Design and construction of an improved manually powered coffee pulper.

Abstract

Coffee is an important cash crop contributing 20% of Uganda's foreign exchange and, about 500,000 households depend on coffee production as a major source of income and mainly is grown by smallholders with an, estimated average coffee farm size of 0.58 hectares processing is done by dry and wet method. Wet processing has been found 10 enhance the taste of both Arabic and Robusta. It has the added advantage of producing coffees of superior quality which translate to better prices in the market Predominant methods amongst the on farm based units are hand pulpers which are owned independently or co-owned and shared in rotation by groups of coffee farmers. However, where fanners can neither access a hand pulper nor afford to pay for its services a lot of improvisation and traditional methods have been employed under wet processing to pulp coffee. This method is time wasting, energy sapping, deteriorates the quality and low output. To overcome this problem, this study chose as its main objective to design, construct arid test pulping efficiency and output of pedal operated coffee. pulping machine, the material of construction was selected based on strength, availability, durability and corrosiveness. The two units pulping and feeding roller units were incorporated in a single machine in order to prevent drudgery associated with the traditional method of pulping and separation of the pulp from the pulped coffee parchment. The first unit consists of a feeding roller; which evenly feeds the coffee cherries into the clearance. The second unit of the machine consists of the pulping drum. The. performance of. the machine was evaluated following optimum operating condition of the length of pulping shaft. speed of rotation of the pulping shaft and the feeding roller rotating shaft, and energy produced by the pedal. The machine was tested and the pulping rate was 31kglhr., pulping efficiency of 76%were obtained. The results were relatively high as compared to the traditional methods and that designed by Muhire Nelson. The pulping efficiency is less than 1000/0 because of the variation in coffee cherries and non-uniformity in the pulping drum since some could pass through the clearance between pulping drum and breastplate which affected the efficiency of the machine, Key-words: pulping, coffee. cherries, pulping efficiency; pulping output.