the effects should not be large.

Summarising then, it can be said that the intermediate shaft is subject to a torsional shear stress which influences the factor of safety and hence resultant working stress, a slight compensation would be allowed for end thrust (reversed), bending and possible variations of torque due to propeller racing.

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