Design And Fabrication Of A Marine Shafting System

Marine Engineering Project and Seminar Materials

Design And Fabrication Of A Marine Shafting System


Ever since man discovered water as a viable means of transportation there has been in increase in the need to have an effective means of propulsion at sea. Today the most widely used means is the mechanical propulsion system which consist of an energy source and a shafting system. Over the years various improvements have been made on the propulsion system but this project will focus in detail on the shafting system.

This project describes in detail, the design, analysis and construction of marine shafting system of a direct drive vessel, with the aim of improving the overall efficiency of the shafting system. The material selection was done to select only cost effective material which have minimal impact on the efficiency of shafting system and ensure efficient shafting of the engine power to the propeller.

Chapter One

1.1. Introduction

Ships are large complex vehicles which must be self-sustaining in their environment for long periods with a high degree of reliability. A ship is the product of two main areas of skill, those of the naval architect and the marine engineer. The naval architect is concerned with the hull, its construction, form, habitability and ability to endure its environment. The marine engineer is responsible for the various systems which propel and operate the ship. More specifically, this means the machinery required for propulsion, steering, anchoring and ship securing, cargo handling, air conditioning, power generation and its distribution. Some overlap in responsibilities occurs between naval architects and marine engineers in areas such as propeller design, the reduction of noise and vibration in the ship’s structure, and engineering services provided to considerable areas of the ship. This project will look into the propulsion system with specific emphasis on the shafting system of a vessel carrying out a detailed design and analysis.

The shafting system which is part of the propulsion system of a vessel is a major a component onboard vessel. The shafting system directs the power generated by the engine to the propeller which then provides thrust for the vessel. Marine propulsion is the mechanism or system used to generate thrust to move a ship or boat across water. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting of an electric motor or engine turning a propeller, or less frequently, in pump-jets, an impeller. Until the application of the coal-fired steam engine to ships in the early 19th century, oars or the wind were used to assist watercraft propulsion. Merchant ships predominantly used sail, but during periods when naval warfare depended on ships closing to ram or to fight hand-to-hand, galley were preferred for their maneuverability and speed. The Greek navies that fought in the Peloponnesian War used triremes, as did the Romans at the Battle of Actium. The development of naval gunnery from the 16th century onward meant that maneuverability took second place to broadside weight; this led to the dominance of the sail-powered warship over the following three centuries.

In modern times, human propulsion is found mainly on small boats or as auxiliary propulsion on sailboats. Human propulsion includes the push pole, rowing, and pedals.

Propulsion by sail generally consists of a sail hoisted on an erect mast, supported by stays, and controlled by lines made of rope. Sails were the dominant form of commercial propulsion until the late nineteenth century, and continued to be used well into the twentieth century on routes where wind was assured and coal was not available, such as in the South American nitrate trade. Sails are now generally used for recreation and racing, although innovative applications of kites/royals, turbo sails, rotor sails, wing sails, windmills and Skysails’ own kite buoy-system have been used on larger modern vessels for fuel savings. A ship moves between two mediums (water and air) hence the increased resistance to motion. To overcome this, a suitable propulsion system with an effective shafting system should be selected to meet the specific vessel requirements. By evaluating and assessing the vessel design and intended operation profile together at an early stage, from a propulsion perspective, this will ensure that all interfaces within the drive-line, control and monitoring systems are precisely defined, resulting in the installation of an optimized, fully integrated shafting system.

The design and general assembly of the shafting system of a vessel is very crucial to the successful operation of the vessel. A well designed shafting system, will reduce fuel consumption and ensure maximum power transfer from the engine to the propeller. In this report we shall look into the design and fabrication of shafting system for a vessel carrying out detailed design analysis of the various components of the shafting as well as make modifications and improvements of existing shafting systems.

1.2. Background Information

Small, mechanically-operated shafting are typically fitted in sailing boats and other small craft. Compact hydraulically-operated shafting, including two-speed versions, are suitable for pleasure craft and workboats including those for fishing, wind farm support, and pilot and harbor vessels, while larger models are specially designed for fast craft such as defense vessels, super and mega yachts and high-speed ferries. For commercial, ocean-going vessels such as freighters and tankers, heavy-duty shafting with various power take-off (PTO) and power take-in (PTI) arrangements can be specified to match medium-speed diesel engines.

Large motor yachts, naval, customs and coastguard vessels and fast ferries all require compact, high performance shafting, most of which are specially configured to comply with a ship designer’s requirements. These shafting can be rigged with optional equipment and monitoring systems to meet stringent environmental and technical specifications where safety, availability and reliability are of utmost importance.

For extremely demanding applications in commercial vessels with extended annual operation. Various non-reversing shafting are also available, with hollow output shaft, designed for controllable pitch propeller (CPP) operation. The shafting system on a ship transmits power from the engine to the propeller. It is made up of shafts, bearings, and finally the propeller itself. The thrust from the propeller is transferred to the ship through the shafting system. The different items in the system include the thrust shaft, one or more Intermediate shafts and the tail shaft. These shafts are supported by the Thrust block, intermediate bearings and the stern tube bearing. A sealing Arrangement is provided at either end of the tail shaft with the propeller and cone completing the arrangement.

1.3. Statement of Problem

The primary function of any marine engineering plant is to convert the chemical energy in fuel into useful work and to use this work for propulsion of the ship. To ensure that this energy generated is effectively utilized for propulsion, an efficient shafting system is required transfer the power generated from the engine to the propeller of the vessel. An efficient shafting system will reduce the energy loss accustomed to energy transfer and reduce fuel consumption of the main engine. This project looks at the direct drive shafting system, carrying out a detailed design analysis of the components.

1.4 Aim of Project

The aim of this project is the design and fabrication of a direct drive shafting system of a vessel.

1.4.1 Objectives of the Project

The objectives of this project include:

  1. To Increase the power output of the shafting system by maximizing the power delivered by the engine.
  2. Selection of low cost energy efficient materials for the design and construction of a direct drive shafting system.
  3. To produce a direct drive shafting system model showing the various component which will serve as an effective teaching aid.

1.5. Significance of the project

The shafting system of a ship is a very important part of the ship machinery.

This project will provide a better understanding of the principle of operation of the shafting system and proffer methods to increase its overall efficiency.

1.6. Scope of the Project

This project will focus on the design analysis and construction of the ship shafting as well as proffer ways to improve the efficiency and reduce energy losses associated with the shafting system.

1.7. Project Structure

The project is structured so as to present it in a coherent and logical manner. The following provides a description of each of the chapters within this document:

  • Chapter 1 presents the introduction to the project which encompasses the background study, the problem definition, and the aims/objectives of the project. It also includes the significance of the project and its scope.
  • Chapter 2 provides a literature review of the project. Focus on existing direct drive shafting in the world history, principles used and usage. Also includes all the research that has been done to provide ideas and specification as a guideline to produce the design.
  • Chapter 3 describes the experimental setup and methods used to design and construct the direct drive shafting system, focusing on proposed design process, product design specification concept Measurement and Evaluation, and provides a recommendation and conclusion.
  • Chapter 4 of these project gives description of tests carried out on the shafting system and provides the results of these test in accordance to the parameters and theories been used. Hence there shall be a discussion of the end result of these project and its viability.
  • Chapter 5 will hence be the conclusion of these project as well as analyzing the limitation and making necessary recommendation pertaining to these project work.

Chapter Five

Conclusion and Recommendations

5.1 Conclusion

In the course of these work which has include the study, design, construction and testing of the marine shafting system, it has allowed a better and more professional understanding of key marine transmission and propulsion system through application. The practical testing and designing to analyze the torsional forces, shear stress and combined stresses on the shaft as well as the efficiency of the propeller, Hence helping us to ensure the power from the engine is most effectively transmitted to the propeller to achieve reduced power loss from the shaft and bearings and high thrust power from the propeller.

Shaft alignment analysis and study showed the importance of proper shaft alignment especially in high speed shaft lines design to undergo a high revolution per minutes, in these ideal also the importance of shaft rigidity became indispensable as to the proper running of the shaft without any form of deformation or deflection.

After several research on shaft diameter importance and consulting essential theorems and formulae, the design of a marine shafting system suitable for application in a marine speed boat will require a relatively small diameter just enough to transmit a high rpm at a reduced torque as required by a typical marine speed boat. Taking into consideration a solid shaft of high density just enough to withstand torsional forces and shear stress experience during rotation without failing when operating on a 80hp rated engine power.
Finally, it would be meaningless to design an economically and structurally successful shaft without an efficient propeller type of propeller, hence the design of the propeller for these project been carried out using ABYC standards and implementing ITTC principle and codes in propeller design resulted in construction of a fixed pitch propeller to match the shaft diameter and efficiently provide thrust.

5.2 Recommendations

Due to the limit financial resources and limited time frame of these project, a complete concept size in terms of larger length of shaft and wider diameter of propeller was not achieved. In the event of future designs a number of issues will require further analysis as well as financial assistance.

Also due to unavailability of resources within reach, a practical application of these project to a marine speed boat was not done. However to achieve a proper, complete and viable shaft line system, one had to perform a practical application of these designed work. Hence in future designs and construction, a practical application of the shaft line system into a marine speed boat or similar vessel should be done so as to ensure the viability and working condition of the designed shafting system.

Finally, for the design of a shaft with better weight to length ration and more economical cheaper, it is recommended for one to adopt the use of a hollow shaft form in future designs of shafting system.

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