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CHAPTER ONE

INTRODUCTION

The project is a pre-requisite for the award of Higher National Diploma (HND) in Mechanical Engineering. The project “Design and fabrication a corn shelling machine” is indeed an essential one in a time like this when almost al human endeavour is embracing technology for efficiency and reliability. First a corn shelling exercise is a function which could either be manually, mechanically or electro-mechanically operated with the simple objective of shelling out the grain from the cob.  Before the middle of the 19th Century, the most widely used method of shelling was manual operation which was either actuated by using hand in contact with cob and subsequently twisting of the grain against the cob.  Though, this method of operation is still in use but technologically it is out-dated and babaric.  Outside the use of hand operation, another manual type of operation is used by different type of farmers, all depending on the type of farming “either commercial or other wise”.

This other type employs the use of hammer to hit on a sack containing the corn, the applied force is usually considerably small, so as to avoid the grain from been crushed as a result of the applied force. As the world population is geometrically increasing, the need to provide this grain in a larger quantity becomes a task to man and technology.  In trying to overcome this task and to reduce the limitations of mass production of corn, a British industrial Company came up with the design of a machine was first operated manually as depicted in the diagram below tagged fig 1. Because of the low level of technology applied in the construction of the above machine.   It was constructively criticized on the bases of low efficiency in production Quantity, and time Consuming.

The emergency of modernized corn shelling temporarily phase out the other types of shelling operations.  This modern corn shelling operate with a higher efficiency of mass production and is more reliable than the other types. It is usually powered by electric motor which is connected to the machine and to the power supply source vise-vise. It is base on this type of Design that we embark on the design of a corn shelling machine.  However, this design is a modification of other existing design.   In other words we considered the feasibility of the design from every engineering details to economics and aesthetics.   The machine is therefore design to be quite reliable, durable and cheap to build and run.

Towards this objective, an depth analysis of the existing similar machines was carried out and necessary modifications base on finding were made, such modifications include using pulleys and bolt, shape of tiny and the inclination of the discharge outlet and also spacing of the perforation and the teeth of the barrels portability, ergonometric heights and aesthetic impact. For the suitable selection of materials, calculations were made with their physical, chemical and mechanical properties or characteristics properly considered. The design (Corn Sheller) is capable of shelling ten (10) tons of maize per an hour.  It is operated with a one phase electric motor of 11/2 horse power at a speed of 145 rpm.  Its shaft rotates at a speed of 400rpm.

The component features of the design are as follows. Barrel: This is subdivided into two, the outer and the inner Barrel. First, we treated the outer barrel and then the inner barrel. Outer Barrel,   This barrel rotates with shaft rote stands on itself inside the shelling chambers.  It is a half of a cylindrical shape perforated below to enable shelled corn to rush out to the conveyor or to the outlet or basin.  It is welded and tight at the endwise of the structure, they are flanges at the end for the location of the bearing for the shaft. At the lower end of one open segments serving as outlet for the cobs and a hood is built covering it.

DIAGRAM OF  OUTER BARREL

INNER BARREL:  This is a Cylindercial barrel which rotates with the shaft supported by end to end to bearing.  The diameter of the shaft is 20mm and for the inner barrel diameter is 190mm having 20 numbers of spikes measuring 30mm from the barrel surface and also wounded vanes that does the operation. Diameter of inner barrel is 120mm and its length is 740 and consequently the diameter of the shaft is 20mm.   Below is the diagram of the inner barrel.

DIAGRAM OF INNER BARREL.

TRAY:  This is just similar to a pot but the different is that it is bigger and not covered and have a rectangular shape.   There is a provision of an entry through which the corn enters the shelling chamber and the inner engulfing the shaft. It is obtained after cutting a mild steel and welded with guage 12 Electrode and it has its dimension as 740mm x 100mm. The diagram of the tray is as shown below in the fig.

DIAGRAM OF THE TRAY  

RECEPTACLE:  This is the outer funnel that collects the shelled corn from the conveyor to the outside. It is welded to the below of the outer barrel

SPIKES : This is the rod attached to the surface of the inner barrel which does the shelling action with the Ina barrel and the spring vanes.  It is up to 20 in number and measures 20mm vertically up from the inner barrel surface each.

COB OUTLET:  This is an exit through which cobs goes out of the barrel after shelling process to the external environment.

CONVEYOR:  This is a carrier that carries the cobs out of the barrel after selling process. It is run on the body of the inner barrel and is about 20mm in height but runs in a snake like movement from end to end of the inner barrel.

Fig.

DISCHARGED CHAMBER: The are holes perforatedf below the outer barrel through the shelled grain falls out to the conveyor.

COLLECTOR/OUTLET BASIN: This is curved mild steel welded below the perforated outer barrel inclined to an angle to enable the falling out of the shelled corn to the receptacle.

INLET: This is the particular place in the tray through which the corn enters the shelling unit chamber for shelling process.  It is about 180mm in length and 80mm in width.

SPRING VANES: This is made up of flat tiny metals welded round the barrel together with the spikes.  It is the part of the machine where corn are shelled.  It is always capable of withstanding impact from the corn and posses good chemical resistance, high working temperature (100%) and tensile strength.  Dimensionally.  It is measured from the surface of the inner wounded horizontally. Finally, after much analysis and synthesis, the design is of minimum cost, simple to operate easy to construct, durable and easy to maintain. We hop our work will certainly provoke great interest in the reader as it house a lot of useful information for furtherance of engineering education and productivity.

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