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Wheelchair Design in Developing Countries: Redesigning the Trike Frame

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Key Features Adjustable Seat Adjustable to user Biomechanically optimized. Stackable Shippable to more clients Lowered shipping cost. Wheelchair Design in Developing Countries: Redesigning the Trike Frame

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Key Features

  • Adjustable Seat
    • Adjustable to user
    • Biomechanically optimized
  • Stackable
    • Shippable to more clients
    • Lowered shipping cost

Wheelchair Design in Developing Countries:

Redesigning the Trike Frame

Fiona Hughes, Gina Policelli, Ashley Thomas, and Jodie Wu; Massachusetts Institute of Technology

  • Most Critical Module
  • Strength of the base frame
    • Current frames can collapse in on the rider and are not strong enough to support rider and cargo, so analysis was needed

Introduction:

Each year, tens of thousands of wheelchairs are donated to Africa in hopes of helping the nearly 20 million people in Africa in need of a wheelchair. However, within months, these wheelchairs lose their functionality as they cannot survive the harsh terrain in Africa. In Africa, many of the roads are unpaved and buses are inaccessible to many wheelchair users, forcing wheelchair users to travel more than 5 km each day over conditions in which an ordinary wheelchair was not designed for.

Local manufacturers have come up with a tricycle design that allows for easy travel over long distances through the use of a hand crank and a three-wheel design for added stability. However, these designs often bend, hindering the movement of the trike. During this project, a thorough analysis was done to create a strong tricycle frame that would satisfy the needs of the manufacturerers and the users..

  • Current Design Facts:
  • Most time consuming part of building a frame: Bending the frame
  • Most expensive frame material: Round hollow tubing 25 X1.5 mm for base frame.
  • Time required to produce a frame: 5 man-hours
  • Design Analysis
  • Yield stress of mild steel: 5.17 E8 Pa
  • Safety factor: 10 yielding a max stress of 5.17 E7 Pa
  • Considerations
    • Users will travel over all kinds of terrain
    • Heavy loads and/or other people will be carried
    • Trike will be used for years in harsh conditions
  • SOLUTION: CENTRAL BEAM
  • Functional Requirements:
  • Strength: strong enough to support the rider and some cargo.
    • Strengthen and stiffen high moment areas to withstand at least 350 lbs of load
  • Robustness: appropriate for the conditions used in, long life
  • Easily Manufactured and Repaired: shops should be able to produce trike with the tools they already have and repair the frame easily
    • Manufacturing time: <5 hours
    • Made from parts that are cheap and readily available.
  • Adjustable: accomodating people of different ages, disabilities, and sizes; easy to get in and out of.
  • Lightweight: light and compact frame design.
    • Size: <= 50” in length and 26” in width (including wheels)
  • Low Cost: affordable to produce, ship, and buy.
    • Frame Materials: Cost<$100
    • Shippable: Stackable Design
  • Problem:
  • Issues with the Current Frame
  • too weak to support necessary weight and retain functionality in the given conditions
  • “one size fits all” (not
  • adjustable for user)
  • too large and bulky to be used indoors or on public transportation
  • difficult to manufacture, very difficult to ship

Solid Model:

  • Community partner response on reason for current tricycle breakage:
    • “Our design is made of round tubing having several bends forming a base frame. If the tube is flattened on bending or the material is a bit thin, then it breaks easily. Also if the type of tubing frame do not withhold the weight of the persons then it breaks.”
  • Improvement of Design
  • Reduced manufacturing time due to fewer bends and pieces
  • Stackable and shippable with angled back
  • Compact design, increasing mobility
  • Storage beneath and behind for convenience
  • Adjustable seat to fit user
  • Sturdier Frame due to center beam
  • Goals:
    • To improve on the design of the tricycle frames so that they are better suited and more convenient for the user
    • Create a design that is easier and cheaper to build and repair

Material Analysis

  • Initial Design:

Special Thanks to… Amos Winter for teaching the course

John Hart for advising this project

Edgerton Center for providing machining tools

MIT Foundry for use of welding equipment

Back slanted

to allow stacking

Removable chair

Sturdier base

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