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rocket mass heaters

Chimney hat

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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hello, I have a batch rochet stove self made , though still ugly , it works fine . The problem is that in heavy rain the chimny cleaning door gets moist . I plan on installing a hat , how do you think that whold affect draft? please advise

thomas rubino

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posted 2 months ago

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With the low exhaust stack temperatures, a chimney cap should be used.
I use a simple rain cap on all of mine.

61YH3jPjfwL._UF894-1000_QL80_.jpg

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Benjamin Dinkel

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posted 2 months ago

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Hi Cerbu and welcome to permies!

Congratulations on building a BBR. I would live to see a picture, I'm sure it's not ugly.

A well designed hat should actually not impact draft significantly. The best design probably depends on where the chimney is (on the roof, against a wall) and the prevailing winds.

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Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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is this fine? it is homemade

83eefa9c-4d2f-4f18-91e6-8fd35a82f608.jpg

Benjamin Dinkel

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posted 2 months ago

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Looks fine to me, from what I can see.

You say "batch rocket stove" in your first post.
Is it to cook with or for heating indoors?

What size did you build?

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Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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the stove itself is not regular, I did not build a bench , but in has a wall with heat channels in two rooms , the outer layer is still in work, but it has functioned well 3 years now as is , the inside plans look similar to that, without the v shaped bottom and other dimensions

BrickSidewinder.jpg

Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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Ilive in eastern europe, so I give the dimensions in centimeters , lenght 65 cm , widh 24 cm hight 36 cm , internal chimney(riser) hight 1 m, about 16 cm square section interior, yellow fire briks, cob insulated

Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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https://www.youtube.com/shorts/HoS8JeBlYJM
the bottom side of the cleaning door gets brown from rain , this year I want to cover in briks the exterior

Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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https://www.youtube.com/shorts/Ap5QMpYexm4

f29deee8-317b-4c3a-9cd6-a42560dc82de.jpeg

Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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sorry, now it shows?

after it exits the riser the smoke descends through a large brick channel, then up the twin bell inside the wall, and than out the roof

and the second in the exaust chimney , you can see the sky , it's straight up about 5 meters

wall interior

3.png

John C Daley

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posted 2 months ago

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What does this mean?

Congratulations on building a BBR

But anyway, Having seen the video I think you can improve on the efficiency of the unit/

John Daley Bendigo, Australia The Enemy of progress is the hope of a perfect plan
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Benjamin Dinkel

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posted 2 months ago

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Hi John. BBR is short for batch box rocket, which is what Cerbu said he built.

Would you share your thoughts on how to improve the design (best case without rebuilding) and comment on how you spotted that from the video?

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Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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ty for your replies. yes, please suggest , I am not a professional builder, I just like efficiency and DIY stuff, the complete burn inside the riser and the brick box's barrel-like function ,I think they're awesome

Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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i try to say what i did .
1 fire box, 2 side channel , 3 riser, in front of the riser there's the descending path like in the barrel ,going to the floor level , from where it rises in grey section in the wall , which i posted before,(2 smallish bells in terra cotta ) somewhat a vertical bench, good for mass, radiant heat in two rooms. It is the heart of the house 4 moth a year, giving good heat with mostly scrap wood, I hope the problem with raining inside the chimney goes away adding the cap i made . Ty , good forum

bbr.png

Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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this is my new floor channel, looks ok-ish?

1.jpg

thomas rubino

master rocket scientist

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Location: latitude 47 N.W. montana zone 6A

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posted 2 months ago

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Hi Cerbu;
That looks like it will work.
Is the stub riser built "Peter Berg" style with a hood?

I built that style secondary air tube when I first started, but discovered that the "hood" quickly spalls away.
Now I only use the Matt Walker 6" open pipe design.
Plain steel tubes have a limited lifespan, but the RA253MA risers I sell last forever.

Take a look at my website.
https://dragontechrmh.com/new-lower-prices-on-dragon-technology-quick-change-secondary-air-tubes/

You can copy my quick change design. It uses Schedule 40 steel pipe, with a 2.5" ID for the receiver and a 2.0" ID for the stub riser.

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Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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only a small hood , a little leftover from cutting, I suspect it will burn out
,the material is zinc covered steel , TY for the link

Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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the air gap for the channel is under the main door in my case , should I make a mini door to close the gap after the fire? do embers still need secondary air ?

IMG_20250705_182310.jpg

thomas rubino

master rocket scientist

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Location: latitude 47 N.W. montana zone 6A

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posted 2 months ago

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It should remain open until you close the primary air.
At that time, you can stand a brick in front of it, or cut a proper-sized piece of ceramic board and close it that way.
Even aluminum foil or a wooden closure would work, as everything is cooling off.

The purpose of shutting off all incoming air is to stop the chimney from drafting your heat up and out.
We want that heat retained in your bricks and not leaving the house.

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Visit me at
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Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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I read mass does not insulate , but IT helps not tot start cold, at one fire a day, what would be a good compromise?

thomas rubino

master rocket scientist

Posts: 6753

Location: latitude 47 N.W. montana zone 6A

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posted 2 months ago

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Hey Cerbu;
I'm not sure what you are asking here.
Mass holds heat, and a warm stove will easily relight if it's warm.
Insulation blocks heat from being stored and allows it to pass through.
Too much insulation and your stove will light quickly, but it will not be much of a masonry heater.
Too much mass and your stove will be hard to start cold.

Insulation is used around your core to keep it hot.
Insulation is used in the riser to allow quick starts.
In other spots, insulation is used to protect wood from overheating.

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
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Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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thank you , I mean at one fire per day would it help to add more mass and a bigger fire, instead of using two fires?

thomas rubino

master rocket scientist

Posts: 6753

Location: latitude 47 N.W. montana zone 6A

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posted 2 months ago

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This past fall, I burned Shorty just once a day until real winter set in. (Most days, the windows were cracked open to cool it off inside.)
At that time, I lit a second fire in the evening to recharge the mass for overnight use.
When we experience a week or two of below-zero temperatures,-17C -25C, I would add a few new pieces to extend the burn time.
And then as soon as it coals out I shut the intake to stop my chimney from drafting the heat.

Heating with bricks is absolutely the very best way to keep your home toasty warm throughout the whole house!
Once you go brick, you will never go back!

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
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Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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here the winters got very mild , and two fires are most of the time too much , I will try to add more bricks , it will help in theory taper the curve i get it, TY. For overall efficiency one would use one or two fires?

thomas rubino

master rocket scientist

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Location: latitude 47 N.W. montana zone 6A

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posted 2 months ago

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I think that depends on your home and how well it holds heat.
There is a learning curve when heating with bricks, and chances are you will heat it up more than you intended.

I suspect that one fire in the evening will be plenty.
But the option of having a smaller fire twice a day might be more to your liking.

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
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Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 months ago

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it holds heat pretty well, outside has 4-5 inch polystyrene, inside cobb or cellular concrete walls, the celling is wood, rockwool and cob

Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 1 month ago

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https://www.youtube.com/shorts/CoAFhuvXPAQ I bought another type of hat , it lines with the wind , but looks fragile , seems ok?

thomas rubino

master rocket scientist

Posts: 6753

Location: latitude 47 N.W. montana zone 6A

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posted 1 month ago

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It looks like that will work just fine.
It appears to be made from stainless steel, and as long as it has good sealed bearings, it should do the job for years.

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 1 month ago

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yes it says stainless steel, but there is no bearing , good idea , I look for to add o couple

Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 1 month ago

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hello, I plan to build a shorty core , what effects do you speculate if the air enters through gaps in the briks near the door? I can't weld

idea.png

thomas rubino

master rocket scientist

Posts: 6753

Location: latitude 47 N.W. montana zone 6A

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posted 1 month ago

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Hi Cerbu;
Your picture does not look to be a Shorty core.
Changing the air intake will not work correctly.
Shorty core has a detailed air intake system; it should not be modified.

You should locate someone in your area who can weld.
Shorty has no internal metal, but her door design is very critical to her proper operation.
Here is my thread on building an airframe.

https://permies.com/t/254292/Airframe-Construction-Shorty-Core

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 1 month ago

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it is shorty as a sidewinder, I only added the proposed air cracks, it is not my drawing . I do not want a frame, just bricks, well, guess I'll find a welder for the door then ?

Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 1 month ago

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by frame if you mean the door only? i can do that , but someone else to weld

thomas rubino

master rocket scientist

Posts: 6753

Location: latitude 47 N.W. montana zone 6A

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posted 1 month ago

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As you can see in my thread, the door and air intake are combined.
The door itself is just a door with whatever size ceramic glass you like.
The critical part of a Shorty core is where the intake enters the firebox.

For all your Montana Masonry Heater parts (also known as) Rocket Mass heater parts.
Visit me at
dragontechrmh.com Once you go brick you will never go back!

Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 1 month ago

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TY, I saved the pictures , I was confusing terms , thought you meant the steel holding the bricks in the core , yes , I can do the cuts and bends in the air frame

Scott Weinberg

Posts: 342

Location: North East Iowa, USA

posted 1 month ago

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Cerbu Ulea wrote:it is shorty as a sidewinder, I only added the proposed air cracks, it is not my drawing . I do not want a frame, just bricks, well, guess I'll find a welder for the door then ?

Perhaps I am missing something, you say "it is a shorty" But you don't show the Exhaust from the fire box "like a shorty" and you propose a change to the basic front door frame/inlet of air, though now it seems like your willing to do the door cuts and perhaps have someone weld. So that is better. So am not sure, how it could still be a shorty.

Knowing Peter has tried every conceivable shape and brick set up. to get it just right. or perhaps better said, A great working and scalable unit, I fail to understand why so many try to create a better mouse trap, in this case, I guess it doesn't hurt to try as long one knows the pitfall is likely.

So with the tension frame so easy to build and actually makes the whole front door frame work so much better, I would be curious as why NOT to make it. Though granted much harder as a side winder. Speaking strictly from a industrial designer aspect.

I don't mean to be discouraging as these stoves are great. But just want to keep folks going down a experimental path to disappointment.

https://permies.com/t/241976/Batch-Rocket-single-bell-build

Cerbu Ulea

Posts: 73

Location: Suceava, Romania

posted 2 weeks ago

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sorry Scott, I missed this post , I will make the normal frame, will buy a welding machine and try

Scott Weinberg

Posts: 342

Location: North East Iowa, USA

posted 2 weeks ago

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Cerbu Ulea wrote:sorry Scott, I missed this post , I will make the normal frame, will buy a welding machine and try

Just a heads up, and having no idea, I will suggest that "buying a welding machine" could be a great cost for a little use, But you may be able to get exactly what you want, if you can draw out and explain to a "welder/fabricator" in good order. There are these people all over the world, perhaps there is someone close to you. They often have on the rack, exactly the metal you may require.

Buying a welder, entails so much more and unless you have projects forever down the road, it may not be feasible. These include, metal cutting tools, welding helmet, welding table maybe, The list goes on. Might I suggest, that getting something to do great cuts on the stone, will cost less and get used more and provide years of use. Cutting bricks to fit the job, seems to work better than making a job to fit the bricks.

Best of success!

https://permies.com/t/241976/Batch-Rocket-single-bell-build

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