Walker Tiny Cook Stove Reflection and Question

Hello Everyone!

After years of waiting and wanting, I built my first thermal mass rocket stove this last fall based on Matt Walker's Tiny Cook Stove Design (https://walkerstoves.com/tiny-masonry-cook-stove-plans.html)

Unfortunately, I don't seem to be getting the kind of heat output I was expecting since I am still burning about as  much wood as I did with my old stove, a large cast-iron box with a blower mount that knocked a good deal of heat around.

This new stove provides gentler, more consistent heat but I am literally constantly burning it. So its coming out to about the same amount of wood.

I'm not too pleased about this fact because I mostly built my stove to improve the efficiency of my wood burning. I had hoped to reduce my burning from 4 cords to like 1.5 but it won't happen with this design.

So what happened and what can I do?

first of all, I think the problem with this design is that it relies on a 'riserless core', i.e. no barrel heat riser. Since the barrel creates an omnidirectional heat flow and helps to suck up air in, through, and up the burn box, not having the burn barrel means I 'm probably not getting the kind of temperatures I need.

Secondly, I am  thinking that the bench I made could be limiting heat capture, however, I am not sure. Walker's design relies on the use of a bell bench rather than the j-tube design. My bench is built out of red bricks, man made stone counter tops, and fireclay/ sand combination. The flue of my stove reads about 90-100 degrees which is great considering my firebox, at that same time, can be 1500+ degrees ( the max of what my heat gun can register). I think this means I am getting optimal heat capture but maybe not optimal heat activation and distribution without the barrel...

Hence,  I am thinking of just remaking my stove using the barrel design but keeping the bench because I like its aesthetic and I don't want to scrap entirely all my hard work (my bench is fairly large). What are your thoughts? I'll upload some pictures soon....

Thanks!

-Jeff

Hi Jeff,
Have you spoke to Matt Walker about your findings?
He is very helpful and provides a lot of very good feedback in a short time.
I know I would personally like to know his response if you both would be willing to share.

Hey jeff
Pictures would be great when you can get them. I am interested in your bench

Some info which I believe most would find helpful.
Where do you roughly live?
How big is the space you are heating?

What is your burn time like? You say constantly. So you light up at 8am and than the stove goes until 10pm? If so I would say you need a bigger stove! Our fisher stove in the big house takes all day to heat the house. Than rinse and repeat the next day

My walker stove heats up a 200SQft tiny house which is very well insulated. Right now I start the fire with a full firebox. this included paper/kindling and 2x2s run the stove with the primary air open for about 10 minutes. When I see the secondary burn start and the "cooktop" get in excess of 600*F I close the primary air. Than about 1 hour later I fill the box up and than call it good until the next evening. Again a small space. I also block the secondary air when I go to bed so air isn't circulating through the mass/bell overnight.

One thing I will say is that I would love to run the stove full blast. However all of the heat will be released from the cooktop with little going into the brick bell. And than my tiny house turns into a sauna! Nice but hard to sleep with.
My thread https://permies.com/t/tiny-house-masonry-heater

Hi Jeff;
Bummer the tiny cook stove is not performing as well as you would like.
Are you using a glass cooktop?   As Jordan mentioned a tremendous amount of heat will fill the room but your mass will get shortchanged.
You might try laying insulation (super wool) over the cooktop to send more heat into your bell and see if that improves things.

If you are still unhappy, then you can switch to a 6" extended-length batch box.
The vertical riser will start to draw quickly.
Your option is to use a barrel (Quick radiant heat) or build a brick bell to go with your brick bench.
The brick bell would take longer to heat but in return, it will hold that heat longer than a barrel.
The firebox on a 6" batch is quite a bit larger than the cook stove firebox.
Once warmed up you can expect 2-3 hrs of screaming hot fire and coals.
Depending on your house and climate you may burn several fires in a day but you will not need to be burning back-to-back fires all day.



How is your home designed?  
What size is it?

Gerry Parent wrote:Hi Jeff,
Have you spoke to Matt Walker about your findings?
He is very helpful and provides a lot of very good feedback in a short time.
I know I would personally like to know his response if you both would be willing to share.

Hi there! Yes, I spoke with Matt about improving the heat and we decided to set it up so that the chimney was drawing in heat from the stove at the furthest end of the bench (rather than in a port which is adjacent to the downdraft chamber).

When I spoke to him last about my results, he said that I was achieving about what one would expect from his Tiny Stove and that I would maybe need to build a secondary or bigger stove to accommodate my needs.

I feel that Matt has been very helpful throughout this process, answering about a million questions I asked.

jordan barton wrote:Hey jeff
Pictures would be great when you can get them. I am interested in your bench

Some info which I believe most would find helpful.
Where do you roughly live?
How big is the space you are heating?

What is your burn time like? You say constantly. So you light up at 8am and than the stove goes until 10pm? If so I would say you need a bigger stove! Our fisher stove in the big house takes all day to heat the house. Than rinse and repeat the next day

My walker stove heats up a 200SQft tiny house which is very well insulated. Right now I start the fire with a full firebox. this included paper/kindling and 2x2s run the stove with the primary air open for about 10 minutes. When I see the secondary burn start and the "cooktop" get in excess of 600*F I close the primary air. Than about 1 hour later I fill the box up and than call it good until the next evening. Again a small space. I also block the secondary air when I go to bed so air isn't circulating through the mass/bell overnight.

One thing I will say is that I would love to run the stove full blast. However all of the heat will be released from the cooktop with little going into the brick bell. And than my tiny house turns into a sauna! Nice but hard to sleep with.
My thread https://permies.com/t/tiny-house-masonry-heater

Hello and thanks for your response! I live in the northern half of Minnesota. My house is 600 sq feet roughly. It is basically a cabin with a loft and a recently built addition that is being heated (fairly well actually) by the brick bench that extends through a wall and into the room.

I think it is a medium-small sized space. The main living room has a high vaulted ceiling that is about 22 feet off the ground.

Right now, I am burning night and day. I burn hard all day to keep the temps inside my house in the 68-71 range and then I try to keep the fire going at night to make sure the house temp doesn't drop below 60 because once it does it takes hours for it to get warmer. My bricks are usually about 170-220 degrees F.

Here are some pictures for those interested to see what I have done. The bench tops only get to about 90 F so I doubt my appliances (a lamp and a speaker) are at any risk (unfortunately) of combusting.

thomas rubino wrote:Hi Jeff;
Bummer the tiny cook stove is not performing as well as you would like.
Are you using a glass cooktop?   As Jordan mentioned a tremendous amount of heat will fill the room but your mass will get shortchanged.
You might try laying insulation (super wool) over the cooktop to send more heat into your bell and see if that improves things.

If you are still unhappy, then you can switch to a 6" extended-length batch box.
The vertical riser will start to draw quickly.
Your option is to use a barrel (Quick radiant heat) or build a brick bell to go with your brick bench.
The brick bell would take longer to heat but in return, it will hold that heat longer than a barrel.
The firebox on a 6" batch is quite a bit larger than the cook stove firebox.
Once warmed up you can expect 2-3 hrs of screaming hot fire and coals.
Depending on your house and climate you may burn several fires in a day but you will not need to be burning back-to-back fires all day.



How is your home designed?  
What size is it?

Hi! Thanks for your response. Yah, I don't think that I would use superwool to cover the cooktop because a part of my difficulty with the stove is getting it to warm up the house quickly enough for my use in the morning. Hence why I am burning the stove practically all day and as soon as I wake up.

So, I would like to probably use a barrel to make it heat up quicker and achieve omnidirectional heat distribution which (according to the rocket stove video series) is a main benefit of the barrel.

I do like the idea of a larger firebox. Can you elaborate on the 6" J-tube design? It sounds like design described by the Wisners in their rocket mass heater's builder's guide. I'd really like something that hits about 2x as hard for my place so that I can cut my burning down by about 1/2 at least.... Thinking about a world without access to gas for my chainsaw and splitter.

So am I right that the bell bench design is about as effective then as the 6" flue pipe surrounded by earthworks?

Hi Jeff, it is hard to see what your cook top is made from but I assume it is ceramic glass?
What sort of temperature is the cook top reaching?

To be fair, you have quite a large space to heat with a pretty small fire and if Mat says you need a bigger or another heater then that would be pretty conclusive that you do!

You could maybe get more radiant heat from less brick and more glass but it really sounds like you need something with a bigger fire box that can burn more wood.

Hi Jeff;
I'm talking about a 6" batch box stove, not a J-Tube.  
A big difference between the two.  You would not be happy with a 6" J at all.
J-tubes use the same size split-down wood as your walker, which is fed vertically rather than horizontally.
They burn 40-60 minutes before needing reloading.

You will not find any info about batch boxes in the Wisner's book.
Nor do they talk about bell systems.  Neither was well known at the time of publishing.
Peter Berg developed the batch box design.  It uses much larger wood, laid horizontally, and it burns much hotter for 2-3 hrs.
Here is Peter's webpage, where you can read all about them.  https://batchrocket.eu/en/

Fox James wrote:Hi Jeff, it is hard to see what your cook top is made from but I assume it is ceramic glass?
What sort of temperature is the cook top reaching?

To be fair, you have quite a large space to heat with a pretty small fire and if Mat says you need a bigger or another heater then that would be pretty conclusive that you do!

You could maybe get more radiant heat from less brick and more glass but it really sounds like you need something with a bigger fire box that can burn more wood.

Hi! My cook top gets to 900 at best. It is ceramic glass.

Yes, I'm going for a bigger firebox! Next year though. I doubt I could make a new stove in the middle of the winter.

TY for your interest