Topic

Batch wood stoves, still hot?

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PostedMay 13, 2014 at 10:58 am

I don't have a wood stove, make wood fires, etc, but it looks fun and I want a go. I've watched a lot of youtube about it. There is a thing that puzzles me.

Most fire building starts with tinder, gets it going, puts slightly bigger wood on top, then bigger still, and so on until it's time to add the pot. Then as the fire burns down you periodically slide wood under the pot and try not to burn yourself.

In the youtube videos of a few years back, there was a wave of "top lit updraft" (TLUD) stoves, burning "batches". You put a tight-ish pile ("batch") of your big sticks in a stove with a vented bottom, then built a small starter fire on top of it. With the right bottom-to-top airflow, smoke and woodgas rose through the fire at the top and got burned. It was low on smoke, and you didn't need to stick around feeding the fire.

These days the TLUDs seem to be out of fashion, all the attention is on dual chamber stoves like the Bushbuddy and Caldera inferno and the Four Dog Nights. People seem to use dual chambers the non-batch way, i.e. start a fire with small stuff then keep throwing bigger twigs on top. They're efficient, but they're not getting the "load and go" aspect.

So I wonder, can you use dual chambers as batch stoves, i.e. put all your bigger wood in then light a starter fire on top?

PostedMay 13, 2014 at 11:53 am

Well, technically, a "batch" stove just means you load it and light it in "batches", versus a continuous feed stove. A gasifier, uses a supply of fresh air injected at the superheated and low-oxygen tip of the flame, to perform a secondary combustion of the smoke. The same process is used in high efficiency home wood stoves. A top-down burn, is just that, and is also the method suggested for starting fires in home high efficiency wood stoves.

Given the nature of a gasifier, a top-down burn works well by getting the upper chamber heated up quickly, to expidite the draw process supplying the fresh air intake for the secondary combustion. There's a bit about the lower fuel supplying smoke, but it's really more about proper draft from an upper high heat level.

I'm only hands-on familiar with the bushbuddy style, and it is a continuous feed gasifier, that is designed to be lit using the top-down method, although from experience, it's not necessary, and a standard bottom-up method works fine. It just takes a minute longer to get a more smokeless fire going. But there will still always be some smoke and soot, since fuel is erratic. Sometimes it's hard and dry, other times it's wet, soft and full of sap. No two burns are ever the same.

And I don't see the "batch" method working so well, as they burn out too quickly, before your water boils. So having a way to continuously feed it is pretty much a necessity. I've got them to burn longest by using a mini saw, and cutting 2 inch "logs" from 1 inch branches, and dropping them in like pellets to keep it burning. But then again, I like to keep the fire going for light and evening warmth to eat by, since I have it going. Half the fun of having a wood stove is playing with the fire and being mesmerized by the flames. It's very therapeutic :-)

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