Static balancing of ship's propellers

Abstract

The main object of this project was to design and build a full size horizontal balancing rig for ship's propellers, to be used by Malta Drydocks. Although the existing method of balancing propellers, i.e. balancing the propeller in a vertical plane, proves to be accepted by all classification authorities and is, in fact, the most common method employed by ship repair yards all over the world, one cannot exclude the fact that other methods do exist. The method of balancing adopted in this project is to balance the propeller- in a horizontal plane, i.e. with the axis of rotation vertical. Sue h method is similar to the one employed by Stone Manganese Marine Ltd., manufacturers of propellers. One of the advantages of this method is that the rig is portable and can be used on the repair site, thus eliminating unnecessary handling of the propellers. The following chapters, comprise a brief description of the commonly used propeller- materials, various types of damage encountered and methods of repair, all of which are directly connected with balancing. The current method of balancing propellers adopted at Malta Drydocks, as well as the method adopted in this project are explained in detail, giving details of balancing tolerances (ISO 484), followed by the actual design of the rig. Finally, the testing procedure, together with the results and an indication of the costs incurred to manufacture the rig are included. Specifications for the hydraulic equipment, the tungsten carbide sphere, an abstract from B.S.M.A.86 "List of equivalent terms for ship screw propellers" and all working and assembly drawings are included as appendices.