Design of an animal powered variable rate combine drill for use in Ethiopia

Ethiopian farmers normally spread seed and fertilizer by broadcasting causing uneven distributions of plants and nutrients and sub-optimal production. Low-tech, animal-powered distributors have been designed which work at a single application rate, but no design has been generally accepted. The potential for using an orbital hub gear to design an animal drawn variable rate combine drill suitable for use in Ethiopia was assessed. The design allowed seven seed spacings and seven fertilizer application rates by adjusting rotational speed of the fertilizer flute and the seed cell wheel. A novel seed cut-off mechanism was also designed for minimal seed damage. Laboratory tests indicated that the performance was good at slower rotational speeds. For development as a production machine, the basic design (without the orbital hub gear) proved acceptable. If the design were to maintain the hub gear, modifications would be needed to achieve slower cell wheel speeds for all gear ratios. It was concluded that the basic design was suitable for construction and use in Ethiopia even though the variable rate aspect is an idea before its time.