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Keith Selbo
(herman666) - F - M

Locale: Northern Virginia
my high efficiency wood burner & two cents worth on wood stoves on 07/12/2008 14:01:06 MDT Print View

I just built a new 3 piece wood stove (see photos). The stove is designed for high efficiency, wind performance, leave no trace and safety. The firebox is fully enclosed and baffled so sparks can't escape. The stove won't scorch whatever it sits on and retains ash in a removable ash bin in accordance with the leave no trace ethic.

Materials: Firebox, ash drop and base are 0.01" stainless steel. Chimney is tinned steel. Outer wall and top of firebox, 0.01" aluminum. Pot is two liter black anodized aluminum.

It weights about 14 oz. It was sized for a big pot for cooking for two or three people. A one man stove would weigh much less.

The firebox is insulated to enhance efficiency and to reduce outside surface temperatures. It's still too hot to hold by the sides, but it won't brand you or set your clothes on fire. The pot sits in the chimney to maximize heat extraction from escaping gases. Fuel is added by lifting the pot every few minutes.

It boils 0.47 liters (2 cups) of 17C water using about 73 grams of wood. Based on the average energy content of wood by weight (which is fairly uniform across species, that works out to about 69% efficiency.

The average heat transfer to the pot is about 590 Watts, which is quite a bit higher than an alcohol stove and a fair amount less than a canister stove.

I believe it is important to characterize wood stoves by their wattage and specific fuel consumption because it allows quantitative comparisons between stoves. I'm a lot more concerned with speed and efficiency than whether a stove is a gasifier or if it keeps my pot clean. Note that the pot stores inside the chimney, so soot on the pot isn't much of an issue for me.

The stove continues to cook in wind and rain although there is a noticeable drop in cooking speed with cold air blowing on it so it's best to seek a partially sheltered location in windy conditions.

I tested the stove with wet wood. I placed a quarter of a paper towel in the fire box and added four drops of kerosene to the towel. I lit it, and then I shook the water off a handful of twigs I'd hosed down, dropped them on top and set the pot over the fire. I didn't measure any drop in efficiency, but that just means I need more sensitive instrumentation. There was no problem keeping the fire going with wet wood.

The stove smokes whenever fresh wood is added. This turns out to be a convenient feature. Since the flame is out of sight, the absence of smoke is what tells me it's time to drop more wood in the fire box. A couple of ounces of wood need to be added about every two or three minutes.

One neat thing I hadn't expected is the simmer capability. After cooking on high for eight or so minutes, the charcoal accumulation is sufficient to simmer for another ten minutes.

Features I think are most important are safety; No open flame, or scorched earth; and leave no trace; once cooled,
retained ashes can be carried out or burried.

The feature I like best? I cook as long and as much as I want. More coffee? No problem. Another pot-baked muffin? Coming right up. I've yet to have to walk more than ten feet from the stove to find all the fuel I need.

ready to cook
ready to cook
bottom view of firebox
Bottom view of firebox. Air enters around ash pan.

The three components
Ash pan, firebox (bottom view again), and chimney.

nested for transport
Stove components and pot nested for transport.

Edited by herman666 on 07/13/2008 08:32:26 MDT.

Michael Mangold
(mkmangold) - F
Wood stove on 07/13/2008 22:07:29 MDT Print View

Nice.
I have a WoodGas stove and like the idea of using a renewable resource. Good job!

Dan Yeruski
(zelph) - MLife

Locale: www.bplite.com
Re: my high efficiency wood burner & two cents worth on wood stoves on 07/14/2008 13:09:01 MDT Print View

Nice craftsmanship and great choice for cooking.

I like using wood for cooking. I like starting fires using the primitive ways, sparks!!!! Gives me time to practice those skills.

ed short
(shortdottedline) - F
Re: Re: my high efficiency wood burner & two cents worth on wood stoves on 07/27/2008 22:20:23 MDT Print View

I just sold my bushbuddy ultra, great engeneering, Now I use a super ul titanium cylinder 5.5 X 5.5in. 2 pop rivets, dirt simple , gnome

Keith Selbo
(herman666) - F - M

Locale: Northern Virginia
ashes on 07/29/2008 07:50:56 MDT Print View

I hope your super simple design has a bottom so it doesn't drop ashes or leave scorched earth.

Huzefa Siamwala
(huzefa)
Re: ashes on 07/29/2008 08:18:45 MDT Print View

Nice! I skimmed through the PDF document and I think you have applied the info well in your design.

But 14 oz?!?!? With CC and Ti Foil I am aiming for something <1.5 oz.

Ashes.. I am thinking about using a piece of fireproof cloth to protect the ground. When finished cooking I can just fold up the cloth with ash inside and place it in my quilt.

Edited by huzefa on 07/29/2008 08:28:08 MDT.

Keith Selbo
(herman666) - F - M

Locale: Northern Virginia
weight & ashes on 07/29/2008 09:34:21 MDT Print View

Don't forget, my stove cooks for two people so the net weight is 7oz. If you convert it to 0.005 TI, that would become 2 or 3 oz without any modifications to the design.

Roger Caffin
(rcaffin) - BPL Staff - MLife

Locale: Wollemi & Kosciusko NPs, Europe
Re: Re: ashes on 07/29/2008 15:50:19 MDT Print View

> When finished cooking I can just fold up the cloth with ash inside and place it in my quilt.
Your quilt will likely stink very soon.

Devin Montgomery
(dsmontgomery) - MLife

Locale: one snowball away from big trouble
Re: Re: Re: ashes on 07/29/2008 21:00:34 MDT Print View

> Your quilt will likely stink very soon.
Amen. Your quilt will smell soon enough without the eau de BBQ. Also, if your stove operates efficiently, there should be very little ash remaining. Sometimes, if I've just put a batch of wood in mine when it boils, I leave the pot on a bit longer to help it completely burn the fuel. What is left is usually cool by the time I'm done eating, so I bag it in a zip-lock and bury it with my other "waste."

Huzefa Siamwala
(huzefa)
Re: Re: Re: ashes on 07/29/2008 21:02:46 MDT Print View

Roger, thanks for the tip.

Derek Goffin
(Derekoak)

Locale: North of England
Re: Re: Re: Re: ashes on 07/30/2008 01:51:51 MDT Print View

"Also, if your stove operates efficiently, there should be very little ash remaining. Sometimes, if I've just put a batch of wood in mine when it boils, I leave the pot on a bit longer to help it completely burn the fuel. What is left is usually cool by the time I'm done eating, so I bag it in a zip-lock and bury it with my other "waste."

I would have thought that burying or dispersing a small quantity of ashes would not harm the environment whereas burying a ziplock plastic bag would.

Devin Montgomery
(dsmontgomery) - MLife

Locale: one snowball away from big trouble
Re: Re: Re: Re: Re: ashes on 07/30/2008 13:48:52 MDT Print View

Sorry, irresponsible use of pronoun. The "it" was the ashes which I bury. The zip-lock I keep for future use. Also, "waste" was my euphemism for stool, which along with urine and the minute quantity of ashes are the only things I don't pack out. I always imagine the charcoal having some hind of neutralizing effect but that's completely without merit. Unless my "waste" is slightly acidic, in which case the infinitesimal amount of lye might give my dookie a better pH balance. :)

Rog Tallbloke
(tallbloke) - F

Locale: DON'T LOOK DOWN!!
Re: my high efficiency wood burner & two cents worth on wood stoves on 08/15/2008 09:27:12 MDT Print View

I've got 0.4mm Ti which is 0.016" not 0.004". Plenty strong enough to support the pot.
For the upper part of the windshield, I'm going to use some kopex I've found. It's that concertina'd alloy tubing used for flues, and should stand the heat. A piece big enough weighs 10g.
I like the bayonet idea, very neat. Not sure what I'll use for the lower part of the shroud yet, maybe an old thin cheap alloy pan. I think it'll take the heat...

Keith Selbo
(herman666) - F - M

Locale: Northern Virginia
looking forward to .... on 08/15/2008 19:46:28 MDT Print View

Looking forward to seeing your finished product.

Edited by herman666 on 08/26/2008 09:08:58 MDT.