Investigation of an affordable multigrain thresher for smallholder farmers in sub-Saharan Africa

David D Wilson, Purdue University

Abstract

As the global population rises, food security is among the most important grand challenges of our time. While agriculture has significantly developed in parts of the world, other parts are severely underdeveloped, inhibiting agriculture productivity, which is a necessary component of the solution to the food security challenge. Sub-Saharan Africa (SSA), in particular, has seen little growth in productivity, something that has been correlated to its low agricultural mechanization. One barrier to mechanization in SSA, where the average farm size is less than 2 Ha, is the cost of farm equipment. This leaves many farmers with just basic tools to perform farm operations. Threshing is a critical part of processing grains, which are staple crops in most countries. Traditional methods of threshing are time and energy consuming and can result in significant grain losses. Threshers that are available are imported, expensive, or too large for most farms. This thesis investigated a locally appropriate and sustainable multigrain threshing machine as a means of improving the productivity and efficiency of smallholder farmers in SSA. An axial-flow threshing machine was designed for the threshing and cleaning of maize and soybeans. The thresher was 5.2 ft (1.6 m) long, 4.3 ft (1.3 m) high and 1.4 ft (0.4 m) wide. At an engine speed of 3000 rpm, the drum had a peripheral speed of 39 ft/s (12 m/s), the sieve oscillated at 10 Hz, and air speed at the fan outlet was 29 ft/s (8.9 m/s). To simplify local manufacturing and minimize costs, only basic parts and materials, like rebar, angle iron, and pulleys, were used in the thresher. Tests of the thresher were performed using pre-weighed stalks of soybeans or un-husked corncobs. The crop was run through the thresher, and afterwards, weights of the grain and material other than grain (MOG) were measured in four different locations: on the ground, in the thresher, out the cylinder discharge, and in the grain bin. After initial tests, minor modifications were made to the thresher, and final tests were conducted. The final results showed that 96% of corn and 94% of soybeans were collected in the grain bin, with MOG amounts of 1.3% and 6.6% respectively. The feeding of material into the thresher, not the power or threshing capacity of the machine, restricted the feed rates. Grain feed rates of over 200 kg/h (corn) and over 20 kg/h (soybeans) were achieved. The results have demonstrated strong potential for the machine to be manufactured and used in SSA as a labor saving device for smallholder farmers to increase productivity and decrease losses.

Degree

M.S.A.B.E.

Advisors

Lumkes, Purdue University.

Subject Area

Agricultural economics|Agricultural engineering|Mechanical engineering

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