Fabrication Of Yam Pounding Machine

CHAPTER THREE
3.0    DESIGN ANALYSIS, CALCULATION, MATERIAL SELECTION AND COST ANALYSIS
In machine design and material selection there are numerous considerations that are being made as well as assumptions. These considerations are in area of the choice of design. Material selection with respect to its properties, load to be overcome by the machine safety of operation, cost of construction, friction resistance and lubrication etc.
However, in this design the machine fabrication, its operation, material selection were carefully done bearing in mind the operation of the machine. Also, the conditions considered in these regards were the tendency of the chosen material to fracture under fatigue, resistance to wear during operation, corrosion when in contact with moisture and ability to conduct heat to the atmosphere to avoid overheating as a result cools the machine while in operation. Also, material toughness and strength were not left out.
3.1    DESIGN ANALYSIS
Osueke  (2010), experimented and determined the density of yam to be 1250kg/m3 and 1950kg/m3 for before and after boiling respectively. This figure have been generally accepted and used in various works analysis of production capacity of a yam flour for producing firm using a mathematical model.
3.1.1 COMPONENT/PART DESIGN
These are unit components of the machine that are assembled together to form the entire machine. The machine components include the machine structural frame, hopper, pressure chamber, shaft main frame, grinding chamber and grinding plate, pulley, bearing, engine seat, and prime mover.

3.1.2 POWER TRANSMISSION SYSTEM
Machines employ power to achieve desired forces and movement (motion). A machine has a power source and actuators that generate forces and movement, and a system of mechanism that shape the actuator input to achieve a specific application of output force and movement.
For the purpose of this design, the power source is a prime mover which is an engine that converts fuel to useful work. The prime mover is a machine that transforms energy between thermal, electrical or pressure and mechanical forms, typically an engine or turbine.
3.1.3 THE PULLEY
The pulley is a wheel on the shaft that is designed to support movement and change of direction of belt along its circumstance. Pulleys are used in a variety of ways to apply forces and transmit power. A pulley may also be called a sheave or drum and may have a groove between two flangs around its circumference. The drive element of a pulley system can be a rope, cable, belt or chain that runs the pulley inside the groove.
The simplest theory of operation for a pulley system assumes that the pulleys and lines are weightless, and that there is no energy loss due to friction. It is also assumed that the lines do not stretch.
In equilibrium, the forces on the moving block must sum to zero. In addition, the tension in the belt must be the same for each of its parts. This means that the two parts of the belt supporting the moving block must each support half the load.
The mechanical advantage of a pulley system can be analyzed using free body diagrams which balanced the tension force in the rope with the force of gravity on the load. In an ideal system, the massless and frictionless pulleys do not dissipate energy and allow for a change of direction of a belt that does not stretch or wear. In this case, a force balance on a free body that includes the load, w and n supporting sections of a belt with tension T, yield:
nT – W = O
The ratio of the load to the input tension force is the mechanical advantage (MA) of the pulley system expressed as:
MA =     frac (W) [T]  = n
Thus, the mechanical advantage of the system is equal to the number of sections of rope supporting the load.
3.1.4 BELT LENGTH AND TENSION
The essential characteristic of the belt drive is to transmit power in the form of rotational motion to the beater shaft. The tension on the two sides of the belt is different that is one side is slack and the other side tight. Hence, this design was determine by the length of belt, wrap angles, belt tension and proper belt selection to transmit the power required.
The center to center distance of both pulleys is determined by the expression.