Lighting a Rocket Mass Heater 

So much that I like about your greenhouse idea. I think it probably needs some more refinements, but using cattle fence to make a hoop house, and just covering it with greenhouse poly is pretty elegant and dirt cheap. As others have said, you probably don't want to use galvanized components. You also might want more length of pipe buried, to improve the exchange of heat. You've got the perfect setup to make mods any time you want. Nice.

I like the idea of a rocket mass heater in a green/grow house! With the gravel it seems like a much quicker build than actual cob! Thanks for posting about your build. I like the smallness of it! Great idea! Thanks!

If you want longer heat you should cover the metal barrel with bricks or earth and use it as heat mass. The barrel is for instant heat but you probably dont want that much instant heat.

Nice work! I built one in my house and these things are AWESOME! You say your dimensions are 1:2:4:6 (opening width, assuming square:wood feed:burn tunnel:heat riser). My dimensions are taken from Erica and Ernie's famous book. I'm using an 8" system (8" diameter ducting, CSA of 50.26 In^2). The wood feed CSA is around 7"x7.5" (52.5 in^2, to match). The wood feed is 16" deep, the burn tunnel is 24" long, and the heat riser is 48" tall. So to get precise, my ratios are 7.25:16:24:48, or 1 : 2.2 : 3.3 : 6.6. My chimney is about 14 feet tall. It drafts without even a fire. Any smoke at startup just gets sucked down to be burned as fuel. I made it out of red clay brick and will fill it with pebbles. It has no mass right now and still keeps my house warm all day after about 1 hour of burning about 10 sticks the smaller than your wrist.

thanks for making and documenting! obviously, replace the trash can with a burned off 55 gal steel drum, and replace ducting with matching pipe csa to the 5" firebrick J tube and it may work better. maybe nonflamable materials under the intake too :) and put the chimney inside the greenhouse to use the heat from it too and avoid cold plugs a bit more

Double insulate the hoop-house will make a significant improvement.

You could also use it to heat a barrel of water as the thermal mass

Something's wrong with this design. It's not safe. The galvanized can itself is not durable and not safe. The opening to the galvanized can (the burning chamber) should form a J-shape in order for the fire to have a draft and to direct the flame to go only one direction. For safety precautions, a pipe or tube should be added for oxygen intake from the outside. There is not enough mass on the burning chamber to keep the heat longer. If the flame in the chamber burns over a thousand degrees, the heat loses too fast when there is not enough mass to retain the heat. The galvanized can may melt anyway. There is not enough draft and the temperature is not hot enough. A good rocket heater may radiate heat for 24-36 hours.

Boy they sure roasted the galvanized trash can! Most of the keyboard warriors have no idea what it’s like to be cold because they’re living in moms basement with warm heat pipes around. They have no problem criticizing others who are doing a lot with very little. I believe the only difference for you is the need to trim the amount of wood used and the output. Sticking with the formula for the ratios you said 1,2,4,6 so it really depends on how small or large you are willing to cut the wood. If you wanted to cut the wood to 3” split wood x 1 foot your looking at a 1 foot opening and a two foot drop which would eliminate the need to chop up the wood to very small pieces. The burn tunnel would be 4x2 or eight feet? Then there’s no pre-made bell big enough to cover the distance of 12 feet 6x2 would you gain any benefit from making the stove larger or is there a method of understanding what the output will be if the design is in keeping with the parameters? Once you achieve the temperature requirements for efficiency in burning all the gasses made by burning wood is there something that can predict your performance?

How come I’ve never known about this Channel sir 7:55 that fire immediately starts drafting. Perfect design. 10:02 what’s the temp of the thermal fan to start spinning?

I don't know who you have been watching or reading but damn you got a lot to learn about rocket mass heaters.

I wonder what the temperature of the gravel, (mass) is? And How long it holds the heat? What a wonderful heat mat substitute for starting seeds! I love this whole idea

Dit you have problems with cold starting it? If so, place you shimney next to the bell (trachcan). this way it heats up better and pulls out the coolt off gasse better.

PLEASE ADD a hopper to auto feed the fire after started.

AHH...good ole galvanized can, yup lets heat that up to help release harmful poisinous gasses....not a hot idea

What if you use sand or sand & stone? And does it matter what kind of stone?

Да такими спичками можно топить вечно😂

I'm surprised no one has commented on the galvanized trashcan. Heating galvanized metal can produce dangerous offgassing. I'm sure your past that by now.

Good concept..but the galvanized to radiate poison gas to plants is just asking to cause tragedy.

Why you get smoke coming out when you lite the stove and why it also happens when you remove the top brick to put more wood in .Is because the opening is to big.The other way to address this is to make the chimney higher this woud give you more draw in the stove

Lets heat up galvanized metal that's smart.

rather you than me toxic air toxic food nice.

This is enough heater for a 2,000 square foot house, in a 150 square foot greenhouse.

Plus your going to have to feed it all the time > Are you going to live in it? To keep it fed? Mine large US cast iron stove is easy to make a rocket stove. all i do is pull out the ash tray a little bit BOY does she sound like a rocket. Plus i don't have to feed it all the time.. Sorry that sucks 👎👎

Heating in a galvanized metal creates a poison Zink gas.

You don’t have a secondary burn chamber without preheated secondary air. Fit a J-Tube shaped pipe inside the J-tube that sticks out of the burn chamber and it ends one or two inches from the top of your riser and your bell temp will double if not burn through that cheap trash can. Have to have secondary super heated fresh air for secondary burn, all that bell does right now is release immediate heat that it makes now.

Aside from the negative comments about the galvanized can (which you should replace). I think you'd benefit by pouring sand into your stone mass. Fill in the air spaces. It will increase your mass and give you more battery for your heat. Some buckets of water and plants on top of the mass will help too.

Good Start, I wonder... how much more heat could be sequestered by surrounding it with masonry?

Hallo erg mooi gedaan. Wij gaan er ook een. Maken mvg Jan

You've already been blasted for the zinc/galvanizing, so I'll skip that. What I would say is that in my experience, for good combustion and draft, you want a 1:3 or even 1:4 ratio between horizontal and vertical of your J-tube. I cannot stress the importance of the horizontal part of the tube, it is the combustion chamber. It depends on draft speed, of course, but you need a long enough horizontal section to break down the fuel and burn the gasses that result. If set up properly, the barrel should see no unburned hydrocarbons (smoke). I think yours is just a tad too short. This will result in the barrell sooting up (potential creasote fire). Otherwise, great job

How do you clean ashes from your burn chamber.

How are you going to clean the creosote out of it? BIG MISTAKE