Wheelchair Gearing System Project Proposal

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Wheelchair Gearing SystemProject Proposal

• Eric Twiest
• Brad Pierson
• Hieu Nguyen
• Matt Miiller
• February 14th, 2007

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Problem Statement

• When operating a manual wheelchair it can be
  very difficult for the user to traverse an
  incline plane or ramp. In addition some people
  dont have the strength required and dangers
  exist, for example rolling back down a ramp. The
  goal of this project is to develop an attachment
  or modification to a manual wheelchair which
  would provide the user with a mechanical
  advantage when traversing a ramp.

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Wheelchair Statistics

• 1.6 million Americans residing outside of
  institutions use wheelchairs.
• Most (1.5 million) use manual devices, with only
  155,000 people using electric wheelchairs.
• Wheelchair users experience among the highest
  levels of activity limitation and functional
  limitation.
• Statistics have by NHIS have shown shoulder
  injuries to be present in up to 51 of the users
  of manual wheelchairs. Also statistics have found
  an abundance of elbow, wrist, and carpal tunnel
  syndrome from manual wheelchair users.

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Alternative Existing Solutions

• Magic Wheels
• Power Assisted

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Functional Analysis
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Constraints

• ADA regulations for ramps
• Maximum incline slope of 121
• A level area must be located at the top and
  bottom of a ramp. No run over 30 feet is allowed
  without an intermediate resting platform. This
  platform may be a straight or turn platform.
• If there is not enough area to install a straight
  ramp, it may be necessary to build cross runs
  from side to side.
• Any platform that changes direction must be at
  least 60" x 60" for wheelchair maneuverability.
  If a ramp has a rise greater than six inches or a
  horizontal projection greater than 72 inches, it
  should have handrails on both sides.
• The top of the handrail should be mounted between
  30 and 34 inches above the ramp.
• Ramps should have non-skid surfaces and
  constructed so water cannot accumulate on walking
  surfaces.

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Constraints Continued

• The system must be able to attach to an existing
  manual wheelchair
• Low cost must be a primary factor
• The system must be safe to use while still
  maintaining functionality
• The system must last for the entire service life
  of the wheelchair
• The system must be manufactured using current
  accessible resources (built at Keller)
• Low weight must be a primary factor
• The product must be easy to assemble (designed to
  be assembled by the end user)

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Operating Conditions

• The wheelchair system will be subjected to many
  harsh environments. The environment will change
  from high temperatures to freezing temperatures,
  from dry surfaces to wet surfaces, to icy
  surfaces, to snowy surfaces. More specifically
• Temperatures from 0-100F
• Debris (Salt, Dirt, other particles)
• Water (Rain, snow, ice)

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Planetary Gear
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Ratchet System
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Bike Pedal System
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Torsion/Stored Energy System
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Preferred Design Selection
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CAD Drawing of Preferred Design
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Preliminary Calculations
Ff,FT
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W
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System Diagram
Calculated Forces, Torques and Effective Gear
Ratios. -Forces Fincline136.1 lbf, Fflat120
lbf -Torques Tincline 816.6 lbin, Tflat720
lbin -Angular Velocities ?incline38.58 rpm,
?flat 43.77 rpm -Effective Gear Ratio -Design
for 21 ratio to guarantee for factor of
safety. Assumptions made( 200 lb person, 0.5 hp
input, wheel diameter 24 in)
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Future Plans

• Build prototype of fully functional wheelchair
  with gear system installed.
• Manufacture gears, arm and housing on CNC
  machine.
• Purchase raw material, bolts, nuts and other
  small components.
• Test prototype on various inclines and level
  ground at full speed for durability, and
  performance.

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Budget