Design is not a linear process. We iterate to gain insights, generate alternatives, represent ideas, and check content. Part of that process is to frequently question and refine our Problem Statement. This page shows that evolution.

04 Aug 2008:
How do we design and validate a $20, 10kg/hr millet thresher suitable for local manufacture and sale in Africa and India?

26 July 2008: 100 word "sales pitch":
Like 1 million African farmers, Fatima spent 4 hours daily pounding millet in a hole with a heavy stick to feed her family. Since buying her Mahangurina thresher, her chronic back pain and calluses on her hands have disappeared. Her family can chew porridge without breaking their teeth on stones. With 2 more hours per day and more energy, she planted additional millet to sell so her daughter can attend college.
The Mahangarina thresher is an innovative, inexpensive, portable threshing machine made by and for small pearl millet farmers and consumers. It produces cleaner, healthier grain faster, safer, and cheaper.

26 July 2008: 1 minute summary:

• Through interviews and research, we’ve focused our Problem Statement from “pounding millet with a stick for 4 hours sucks” to “how to build a $20 30 kg/hour human-powered thresher?”
• Through experiments, we’ve explored the mechanical properties of millet. Threshing involves combinations of up to 5 operations, each requiring specific forces and energy. We’ve begun to explore rubbing, spinning, shearing, grinding, blowing, vacuum, and blending with a range of materials.
• Through brainstorming, we’ve sketched design concepts to implement various threshing sequences. We wish to generate more, innovative concepts.
• Our team is more knowledgeable, enthusiastic, and optimistic that we can solve this challenge.

25 July 2008:
How do we design, mfg, and sell a $20/10kg/hr millet thresher in Namibia?



23 July 2008: we have iterated on the problem statement and solution concept, exploring and comparing two alternatives: a ~$20/1kg thresher sold to small farmers or families, vs. a ~$800/100kg scale thresher sold to larger farmers, communities, or cooperatives. We suspect these represent two "sweet spots" where devices could offer sustainable value (in addition to the $100k/10000kg scale commercial machines on the market). We constructed a couple of tables to explore the relative merits and value of these two concepts.

21 July 2008: Design and validate a radically simple, reliable, and inexpensive millet threshing (and ideally winnowing) machine, appropriate for small (<~ 1 acre) farmers.

In spite of a serious dearth of information directly from the field, we believe the following:

Target customers are primarily women who currently thresh and winnow small quantities of millet for their daily use or to sell a small surplus.

Their capital and technology constraints will force us to keep it cheap and keep it simple, which is also consistent with Paul Polak's mantra.

Likely trade-offs to achieve minimal cost and simplicity include:

• manual power source, ideally without complex transmissions or linkages.
• Scalability to high throughput or other grains is less important (although the principles we discover and elaborate on might give us insights and shorten the design path towards development of such devices).

This was the process of brainstorming ... which helped us refine our problem statement



















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