Can I ask about a home-built wood stove ?

[sesmith]

First, I'm assuming you can weld/ fabricate and have some mechanical drawing and/or caad program to design it all before hand and avoid major unforeseen problems while you're making it. Even so, I can't imagine being able to make a stove that burns better and would be cheaper to build than the cheap stoves available at the big box stores on sale this time of year.

However, since you insist , I can point you to a post I put on the other forum a couple of years ago that detailed the secondary burn tubes I put in my older stove:

(broken link removed)

They continue to work great and cleaned up the burn a lot, and increased the efficiency of the stove . I'm currently working on a cat add-on for the stove that should be ready to test in a week or two. This should clean it up the rest of the way and squeeze a little more heat out of it...or be a miserable failure

Yea, I like to tinker too, but I still wouldn't spend my money making a stove when I could buy a much better one for the same price or a little more.

 

[Poodleheadmikey]

What size secondary air pipes you used?

BTW: in contrast to you; I feel strongly that I can fabricate a stove which is superior to those I might buy. <g>

Since you don't have a glass door why not make an observation port? If you weld a few 2" pipe couplings around the stove you can also make up a 2" nipple with a cap and gasket and glass in it. Drill a 1 3/4" hole in a pipe cap and use two round flat gaskets to hold the glass onto the end of the pipe with the drilled cap.

With that removable port installed you can look into the stove whenever you want, see what is happening, and then re-plug the opening you used.

Or that is what I am going to do anyway. <g>

PHM
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First, I'm assuming you can weld/ fabricate and have some mechanical drawing and/or caad program to design it all before hand and avoid major unforeseen problems while you're making it. Even so, I can't imagine being able to make a stove that burns better and would be cheaper to build than the cheap stoves available at the big box stores on sale this time of year.

However, since you insist , I can point you to a post I put on the other forum a couple of years ago that detailed the secondary burn tubes I put in my older stove:

(broken link removed)

They continue to work great and cleaned up the burn a lot, and increased the efficiency of the stove . I'm currently working on a cat add-on for the stove that should be ready to test in a week or two. This should clean it up the rest of the way and squeeze a little more heat out of it...or be a miserable failure

Yea, I like to tinker too, but I still wouldn't spend my money making a stove when I could buy a much better one for the same price or a little more.

 

[Beetle-Kill]

Since you're bound and determined,... I used 3/4" sch. 80 for my secondaries. 4 rows of pipe. Hole layout was loosly based off the NC-30 hole pattern. You can find the pattern on their website. Good luck, looking forward to pics.

 

[moosetrek]

Just a comment on your point-top design - that's a great idea for radiant heating, but if you want the flexibility to add convection to the stove you might go with a wider top. I think you could use the 2" square tube across the top, open ends front-to-back, as a bolt-on cover for the top and blower into it. That way you have a big plate on top for radiant heat, but just drop a 2" thick "lid" of tubes on it and fire up a blower to moderate the intensity and spread the hot air. If you really wanted to go crazy, do the same on the sides - solid heavy box with a "bolt on" shields. The difference from store-bought ones is the tubes help direct the heat, and using 14-16 ga steel tubing for spacers would really add a lot of surface area. I bet if that was cranking, with a serious blower (or two) you could heat anything you wanted pretty quickly, and have lots of permutations of top / side / no convective heat.

 

[Poodleheadmikey]

I'm not sure I know what you mean.

Or: maybe you don't know what I mean. <g>

The point-top design is based on pure convection. The top "point" is being formed by the top inner edges of two hollow 3" by 5" tubes touching each other. Their open bottoms will be spread apart about 36".

My concept is that the tubes forming the body of the stove will be heated by the fire within, the tubes will heat the air inside them, it will rise and flow out the tops of the tube. This will draw more cold floor level air into the tubes which which then be heated and rise/flow out the tops of the tubes.

My whole point is to avoid the need for powered air flow.

PHM
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Just a comment on your point-top design - that's a great idea for radiant heating, but if you want the flexibility to add convection to the stove you might go with a wider top. I think you could use the 2" square tube across the top, open ends front-to-back, as a bolt-on cover for the top and blower into it. That way you have a big plate on top for radiant heat, but just drop a 2" thick "lid" of tubes on it and fire up a blower to moderate the intensity and spread the hot air. If you really wanted to go crazy, do the same on the sides - solid heavy box with a "bolt on" shields. The difference from store-bought ones is the tubes help direct the heat, and using 14-16 ga steel tubing for spacers would really add a lot of surface area. I bet if that was cranking, with a serious blower (or two) you could heat anything you wanted pretty quickly, and have lots of permutations of top / side / no convective heat.

 

[sesmith]

What size secondary air pipes you used?

BTW: in contrast to you; I feel strongly that I can fabricate a stove which is superior to those I might buy. <g>

Since you don't have a glass door why not make an observation port? If you weld a few 2" pipe couplings around the stove you can also make up a 2" nipple with a cap and gasket and glass in it. Drill a 1 3/4" hole in a pipe cap and use two round flat gaskets to hold the glass onto the end of the pipe with the drilled cap.

With that removable port installed you can look into the stove whenever you want, see what is happening, and then re-plug the opening you used.

Or that is what I am going to do anyway. <g>

PHM
------

I used 3/4" black steel pipe. Stainless would probably be a better choice, but I've had no problems with the black pipe so far (2 years). I probably just got lucky with the amount of secondary air flow I have as it seems to work out ok. The elbows needed to route the air flow to the back of the stove, then forward, reduce the flow for sure, but you need the air superheated for the secondary burn to work, and routing it through piping in the stove does this.

View ports might be kind of fun, but they really aren't necessary. I found I can pretty much know when the secondary burn kicks in by the stove top temp. and looking at the smoke from the chimney.

 

[Beetle-Kill]

I hate to throw a wrench in the thought process, but what the heck. You're talking a pyramid in profile, correct? What if you inverted the design, put the "point" on the bottom? Change the point to become a channel, to incorporate the use of fire brick in the bottom and sides. You can still use the TS for hot air, but it would be pulled from a centered location on the bottom and spread out on top. Incorporate a diamond style top plate, lots of room for secondary air system, and a large surface top for steamers or cooking. Plus, an inverted pyramid style would allow a lot of wood to be loaded, and let gravity feed the fire as it burned down. Does that make sense? The design, while odd, would be pretty effective in my head.-(this is the crap that keeps me up at night.)

 

[Poodleheadmikey]

So far I have all the steel and some of it fabbed into a very substantial floor and all the 3" by 5" by 48" tubes welded into position.

I thought I had taken a picture of the base before I turned it right-side-up - but I can't find them now.

I do have some pics of the tubes going in (the first two wrong <g>) to place.

I am bricking the firebox now. Can the firebox be too big?

What does " too big" mean in this context?

PHM
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Poodle:

I've wanted to build a stove of my own forever... like since the first EPA stoves came on the scene. I 'studied' them at the time and thought and thought and _still_ figured I could do better.

But I never got 'round to it.

I say if you want to do it, go ahead, but STUDY the craft and don't reinvent the wheel. Learn from what's out there, incorporate your own ideas and...

If you actually get to torturing some steel into rough shape, get back to us.

Peter B.

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[Wood Duck]

Maybe it is too late, but I thought I'd respond to your thoughts about where the secondary burn tubes should go. I would put the secondary air in a place where you can see the secondary flame, in other words below the smoke shelf. I guess the smoke shelf is a baffle that forces air to leave the stove from the front (or back?) top of the stove. My stove has this arrangement. The secondary air tubes are below the shelf so that the secondary flame occurs inside the firebox where I can see it. Perhaps there are more efficient ways to set up the stove, but seeing the secondary flame is very enjoyable and it allows me to adjust the primary air while monitoring the secondary flames. I don't see how I'd adjust the air without seeing the secondaries.

FWIW in my stove the primary air enters at the top front of the stove above the door. Air goes down the door, across the bottom of the firebox (through the fire), then rises to the top. This air mixes with secondary air that is introduced at the top and moves forward. The exhaust air leaves the stove near the top front just behind the place where it enters. Advantages of this include 'air wash' over the glass to keep it clean, and the air from primary combustion (which occurs in or near the pile of wood at the bottom of the stove) has to travel across the top of the stove to leave, so it is exposed to the secondary air and hot temps so secondary combustion can happen. You definitely want to think about air flow when placing intakes and exhaust from your stove.

 

[Poodleheadmikey]

Not too late yet - I am still working out how much I can leave out.

I have to support the smoke-shelf/baffle with something - so it may as well be two secondary air pipes / airways. I'm trying to work that out now.

But I'm thinking that, as the secondary air needs to be preheated; I want to introduce the air low on either side of the loading door, run the secondary supply air piping to the back of the firebox, just over the firebrick retainer, then double-90º it up and forward just under the baffle. Under the baffle the piping would be drilled.

1/4" air outlet holes OK?

I guess I should work out the cross section of the secondary air piping and then provide an equal area in the total of the outlet holes.

BTW: I want the firebox exit to be at the top rear - then up into the space above the baffle - then forward to the flue connection.

PHM
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[Poodleheadmikey]

OK: I welded up some 1" pipe and 90's into a secondary air manifold. It has 13 1/4" air outlet holes in the top tube - facing in towards the center of the smoke shelf/baffle.

I have the air inlet ends coming in through the rear wall to give more air heating time in the manifold. A single pass didn't seem like much to me.

http://www.flickr.com/photos/57525667@N06/5524291705/

Will this be OK?

PHM
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[Poodleheadmikey]

I like this idea a lot - and it would be really easy to brick the stove. <g>

The falling fire would always be concentrating itself into the bottom apex of the fire box.

PHM
-------

I hate to throw a wrench in the thought process, but what the heck. You're talking a pyramid in profile, correct? What if you inverted the design, put the "point" on the bottom? Change the point to become a channel, to incorporate the use of fire brick in the bottom and sides. You can still use the TS for hot air, but it would be pulled from a centered location on the bottom and spread out on top. Incorporate a diamond style top plate, lots of room for secondary air system, and a large surface top for steamers or cooking. Plus, an inverted pyramid style would allow a lot of wood to be loaded, and let gravity feed the fire as it burned down. Does that make sense? The design, while odd, would be pretty effective in my head.-(this is the crap that keeps me up at night.)

 

[begreen]

OK: I welded up some 1" pipe and 90's into a secondary air manifold. It has 13 1/4" air outlet holes in the top tube - facing in towards the center of the smoke shelf/baffle.

I have the air inlet ends coming in through the rear wall to give more air heating time in the manifold. A single pass didn't seem like much to me.

http://www.flickr.com/photos/57525667@N06/5524291705/

Will this be OK?

PHM
------

Photo is private. Make it public or post it directly to the forum.

 

[Poodleheadmikey]

How do I post it directly here?

I did change it and a few others to public view.

So try it now and see what you can see.

PHM
-------

OK: I welded up some 1" pipe and 90's into a secondary air manifold. It has 13 1/4" air outlet holes in the top tube - facing in towards the center of the smoke shelf/baffle.

I have the air inlet ends coming in through the rear wall to give more air heating time in the manifold. A single pass didn't seem like much to me.

http://www.flickr.com/photos/57525667@N06/5524291705/

Will this be OK?

PHM
------

Photo is private. Make it public or post it directly to the forum.

 

[Jimbob]

Here.
Looks like you have LOTS of firebrick in there!

 

[begreen]

Yes, that worked. Why is the side firebrick set edgewise instead of flat face forward? Secondary air looks like an interesting design for preheating, but I would think that it should evenly introduce air back to front instead of from one side.

 

[Poodleheadmikey]

Yep - I have a lot of fire brick in there.

So?

Good? Bad? Why do you mention it? <g>

I originally bought 50. Then 12 more. And then 6 more. But I think I will end up with 64 or 65 bricks total.

It is what it is - is there a problem with it? <g>

And . . . what about the secondary air? <g>

PHM
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Here.
Looks like you have LOTS of firebrick in there!

 

[Poodleheadmikey]

That's the first and last front-wall brick that you're looking at the side of - along the sides the brick is flat behind those retainers.

If you want to See what I mean - let me know and I'll take some pics showing how the side-wall bricks are installed.

Also: that is only one of the two secondary air manifolds - there will be another exactly like it on the other side. I didn't build the second one yet - but I wanted to ask you all about it anyway. <g>

Oh wait - I guess you can't see the air holes - look here:

http://www.flickr.com/photos/57525667@N06/5524292091/

That pic shows the row of holes in the uppermost tube of the secondary air manifold. The holes are towards the center of the stove.

PHM
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Yes, that worked. Why is the side firebrick set edgewise instead of flat face forward? Secondary air looks like an interesting design for preheating, but I would think that it should evenly introduce air back to front instead of from one side.

 

[Poodleheadmikey]

Here you can see the air holes in the semi-installed manifold:

http://www.flickr.com/photos/57525667@N06/5524291461/in/photostream/

PHM
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[Jimbob]

Having lots of firebrick is good, it'll add to the thermal mass.
To post the pics into the thread, just copy them into a folder on your computer, then attach them to your post.

 

[Poodleheadmikey]

It says that the pics are too big?

Error Message: The uploaded file exceeds the maximum allowed size in your PHP configuration file

Zupwidat?

PHM
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[begreen]

https://www.hearth.com/econtent/index.php/forums/viewannounce/27_2/

 

[Poodleheadmikey]

I stopped to look at wood stoves today and found that their secondary air distribution tubes have LOTS of holes in them. The area of the holes appeared to far exceed the cross section area of the manifolds themselves.

Whereas what I did here was to calculate the cross section area of the 1" black pipe's ID and then drilled enough 1/4" diameter holes to equal the pipe's cross section area.

Can I have Too Much secondary air?

Maybe I should use more holes in my air tubes?

What do you all think?

PHM
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[sesmith]

FWIW, I think that the secondary air is too far from the fire. If you notice the firebox size of most of the stoves in the store, the burn tubes are located directly above the firebrick burn chamber. I'm wondering that, in your stove, too much heat will be lost from the smoke before the secondary air has a chance to do it's thing. As far as hole size, 1/4" sounds a little large to me. I went with something a little smaller when I retrofitted my stove with burn tubes. I also made the last few holes in the run a little larger than the 1st few. The newer stoves with burn tubes have a lot of tubes and have the flow computer designed for the best combustion, so I can't really make any guesses except get superheated air in the right place and it'll do something. Yes, you can have too much secondary air so you have to have a way to regulate it. You should also have a way to shut it off completely in case of a chimney fire.

 

[Beetle-Kill]

PHM, I agree with sesmith, that 1/4" air ports are too large. I also agree that the secondary tubes are higher than we would consider normal, but your design isn't normal, so it may work. If you really want to crunch numbers, pull up the spec.s for the Englander NC-30, take the dimensions for the stove and deduct for 1/4" plate thickness. Then reduce that by the bricks. That should give you a baseline, as far as interior capacity. Then look at the secondary air system, the site gives you a nice layout with port diams. Figure that you want your wood about 2" below the burn tubes. Try and carry those dimensions for your interior capacity. But that's a conventional design, your design may behave differentlly. Unless you plan on chucking in about 7CF of wood per load, you may want to make you baffle height adjustable. That will screw with your secondaries, so I really don't know what to tell you. Just my .02. JB