Amos Winter: How Do You Build An All-Terrain Wheelchair For The Developing World? In many countries, uneven and unpaved roads make it hard to get around in a standard wheelchair. MIT engineer Amos Winter describes his design for an affordable, lever-powered, all-terrain wheelchair.
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Amos Winter: How Do You Build An All-Terrain Wheelchair For The Developing World?

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Amos Winter: How Do You Build An All-Terrain Wheelchair For The Developing World?

Amos Winter: How Do You Build An All-Terrain Wheelchair For The Developing World?

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But the thing with simplicity is that sometimes it requires a lot of complexity to get there.


RAZ: Right?

WINTER: Yeah. Because to make something simple and cheap and reliable often takes very rigorous engineering.

RAZ: This is Amos Winter. He's a mechanical engineer at MIT, and his research group tries to build solutions to problems in developing countries.

WINTER: And the common theme in all that we do is, even though it may look simple and be constructed of cheap simple elements, the math and the physics and the engineering rigor that went into it was not simple.

RAZ: Like one specific problem that was presented to him in Tanzania with wheelchairs.

WINTER: Yeah. I spent that summer talking to wheelchair users, wheelchair manufacturers and disability advocacy groups to get a sense of, you know, what the lay of the land was and how well current products were meeting people's needs.

RAZ: And you might think, what's the problem? A wheelchair is a wheelchair. It's already a pretty straightforward, simple solution.

WINTER: No. A wheelchair is not a wheelchair, depending on where you are. Much of our country, I'd say, is ADA accessible and has been designed to meet the needs of wheelchair users. That is not the case in most other countries, particularly if you're living in a rural area. And so if you have to go a few kilometers from your house to your school or house to a job, just a small crack in the road can be a major barrier if you're using a conventional, hospital-style wheelchair, which is what most people get. Typically, you would be dependent on a family member to push you around your village, but actually, even more commonly, you're probably going to be stuck in your house most of the time and maybe even viewed as a burden on your family.

RAZ: Amos Winter spoke about the problem on the TED stage.


WINTER: What stood out to me is that there wasn't a device available that was designed for rural areas that could go fast and efficiently on many types of terrain. So being a mechanical engineer, being at MIT and having lots of resources available to me, I thought I'd try to do something about it. Now, when you're talking about trying to travel long distances on rough terrain, I immediately thought of a mountain bike. And a mountain bike's good at doing this because it has a gear train, and you can shift to a low gear if you have to climb a hill or go through mud or sand, and you get a lot of torque but a low speed. And if you want to go faster, say, on pavement, you can shift to a high gear and you get less torque but higher speeds. So, you know, the logical evolution here is to just make a wheelchair with mountain bike components, which many people have done. But these are two products available in the U.S. that would be difficult to transfer into developing countries because they're much, much too expensive. And the context I'm talking about is where you need to have a product that is less than $200. And this ideal product would also be able to go about 5 kilometers a day so you could get to your job, get to school and do it on many, many different types of terrain. But when you get home or want to go indoors at your work, it's got to be small enough and maneuverable enough to use inside. And furthermore, if you want it to last a long time out in rural areas, it has to be repairable using the local tools, materials and knowledge in those contexts.

RAZ: OK. So you have this idea for, like, a mountain bike kind of wheelchair, and then what do you do from there?

WINTER: So I worked with a team of students at MIT through many iterations trying to make this cheap, simple, you know, fast and efficient off-road wheelchair device to give you a low gear to climb hills and a high gear to go fast. And we failed a number of times. We could not do that with the conventional mountain bike solution because you need a chain to switch from gear to gear to get those different gear ratios. And then about a year and a half later, I was actually back in Africa at a conference. And I was sitting there just doodling in a notebook, and I realized, boy, you know, we could get a variable mechanical advantage, you know, to get this mountain bike effect very simply by grabbing a lever at different points. And that was, I'd say, the real breakthrough for us realizing how we could make a cheap, simple bike-part based solution that would be viable in this context of developing countries.

RAZ: OK. So we're talking about simple solutions. So can you, like, simplify this and walk me through it? You, like, you thought of levers? Like, I'm imagining, like, broom handles or, you know, like, sticks on a wheelchair. How does that simplify things?

WINTER: So if you're in a wheelchair, your power source is your upper body, right? And so conventionally, you'll grab the wheel, or you could do some other motion that's engaging the muscles in your chest and shoulders. And so one reason I thought of levers is because it engages the largest muscle groups in your upper body, your chest muscles. And so what was nice about a lever is if you imagine a person sitting in a wheelchair, grabbing two levers in front of them, that if they are pushing forward and back on those levers, if they just shift their hands up or down a little bit, it effectively changes the length of the lever. So the distance between where their hand is and where the pivot is of the lever. So if they grab high on the lever, they get a long lever, get a lot of leverage and get a lot of torque. If they grab low on the lever, they're able to push through a bigger angle every push, which makes the wheels spin faster.

RAZ: So if they're in the wheelchair on rough terrain or going uphill, they can grab up at the top of the lever, and it's easier to get through that rocky area. And if they're on a straight path on paved concrete, they can just grab lower and go faster.

WINTER: Yup. Exactly.

RAZ: So I mean, this is not new technology. I mean, leverage and levers are, like, this is, like, ancient Egypt stuff.

WINTER: Yeah, and even levers on wheelchairs is ancient technology. People have done many, many different iterations of that idea. The critical factor and the critical value of our idea was that ability to shift your hands up and down the levers.

RAZ: Yeah. And what's so cool about this is you're kind of taking this old technology to something that most people would think to innovate with, like, mechanized changes, like, making them electronic or more complex.

WINTER: Yeah. And again I have to come back to the constraints of the problem we are trying to solve. You know, think about out in a village, what parts can you service this thing with? How would you ever recharge if it's electric? And that's what drove us to this simple, cheap solution, the Leverage Freedom Chair.


WINTER: Now, also being engineering scientists, were able to quantify the performance benefits of the Leverage Freedom Chair. So here are some shots of our trial in Guatemala where we tested the LFC on village terrain and tested people's biomechanical outputs, their oxygen consumption, how fast they go, how much power they're putting out, both in their regular wheelchairs and using the LFC. And we found that the LFC is about 80 percent faster going on these terrains than a normal wheelchair. It's also about 40 percent more efficient than a regular wheelchair, and because of the mechanical advantage you get from the levers, you produce 50 percent higher torque and really muscle your way through the really, really rough terrain. I think this project worked well because we engaged all the stakeholders that buy into this project and are important to consider in bringing the technology from inception and idea through innovation, validation, commercialization and dissemination. And that cycle has to start and end with end users. These are the people that define the requirements of the technology, and these are the people that have to give the thumbs up at the end and say, yeah, it actually works and meets our needs. And this picture was taken in India in our last field trial where we had a 90 percent adoption rate where people switched to using our Leverage Freedom Chair over their normal wheelchair. And this picture specifically is of Ashok. And Ashok had a spinal injury when he fell out of a tree and he had been working at a tailor. But once he was injured, he wasn't able to transport himself from his house over a kilometer to his shop in his normal wheelchair. The road was too rough. But the day after he got an LFC, he hopped in it, rode that kilometer, opened up his shop, and soon after landed a contract to make school uniforms and started making money, started providing for his family again.

RAZ: Do you think that most of the time the simplest solution is the best one?

WINTER: I think I think about the word simple maybe differently than you are. I think the best solution is the best solution. And I'm so sensitive about imposing unnecessary constraints on a design problem. I try not to design in terms of simplicity. I try to design in terms of what is the solution that will give you the required performance for as little money and as little complexity as possible? And so I think the idea of simplicity that you're touching on is that that I'm thinking about, that I don't want to overcomplicate things. I want to make things robust. I want to have as few parts as possible, but I don't want to compromise value in performance by making it cheap and simple. And so I think people will sometimes confuse, like, developing world technologies as low quality and cheap and non-dysfunctional, and I don't think that way at all. People have a core level of functionality they need to be met for that product to be successful. And there's a price point and there's maybe a serviceability associated with that, and those are the design requirements you have to satisfy in order to be successful. And our wheelchair absolutely does do that.

RAZ: That's Amos Winter. His wheelchair is called the Leverage Freedom Chair. So far his team has built about 2,000 of them. You can see his entire talk and the wheelchair at


BLACHMAN THOMAS AND THE JAZZ RAP EVOLUTION: (Rapping) This is a must to keep it simple. My (unintelligible). Keep it simple. My business. I keep it simple. The I way I walk and talk. Keep it simple. The way I do it. I keep it simple.

RAZ: Hey, thanks for listening to our show on simple solutions this week. If you want to find out more about who was on it, go to, and to see hundreds more TED Talks, check out or the TED app. You can also listen to this show any time by subscribing to our podcast. You can do it now on Apple podcasts or how ever you get your podcasts. Our production staff at NPR includes Jeff Rogers, Sanaz Meshkinpour, Janae West, Neva Grant, Rund Abdelfatah, Casey Herman and Rachel Faulkner, with help from Daniel Shukin. Our intern is Benjamin Klempay. Our partners at TED are Chris Anderson, Colin Helms, Anna Phelan and Janet Lee. I'm Guy Raz, and you've been listening to ideas worth spreading right here on the TED Radio Hour from NPR.

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