Shaft material and Vulkans Coupling RATO S

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Propeller shaft, tail shaft – The aftermost section of the propulsion shafting in the stern tube in single screw ships and in the struts of multiple screw ships to which the propeller is fitted. Propulsion shafting constitutes a system of revolving rods that transmit power and motion from the main drive to the propeller. The shafting is supported by an appropriate number of bearings. Shaft materials and couplings : The intermediate shafting and the propeller shaft for a fixed propeller are of solid forged ingot steel and usually with solid forged couplings. Shafts are machined all over but of a larger diameter and smooth turned in way of the bearings. The faces of flanged couplings (except where undercut in the centre area) are also smooth turned, with bolt holes carefully bored and reamered to give an accurate finish. Torque is transmitted by the friction between flanges and also through the shanks of the bolts. Each tightened bolt holds the flanges hard together in the area local to it. A circle of bolts is needed for a good all round grip. The design of flange couplings can be checked by formulae given in Lloyds or other classification society regulations.


Flexibly mounted engines, rigidly mounted engines.

The highly-flexible RATO S coupling is a torsionally flexible rubber coupling that compensates radial, axial and angular shaft displacements of the connected machinery. The torque is transmitted by elements loaded in shear. The different torsional stiffnesses and damping factors available provide the possibility to satisfactorily tune the torsional vibration behaviour of the drive system. The essential parts of the coupling are: the torsional flexible element, the membrane package to absorb the axial displacements and the connecting parts to the drive and driven machinery.


  • Easy and quick installation of the coupling thanks to the segmented design with reduced weights of the individual segments.
  • The segments are arranged for maximum thermal load and therefore long service life of the system.
  • Compact design with an internal hub for space-conserving and weightsaving drive dimensions in order to cut down on the project costs.

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