Design of a Pull-type Combine Harvester for an Alternative Tractor Form in Sub-Saharan Africa

Access to affordable and appropriately scaled agricultural machinery remains a major challenge for smallholder soybean farmers in sub-Saharan Africa. As a result, many farmers continue to rely on labour-intensive and primitive harvesting methods, often requiring up to five people per acre per day. Although grain thresher services exist, they frequently fail to reach all farmers in time, leaving harvested crops exposed to termites, theft, germination, and adverse weather conditions, ultimately diminishing grain quality and value.
While combine harvesters offer a complete solution by integrating harvesting and threshing, their large size and dependency on conventional tractors make them unsuitable for smallholder farming systems. This paper presents the design of a pull-type combine harvester specifically developed for an Alternative Tractor Form (ATF), namely the cargo tricycle, to address this gap. The cargo tricycle was selected for its widespread availability in Ghana, sufficient drawbar capacity and bucket which can be used as a grain bin.
Using an axiomatic design approach, the proposed combine harvester was conceptualised through the reverse engineering of an antique All-Crop 66 pull-type combine harvester. Functional requirements and design parameters were systematically identified and adapted to suit the operational context of small farms. The resulting machine is powered by a 12 hp engine, features a cutting width suitable for harvesting two rows of soybeans at a 10 cm cutting height, and is designed to enable, at most, two operators to work multiple acres in a single day, significantly reducing labour demands.
With dimensions of approximately 3.5 m in length, 2.5 m in width, 1.6 m in height, and a total weight of about 700 kg, the machine is compact and light enough to be towed by cargo tricycles, making it a viable and scalable mechanisation solution for smallholder soybean production in the region.