A machine for corn threshing is highly and greatly needed to consistency of usage of corn in local and international levels. With regards to this indispensable needs, a corn threshing machine is designed which operates to remove the corn grains and leaving the cobs intact. In attainment to this design objective and aims, a proper considerations was given to the machinability factor which includes installation, simplification, durability, choice material, machine, low costly and prolonged life span when operate with high utilization with minimal down fine.
In later years, maize cultivation spread widely into Africa down to Nigeria as well as many parts of Asia all at the same span of time. Its production in the southern states of the United States of America also expanded greatly just as it was in Africa and Asia (Adaokoma 2001). The use of sticks for threshing was predominant in the pre-historic era. In Egypt, livestock was earlier employed for threshing out grains after which it was winnowed. In Palestine, threshing sledge was used 3,000 years earlier. In Nigeria, maize was threshed originally by bare hands. Other popular method was the use of pestle and mortar (www journal .au. edu).
The major steps involved in the processing of maize are harvesting, drying, de-husking, shelling, storing, and milling. For the rural farmers to maximize profit from their maize, appropriate technology that suites their needs must be used. The processing of agricultural products like maize into quality forms not only prolongs the useful life of these products, but increases the net profit farmers make from mechanization technologies such products. One of the most important processing operations done to bring out the quality of maize is shelling or threshing of maize.
Traditional shelling methods do not support large-scale shelling of maize, especially for commercial purposes. Locally in Nigeria, the region that is the highest producer of Maize is the northern part of the country. It was observed that most shelling of maize was done by hand shelling. Hand shelling take a lot of time, even with some hand operated simple tools. It was also observed in the study area, Nasarawa State, most mechanical shellers were designed for multi-grain threshing or shelling, which causes great damage to the maize seeds besides breaking the cob to pieces.
The available sheller locally, were equipped with rotating threshing drum with beaters or teeth, which cause damages to the seed. Besides, the cost of purchasing such shellers were high for the poor rural farmer and therefore necessitated the design of low cost system that will be affordable and also, increase threshing efficiency with reduced damage done to the seed.
Many farmers grow maize but could not afford the cost of acquiring some of the imported threshing machines because of their cost, and such people resort to manual means of threshing which results into low efficiency. This work is necessary as it was aimed at constructing the machine that shells maize and separates the cob from the grains. Since the machine was constructed from locally available materials and its cost is very low and affordable, farmers can now adopt this kind of machine for their farming improvement.
The specific objectives of the work were to design, construct, and test a low-cost maize sheller. To evaluate the efficiency of the maize sheller. To use the maize sheller in establishing an agro-processing centre for rural farmers.This project work is to achieve the following:
This project involves the design and construction of a system with a hopper which is designed to be fed in a vertical position and the shaft design which has a threshing tool attached to it (by welding) at two opposing sides and a pulley mounted on it, which is used for threshing of corn effectively.
The work includes feasibility studies, planning, design, applying related calculation, material selection and procurement constructional analysis and preparation of components of the threshing and subsequent assembly.
The design and construction of the corn threshing machine has been completed. Grains loss and mechanical visible damage have been very minimal. Performance test has revealed that the efficiency of the machine is 73.12 . The machine threshes 36.69kg of maize within an hour. The machine can either be powered by an electric motor or engine (diesel or petrol).
The relevance of this machine in our present day life cannot be overemphasized because of the increasing population and high demand for maize for domestic and commercial purposes. It is necessary that an affordable maize threshing machine should be made available for farmers.
This study recommends that the production of this corn threshing machine in commercial quantity should be encouraged with a view of increasing large-scale shelling of maize, especially for commercial purposes as it will be more affordable than the imported ones.
1 The Design and Construction of Maize Threshing Machine Abdulkadir Baba Hassan, Matthew Sunday Abolarin, Olufemi Ayodeji Olugboji and Ikechukwu Celestine Ugwuoke Department of Mechanical Engineering, Federal University of Technology Minna, Niger State, Nigeria > Abstract Many farmers grow maize but could not afford the cost of acquiring some of the imported threshing machines because of their cost. Such people resort to manual means of threshing which results into low efficiency, high level of wastage and exerting of much labor. This machine was constructed to shell maize and separate the cob from the grains. It was constructed from locally available materials and its cost is very low and affordable. Its threshing efficiency is 99.2% and breakage is very insignificant, as well as losses. Keywords: Hopper, shutter, threshing chamber, breakage, collector, wastage. Introduction Grains, according to Okaka (1997) are fruits of cultivated grasses belonging to the monocotyledonous family, Gramineae. The principal cereal grains of the world include wheat, barely, rye, sorghum, rice and maize. The last has become a popular staple in West Africa. Maize is another world s most versatile seed crop. Its cultivation originated from Europe but was soon brought to Africa by explorers early in the sixteenth century. Within hundreds of years, it was well established as a staple food in areas around the north and south shores of Mediterranean Sea. In later years, maize cultivation spread widely into Africa down to Nigeria as well as many parts of Asia all at the same span of time. Its production in the southern states of the United States of America also expanded greatly just as it was in Africa and Asia (Adaokoma 2001). The use of sticks for threshing was predominant in the prehistoric era. In Egypt, livestock was earlier employed for threshing out grains after which it was winnowed. In Palestine, threshing sledge was used 3,000 years earlier. In Nigeria, maize was threshed originally by bare hands. Other popular method was the use of pestle and mortar. This method is still used in the rural areas today. The above methods became Technical Report 199 unsatisfactory because of their low output, tediousness and their requirement of extra strength. According to Kaul and Egbo (1985), the performance of a thresher depends upon its size, cylinder speed, cylinder concave clearance, fan speed and the sieve shaker speed. Oni and Ali (1986) reported that the factors influencing threshability of maize in Nigeria are field drying, maize varieties, ear size cylinder speed and feed rate. The properties of the crop that affect the thresher performance are crop variety, shape and size, hardness of the seed, the moisture content of the seed and the density. The Hopper Design Analysis The hopper (Fig. 1) is designed to be fed in a vertical position only. The material used for the construction is mild steel sheet metal, which is readily available in the market and relatively affordable. The hopper has the shape of a frustum of a pyramid truncated at the top, with top and bottom having rectangular forms. Calculation of the Overall Height Lengths AC and EG are calculated by
2 using the Pythagorean theorem, AC 2 = AB 2 + BC 2. Also, AC = (AB 2 + BC 2 ) 1/2, and OC = (AB 2 + BC 2 ) 1/2 /2, EG 2 = EH 2 + HG 2, EG = (EH 2 + HG 2 ) 1/2, and MG = [(EH 2 + HG 2 )/2] 1/2. A E F D P H B Fig. 1. Schematic diagram of the hopper. From the principle of similar triangles, for triangles PMG and POC: PM/MG = PO/OC, or PM = PO x MG/OC. Then the volume of the hopper is given by: V hopper = [(area of base) x height]/3 = [(AB x BC) x h (EH x HG) x x]/3, h = overall height; x = height of the truncated top. The Main Frame The main frame supports the entire weight of the machine. The total weights carried by the main frame are: - weight of the hopper and housing; - weight of the threshing chamber; - the collector and pot; and - the bearings and pulleys. The two design factors considered in determining the material required for the frame are weight and strength. In this work, angle steel bar of 1 1 / 2 by 1 1 / 2 and 2mm thickness is used to give the required rigidity. G C The Threshing Bars Weight, W, of threshing bar is given by: W = mg, m = mass of threshing bar; g = acceleration due to gravity. Mass, m, of threshing bar: m = ρ x V, ρ = density of mild steel; V = volume of threshing bar. Volume, V, of threshing bar: V = l x b x h, 1 = length; b = breadth; h = height. Shaft Design A shaft is a rotating or stationary member, usually of circular cross-section having such elements as gears, pulleys, flywheels, cranks, sprockets and other power transmission elements mounted on it Shigley (1986). The shaft of this machine has a threshing tool attached to it (by welding) at two opposing sides and a pulley mounted on it. It is supported on bearings. Shaft design consists primarily of the determination of the correct shaft diameter to ensure satisfactory strength and rigidity when the shaft is transmitting power under various operating and loading conditions. Shafts are either solid or hollow. The following presentation is based on shafts of ductile materials and circular cross-section. The length of the shaft has been pre-determined at 770mm. Power Delivered By Shaft Power, P = work done per second: P = (work done)/time = (force x distance)/time = force x velocity. Calculation of Reactions R B and R D From Fig. 2: X T = total length of shaft; X = distance along the shaft; W p = weight of the pulley; Technical Report 200 2b1af7f3a8