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owb build

Started by coxy, May 16, 2018, 08:31:20 PM

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coxy

what do you think about making it out of 1/4in steel i know it will be heavy 

Southside

I know a guy that made one out of two pieces of large steel pipe, one for the chamber, the other for the chimney.  The whole thing sits in a SS box which acts as the water jacket, very, very simple to build and works like a charm. 
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hedgerow

Quote from: coxy on May 16, 2018, 08:31:20 PM
what do you think about making it out of 1/4in steel i know it will be heavy
I don't think they can be too heavy. Have seen a few made out of old propane tanks like a 250 gallon into a 500 or 1000 gallon one they are thick and last. Cost of not usable propane tanks aren't bad. Years ago I had a 1000 gallon one we made into a stove for a large shop with no insulation it worked well and lasted. Good luck with the build and post lots of pictures we love the home grown stuff. 

coxy

i was thinking about the heat transfer through the 1/4in steel then to the water i think it will be ok it may take longer to get the water hot but it should take longer to cool also no  

mike_belben

Praise The Lord

E Yoder

Heat transfer has a lot more to do with the exhaust making hard impact with the water jacket and having water flow behind it to carry the heat away. Thickness can slow things some but not as much as you'd think.
I've heard of guys hanging a piece of auger in the chimney below the water line to force the hot exhaust to scour the walls before exiting. Ideas..
HeatMaster dealer in VA.
G7000

mike_belben

You dont need to put an auger.  Just fabricate a pipe elbow where the horizontal run meets the stack at a tangent and the gas will coil.   

Think of how you enter a spiral staircase.  Not at the center, but at the peripheral edge.  I built a rocket stove J pipe this way and it spun like crazy.. Probably 3 turns per foot before the flame disappeared.  Smoke free and tons of heat from a tiny fuel chamber.  

Be warned tho, the stack better be thick.  Turbulent flame erodes faster than a lazy one, the cost of high efficiency. 
Praise The Lord

thecfarm

I have a Heatmor,the smoke goes up in front of the door,travels the full lenght of the OWB inside of a 3x8 inch tubing and exits in the back.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

E Yoder

Quote from: mike_belben on May 28, 2018, 08:14:54 PM
You dont need to put an auger.  Just fabricate a pipe elbow where the horizontal run meets the stack at a tangent and the gas will coil.   

Think of how you enter a spiral staircase.  Not at the center, but at the peripheral edge.  I built a rocket stove J pipe this way and it spun like crazy.. Probably 3 turns per foot before the flame disappeared.  Smoke free and tons of heat from a tiny fuel chamber. 

Be warned tho, the stack better be thick.  Turbulent flame erodes faster than a lazy one, the cost of high efficiency.
Good point on the entering at the edge. With the erosion- I'd imagine stainless holding up better.
HeatMaster dealer in VA.
G7000

coxy

the OWB i have now has 385gal of water is that needed  or could you just make it big enough for enough water to fill the lines and maybe 30-50 gal of storage or would the stove work to hard to keep the temp up  another thing how would one test for leaks of the fire box before putting the out side water storage on the door is supposed to be air tight so could i weld  an air nipple in the fire box to test the weld for leaks or would it leak out the damper because there is no real way to seal it this is where I'm having trouble 

Hilltop366



Cap the stove pipe hole (inner tube rubber and large hose clamp?) and fill it with water door side up to test the firebox.

I would add a adjustable second air intake near the end of the flame to help get a more complete burn, you will get more heat from your wood with less smoke and creosote.

Make the smoke pathways easy to access for cleaning.

My way of thinking is a larger water capacity is better if well insulated, it would keep the fire from short cycling and allowing longer burn times with will allow the fire to get burning well instead of a continuous smouldering fire. 

mike_belben

Yeah, My J tube is stainless. 


Coxy can you bolt on a cap plate and rubber inner tube gasket to leak check it?  


The more water, the more capacity you will have to store BTU but the slower your recovery times to bring it back up to temp.  In general terms, If you had a big firebox and a small water tank it would achieve limit temp quickly then damper fast, but calling for heat in the house will use up that stored energy quickly so youll have a pretty active damper with relatively shorter on/off times. 

Going the other direction to a big water jacket gives much more thermal units of storage.  The storage temp is another consideration.  If you had a small water jacket youd probably have to keep the storage temp higher to pack in sufficient energy for the houses demands.

A hotter tank is like a bigger one.  Say we're talking hot water heaters.  If you set your 40 gallon HWH to 135f and take a 135f shower, maybe it runs 40 minutes then goes cold.  If you bought a 60 gallon tank it would run longer, true.. But you can get the same effect by turning the temp on your 40 gallon tank up to 150f and still taking 135f showers.  Your hot water is hotter so you set your mixing valve to flow it a lesser rate and thus it lasts longer.  

Applying that concept to your boiler, the hotter the temp in the lines, the shorter durations your thermostat will cycle the pump because the rate of heat rise is faster.. It doesnt take as many minutes to bring the stat back up to your preset indoor temp.  This small tank and high temp does come at a cost.  The tank loses more heat to the atmosphere due to higher delta T than a cooler tank.. And also there will be more noticeable temp swing indoors because that water coming in is quite hot and noticeable.  Warm draft cool draft warm draft cool draft.  A normal joe has a stick framed low mass, shoddy insulated house with an on off furnace and is used to lots of noticeable heat cycles.  A rich man has a high mass home with silent inverter furnace thats always micro adjusting the fan speed and maintains constant temp to the half degree without anyone ever feeling it.  If you graphed temp, its a sawtooth vs a flatline. 


My personal opinion is it is a more efficient use of wood to have a smaller firebox and a big storage tank.  You may have to feed this stove a few times per day but itll rarely ever damper or smoke and will extract more btu from a cord.  My stove builds have all been tiny chambers running balls out.  They heat a lot of space on a small amount of wood but you feed alot.  Pellet stoves have taken this to the extreme.  A coffee cup sized burner and a feeding every 40 seconds.   


Its all in finding the balance that works best for you.  


Praise The Lord

Crusarius

Coxy, I have one of these in my house. works amazing I love it. roughly 750 gallon capacity and is dual fuel. Has wood firebox  but also has a fuel oil burner plumber into the same firebox. Have a look at it. May give you some ideas. it is super easy to clean to.

Switzer's Custom Woodburning System, Inc. - Home

Just another note, this is in a room on the back of my garage. It feeds my radiant floor. It does have a preheat loop for my hot water heater as well.

hedgerow

I have a Garn with a factory 1000 water tank and I have added another 2000 gallon tank. That is the way this system operates you load the wood burn full tilt and I usually bring the water temp up to around 200 at the end of the burn and then run off the stored BTU's of the water for heating. I like doing that way cutting down on the smoke. 

E Yoder

My .02,
I would recommend at minimum 75 gallons per 100,000 btu/hr output just to avoid overshooting temp at shutdown. The lower the water volume the tighter the damper needs to close. Ideally it should choke down til it almost goes out.
A big tank doing batch burns is the most efficient, obviously with a cost in the initial build and in water treatment. Most brands don't go the big tank route for that reason.

You might get some good ideas looking at various models at a farm show, fair etc this summer.

HeatMaster dealer in VA.
G7000

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