1. 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 Group Members Tim Baumer Agatha Bone Melissa Carrier Sam Leitkam Industry Sponsor Roy Bailiff Michigan State University Faculty Advisor Dr. A Loos -Eliminate pinch points -Reduce the complexity and number of parts -Redesign for standard “off the shelf” parts -Fix ergonomic issues Redesign the old Mr. T wheelchair connector to improve safety, manufacturing ease, and cost to manufacture. Old Mr. T with relevant issues marked Sharp edges Twist locks located on top and bottom Safety Issues Complex Machining  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  5  4  3  2  1 Spring Clamp (Fits all bars) Detachable Cross Bars (Greater flexibility) Twist Lock System (External easy locking) Three Tubes (Allows a greater range of extension ) (1) (2) (3) (4) Final Design Concepts 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) An AutoDesk Mockup The Built Final Product 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 refined from 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 Physical Modeling- Analytical modeling was performed for necessary aspects of the product. The findings are listed below. Economic Implications- The old and new Mr. T’s were compared. 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. Aluminum vs. Steel (1) Square Tubing vs. Circular Tubing (2) Heavy-Duty Clamp vs. Light-Duty Clamp (3) Cost to Produce One Mr. T Time to Manufacture One Mr. T 66.3% Cost Reduction 75% Manufacturing Time Reduction