Super sucker

[BillyBones]

Frosty, thanks for the explanation. 

Nat, that is why i said if they crimped together. You can work those apart by hand with a little help from a pair of pliers. 

 

[Frosty]

It comes from almost 50 years of heating or supplementing with wood heat. I use a couple small screw drivers to open the female side of the crimp till it will let the lip pass. We almost never see stove pipe closed up in the store except the displays. 

Here's a wood stove trick I bet hardly anybody knows. Living remote batteries are a big deal, especially before Ni cad, about our only news came from the radio and walking around light flashlights. 

One trick for stretching battery life was to carefully roll them on the wood stove, heating them a little would get a couple few more hours of life from them. 

Then someone clued us into the big trick which worked really well on ni cads but pretty well on the old carbon ones. Wrap a few turns of bare copper wire around the stack and attach the free ends to your battery. The number of turns determined the voltage and wire diameter the amperage to a degree. The hot smoke moving up the steel stove pipe generated a moving magnetic field, copper windings turned it into electricity. 

I moved back to the city about then so I never found out how many winds it took to charge a car battery.

Frosty The Lucky.

[LarryFahnoe]

Well the idea of hot smoke generating a moving magnetic field was curious sounding to me, so after I didn't come up with much of an explanation with some general searches, I thought, this might be an interesting question to put to ChatGPT. I didn't know what to expect, but this is what came back. Curious though as the explanation seems to require a moving magnetic field, but I'm guessing that these are related phenomena.

--Larry

My question: how does hot smoke moving through a stove pipe generate a moving magnetic field?

ChatGPT's response:

The generation of a moving magnetic field by hot smoke moving through a stove pipe is a phenomenon known as the "thermomagnetic effect" or "magneto-thermoelectric effect." This effect arises due to the combination of thermal gradients and the presence of a magnetic field.

When hot smoke flows through a stove pipe, it creates a temperature gradient along the pipe. This temperature gradient causes the free electrons in the material of the pipe to move, resulting in the accumulation of charge at one end of the pipe and the depletion of charge at the other end. This accumulation of charge creates an electric field along the pipe.

Now, if a magnetic field is applied perpendicular to the direction of the electric field (i.e., perpendicular to the stove pipe), the Lorentz force acts on the moving charge carriers (electrons) due to their motion in the presence of the magnetic field. This force causes the electrons to experience a sideways deflection, resulting in a buildup of charge on one side of the pipe and a deficit on the other side. This charge separation creates an additional electric field perpendicular to both the temperature gradient and the applied magnetic field.

The combination of these electric fields results in the generation of a current perpendicular to both the temperature gradient and the magnetic field. According to Ampère's law, a current generates a magnetic field around it. Therefore, the flow of hot smoke through the stove pipe generates a moving magnetic field perpendicular to both the temperature gradient and the direction of smoke flow.

This phenomenon is often studied in the field of magnetohydrodynamics, which deals with the behavior of electrically conducting fluids (such as the hot smoke in this case) in the presence of magnetic fields.

References:
1. Cheng, K. S. (2010). Fundamentals of Engineering Magnetohydrodynamics. World Scientific.
2. Davidson, P. A. (2001). An Introduction to Magnetohydrodynamics. Cambridge University Press.

[Mike BR]

Wrapping bare copper wire around a steel stack sounds like a big short circuit. But maybe the dissimilar metals and the temperature difference between the stack and the battery would set up some form of thermocouple?

[Frosty]

Thank you Larry. My voices kept saying it was very similar or the same as a magneto hydrodynamic drive mechanism and is being used to drive boats. They'd been around years before the movie "Red October."

All I knew was it worked. I thought perhaps the moisture in the smoke was the secret but I guess not. Well, maybe not.

A low volt short circuit is exactly what I thought first time I saw a copper wire wrapped stovepipe with jumper wires leading to a salvaged battery holder thingy and battery. Maybe the charge flowing through the iron to the next coil isn't perpendicular to the flow of the magnetic field, smoke, Aether, magic spells, or? 

Frosty The Lucky.

[George N. M.]

RE charging batteries:  Back in the '70s I had a friend who lived across the road from the National Bureau of Standards antenna farm for WWV, the short wave station broadcasting the time signal for setting clocks.  This is a BIG operation just nort of Ft. Collins, CO with 8-10 large masts and can be seen for miles at night.  He set up an antenna (IIRC about 6-8' of copper wire) and was able to capture enough energy to run a battery charger.  I don't think I would have wanted to live 24/7 in that powerful of an EMS field.

GNM  

[natkova]

Frosty here seams can't be opened up you got § circle if this is greek f symbol you got like 4 inches closed circle and that's all 

So I would be better making hole larger or building this like branch type stove it would suck air better 

Maybe two separate pipes suck better then one but Ian not sure I will look up to it maybe I can build something from sheet metal it can be squerish.

What about spiral pipes are they toxic because they have Zink in it or some sort of thing .

 

 

 

[Latticino]

Many folks use spiral duct for their forge flues.  You are correct that typically this duct has a galvanized coating and, if overheated, can be a problem.  In my experience an old school overhead hood entrains enough shop air to cool down the flue gasses to a point where it is not a problem, but the super sucker style is so effective that the flue can get overheated, particularly if you are building a larger forge fire.  You can probably go with spiral duct if you have some kind of black steel or stainless connector between the super sucker hood and the following duct.  I would use a piece that is at least 3' long for this purpose.  Please note that most of the snap together duct with the snap together longitudinal seams that others have been advocating are also typically made using galvanized sheet metal as well.  IMHO spiral duct is a significantly better option than snap seam duct, but usually a lot more expensive and only available from a sheet metal duct manufacturer (snap seam duct is available here in hardware stores).

[natkova]

Can I use aluminium flexible pipes that are used for kitchen hoods ?

[Latticino]

In my opinion flexible aluminum duct is not appropriate for either kitchen hood exhaust or forge flues.  It is just barely acceptable for laundry dryer or bathroom shower exhaust.

[Frosty]

Shower exhaust!? I'm pretty sure you mean bathroom ventilation exhaust. Yes? 

I might accept aluminum as a super sucker stack IF you can lay your hand on the hood with a max size fire going, without discomfort. Say no hotter than a cup of cooling tea. 

That doesn't leave you any safety margin so I strongly recommend against anything but steel or masonry.

Frosty The Lucky.

[Latticino]

Frosty,

Yeah, on my phone to answer and conflated locker room showers and residential restrooms....  It is exhaust duct either way.  We typically don't call it "ventilation" exhaust.

[Frosty]

DANG I got myself hung up in semantics again. <sigh>

Frosty The Lucky.