A new twist on power walking

In an unprecedented breakthrough in the development of portable and renewable human-driven energy sources, an MBL (Marine Biological Laboratory) biomechanics expert who studies how muscle moves skeletons in fish and frogs has invented a backpack that gives new meaning to the term power walking.

In a paper published in the September 9 issue of Science, Lawrence C. Rome, a University of Pennsylvania biology professor who spends his summers conducting research at the MBL, and three colleagues describe the mechanics of, and physics behind, the Suspended-load Backpack, a piece of gear that will one day enable field scientists, hikers, explorers, soldiers, and disaster workers to convert mechanical energy generated by walking with a heavy load on their backs into electricity.

By carrying a load weighing from 44 to 84 pounds (20 to 38 kg), Suspended-load Backpack testers were able to generate up to 7.4 Watts–more than enough electricity to simultaneously power an MP3 player, a PDA, night vision goggles (or 3 LED headlamp), a handheld GPS, a CMOS image decoder, a GSM terminal in talk mode, and Bluetooth. The electricity can be used while it is being generated, or it can be stored in a lightweight rechargeable battery for later use, greatly reducing the need to haul and use heavy replacement batteries.

“The need for electronic devices in remote areas is an increasing reality these days,” says Rome. “Throughout history, humans have solved many problems by inventing passive devices to enhance the movements made by their muscles, such as springy bamboo poles to carry loads and skis to move through snow,” he says. “The Suspended-load Backpack represents another passive device that may help solve a growing problem in the 21st century.”

The backpack, which is currently in its working prototype stage, is based on the external frame design once popular with overnight backpackers. It works by capitalizing on the up-and-down motion of the body during walking.

When walking, the body is like an inverted pendulum. After the foot is put down to take a step, the body vaults over it, causing the hip to move up and down about 1.6 to 2.7 inches (4 to 7 cm). The Suspended-load Backpack frame sits still on the wearer’s back, and the load is mounted on a load plate that is suspended from the frame by springs. The springs allow the load to slide up and down on bushings constrained to vertical rods, thus allowing the load to move with the same vertical motion as the hip, but lagging it by a fraction of a second, producing differential movement between the frame and load. The pogo-stick-like movement of the load generates mechanical energy that drives a rack-and-pinion device that powers a geared DC motor that acts as a generator mounted on the frame. The load plate can be locked to stop the device from sliding up and down and generating electricity.

To assure that the backpack wouldn’t require users to expend too much additional metabolic energy, the scientists performed a variety of tests on six male subjects, who used the backpack while walking on a treadmill.

The backpack was instrumented with force transducers and length transducers, which measured the amount of mechanical energy going into the backpack’s generator. The scientists also measured the test subjects’ oxygen consumption and carbon dioxide production rates to gauge the metabolic cost of generating electricity with the backpack.

The scientists discovered that the Suspended-load Backpack altered the gait of the test wearers, causing them to walk more efficiently. Because of this, the testers used less metabolic energy to generate electricity than anticipated. The tests also showed that the backpack wearers could generate more electricity by either walking faster or carrying a heavier load or both.

While Rome and his colleagues haven’t yet determined the biomechanical causes of the backpack’s better-than-expected efficiency, they say it confirms that the backpack is practical and that the technology can be applied to making a standard backpack that is more ergonomic.

“It seems that most everyone in the world uses a backpack to carry things, and the possibility of doing it more ergonomically and also providing electricity in remote areas may have widespread benefits, some of which we can’t even anticipate today,” says Rome.

A Pennsylvania-based company called Lightning Packs LLC has been formed to further develop and refine the Suspended-load Backpack and to develop an ergonomic backpack based on the working prototype and initial findings. Lightning Packs has applied for patent protection on both inventions.

From Marine Biological Laboratory

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6 thoughts on “A new twist on power walking”

  1. I’m in the (airborne) infantry and I love anything that makes my pack lighter or easier to carry. For this though, the only thing interesting is that they said it made them walk more efficiently. I’m not sure if this would be true over broken terrain, which is where it must be proven. The individual soldier really doesn’t need to generate much power, most items carried by the individual soldier have very light power requirements (i imagine that is more by design than anything else). There are a few exceptions though. Radio batteries are heavy, but that is more a fault of purchsing from the lowest bidder than necessity. Commercial laptop batteries are much more efficient. Outside of radios the individual soldier can go weeks on a pack of AA’s and watch batteries (infra-red lasers, nightvision, powered optics). I changed the batteries in my night vision goggles a handful of times in Iraq over a year. Some of the more advanced man portable weapons might be able to benefit, might. There’s a system called the Javelin, it can be carried by one man (realistically two, missle and launch unit) and the thermal sight sucks batteries big time. The problem is, if you are walking around you are not sitting there in an OP (observation point) watching. If you expecting company from tanks anyway chances are you have a vehicle not to far away so you can GTFO (you can guess what that means). A vehicle means supplies, so new batteries. Really if the vehicle had an AC converter as many are popping up in HMMWV’s and other places, you could just use rechargables. I always took **** loads of batteries with me on patrols when I had the Javelin, but it was in the trunk of the HMMWV so I could care less what they weighed.

    The folks who might really enjoy this would be LRRS (recon), RRD, and SF in some capacities. They go long distances for long amounts of time and don’t expect much resupply. Like I said though, if you have to get up and move to recharge your batteries it’s going to suck. It’s only while you are sitting still in a hide site, snapping pictures, uploading from your laptop via your sat coms, and talking on the radio or sat, that you are going to run out of power, and you might not have the luxury of moving for a damn long while. Maybe you could just send the lowest ranking joe to run laps around the objective to recharge your batteries. Then if he makes it back alive you can use the recharged batteries to call for fire on your now througly pissed of enemy.

    At the end of the day though the Army uses the WORST ruck frame design I have ever used and that’s because of one thing, cost. When I joined I could carry alot more weight being in worse shape than I am now, but using my civilian pack. Moving 25M with an Army ruck makes you feel like someone beat you with a baseball bat. It’s probably because I’m tall too. The rucks are made for short people. I guess they get their heads blown off less, hadji can’t shoot straight anyway so who cares.

  2. This is fabulous. I do alot of backpacking with packs over 50 pounds. I would love to try this out. Please roll out a fully tested DURABLE product, and I will buy one. I get alot of dirt in my pack at times, please endevour to seal the gear track and generator well. Make the product repairable, brushes, gears, and etc. I would love to pound this gadget through Eagle pass in the Rockies powering a sat uplink, so cool it would be!

    Thanks! daed

  3. hmm, a “few extra pounds”… I travel a lot, and I use a backpack for all my gear (as well as at home in NYC, which is like being in the wilderness). One should never forget the rule of Time = Weight – where the longer you carry a thing on your back, the heavier it gets!

    Or maybe I’m just a wimp… :^)

  4. Perhaps one should consider the average weight a military personel would carry in the field.

    As a side note, I usually carry a 30lbs backpack. Adding a “few” extra pounds wouldn’t hurt too much. In fact the effect should be reduced slightly due to this “efficiency” that was recorded from the tests. Mind you, they never did state how much of an improvement. I’m assuming its so miniscule the wearer probably wouldn’t notice.

  5. “The electricity can be used while it is being generated, or it can be stored in a lightweight rechargeable battery for later use, greatly reducing the need to haul and use heavy replacement batteries.”

    You don’t have to haul around as many heavy batterys but you have to carry a 44-84 lb weight? hahahaha…

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