Abstract
This paper describes the motivation, design, and testing of a specialized farm tractor designed to replace draft animals in small farms, particularly in rural India. The proposed tractor matches the low capital cost of draft animals and has their unique ability to operate between growing crops in narrow inter-row spaces while retaining the major advantages of conventional tractors, such as low maintenance cost and reduced operator physical effort. The proposed tractor was conceived based on user needs and our implementation of a detailed terramechanics model. This tractor has a higher drawbar pull per unit mass compared to conventional tractors – a high drawbar force is needed to match the peak pull of animals, and a low mass is necessary to reduce material and vehicle costs. This quality is achieved by applying nearly the full vehicle's weight on the drive wheels, placing drive wheels in line, and locating the tillage tool between both axles. A proof-of-physics prototype of the design was instrumented to measure drawbar pull and tire slip to validate the terramechanics model and quantify traction performance. It was capable of pulling with more drawbar force per unit mass than conventional tractors and its performance can be accurately predicted by the model. During field tests on a working farm, the vehicle successfully operated in the narrow spaces between growing crops that would typically not be accessible to a low-cost, conventional small tractor. Initial farmer feedback on the design confirmed its high potential for performing farming operations.
