Freedon Concepts Drive Mode Mechanism

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Drachuk, Jeremy
Friesen, Iain
Hofer, Jordan
Linsangan, Josh
Vercaigne, Scott
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This report marks the completion of phase one (design) of the Drive Mode Mechanism project submitted by Freedom Concepts Inc. for the MECH 4860 –Engineering Design course at the University of Manitoba. The second phase (prototype) will begin in January 2019and will be completed in April 2019. Freedom Concepts Inc. is a Winnipeg based company that designs and manufactures adaptive tricycles and mobility devices for people living with disabilities. The company has tasked the student design team with the development of a tool-free mechanism to accomplish two separate drive modes for the rider (freewheel and direct drive) and that is compatible with all current tricycle models. The current mechanism being used on the tricycles relies on frictional contact between four set screws and a standard freewheel sprocket to toggle between the two modes. Although functional, actuation requires the use of a tool and has proven too cumbersome for the average caregiver. The design team conceptualized a two-way ratchet mechanism capable of supporting a freewheel and direct drive mode with a single switch actuation. This concept was developed through research, concept development, and feedback from the client and the course advisor. The mechanism consists almost entirely of laser cut sheet metal and off-the-shelf components from McMaster-Carr® to reduce low-volume production costs and facilitate design changes in the prototyping phase. The estimated cost of the prototype design is$133.99.Tomeet the requirements set by the client, the design features two spring loaded pawls, one of which can be rotated away or toward an internal gear profile using a switch to support the freewheel or direct drive modes. The sprocket can be easily interchanged with any of the 18, 22 or 26-tooth variations to deliver all three pedaling difficulties that a customer may order. To maximize the lifespan of the device, the design is supported by a full stainless-steel construction, sealed bearings and maintenance plan. Included with the final design is a detailed installation procedure, bill of materials, cost breakdown, preliminary failure modes and effects analysis, and a complete package of preliminary drawings including all three custom sprocket sizes. These deliverables fulfill all requirements of...