Overview

The Opportunity: The product retrieval area of the Sanford Fleming building vending machine required users to reach deep into a low-clearance compartment — creating discomfort, hand strain, and accessibility barriers for Engineering Science students.

My Role: As one of five team members, I owned the wrist ergonomics validation phase — designing and executing the proxy test that generated the primary data used to converge on the final mechanism. I also contributed to stakeholder framing and the reverse brainstorming session that broke our team's initial design fixation.

The Outcome: Our team delivered a one-way gravity flap chute that eliminated the need to reach into the machine, repositioned the retrieval bay closer to the ergonomically optimal height, and met all anti-theft requirements — with every design decision backed by measurable evidence.

Process & Methodology

Stakeholder Framing and Requirements Development

I identified the primary user group as Engineering Science students across a range of anthropometric profiles and developed retrieval height requirements by synthesizing ergonomic research papers and the CSA B651 Accessible Design Standard. This produced a functional range of 600 mm to 1200 mm, with a target centered on reducing trunk inclination for standing users.

This framing process exposed an early assumption I had to consciously correct: I initially treated the midpoint average (900 mm) as the "correct" answer. Through deeper stakeholder analysis, I recognized that averaging two extreme bounds without weighting stakeholder representation is not evidence-based design — it avoids the responsibility of prioritizing. For a population of mostly standing students, the lower bound (wheelchair accessibility) and upper bound (standing reach) do not deserve equal weight.

Breaking Design Fixation with Reverse Brainstorming

Our team's initial convergence was toward a mechanical extension claw — a solution anchored to our own intuitive experience of retrieving items. To break this fixation, we ran a reverse brainstorming session focused on worsening the problem. This technique surfaced the "no door" concept by deliberately eliminating the anti-theft mechanism. Rather than dismissing it, we inverted it: by adding a one-way spring-hinged flap above the opening, we could eliminate the reach problem entirely while strengthening anti-theft.

This pivot from claw to flap was the most impactful design shift of the project — and it came entirely from systematic de-biasing, not intuition.

Wrist Ergonomics Proxy Testing

With six candidate closure mechanisms remaining after initial convergence, we lacked published data on comparative wrist loading for vending machine interactions. I proposed and built a wrist flexion/extension measurement device from green construction paper and wire, calibrated against a protractor, to capture the maximum wrist deviation angle each mechanism imposed.

I recruited multiple participants and measured wrist flexion and extension across four closure types:

• Standard spring-loaded flap
• Lifting door
• Automatic flap
• No-door / one-way flap

Result: The one-way flap produced the minimum wrist deviation from neutral posture, providing the primary evidence used to converge on the final design. This shifted our team from subjective preference to defensible, data-driven selection.

Key Design Decisions

One-Way Gravity Flap Mechanism

The final design uses a spring-hinged flap that allows the product to fall through under gravity, then snaps back to a closed position to prevent reverse access. This eliminates the need for any reach into the machine, directly addressing the primary ergonomic concern.

Retrieval Bay Height

The retrieval interface was repositioned as close to 900 mm as the existing machine frame permitted. While I later recognized the limitations of the averaging approach that produced this figure, the repositioning still delivered a measurable improvement from the original height of ~211 mm above ground.

Results

• Wrist deviation from neutral posture: minimized to lowest measured value across all tested mechanisms
• Anti-theft security: maintained via spring-return mechanism with no sacrifice to the original functionality
• Retrieval height: improved from ~211 mm to ~900 mm from ground level
• Design decisions: 100% evidence-backed — no selection made without proxy data or published research

Lessons Learned

Diverging before converging is not optional. Our team's fixation on the claw was strong and felt natural — we had all experienced the problem the same way. The Reverse Brainstorming session was the first time I consciously chose to trust a formal process over my initial instinct, and it produced a fundamentally better solution.

Averages are not answers. Calculating the midpoint of a research-backed range feels rigorous, but it implicitly equalizes the importance of every edge case. Real engineering framing requires asking whose needs matter most here and weighting accordingly. This is the difference between discovering a fact and making a defensible decision.

Build to generate evidence, not to display a solution. My wrist measurement device was not a prototype of the final design — it was a tool built specifically to produce data. Separating "evidence prototypes" from "representation prototypes" gave our team a vocabulary for accountability.