brownian motion

[gavin]

was thinking recently about extracting energy from the movment of tiny particles in water which lead to a wheel design.

take a pendulum, lift the weight to one side and let it swing. it will rise to either side many times with a cumulative height many times that of the original lift. the question is - could we convert the swings to the left (for example) into positive energy without the swings to the right becoming nagtive energy.

was thinking of a very simple design with one cross beam and a swinging pendulum on either side. lets just say the pedulums are completely independent such that sometimes the net CoG is shifted to the right and sometimes to the left.

now make the cross beam uni directional such that a net gain to the right will be ignored (no turn) and net gains to the left will turn the beam around a centre point.

this is where the external pendulum could come in (the one seen on the drawings). not only would it smooth out the iregularities of shift in CoG, but it may also prevent the wheel from turning backwards (i.e the swing of this pendulum would out weigh the internal ones).

does anyone happen to know if the first uni-directional wheels had the pedulums on the outside, i can only seem to find drawings of the bi-directional ones?

[Fletcher]

As far as I'm aware physical pendulum's were never observed. They did appear in the woodcut depictions of the Kassel & Merseberg wheels though.

I think I remember a thread recently & comment by Stewart that one witness had commented on the pendulums which may mean they were actually physically displayed ?

Your design sound like a one-way rachet hub at the center. The random swings would allow the mech to falteringly rotate in one direction until it ran out of energy imo. Then it would stop in its last position providing everything was symmetrically balanced to begin with.

I think it reminds me of the 'devils gate' paradox (can't remember the correct name) which supposedly allows for the flow of atoms or molecules in one direction thru a permeable membrane ? I think they were using Brownian motion as part of the hypothetical example ?

[gavin]

Thats pretty much what i'm thinking - just wondering if since you get many swings for one lift of the pendulum, would you be able to accumulate enough energy to swing it again.

Thanks for the 'devils gate' reference. Just looked it up, i think it's the devils staircase and looks an interesting read.

[jim_mich]

Fletcher, did you mean "Maxell's Demon?"

[Fletcher]

Yes, sorry & thankyou. The memory's a bit erratic at times & too lazy to do a search without more recall ;)

gavin .. you might get more than one rotation out of it but this would depend on how high you lifted the pendulums to start with. Friction would rob the system over time.

[gavin]

had a think about this overnight. if there were any merit in this at all i think the optimal situation would be for the pedulum to be still on the decending side and have movement on the ascending side.

i'm thinking since the force exerted by the pedulum is a function of cos(theta) movement in either direction will effectively mean the still penulum weighs more, and the two sides will only balance when the swinging pendulum is vertical.

4 swinging pedulums on the upside, and 4 still ones on the downside. give each one a nudge as it reaches 6 o'clock. stop it swinging at 12 o'clock.

[scott]

You may be interested to read about Feynman's Ratchet:

http://en.wikipedia.org/wiki/Brownian_ratchet
http://monet.unibas.ch/~elmer/bm/
http://www.iop.org/EJ/article/1367-2630 ... 1_010.html

[Vic Hays]

Brownian motion is very similar to two different mechanisms.

1. An array of buckytube diodes that take advantage of electrical potentials at nanoscale.

2. Plates of metal such as aluminum with a very thin coating (can be aluminum oxide) which allow electrons to tunnel through and produce a potential.


The buckytube diode array seems like its time may have come in regards to our technical capability. It would decrease ambient temperature to produce power.

http://www.freewebs.com/diodearray/

[gavin]

one more thought on this.

take a see saw, fixed weight on one end, pendulum (same weight) on the other. give the pendulum a swing and the see saw will rock up and down with the movement of the pendulum and will do so until the pendulum stops.

as far as i can see, the movement of the see saw does not inhibit the pendulum at all, such that the main force slowing the pendulum down will be air resistance.

if we now place the pendulum inside a vacuum, in theory it should swing for a very long time - a tiny heat / friction loss from the string.

i must be missing something here - the maths isn't hard and even allowing quite a generous loss to heat / friction, i'm getting way more energy out of the see saw than it takes to give the initial swing.

i think vacuums were around in JB's day - any work done on using one?

[Fletcher]

i think vacuums were around in JB's day - any work done on using one?

I once used them in an apparatus that was a combination bellows/piston i.e. pipes fed fluids to a moveable bellows with solid end cap [think of a rubber boot or dust protector on a motorbikes suspension forks]. On one side compressed air which was allowed in or out thru valves. The idea was to create a partial pressure drop [like a vacuum pump] using levers & weights, then atmospheric pressure did the work for you & shifted the fluids around.

The vacuum pump was invented by a German b4 Besslers time & the creation of a partial vacuum is the basis of a water lift pump.

As for the see-saw & pendulum, it has been the basis of a recent discussion topic. The comment was why hadn't he closed the system so that it produced its own energy to re-energize the pendulum ?

A true vacuum is very hard to attain even with todays technology. A pendulum swinging inside a box would have less air friction but the container encasing the vacuum would still have to swing in the surrounding atmosphere. This causes a lag or dampening effect same as a pendulum in free air.

P.S. are you getting way more energy out of the system with a load ?

[Kirk]

Feynmans ratchet is proposed but his mechanical solution is a macro object. The random brownian motion is molecular and the machine has to be as well. not paddles and pulleys.
a "Velcro" molecule that is free in 1 direction would migrate in the free direction. - Think in terms of a surface that rectifies motion.

[Kirk]

+--------------------------------------------------------------------+
| Maxwell's Demon Soon A Reality? |
| from the chomp-chomp-evil-snacking dept. |
| posted by Zonk on Thursday February 01, @16:23 (Biotech) |
| http://science.slashdot.org/article.pl? ... 01/2049239 |
+--------------------------------------------------------------------+

DMiax writes "Reuters reports that a group of scientists from
University
of Edimburgh [0]may have realized a nanomolecular engine - a Maxwell's
Demon. The device selects and traps other molecules based on their
direction of motion. Physicist James Maxwell first imagined the
nano-scale device in 1867, and the research team cites him as the basis
for their understanding of how lights, heat, and molecules interact.
The
device is powered by light, and may spur advances in nano-scale
technology to new heights in coming years."

Discuss this story at:
http://science.slashdot.org/comments.pl ... 01/2049239

Links:
0.
http://www.iol.co.za/index.php?set_id=1 ... 561317B216