eric twiest brad pierson hieu nguyen matt miiller february 14 th 2007 l.
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Eric Twiest Brad Pierson Hieu Nguyen Matt Miiller February 14 th , 2007. Wheelchair Gearing System Project Proposal. Problem Statement.

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eric twiest brad pierson hieu nguyen matt miiller february 14 th 2007
Eric Twiest

Brad Pierson

Hieu Nguyen

Matt Miiller

February 14th, 2007

Wheelchair Gearing SystemProject Proposal
problem statement
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 don’t 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.

wheelchair statistics
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.
alternative existing solutions
Alternative Existing Solutions
  • Magic Wheels
  • Power Assisted
  • ADA regulations for ramps:
    • Maximum incline slope of 12:1
    • 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.
constraints continued
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)
operating conditions
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 0-100°F
    • Debris (Salt, Dirt, other particles)
    • Water (Rain, snow, ice)
preliminary calculations
Preliminary Calculations





System Diagram

Calculated Forces, Torques and Effective Gear Ratios.

-Forces: Fincline=136.1 lbf, Fflat=120 lbf

-Torques: Tincline= 816.6 lb·in, Tflat=720 lb·in

-Angular Velocities: ωincline=38.58 rpm, ωflat= 43.77 rpm

-Effective Gear Ratio:

-Design for 2:1 ratio to guarantee for factor of safety.

Assumptions made( 200 lb person, 0.5 hp input, wheel diameter = 24 in)

future plans
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.