Motion Generator

[ovyyus]

I think the market for a small $100 'designer' hip-mounted 5 Watt 'bio-charger' would be enormous. Someone should invent one!


http://www.newscientist.com/article.ns?id=dn7970

Backpack generates a powerful punch
19:00 08 September 2005
NewScientist.com news service
Paul Marks

A backpack that generates electricity as its wearer strolls along has been developed by experts in human locomotion in the US.

By harnessing the loping up-and-down motion of our hips as we walk, the backpackÂ’s freely-moving load bounces up and down, generating up to 7 watts. That is more than enough to power cellphones with power-draining functions like colour widescreens or Wi-Fi and GPS connections.

The developers hope their suspended-load backpack will be a particular boon for troops, field scientists, explorers and disaster relief workers in remote locations.

The generator has been developed by Larry Rome and his colleagues at the University of Pennsylvania, US, with funding from the US Office of Naval Research. Their aim was to relieve soldiers already carrying 36-kilogram backpacks of the need to carry many spare batteries to power their GPS, communications and night-vision devices.

“The extra weight [of the batteries] compromises the amount of food, medicine and armament they can carry,” Rome explains.

Upside-down pendulum
An earlier answer to this was the “heel strike” generator – a piezoelectric crystal-based device in a boot heel that generates a battery-charging current when crushed by the wearer’s weight on every footstep. But these gadgets only produce power in the region of 10 to 20 milliwatts. A basic cellphone uses between 1 and 2 watts.

So RomeÂ’s team has worked out how to electrically capture some of the energy a backpack wearer expends when carrying a load.

Their trick is to make use of the fact that a walking person moves like an upside-down pendulum. “One foot is put down and then the body vaults over it, causing the hip to move up and down by 4 to 7 centimetres,” he says. And as the hip goes up and down by that vertical distance, so does any load, with the backpack-wearer expending the energy to make it do so.

To retrieve some of that energy as electricity, the team separate the load-carrying sack from the backpackÂ’s frame by mounting it on a spring-loaded plate that is free to move up and down on rail-like rods.

Gaggle of gadgets
The result is that as the wearer walks, their hip motion makes the load oscillate up and down (see a video – mpeg format, 15 MB). To harvest energy from the load’s motion, a toothed rod fixed to the mobile load-plate meshes with a gear wheel on a dynamo fixed to the top of the frame. The load-motion generates a current which can either run a gaggle of gadgets or charge a battery.

In tests of a prototype, six men carried different loads at varying walking speeds. The backpackÂ’s power output increased with walking speed and with the weight of the load in the pack.

Nevertheless, Rome says: “The suspended load backpack is much more comfortable to wear than a normal backpack, because the springs cushion the load and reduce peak forces. So everyone from the military to kids carrying heavy book bags will be benefit from lower forces.”

He has now set up a company, Lightning Packs, to commercialise the idea. “We need to reduce the weight and put in a more efficient generator,” he says.

Chris Bonington, the British explorer and mountaineer, currently carries solar panels to charge the digital camera batteries he uses in remote places. “Whether this backpack is going to be any good depends on how heavy it is to be useful and how bulky it is. I’d really like to try it though,” he told New Scientist.

Trevor Baylis, inventor of the clockwork radio, warns that after events like the London tube bombings, strange-looking backpacks might raise interest at security checks at airports. He abandoned a heel-strike generator he developed in 2001 for this reason: “With the electronics fixed to the side of the shoe, it made the wearer look like a shoe bomber,” he says. “Investors didn’t want to know.”

Journal reference: Science (vol 309, p 1726)

[Joel Wright]

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[ovyyus]

I've had a play with one of those shake-charge flashlights. I think they're a great idea. The generator consists of a magnet able to slide inside a plastic tube which is wound with an external coil - all you do is shake the magnet back and forth inside the tube in order to generates a voltage on the coil - really simple stuff. It wouldn't work to capture walking motion without considerable modification though.

Maybe something along the lines of a balanced 'neutral line' magnet/keeper/coil system, ah-la Wesley Gary? That might make for a very simple, small, and sensitive energy capture system that is able to couple to normal walking motions.

[Jonathan]

Joel, I thought of that same thing when I heard this. I have never used one though, so what is it about them that they can't be readily used Bill? It seems to me that the bulk of the flashlight, sans the bulb, would be mounted vertically in the backpack. You'd have a spring in the tube with the magnet, so that the magnet is essentially weightless and would move under the easy bobbing of someone's gait.

[ovyyus]

Yes, adding some form of counterbalancing spring system to the magnet would be required - as I said, "It wouldn't work to capture walking motion without considerable modification though."

I think a more popular product would involve a device that does not require a large, cumbersome backpack, but rather one that is small and perhaps clips to a persons belt - maybe about the size of a mobile phone?

[rlortie]

Yes Bill, it would not work without considerable modification and that being "Lenz law" Hand shaking will overcome this as it is what is making the energy but walking would not create enough forceable motion.

Remember the trick, drop a magnet down a piece of conductive pipe and wait for it to fall through. Your shaker flashlight works the same way.

Ralph

P/S: If you find a way to violate Lenz, Butch Lafonte would like to shake your hand with or without the flashlight. :-)

[ken_behrendt]

All that backpack does is allow the wearer to convert some of his muscular energy into electrical energy. There are other ways to this that would not require the soldier to work harder while marching along. How about some sort of photovoltaic material on the surface of the soldier's clothing that would convert sunlight into electricity that would be stored in a battery built into his belt? He could then recharge his other electrical gadgets by plugging them into an outlet on the belt.

ken

[ovyyus]

Ralph, you seem to be confusing Lenz Law with coil loading - ie: no load on the coil will allow the the magnet to move completely freely. Of course if too much load is placed on the coil it will just lock up (although that probably can't happen with the flashlight system because it uses an air-core coil and also the magnetic coupling is pretty loose).

[Techstuf]

Motivating thread title, Ovyyus.


It is probable that some here on the forum have accumulated sufficient knowledge regarding the generation, modulation and transduction of angular momentum to effect meaningful leaps in efficiency regarding the ways in which EM induction is exploited.....Should any be so inclined.

http://www.freelights.co.uk/how.html

The dynamics at work are a mechanical analogue to some of Gary's observations on a certain level. There appear to be numerous possibilities regarding passive field suppression/swtiching, here.

The above demonstration is a great launch point for those motivated by it's obvious merits, or even illusory inference as the case may be. As well, anyone who as ever watched vertical window blinds fluttering in a steady breeze and compared such observation to standard wind generators may wish to explore various possibilities.



Peace,

TS

[rlortie]

Bill,

You and I both have been around the block more that once when it comes to magnets and a conductor. So I do not see a need for me to get ambiguous about an open air coil and Lenz. We both know without Lenz there will be no battery charging.

My point being is that if there is no load on the coil then that means an open circuit. With an open circuit you can shake the magnet all day and still have nothing. Drop the same magnet down a copper pipe and you will have resistance, the pipe is a closed loop!

Gary and I discussed this on his forum about an open coil building a static charge. Problem is if you attach a volt meter you have closed the loop and it is gone if it was ever there.

Ralph

[ovyyus]

My point being is that if there is no load on the coil then that means an open circuit. With an open circuit you can shake the magnet all day and still have nothing. Drop the same magnet down a copper pipe and you will have resistance, the pipe is a closed loop!

Yes, with an open circuit the magnet is free to move unimpeded - it's not doing any work. I also agree that a short circuit is useless for charging a battery.

I'm not talking about an open circuit or a closed circuit. The load should be matched to the supply, as usual.

[Michael]

Ah ithe rule of the universe, inertia, one of it's many manifestations; Lenz law.

Irrelevent to this discussion but true.

[Wheeler]

I happened to have a magnet and a piece of pipe with me the other day.
I showed it to a friend That had never seen the magnet/pipe trick.
After some time, we picked up a piece of alum pipe. Same result.
Slow fall rate.

'Then we went over to a large piece of flat alum. It was approx. 4 in. thick,and the surface was very flat.
We laid the spear magnet on it and when given a slight push, the magnet did not roll at the normal rate it would if it were just a bearing.
What do you think is going on?
My simple theory on the magnets in the pipe is that it is no more than impurities in the material.

You do not get pure copper in copper pipe. The impurities may be iron.

[ovyyus]

Wheeler, induced eddy currents in the conductive metal produce a magnetic field that opposes the motion of the magnet. Irreversible eddy current heating of the metal is driven by momentum loss of the magnet.

[ken_behrendt]

I've saw a similar effect that demonstrates Lenz' Law which used a super conducting alloy disc. In the demonstration, a disc of special super conducting alloy (I think it was a tin/niobium alloy) is dipped into liquid helium and, at that temperature, it loses all electrical resistance and becomes a perfect conductor.

Next, a small cube shaped permanent magnet is dropped onto the center of the frozen super conducting disc of alloy and mysteriously begins floating in the air above the disc! The explanation is that, as the magnetic fields from the magnetized cube penetrate the super conducting disc, they induce electrical currents there that then generate their own magnetic fields that oppose the magnetic fields of the magnetized cube. Because of magnetic repulsion that results, the magnetized cube will continue to "levitate" above the disc until the latter warms up and loses its superconductivity.

ken