Gas bottle wood stove & saw dust burner

[kinsella]

Colleagues
With the recent cold spell I came back to the house and my wife said i was blue with the cold. As a result I decided I'd embark on a stove build. What I also thought I'd do is combine wood burning with saw dust burning. Those of you that have ever tried to burn saw dust will know that it doesn't burn easy unless you use some industrial burner that blows it into the fire chamber. Having looked on the Internet for saw dust burners I though I'd have a go at making a gas bottle stove that can switch between wood burning and saw dust, saw dust is something I'm not short of.

It's another gas bottle stove but the difference is that it will also convert to a saw dust burner. The principle of both methods of burning are different. Hopefully the images explain the principle.

See below my initial sketches and I'll add WIP photos as I go along. The goal is to do it as cheap as possible.

 

[twothumbs]

First a question....Why are you taking the vent pipe off the back? I am sure you have checked this out but old stoves from my youth always came out the top. Perhaps offset as there was a cover for filling and I know flues are a carefully worked idea going back yonks. It did see an an example nearly 20 years ago with the flue out the top and a door set into the front..burnt out and a flange welded aound the edge. If the flue comes out the top directly it may draw too much. Will you need an adjustable damper. Best Wishes.

 

[kinsella]

I have to for dual use, ie saw dust/wood stove, i intend to put a damper in the outlet and adjustable air intakes at mid height of the fire as i won't be using coal. i think you do get a bit of both, top or bottom.

 

[kinsella]

No comments on quality of welding please, it was secondary school since i last welded.

i've ran out of material. now trying to find some 100mm steel pipe on site. At this rate it will be ready for next winter.

 

[Jacob]

..... Those of you that have ever tried to burn saw dust will know that it doesn't burn easy unless you use some industrial burner that blows it into the fire chamber. ..........

There is another way but it wouldn't fit with gas bottle designs. A pyramid shaped burner can be filled with sawdust and it burns from the top and on the outside of the heap, as it always settles a bit and leaves an air gap.

We've got one of these:

It's multi-fuel and burns sawdust fine but it's a bit small so you have to keep refilling it - but not until the previous batch has burned out or you get blowback.
A purpose made sawdust burner could be bigger and with a more pronounced pyramid shape. This could also be good for paper and other rubbish burning where there is a lot of ash which blocks air flow in rectangular shaped designs.

 

[kinsella]

How does it mix with air? The design I have is basically a chimney that burns from the inside out. The down side is, only the top and exhaust gets hot, but it burns for hours! I think once I fill it, it will burn for 6 hours. I'll tried it on a cooking oil can and it burned for around 3 hours, the is much bigger.

Have you got any design info on yours, I haven't come across that type on my Internet search.

 

[Jacob]

How does it mix with air? The design I have is basically a chimney that burns from the inside out. The down side is, only the top and exhaust gets hot, but it burns for hours! I think once I fill it, it will burn for 6 hours. I'll tried it on a cooking oil can and it burned for around 3 hours, the is much bigger.

Have you got any design info on yours, I haven't come across that type on my Internet search.

When its full of sawdust it burns from the top with air from the top inlet just like most wood-burners.
But because it's essentially a conical heap of sawdust in a box it doesn't spread out to the sides and eventually air finds its way around the heap and the whole surface can burn, drawing air from the bottom. So it's exactly the opposite of your burning from the inside out.
There is no design info as such on the net as it is an original idea as far as I can see. The stove we have is a Dowling firebug, not designed for sawdust so it's just by chance that I discovered how it can work.
Next time I burn a load I'll do some snaps.

 

[kinsella]

i suspect as a space heater, your one is more efficient. as it has more surface area to heat. i'll let you know when i finish mine.

i'm on the blag for the next bits of steel in work. its a novelty to do some metalwork instead of wood.