Analyze

1. Aluminum vs. Steel (1) Square Tubing vs. Circular Tubing (2) Safety Issues Complex Machining Heavy-Duty Clamp vs. Light-Duty Clamp (3) • 4 • 2 • 1 • 5 • 3 66.3% Cost Reduction 75% Manufacturing Time Reduction “Mr. T” Wheelchair Connector Redesign Redesign the old Mr. T wheelchair connector to improve safety, manufacturing ease, and cost to manufacture. Physical Modeling- Analytical modeling was performed for necessary aspects of the product. The findings are listed below. -Eliminate pinch points -Reduce the complexity and number of parts -Redesign for standard “off the shelf” parts -Fix ergonomic issues Twist locks located on top and bottom • Background-To date there are no other products designed to connect two wheelchairs together for steering • Initial Thoughts • External features are easier and cheaper to make • The new product must maintain functionality • Custom-made pieces should be eliminated if possible • Changing the clamp mechanism will remove pinch points • The price of labor is the largest influence on cost • A smaller variety of materials will allow lower costs • The product is in consideration for mass production • Priorities are listed below in order of significance • (5 being the most important) • Primary Priorities Secondary Priorities • Delivery Date • Function/ Performance • Human Factors • Mechanical Loading • Quality • Reliability • Safety • Spatial Constraints • Health Issues • Personnel • Quantity • Service Life Sharp edges Old Mr. T with relevant issues marked 1) Aluminum has a sufficient yield strength for this application, and aluminum is the lighter material. 2) The moment of inertia for a hollow circular cross-section is sufficient for the stresses being applied. In addition, the circular bars allow the clamps to rotate freely. 3) There are no internal forces that act to separate the clamps from the wheelchair bars, so the clamp strength is irrelevant. Problem Clarify • Ambient Environmental Conditions • Maintenance • Operating Cost • Product Cost • Shelf Storage Life • Transportation and Packaging • Weight • Energy Consumption • Environmental Issues • Government Regulations • Size • Aesthetics • Noise Radiation • Operating Instructions Economic Implications- The old and new Mr. T’s were compared. Group Members Tim Baumer Agatha Bone Melissa Carrier Sam Leitkam Faculty Advisor Dr. A Loos Design Industry Sponsor Roy Bailiff Michigan State University Build and Test Analyze Time to Manufacture One Mr. T Cost to Produce One Mr. T • Manufacturer Issues-The current manufacturers were consulted • -Holt Middle School: • Cutting slots creates chatter (1) • The Delrin is the only serviceable part (2) • The inside square bar needs sanding (1) • -Michigan State University: • The manufacturing of the slider is complicated (3) • The U-shaped ends are custom made • Lining up the pieces correctly for welding takes time • User Concerns- Discussions were held with end users of the original design • -Heartwood School: • The U-shaped ends did not fit all wheelchair types, and are not strong enough • The device did not have a large enough extension • The twist locks were inconveniently placed, broke easily, and were non-repairable (4) • Testing- The three redesigned Mr. T’s were given to Heartwood School to test • -Feedback: • The clamps that were harder to open were preferred • Tubes that fell out were a hassle • The detachable feature was not sufficiently explained • Redesign- The product was refinedfrom the user response • -Reactions: • The stronger clamps were used even though structurally there was no need (see the analyze section) • Kevlar string was employed to restrain the tubes • A push pin replaced the detachable feature bolt, making the usage prominent (3) (2) (1) (4) Final Design Concepts Three Tubes (Allows a greater range of extension ) Spring Clamp (Fits all bars) Detachable Cross Bars (Greater flexibility) Twist Lock System (External easy locking) An AutoDesk Mockup The Built Final Product