The Figure-Eight Drive is an implementation of
a Retro-direct bicycle drivetrain on a hand-powered tricycle.  It provides tricycle users with a reliable two geared system.  Users can switch between the two gears by changing the direction of their pedaling, with both directions resulting in forward propulsion.  Pedaling in the standard forwards direction provides users with an approximately 1:2.25 cruising gear, while pedaling in the reverse direction allows users to climb and maneuver easily with a 1:1 gear ratio.  The tricycle can freewheel in the forwards direction, though no backwards movement is allowed.  The steering column can be rotated 180 degrees, allowing one to ambulate and freewheel in reverse.
 
The drivetrain was developed by a group as part of the class Wheelchair Design for Developing Countries during Spring 2007 at the Massachusetts Institute of Technology.  I was granted funding by the MIT Public Service Center to travel to Nairobi, Kenya and develop the drivetrain with the Association for the Physically Disabled of Kenya (APDK), an NGO that manufactures and distributes mobility aids throughout East Africa.
The Figure-Eight Drive
this site last modified on 16th August 2007 by Mario Bollini