College - Author 1
College of Engineering
Department - Author 1
Biomedical Engineering Department
Degree Name - Author 1
BS in Biomedical Engineering
College - Author 2
College of Engineering
Department - Author 2
Biomedical Engineering Department
Degree - Author 2
BS in Biomedical Engineering
College - Author 3
College of Engineering
Department - Author 3
Biomedical Engineering Department
Degree - Author 3
BS in Biomedical Engineering
Date
6-2021
Primary Advisor
Britta Berg-Johansen, College of Engineering, Biomedical Engineering Department
Abstract/Summary
Our design process began with developing a list of questions for our sponsor based on the problem statement we were provided. We took these questions to interview our sponsor. From this interview, we derived a series of customer requirements, which were then used to develop our more specific engineering specifications (Table 8.1). We used these engineering specifications to develop a design morphology. Each of our group mates used the concepts from our design morphology to develop their own full concept sketches. We used Pugh charts to compare the different aspects of each design. The designs were compared based off their effectiveness to achieve the customer requirements and engineering specifications. The highest scoring conceptual design was chosen to be developed further into our first prototype. We developed this prototype design using SolidWorks to better visualize our final design. Once the first prototype design was finished in SolidWorks, we planned out our manufacturing plans and bought the materials to build our prototype. Throughout the build process, several dimensional and manufacturing changes were made to our design in order to optimize its performance. Of the engineering specifications that we developed during our design process, the most important include the wagon’s maximum volume and weight capacity, the wagon’s ability to collapse, the amount of force required to move the wagon up and down stairs, the wagon’s turning radius, and the user ergonomics. Meeting these specifications as described in Table 8.1 would ensure our wagon would be easy and convenient to use for the user. After a full wagon prototype had been created, we began performing user and functionality testing. Our wagon was able to carry the required 30lbs with little deformation to all parts. The only susceptible parts were the elbows, which had a maximum tilt of 5.7deg, and the basket platform, which hung under the outer frame no more than 1.1in. In its folded state the wagon is able to collapse from a 19in height to a 12in height, which allows it to fit in most car trunks. When the Stair Wagon was first put on the Engineering IV (building 192) staircase, the tri-star wheels were not tall enough to prevent the forward axle from scrapping the stairs. After this realization, we changed the testing site to the Engineering East (Building 20) staircase, which had a shorter step height (5.25in) than the Engineering IV steps (6in). The handle placement and shape caused the wagon to fail the Ergonomics Test; all spine angles were greater while using the wagon than carrying the cargo with a traditional basket. The user interface was intuitive, with all participants grasping the mechanisms within the first two trails and completing the first trail in less than the Target Value. Our Stair Wagon was able to succeed in most of the tests we outlined, and if it failed, we fixed it or made plans to fix it for future prototypes.
URL: https://digitalcommons.calpoly.edu/bmedsp/162