Project Overview

My capstone senior design project was sponsored by Gypsum Management Supply, INC. who presented the challenge of improving the safety and usability of an age-old tool they use every day: the drywall cart. The motivation was that GMS spends nearly $1 million per year in worker’s compensation due to worksite injuries where a loaded (1 ton) drywall cart tips over and crushes the operator. The goal of the project was to develop a novel drywall cart that improves the operational safety by addressing maneuverability and minimizing risks of tipping.

Problem Discovery and Ideation

Our team first visited several ongoing construction sites to understand how drywall carts are typically used. The greatest insightes we gathered were from construction workers themselves – their concerns lied more with efficiency and ease of use rather than safety itself. The challenge then became how to improve safety while maintaining the current design’s functinality. It became clear that a retrofit mechanism that could be installed on existing carts was the correct direction to take the project.

We went through several rounds of brainstorming - my personal favorite phase of the project - and generated a House of Quality (HOQ), morphological chart with several design alternatives, and simple “napkin” calculations to validate our initial designs. There were two aspects of the redesign that we chose to pursue. The first was a fail-safe mechanism that would trigger when the drywall on the cart began to tip, extending a spring-powered “kickstand” that would catch the weight of the drywall and prevent it from fully flipping over. The second was a more proactive approach that attempted to increase control over the cart while pushing it by introducing a hand-crank workers could use to direct the wheels of the cart as they go around tight corners.

Mechanism Design

I was elected as the lead for the development of the fail-safe kickstand mechanism. My focus was on creating a purely mechanical mechanism that would actuate as soon as the drywall began to tip off the cart. We were adamant about not obstructing the free side of the cart which was the side used to load and unload, and so we experimented with several fail-safe mechanisms that could rotate into position when there was a risk of tipping, and rotate away when the cart needed to be loaded/unloaded.

The final design was a 2-bar linkage kickstand with a trigger at its top that would release the spring-loaded kickstand legs once drywall came in contact with it. With lead times in mind, we chose off-the-shelf components like black steel pipe to construct the prototype. The prototype worked in all scenarios we tested where the drywall cart begins to flip as a result of the drywall itself leaning towards the free edge of the cart. Videos of our experiments can be seen in the final presentation video attached below.

Document Links

• Design Expo Poster: Poster displayed at the senior design expo
• Final Report: details design process, and includes final CAD models and FEA validation.
• Fabrication Package: Fabrication Package submitted to GMS
• Report #2: Second update report detailing mechanism design
• Report #1: First update report detailing ideation and market analysis