Need input on a stove

I need critique and suggestions on how to improve this stove design.



It's meant primarily for cooking, and the space beneath is supposed to be for storing fuel. It's built entirely out of brick, with a steel plate and aluminum (or similar) chimney.

About 200 of these things will be built in rural communities up in the mountains. Currently, they're still using the 3-stone method for cooking. The reason for the simplicity of the design is that we only have a few days to teach them how to make the stove, and each family will build their own. It's the most basic thing I could find, but I have this nagging feeling it won't work.

The design has been approved by my boss (who has experience with these things), but I have this nagging feeling it won't work. Mostly, I'm worried about the floor of the fuel chamber. I don't think pure brick and mortar will hold together to form the box shape shown. Any input?

Zanne Charlotte wrote:I need critique and suggestions on how to improve this stove design.

It's meant primarily for cooking, and the space beneath is supposed to be for storing fuel. It's built entirely out of brick, with a steel plate and aluminum (or similar) chimney.

About 200 of these things will be built in rural communities up in the mountains. Currently, they're still using the 3-stone method for cooking. The reason for the simplicity of the design is that we only have a few days to teach them how to make the stove, and each family will build their own. It's the most basic thing I could find, but I have this nagging feeling it won't work.

The design has been approved by my boss (who has experience with these things), but I have this nagging feeling it won't work. Mostly, I'm worried about the floor of the fuel chamber. I don't think pure brick and mortar will hold together to form the box shape shown. Any input?

Look up Masons on a Mission (I don't have a link right now) for really nice ones. Try these folk here too. The second one is very easy to teach and could sit on top of a brick bench. Also Aprovecho has done a lot of research into site appropriate cooking. They have some good free publications on heating food effectively, though if you look around the rechoroket site above they have a lot of it in really easy to understand bits they use for teaching.

The one you show will "work", but may not burn as well (clean) as a three stone setup and it will use a lot of wood for the same work as a three stone fire as my first guess. The only way to tell for sure is to test build.

Some questions:
1) does the area have lots of wood? (or other burnable)
2) do the people cook flat breads like pancakes or other things that cook on a flat surface or would they be using pots to make stew like food? The design you show would not be great for heating pots of stew. The heat transfer would be less than stellar. but may be ok for making tortillas direct on the plate.
3) is this stove supposed to provide warmth in cold weather? or is this an already hot place where cooler (and less fuel) would be welcome. An all brick stove will add heat to the room even hours after the fire is out as it has more mass than the three stones being used now.

Approvecho and many others have masonry rocket cookstove plans. Don't reinvent the wheel.

http://www.rocketstove.org/images/stories/design-principles-for-wood-burning-cook-stoves.pdf

Len, first things first: thanks for the great resources!

Len Ovens wrote:Some questions:
1) does the area have lots of wood? (or other burnable)

Fuel is definitely available.

2) do the people cook flat breads like pancakes or other things that cook on a flat surface or would they be using pots to make stew like food? The design you show would not be great for heating pots of stew. The heat transfer would be less than stellar. but may be ok for making tortillas direct on the plate.

Tortillas and similar flat, corn-based things are a staple, but I'm pretty sure they have some use for pots. No one lives on grain alone.

3) is this stove supposed to provide warmth in cold weather? or is this an already hot place where cooler (and less fuel) would be welcome. An all brick stove will add heat to the room even hours after the fire is out as it has more mass than the three stones being used now.

According to my research, temperature is 50°-65°F through most of the year, except in winter, when it really drops. The association I'm working for does not take us there during winter because most volunteers can't handle the weather (or so I've been told) so the actual temps are likely lower than the data I found.

Zanne Charlotte : Thumbs up for trying to connect with the people you are trying to serve, and a strong recommendation to Connect with the designs at Aprovecho!

And a really strong Thumbs down for any GMO that will not trust their volunteers to 'winter-over' with the 'Indigenous population' !

If they have doubts in your ability to solo with 'natives' they should require that you 'winter over' with Volunteers that have Experience in the Area !

To merely cll this 'Chicken-shit' is to overstate the obvious! If I were informed of these circumstances I would probably leave their program at the earliest excuse !

This is one mans 'Personal Opinion !" Big AL !

Zanne Charlotte wrote:
According to my research, temperature is 50°-65°F through most of the year, except in winter, when it really drops. The association I'm working for does not take us there during winter because most volunteers can't handle the weather (or so I've been told) so the actual temps are likely lower than the data I found.

Be aware that the people you are working with are probably somewhat acclimatized to living cooler. I finally started wearing a jacket this week as the temperature hit freezing. I have been working outside (3 or more hours at a time) in a short sleeve shirt at only 35F or so (2C as they say here). I would check into this design (free to download BTW), which can be used for cooking and heating. The fire box could also be used as a retained heat oven after the fire goes out. It has a bypass for summer use that sends most of the excess heat from cooking up the flue.

Here it is.

It is similar to what you have there except the firebox is properly proportioned for a good clean burn. In the winter with the damper closed, the flue gas is routed under the firebox so that the whole stove mass is used as heat storage/radiator.

Too many bricks? Check this out. This is a bigger heater that would provide more warmth, but the reason for pointing it out is that these are made with hand made bricks of adobe. Again this has a well designed firebox and produce negligible smoke.

Both of these have a minimal footprint and would fit in a small dwelling. You will notice that both where test built before being put into an actual house. Unless you use a design someone else has tested, I would test build your own creation (outside) to make sure it works well. Use a clay mix as mortar, keeping the space between bricks as small as possible. The Russian heater guys try to keep the mortar only 1mm (1/16 inch or less) thick. Portland cement has no place inanything to do with fire as it will crumble at high (even not so high) heat as found in wood burners.

So, I've done a load of reading and done my best to contact MOM and Aprovecho. My re-design is almost ready, but I have one question left: what thickness of steel plate would be best for the flat cooking surface? My boss is adamant on keeping that particular feature.

Zanne Charlotte wrote:So, I've done a load of reading and done my best to contact MOM and Aprovecho. My re-design is almost ready, but I have one question left: what thickness of steel plate would be best for the flat cooking surface? My boss is adamant on keeping that particular feature.

I can't help there. Using steel plate (even 1/4 inch) seems to have issues with the centre heating and expanding more than the edges causing it to dome. That is why most (even cast iron) stove tops have loose burners at the hottest part. Some people have tried welding braces (L-shaped) across the bottom but I have not heard if this worked or not. Maybe cut a circle in the middle add a one inch or so ring that is 1/2 inch bigger in diameter bigger than the hole you cut out to the bottom of the plate. The circle you cut out should now rest in there and the thickness of the cut would give it room to expand before touching the outside cut. Depends on if you have welding/cutting equipment or if you are teaching people to make one who don't have these things. I get the idea that this is the major expense for a stove. You may note that most of the ones use clay for the top and have the cook pot sit through a hole in the flue gas stream to pick up the heat. However, one of your uses requires a flat surface. I think I might be inclined to talk with the people who are going to end up using the stove and involve them in the planning. Maybe providing a hole the size of a 12 inch cast iron skillet would work. These can be had for around 10 to 15 dollars. If that is not big enough maybe use two holes and two pans. It is important anyway to know what size cooking area they use now.

Wow! I'm almost tempted not to reply to this...but maybe if you can answer some questions. Is this a patio stove or will it be inside? DO NOT use a unit like this inside your house or on a combustible floor. Back to the patio unit on a cement patio: line the firebox with traditional firebrick, not the red building bricks. Masonry stores usually offer a fire resistant mortar. Do not use regular portland mortar unless you plan on rebuilding the firebox every few years. Your vent should extend to a height of 12' above the top of the firebox, with an additional 12" to 18" for every 1000' of elevation at your location. Additionally extend the vent two feet higher than combustibles within ten feet, and three feet higher if you have a penetration through a flat roof. Under no circumstance should you use aluminum or zinc coated (galvanized) pipe for vent. Depending on surrounding structures, use only black or stainless steel connectors and UL listed insulated (triple wall or solid pack) chimney systems. Jerry rigged insulation in your chimney is a quick way to disaster. And, just out of curiosity, what does your boss do that makes him willing to accept the responsibility for your damaged house or lost loved one by "approving" the unit? Amazing.