Design and construction of an adjustable pedal operated coffee pulper for small-holder farmers
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Coffee is one of the most tradable commodities globally in most of the developing countries with high foreign exchange earnings. In Africa, Uganda was the second largest coffee exporter after Ethiopia in the year 2017 with 4.19 million bags of 60 kg, of which 3.19 million bags were Robusta. Primary coffee processing plays an important role in quality and price determination of coffee beans. In Uganda, coffee is dry and wet processed with Arabica being the wet processed variety. The wet processing method involves a series of unit operations such as sorting, pulping, washing and hulling, each handled at different stages. Although this process yields coffee of high quality and has higher market price, it’s very laborious noting that most of these unit operations are done manually. Pulping is done using hand cranked or motorized coffee pulpers of different pulping chamber designs such as disc pulpers and rotating drum pulpers. Such machines are imported and require high initial running costs for those which are motorized. The research focused on design of a pedal operated coffee pulping machine (drum type) that can reduce drudgery, time wastage due to use of hand-cranked coffee pulper, taking consideration of anthropometric study with 30 participants. Other design considerations include cost of construction, availability of materials, and gender groups that carry out this process. The coffee pulping machine designed has a capacity of 315kg per hour but can pulp 175kg/hr when hand-cranked. The fabricated coffee pulper has a pulping efficiency of 93% and a percentage mechanical damage of 0.49%. The machine was tested to evaluate its performance against a hand cranked coffee pulping mechanism to determine the significance in time saving using a 2×3 factorial experiment with three replications. A subjective assessment to users was conducted and their responses to the use of the machine obtained. Based on the feedback from users, the overall machine preference was over 90% especially for women, this indicated that the machine can be adopted. The machine was designed to enable replacement of the pedaling mechanism with a hand wheel depending on operator’s convenience. There was a significant difference in machine performance when powered by pedal power and hand-cranking power. The difference was more pronounced as the quantity of coffee was increased. The machine constructed was economically justified. It is recommended that a manual gear box maybe used in the power transfer mechanism to further reduce the energy requirement from the operator.