Sustainability · User-Centered Design · 2023

Beans Unwrapping
Machine

An automated double-groove pulley system designed for small and medium farmers across Cameroon — portable, locally maintainable, and built to achieve 85%+ yield performance with minimal operator effort.

Beans Unwrapping Machine — complete assembled prototype
Year 2023
Role Lead Designer · Sole Engineer
Duration 2 months
Team Nepitimbaye · Grace · Tatsinda
Category Sustainability · User-Centered

Project Case Study

The Problem

During a visit to Maroua in northern Cameroon, I observed local farmers manually unwrapping beans — a process so slow and labour-intensive that it severely limited production efficiency. This firsthand encounter with traditional agricultural methods made the need for an automated solution clear.

Existing machinery was either unavailable locally or unaffordable for small and medium enterprises. The solution had to be designed specifically for the realities of rural Central Africa: limited material availability, no specialist maintenance infrastructure, and the need for portability to serve dispersed farming communities.

The project required balancing strict performance targets — over 85% yield, significantly reduced operator effort, and health and safety compliance — against the hard constraints of local manufacturing and limited budget.

The Approach

I developed competing prototype configurations before selecting the final design based on raw material availability, parallel motor positioning, and fan placement for optimal stability and reduced vibration.

The shaft design became the critical engineering challenge. I engineered variable-dimension blades mounted at 120-degree intervals with 5 cm spacing, carefully calibrating rotation speed against motor driving force to unwrap beans without breaking them. Power transmission used a double-groove pulley system connecting motor, shaft, and fan to partition driving force efficiently.

When the specified 1.1 kW motor proved unavailable, I adapted the design for an alternative motor while maintaining all performance targets. Steel thickness selection balanced structural integrity against machine weight — a critical decision for the portability farmers required. External pulley and belt positioning allowed easy interchangeability and direct shaft access for repair.

The Outcome

The project delivered a functional prototype meeting all primary performance targets. Working with Nepitimbaye, Grace, and Tatsinda taught me that technical excellence in constrained environments must accommodate real-world unpredictability — their perspectives on material substitution and component failure modes proved essential when ideal specifications could not be met.

Beyond the machine itself, this project reshaped how I approach team leadership in engineering work. Initially I defaulted to executing small tasks myself rather than investing time explaining requirements. Once I committed to thorough onboarding, the team operated increasingly autonomously — extrapolating from base principles to solve problems independently.

The lesson was clear: in engineering teams, doing it yourself is rarely optimal. Setting teammates up for success through patient communication yields far better outcomes than shouldering every responsibility alone.

See the BUR machine in action — Watch the animation on LinkedIn

Technical Documentation

Engineering Drawings

BUR machine detailed explanation drawing 1 — component layout and assembly overview
BUR machine detailed explanation drawing 2 — power transmission and shaft assembly

Project Gallery

Interested in this type of work?

I design practical, locally-buildable machinery for agricultural and industrial applications across Central Africa. Available for design consulting and research collaboration.

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