Mobility made tougher and cheaper
2010 R&D 100 Winner
2010 Editors' Choice Recipient
Modern electric wheelchairs are marvels of engineering, but they do not work well on rough terrain and are often unavailable to those in rural areas or developing countries. With this in mind, the Massachusetts Institute of Technology’s Mobility Lab, Cambridge, Mass., has developed the Leveraged Freedom Chair (LFC), which is maneuverable within the home and can travel long distances on rough roads far from urban centers.
The key innovation behind the LFC is its single-speed, variable mechanical advantage lever drivetrain. Instead of using multiple gears, an LFC user varies mechanical advantage and chair speed by sliding his or her hands up or down the levers. Changing user geometry instead of machine geometry allows the use of a simple, light-weight, low-cost, single-speed chain drive. Pushing forward on the levers provides up to a 4-to-1 mechanical advantage, and pulling back ratchets and resets the drivetrain for the next power stoke. Pulling the levers back further brings the brakes—small bars that protrude from the levers—into contact with the tires. The wheelchair can be used indoors simply by removing the levers.
Real-world performance tests yielded a propulsion efficiency gain of about 20%. The LFC has a targeted cost of about $200, far less than most commercial options, and has an open-source design to encourage investment.
|(Top row): The Association for the Physically Disabled of Kenya
(Second row, l-r): Xuefeng Chen; Slava Menn; Harry O’Hanley; Mario Bollini
(Third row, l-r):: Danielle Delatte, Tish Scolnik with Fatuma Acan; Amos Winter; Ben Judge
(Bottom row): Transitions Foundation of Guatemala
The Leveraged Freedom Chair Development Team:
Amos Winter, Massachusetts Institute of Technology Mobility Lab