Amos G. Winter
Assistant Professor
Director, Global Engineering and Research (GEAR) Lab
Department of Mechanical Engineering

Massachusetts Institute of Technology


The Leveraged Freedom Chair
Topic of Postodoc
Supervisors: Prof. Daniel Frey, MIT/SUTD and Prof. Sudipto Mukherjee, IIT Delhi

The purpose of the Leveraged Freedom Chair (LFC) project is to create a mobility aid specifically for developing countries. Conventional western-styled wheelchairs are nearly impossible to propel on the sandy roads and muddy walking paths frequently encountered in the developing world. The LFC has a variable mechanical advantage lever drivetrain that enables its user to travel 10-20% faster on tarmac than a conventional wheelchair and off road like no other mobility aid available. The user effectively changes gears by simply varying hand postition on the levers; grasping high increases torque while grasping low increases angular velocity. Human upper body force and power outputs were used to optimize the drivetrain geometry for optimal performance on a wide range of terrains. All moving parts on the LFC are made from bicycle components, making the chair manufacturable and repairable anywhere in the developing world. The LFC is currently being trialed in Guatemala and India, with plans to start large-scale production in the summer of 2011 with BMVSS Jaipur Foot and its partners. Additionally, a developed world version of the LFC is under development in collaboration with Continuum.

To learn more about this project, visit the LFC webpage.

Selected publications:
A.G. Winter, V, et al. “Stakeholder-Driven Design Evolution of the Leveraged Freedom Chair Developing World Wheelchair.” ASME IMECE 2012.

Winter V, A.G., et al. “The design, fabrication, and performance of the East African trial Leveraged Freedom Chair.” ASME IDETC 2010.

A.G. Winter, V, et al. “The design and testing of a low-cost, globally-manufacturable, multi-speed mobility aid designed for use on varied terrain in developing and developed countries.” ASME IDETC 2009. Paper# DETC2009-86808.

LFC Africa
Continuum LFC

Biologically inspired mechanisms for burrowing in undersea substrates
Topic of PhD thesis
Advisors: Prof. Anette "Peko" Hosoi and
Prof. Alex Slocum, MIT

The aim of this project is to generate low-power, compact, lightweight, and reversible sub-sea burrowing technology. Sponsors Battelle, Bluefin Robotics, and Chevron provided motivation through applications ranging from dynamic and reversible anchors, littoral reconnaissance, subsea cable installation, and self-installing ultra-deepwater oil equipment. We discovered that Atlantic razor clams, (Ensis directus) drastically reduce burrowing drag by using motions of their shell to fluidize surrounding soil, making them an ideal candidate for biomimicry. Accounting for the soil, solid, and fluid mechanics at play during this event, we derived an analytical model that shows fluidization is created by local soil failure around a contracting clam shell and verified the model through 3D substrate/fluid index of refraction-matched particle image velocimetry in collaboration with Prof. Wolfgang Losert at the University of Maryland. The project culminated in the construction and testing of the RoboClam robot, which uses a genetic algorithm to optimize burrowing kinematics in order to achieve the same performance as Ensis, with burrowing energy scaling linearly with depth, rather than depth squared for moving through static soil.

Selected publications:
A.G. Winter, V., R.L.H. Deits, A.E. Hosoi. “Localized fluidization burrowing mechanics of Ensis directus,” J. Exp. Biol. 215 (12): 2072-2080 (2012).

A.G. Winter, V., A.E. Hosoi. “Identification and Evaluation of the Atlantic Razor Clam (Ensis directus) for Biologically-inspired Subsea Burrowing Systems,” Integr. Comp. Biol. 51 (1): 151-157 (2011).

S. Jung, A.G. Winter, V., A. E. Hosoi, “Dynamics of digging in wet soil,” Int. J. Nonl. Mech. 46, 602 (2011).

A.G. Winter, V, et al. “Teaching RoboClam to Dig: The Design, Testing, and Genetic Algorithm Optimization of a Biomimetic Robot.” IEEE IROS 2010.

A.G. Winter, V, et al. “The Design and Testing of RoboClam:  A Machine used to Investigate and Optimize Razor Clam-Inspired Burrowing Mechanisms for Engineering Applications.” ASME IDETC 2009.


A.G. Winter, V. Biologically Inspired Mechanisms for Burrowing in Undersea Substrates. Ph.D. Thesis, MIT Department of Mechanical Engineering, September 2010.

razor clam figsRoboClam at the ocean

Femur fracture during hip replacement (arthroplasty) surgery
Consulting research with Dr. Timothy Bhattacharyya at Mass General Hospital

In approximately 5% of hip replacement (arthroplasty) surgeries, inserting the implant into the femur results in bone fracture. The focus of this research is to determine whether hammer blows to the implant during insertion, or other factors, cause femur fracture. By experimentally varying size differences between implant and bone, we found that implant geometry, and not axial forces due to hammer impact, were the cause of fracture. The above picture shows the experimental setup used to press various sized implants into sections of human femur.
Femur fracture jig

3D wrapped network hydrostatic fluid film bearings
Topic of Masters thesis
Advisor: Martin Culpepper

Hydrostatic journal bearings support a shaft load on a thin, high-pressure film of fluid. These bearings are costly to manufacture, as they require high precision surfaces to avoid asperity contact between shaft and bore, as well as complex ducting to convey fluid to the bearing pads. 3D Wrapped Network (3DWN) bearings are formed by wrapping a thin sheet of shim stock with 2D through-cut features around a precision shaft. During wrapping, the through-cut features overlap to form 3D fluid routing networks. All required precision is inherited form off-the-shelf parts – surface finish from the shim stock and diameter from the precision shaft. As a result, 3DWN bearings can be produced for 1/10 the cost of current hydrostatic journal bearings. 

A.G. Winter, V. Design of fluid film journal bearings containing continuous 3D fluid pathways which are formed by wrapping a sheet containing 2D through-cut features. Masters Thesis, MIT Department of Mechanical Engineering, June 2005.

Bore of 3DWN bearing
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