Author Topic: A small pot belly stove.  (Read 4060 times)

Offline NeoTech

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A small pot belly stove.
« on: October 23, 2016, 12:00:28 PM »
So i made this little Pot belly stove. And are trying to figure out if i should put in a extra level into it. Its kinda hard to start and the flow dies off if its not hot enough and thus i need the bbq lid in the start.. When its hot it runs 250C (480F) steady on just sticks and fallen down dead wood from the woods behind my house. And i can put a plate ontop of it and it will just burn clean.

So how can i make this little stove easier to start, more efficient and well safer.. Im gonna install it into my workshop when i get hold of good fire protection for my dry walls.

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Offline John Rudd

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Re: A small pot belly stove.
« Reply #1 on: October 23, 2016, 12:04:51 PM »
Is the square tube part if the flue?

If so, I think its angle is wrong....and is strangling the air flow....ideally the flue should go as straight as possible so the air flow is unhindered....
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Offline NeoTech

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Re: A small pot belly stove.
« Reply #2 on: October 23, 2016, 12:16:08 PM »
Yeah its the flu "connection" it will go into a box im making atm, that will beasicly be a large heat exchanger and from that it will exhaust into a chimney.
(Box with alot of pipes and the exhausts goes around the pips and a fan on one side sucking in air into the box pipes and pushes it out on the other side.)

I made it like that because it was easiest to stick wood into the stove from the top..and i can just go out and wrangle some dead old tree and chop it up into meter bits and stick it down into there..
Its not really a problem when its hot.. but before that when the whole thing is dead cold.. it takes a good hour of slowly feeding the thing until you get around 100C into the steel.. then it just starts eating anything i put into it.
Machinery: Optimum D320x920, Optimum BF20L, Aciera F3. -- I have not failed. I've just found 10,000 ways that won't work. http://www.roughedge.se/blogg/

Offline awemawson

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Re: A small pot belly stove.
« Reply #3 on: October 23, 2016, 12:21:49 PM »
 If the box section flue exited at 45 degrees it would enhance your draught at start up very considerably, which should make it burn better from the beginning.
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Offline NeoTech

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Re: A small pot belly stove.
« Reply #4 on: October 23, 2016, 12:26:57 PM »
Hmm yeah that was an obvious one i missed.  :bang:

Well i will try that.. the starting draft is the big issue basicly.. and where to fit the heat exchanger when getting that far. Gonna heat 80 square meter with this thing in the winter . =)
Machinery: Optimum D320x920, Optimum BF20L, Aciera F3. -- I have not failed. I've just found 10,000 ways that won't work. http://www.roughedge.se/blogg/

Offline angus

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Re: A small pot belly stove.
« Reply #5 on: October 23, 2016, 03:15:32 PM »
you will find that a heat exchanger may make it worse.... you need the hot gas to creat enough of a draw..i messed up the burn on one of my home made stoves by adding heat sinks to the stove pipe inside the workshop

Offline NeoTech

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Re: A small pot belly stove.
« Reply #6 on: October 23, 2016, 03:57:26 PM »
Yeah if i understand the regulations right the hot gasses out of the stove should not be higher than 135C, but not lower than 85C (due to moisture and other bad things).. That would mean my heat exchanger cant remove more than  125C from the exhaust without effing up the burn. So started to think maybe a glycole based heat exchanger with heat pipes inside the stove.
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Offline Manxmodder

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Re: A small pot belly stove.
« Reply #7 on: October 23, 2016, 04:07:30 PM »
If the heat exchanger is just to air then it is only a static mass until the fan is turned on.

I had a sump oil heater in a workshop years ago and it had a cross flow tube heat exchanger that worked really effectively but we didn't switch the fan on until the flue pipe had got up to temperature.....OZ.
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Offline NeoTech

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Re: A small pot belly stove.
« Reply #8 on: October 23, 2016, 04:14:05 PM »
So if i make the heat exchanger of say, 1 inch tubes spaced 1 inch apart, and packed about 100 tubes in there and welded a baffel sides with intake and exhaust.. That box would be about as hot as the exit flue pipe after a while? Or well until i switch the fan on.. The exit flue is about 200C when it runs properly. So basicly some kind of thermostat in the flue on the exit side of the exchanger and it could switch the fan on and off as it see fit.

In the end i just wanna dump as much heat into the air of my garage/workshop (old shed with some stuffing in the walls). And being able to put a bunch of logs in there and strangle it before i go indoors.
Machinery: Optimum D320x920, Optimum BF20L, Aciera F3. -- I have not failed. I've just found 10,000 ways that won't work. http://www.roughedge.se/blogg/

Offline awemawson

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Re: A small pot belly stove.
« Reply #9 on: October 23, 2016, 04:22:48 PM »
The Victorians heated Cathedrals and large Churches with cast iron pot belly stoves that had many cast fins on the outside to radiate the heat.

Why not weld some vertical fins on the out side as your heat exchanger - simple and shouldn't interfere with initial combustion.
Andrew Mawson
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Offline NeoTech

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Re: A small pot belly stove.
« Reply #10 on: October 23, 2016, 04:29:30 PM »
Thats actually a great ide.. will try that. Can just plasma cut the strips from some 1.5mm sheet. =)
Machinery: Optimum D320x920, Optimum BF20L, Aciera F3. -- I have not failed. I've just found 10,000 ways that won't work. http://www.roughedge.se/blogg/

Offline Manxmodder

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Re: A small pot belly stove.
« Reply #11 on: October 23, 2016, 05:13:09 PM »
The fins are a good and simple method of increasing the heat exchange rate. I think they will need to be somewhat thicker material than 1.5mm sheet. To get good effect the fins need to have some mass,and I would be thinking of making them from something like 10mm thick steel.Also the more continuous the weld joint is then the better the conductive exchange rate will be. Tack welding won't give as good a transfer area rate....OZ.
Helixes aren't always downward spirals,sometimes they're screwed up

Offline DavidA

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Re: A small pot belly stove.
« Reply #12 on: October 24, 2016, 05:56:51 AM »
Glycol is flammable, be careful.

It is one reason never to inspect the antifreeze level in your car's radiator with a naked flame (a match).

I find that most of the heat with my own pot bellied stove comes from the exhaust stack. It is vertical from the top and the draw effect is very helpful in getting it going.

Dave.

Offline wgw

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Re: A small pot belly stove.
« Reply #13 on: October 24, 2016, 07:20:24 AM »
If you cool the pipe to much you will get tar oil etc. condensing in the pipe, as well as affecting the draught. What arrangement have you for getting air into the bottom for combustion ?. To get a cold stove going get a couple of sheets of newspaper and light them in the stove near the flue outlet, that will get hot air flowing up the pipe. Can make a big  difference.

Offline NeoTech

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Re: A small pot belly stove.
« Reply #14 on: October 24, 2016, 10:30:07 AM »
Oh the arrangement is only a piece of 80x40mm square tube welded into the bottom. Should put a grate in there as well would prob. help.
Machinery: Optimum D320x920, Optimum BF20L, Aciera F3. -- I have not failed. I've just found 10,000 ways that won't work. http://www.roughedge.se/blogg/

Offline wgw

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Re: A small pot belly stove.
« Reply #15 on: October 25, 2016, 05:27:16 AM »
If you are burning wood you do not want a grate, just build up a good bed of ash.

Offline Bee

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Re: A small pot belly stove.
« Reply #16 on: October 26, 2016, 06:01:36 PM »
A flue should only have 45 degree bends so that it can be swept, brushes don't go round 90 degrees. There should not be horizontal sections as soot can fill up and block. Both above are UK regulations I believe.
At the bottom 9 inches insulate with vermiculite boards up to 1 in thick to provide a hot spot that can heat up quickly with small sticks and get the draught going.
Provide an air feed at the very bottom for starting and higher up once going.
Have a bypass on the heat exchanger for starting. (you find these on most kitchen ranges to bypass the cold oven until the fire is going well.)