The Water Buffalo: Design of a Portable Bicycle Powered Irrigation Pump for Small-Scale African Farmers

This project is to develop a low cost and mass-producible bicycle powered irrigation pump for small-scale (100–1,000 m2 plot) African farmers. The pump is intended to be made and distributed by World Bicycle Relief’s Buffalo Bikes program. This project’s process is divided into three parts: an investigation into the use-environment, quantitative testing of a prototype pump, and the redesign of the pump. In order to clarify the user needs, I conducted in-depth interviews and informal demonstrations with small-scale farmers in Kenya. I learned of additional user requirements; for example, that the pump must be usable by children. I also learned of critical problems with the early design; for example, that air leaks on the suction side of the pump will hobble its performance. Though imperfect, the limited success of the trials verified the viability of a bicycle irrigation pump in the target market. To quantify the effectiveness of a centrifugal bicycle powered pump, I measured the pump’s water flow at various input power levels and outlet heights (vertical heads). The efficiency of the pump system (η ≈ 55%) approached the claimed manufacturer’s maximum efficiency of η ≈ 66%. I then compared the bicycle pump to two other human powered pumps, both of which use a treadle pumping style. The bicycle system pumps water at similar or possibly higher flows than the tested treadle pumps. Friction calculations additionally revealed that at fast flow rates of 1 liter per second (16 gallons per minute), hoses with a 1 inch diameter (25.4 mm) have significant friction losses, while 1.5 inch (38.1 mm) hoses have negligible friction losses. Based on the interviews and efficiency tests, I redesigned the pump and gearbox to be made of plastic and to address the main issues identified in the field. The pump-to-hose attachments are designed to reduce air leaks, reduce tipping, and simplify the pump’s setup. The form of the gearbox is designed without overhangs so that it can be manufactured by casting. By creating an inexpensive irrigation method, I hope to empower small-scale African farmers to lift themselves into prosperity.