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Slide 1 - Michigan State University

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									    Physical Modeling- Analytical modeling was performed for                                                                    Redesign the old Mr. T wheelchair connector to improve
  necessary aspects of the product. The findings are listed below.
                                                                                                                                 safety, manufacturing ease, and cost to manufacture.

                                                                                                                             -Eliminate pinch points        Twist locks
                                                                                                                                                         located on top                                                                      Background -To date there are no other products
              Aluminum                vs.        Steel                       (1)                                             -Reduce the complexity
                                                                                                                                                            and bottom
                                                                                                                             and number of parts                                   Sharp edges                                               designed to connect two wheelchairs together for steering
       Square Tubing                  vs.       Circular Tubing                                                              -Redesign for standard
                                                                             (2)                                             “off the shelf” parts                                                                                           Initial Thoughts
                                                                                                                                                                                Safety Issues
                                                                                                                             -Fix ergonomic issues                              Complex Machining                                                •External features are easier and cheaper to make
         Heavy-Duty Clamp              vs.       Light-Duty Clamp            (3)                                                                       Old Mr. T with relevant issues marked                                                     •The new product must maintain functionality
                                                                                                                                                                                                                                                 •Custom-made pieces should be eliminated if possible
1) Aluminum has a sufficient yield strength for this application, and                                                                                                                                                                            •Changing the clamp mechanism will remove pinch
aluminum is the lighter material.                                                                                                                                                                                                                points
                                                                                                                                                                                                                                                 •The price of labor is the largest influence on cost
2) The moment of inertia for a hollow circular cross-section is sufficient for                                                                                                                                                                   •A smaller variety of materials will allow lower costs
the stresses being applied. In addition, the circular bars allow the clamps to
                                                                                                                                                                                                                                                 •The product is in consideration for mass production
rotate freely.
3) There are no internal forces that act to separate the clamps from the                                                                                                                                                                      Priorities are listed below in order of significance
wheelchair bars, so the clamp strength is irrelevant.                                                                                                                                                                                                      (5 being the most important)
                                                                                                                                                                                                                                                              5         4      3     2      1
   Economic Implications- The old and new Mr. T’s were compared.
                                                                                                                             Group Members                                                                                                   Primary Priorities               Secondary Priorities
                                     Old Mr. T                                      Old Mr. T
              1200                                           18
                                                                                                                             Tim Baumer                                                                                                       Delivery Date                   Ambient Environmental Conditions
                                     New Mr. T
                                                             16                     New Mr. T                                Agatha Bone                                                                                                      Function/ Performance           Maintenance
              1000
                                                                                                                                                                                                                                              Human Factors                   Operating Cost
                                                             14
                                                                                                                             Melissa Carrier                                                                                                  Mechanical Loading              Product Cost
               800                                           12
                                                                                                                             Sam Leitkam                                                                                                      Quality                         Shelf Storage Life
                                                                                                                                                                                                                                              Reliability                     Transportation and Packaging
                                                                                                                                                             Faculty Advisor
                                                     Hours




                                                             10
                                                                                                                               Industry Sponsor
    Dollars




               600                                                                                                                                                                                                                            Safety                          Weight
                                                                                                                                                                   Dr. A Loos
                                                              8
                                                                                                                                     Roy Bailiff                                                                                              Spatial Constraints             Energy Consumption
               400
                                                              6                                                                                                                                                                               Health Issues                   Environmental Issues
                                                              4
                                                                                                                                      Michigan State                                                                                          Personnel                       Government Regulations
               200
                                                                                                                                          University                                                                                          Quantity                        Size
                                                              2
                                                                                                                                                                                                                                              Service Life                    Aesthetics
                 0
                                                              0                                                                                                                                                                                                                Noise Radiation
                         One Complete Unit                            One Complete Unit                                                                                                                                                                                        Operating Instructions
                 Cost to Produce One Mr. T                   Time to Manufacture One Mr. T




                                  66.3% Cost Reduction                                                                                                                                  Manufacturer Issues- The current                   User Concerns- Discussions were held with end users
                                                                                                                                                                                        manufacturers were consulted                       of the original design
                       75% Manufacturing Time Reduction                                                                                                                                                                                     -Heartwood School:
                                                                                                                                                                                          -Holt Middle School:
                                                                                                                                                                                            •Cutting slots creates chatter (1)                    •The U-shaped ends did not fit all wheelchair
                                                                                                                                                                                            •The Delrin is the only serviceable part (2)          types, and are not strong enough
                                                                                                                                                                                            •The inside square bar needs sanding (1)              •The device did not have a large enough extension
                                                                                                                                                                                          -Michigan State University:                             •The twist locks were inconveniently placed, broke
                                                                                                                                                                                            •The manufacturing of the slider is                   easily, and were non-repairable (4)
                                                                                   Testing- The three redesigned Mr. T’s were given to                                                      complicated (3)                                             (3)
                                                                                   Heartwood School to test                                                                                 •The U-shaped ends are custom made                                                   (2)
                                                                                   -Feedback:                                                                                               •Lining up the pieces correctly for welding
                                                                                                                                                                                            takes time
                                                                                      •The clamps that were harder to open were preferred
                                                                                                                                                                                                                                                                   (1)
                                                                                      •Tubes that fell out were a hassle                                                                                            (4)
                                                                                      •The detachable feature was not sufficiently explained

                                                                                   Redesign- The product was refined from the user response
                                                                                                                                                                                      Final Design Concepts
                                                                                   -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                                                                                                                                                                 Three Tubes
                                                                                                                                                                                      Spring Clamp        Detachable Cross Bars
An AutoDesk Mockup                           The Built Final Product                                                                                                                                                                  Twist Lock System
                                                                                                                                                                                                                                                                              (Allows a greater range of
                                                                                                                                                                                          (Fits all bars)     (Greater flexibility)   (External easy locking)                        extension )

								
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