Tractor design for small farms in resource limited markets

Abstract

This thesis describes the design of a tractor for small farms (<2 ha) in resource limited markets, particularly India, and the analytical framework used to arrive at the design. Indian smallholder farmers typically rely on draft animals, which compared to tractors are more expensive to maintain, more exhausting to use, slower, and incompatible with many modern farming tools and methods. These disadvantages are detrimental to the farmer's income and crop yields. However, existing small tractors are too large and expensive to directly replace draft animals. The presented tractor design is unique in its ability to compete with draft animals' physical dimensions, pulling performance, and sale price, while retaining key tractor advantages like compatibility with modern tools, low maintenance costs, and reduced drudgery.

This tractor features motorcycle-like controls and seating, inline drive wheels, stabilization via an outrigger arm or a specially-developed balance board attachment, and the ability to attach implements ahead or behind the rear axle. The design was created to satisfy unmet farmer requirements identified during on-site interviews with Indian farming stakeholders. Before deviating from the conventional tractor design, a comprehensive description, from a historical and physical perspective, of why the conventional tractor came to be was elucidated. Then, the proposed tractor design was conceived by leveraging historical, physics-based, and user-focused insights. Experimental results with an instrumented proof-of- physics prototype validated the new tractor could produce traction forces as predicted by the analytical framework used to create the design, as well as meet or exceed the maximum pulling forces generated by draft animals.

A functional prototype of the tractor was built, and its ability to complete key farming operations was demonstrated on a Massachusetts farm. The vehicle was able to complete plowing, disc harrowing, rotary tilling, planting, cultivating, spraying, and towing of a trailer per Indian industry specifications. A study was conducted to assess whether the vehicle would meet the needs of small and marginal farmers in India through on-site, one-on-one interviews with 24 farmers in Karnataka, Gujarat, and Tamil Nadu. Farmers generally reported that the prototype tractor would meet their needs, with an average likelihood of 4.8/5 that they would use the vehicle for planting, inter-cultivation, and spraying, and an average likelihood of 3.8/5 that they would use the tractor for primary or secondary tillage.