Woodstove sizing?

[tomas_maly]

I'm starting to think about scrapping the propane stove project and just working on a woodstove instead. Specifically I want to weld a stove instead of buying one, so I'm curious as to size that would sufficiently heat a 30+ ft bus, hopefully sufficient for 5-20 deg F outside. I'm wondering what the size of the firebox should be. I'm coming up with a dual stove+oven design (two separate compartments, where the hot air flow is manipulated around the isolated oven compartment toward the flue), and so I don't want a firebox that's too big that it gets boiling inside (even when it's 5 deg outside), and I don't want it too small.

And in general, how do people manipulate the overall temperature? By filling the box with more wood? Would firebrick help much in terms of radiant (long term) heat, so it doesn't burn so hot and fast? With the oven compartment, I was going to have a sliding rod that adjusts the airflow to go down and around the oven (making the escape path more complicated), which may help slow/cool the fire from my understanding.

I was thinking of making the firebox lined with 2 1/2 " firebrick and then the firebox itself be 17" x 17" x 16" inside of the brick. Is that too big? Too small? I'm trying to plan for cold winters if need be. But I'm also planning a dual-fire setup where the top right corner of the firebox is going to have a separate grate for a much smaller fire (probably 9" x 9" x 17", with a grate bottom so air can come from underneath). And I was hoping that smaller firebox could handle baking, cooking, etc in warmer months. I may or may not be in a place where I can set up a solar oven or campfire outside. I'm curious how others who normally rely upon a woodstove (not a propane stove) end up cooking/baking in the warmer months. I was originally planning on utilizing a solar oven or campfire setup outside.

I was also planning on 1/8th inch steel for the sheets and was curious if that was overkill or on par with other woodstoves. I get the impression that the thinner the steel is, the shorter lifespan, ie barrel stoves many only last 5-10 years if not designed well. What causes the deterioration? Excessive heat? Rust (from vaporizing moisture content in the wood)? I'm hoping the firebrick will lower the temperature a bit and extend the lifetime maybe. Does 1/8th steel seem overkill? I may end up needing about 2 4x8 sheets and that will cost me around $175. (yes I know that's what I can get a used woodstove for or less, but I'm quite particular about this exact design) Will there be much a difference between 16g and 1/8th in terms of lifespan/quality?

I was curious on how to secure the firebrick, if I need to place them between two sheets of steel (ie an interior box and an exterior box), or if it'll be ok as long as it's built to fit - ie 2 wide x 4 tall x 2 deep (around 8 1/4 x 4 x 2 1/2 per brick). I'd like to be able to remove/replace them, ie through the front door.

Right now I'm just trying to size the thing properly and I'll be worrying about stove safety later, after I have a working prototype in my garage.

Thanks!

[chev49]

Lots of questions:
1/8 should be ok, esp with firebrick
my wood stove has angle welded inside so that firebrick can slide in its own framework, and the fire is built directly on it. (high temp insulation goes between the firebrick and the exterior walls and floor pan. Final locking piece for the firebrick to lock it in is flat bar pieces that slide into another one.

I do not have an oven, but i built the top of my wood stove flat (with a lip around the outer edges) so that i can place a camp oven on top of the stove.
My stove can take 18 inch pieces.. you might want to do that in case you have to buy some for some reason.
I only build a small fire in my stove, as even a medium fire will heat the bus too hot even in 20 degree weather.. and i have to open the windows...
In fact, i am thinking of making a pellet stove burner for inside the stove as a very small fire pretty much keeps the bus warm most of the night in the winter... but i will have to see how that works out later on this year.

My stove is directly behind my dinette and across from the bathroom door entrance, which leaves 24 or so inches between the stove door and the bathroom door.

[lapeer20m]

Building stuff is cool, however You could find a used wood.stove on craigslist for $50 or $100.

I heat my house, my cabin, and my workshop almost exclusively with wood using propane as an expensive backup. I am a fan of having a large stove and turn the intake air and the damper both almost closed most of the time. This makes it so your wood lasts all night long. Keep your pipe straight with zero bends and no reducers and you will rarely have to clean the chimney pipe.

Small stove = not being able to put enough wood inside to burn all night long.

I've never used a stove in a bus.

[tomas_maly]

Originally Posted by chev49

Lots of questions:
1/8 should be ok, esp with firebrick
my wood stove has angle welded inside so that firebrick can slide in its own framework, and the fire is built directly on it. (high temp insulation goes between the firebrick and the exterior walls and floor pan. Final locking piece for the firebrick to lock it in is flat bar pieces that slide into another one.

I do not have an oven, but i built the top of my wood stove flat (with a lip around the outer edges) so that i can place a camp oven on top of the stove.
My stove can take 18 inch pieces.. you might want to do that in case you have to buy some for some reason.
I only build a small fire in my stove, as even a medium fire will heat the bus too hot even in 20 degree weather.. and i have to open the windows...
In fact, i am thinking of making a pellet stove burner for inside the stove as a very small fire pretty much keeps the bus warm most of the night in the winter... but i will have to see how that works out later on this year.

My stove is directly behind my dinette and across from the bathroom door entrance, which leaves 24 or so inches between the stove door and the bathroom door.

I have the book 'Wood Stoves: How to Make and Use Them' by Ole Wik - which has quite a few good designs...

The book suggest one plan with two fireboxes (one smaller inside/above the other, doors on adjacent sides) for usage in the warmer months, etc, though I'm not sure if that's necessary.

There's also a design with an ash drawer, though I'm curious from someone with experience if that's necessary.

My understanding is that using one (or more) baffles can help slow the heat from escaping out the flue. Especially if it has to zig-zag out.

I've seen 'rocket' stoves designed so they take much smaller pieces, and burn very efficiently, though I think they require more fiddling to keep going.

How do you cook in the summer?

I like the camp oven idea, seems simpler.

How big is your firebrick? I was thinking of going with 2 1/2" thick so I could get more radiant heat for longer with smaller fires.

Ideally I'd like to have a fire that can burn through the night, but isn't so hot to start out with.

Do you have your design somewhere on here or elsewhere? I'm curious what it looks like on the inside, especially with the angle holding the brick and how they can be installed/removed and yet kept secure.

I realize i can get stoves cheaper used - but I like the sheet metal design so I can modify it later, for pellet, (waste veg) oil, etc. Can the pellet run through the night, and if so, is this by some automatic/natural/gravity feeding setup?

[chev49]

my wood stove is mostly for a nice wood fire in the winter..i can easily remove the door. i have propane furnace, electric heaters and the wood stove, as well as the stove cook top which is propane, so each is a redundant system. i also have electric cooktop and oven, and also a built in micro.
my firebrick is around 1 1/2 inch size in thickness.
i did not build this entire stove, (although i have build tent stoves for resale), but i took a small stove from a company that manufactures certified ones near me, and cut the top and the back and rewelded them cause i wanted a top 6 inch straight stove pipe, and fixed the firebrick on the floor and walls so that it would stay in place with angle and flat bar. i also put concrete board in 3 layers under the stove and on all sides of it, (except the front of course)
Reweded a heavy flat plate on the top with a outside lip as mentioned in previous post, so small camp oven can fit there.
if i build a medium size fire and shut it down, the fire lasts several hours, usually long enough so the fire doesnt go out before i get back to it.
you can make your own pellet feeder and burner, i dont remember where at the moment except for maybe youtube, anyway, it can be done with a small motor, chain, etc. and i think you can also buy parts such as the feeder for a universal pellet stove online.

[tomas_maly]

This is actually the book I have that I'm basing my ideas from. it's really in depth...
http://<br /> <a href="http://autono...html#part2</a>

[lapeer20m]

There's also a design with an ash drawer, though I'm curious from someone with experience if that's necessary.

having a stove with an ash drawer is a HUGE bonus. Especially if you like to keep your fire going all winter long. Without an ash drawer you basically have to let your fire go out while you are sleeping, letting the stove, (and your bus,) cool down completely before you can clean the ashes out of the stove. Then you can remove all the ashes and unburnt coals. Then you have to restart the fire from scratch. Yet another reason to have a big stove, you have to clean it out less frequently!


If you have an ash drawer which includes a trap door inside the stove, you don't have to let the fire go out completely before removing ashes. You can move the hot coals off to one side, then sweep all the ashes down the trap door. This is much easier to having to scoop ashes out. You may have to move the coals around a couple times to get all the ashes out, but if you are careful you can just add more wood to the hot coals and the fire will take off again without much work on your part.

The latter is definitely preferred to the former, especially if you are burning full time. An ash drawer is less important if you just have an occasional fire.

Some wood creates more ashes than others. For instance, i like to burn ash trees, because it is easy to find here in MI, but it creates a lot of ashes (I think that's where it got it's name)

[chev49]

ash drawers are great if you keep them cleaned out. i did not put one in the stove i remade for my bus as i am not going to keep a fire going continually.
they also work great when you can get coal to burn.. which is my first choice for stuff to burn.

thanks for the long article.