Josef Irons

1st Anyone reading this thread ask yourself this question: Do I want to spend any money? No, then learn to make a working rocket stove. Its worth every penny. Watch out! RMH proponents are now trying to make money off this "ok" option. So be weary.

Everyone else spend the money on any of the better alternatives out there. I have always just asked for good testing with some science, We augmented the rocket stove to every internet guru's specs and found no real change except burn right or bad burn.

So here is the truth i didn't want to offend my fellow permies with until now:


If you are burning and it sounds like a low rocket sound you got it.

No smoke is coming out the exhaust you got it.

High heat in fire box low heat in exhaust you got it.

The thermal mass absorbs all you heat and you are happy with that you got it. No guru needed.

Take a look at the thermal images provided and decide for yourself. BTUs (heat) are going through my rocket stove system, Heat is going into the thermal mass, little heat is exiting the exhaust and i was impressed but not warm.
BTUs (heat) are going through my Wood stove, Heat is going into the air, heat is exiting the exhaust i was not impressed but I was warm.

I am sorry we have demolished the rocket stove. It took up to much space but wasn't much value in our operation. The simple diagram above shows that the air intake is from outside but the barrel was inside. I know its hard to see but the lines on the sides represent the greenhouse enclosure. Many people don't understand that if your intake air is from inside the greenhouse the air that replaces that intake air will be outside air temp say 35 degrees unless your exhaust enters the greenhouse (which is really dangerous). Ultimately your stove should not make a negative non pressurized greenhouse.

If anyone has a real science based article that discusses rocket mass vs other systems please let me know. From what I see and experience an old fashioned buck stove with a tall exhaust pipe inside the greenhouse seems to do much better that the RMH.

I have ultimately found that a wood fire hydronic system is the best for me. I like the simplicity of the wood fired boiler paired with the versatility of water heat storage and delivery. I state that solar water pump systems are not low tech, cheap, or easy. Water mass systems in greenhouse just work better. I also like having a way to use my well water for cooling and heat storage. A greenhouse that is 75 degrees during the day can store a lot in water to release on a 35 degree night and that is all I need.
Unfortunately I am in the process of a rebuild and I hope the new system cost will have an good return on investment. I am hoping to use DC solar pumps and aquaculture combined in my thermal mass. I should have some pictures of that by Spring meanwhile here is a simple diagram without the wood fired boiler and PV solar pumps.

I have been playing with shut offs on both the feeder(a washtub) and on the air intake(an old damper). Surprisingly the grate never gets plugged. As the ash burns it gets smaller and falls through. Eventually it would plug but it is easy to rake it clear with a hoe when you load the feed tube. You all are right the diagram is not to scale and the outside air will infiltrate the system after the fire dies.

Based on this input I am going to take it apart and redesign with full thermal mass. After that I will burn for 5 hrs and retake a thermal image. I know I can get 500 degrees in 5hrs. We then can see how much heat is absorbed into the mass. Then I will take pictures every hour to show how slowly the heat dissipates into my WV clay earth.

Installing this into the 2000 dollar sollex greenhouse is nerve racking. Move over chickens here comes a rocket stove!

Yeah it is about 3x taller. I flow air through my grate so i don't need the burn chamber to be designed like other RMHs. I would like the riser be as tall as humanly possible, but i was lazy. Ideally Dry Wood is stored outside under a shed roof so that we don't have to open the greenhouse doors to feed the stove. I don't see any wood ash where we have heavy condensate. It is dry everywhere in the fire chamber and all the way untill the air begins to condensate in the ducts under the thermal mass. I put drains everywhere! I now have to make a small roof to protect the fire chamber from snow/rain though.

I would like to throw out there that a regular buck stove could give you similar if not better results if it were design right. although i chose the rocket stove because i could make it for free, others might have the money to spend on a better system.

allen lumley wrote:- i'm a little surprised that the Rocket stove did that well not having a chance to run on prewarmed room air, but you at least proved that some one could go away/come back to a cold house and the stove would still light, can you report on your lighting technique ?

This rocket stove is for a greenhouse. Because of efficiency reasons the rocket stove will burn outside air. Burning inside air and exhausting it causes cold outside air to come in to replace the exhausted air.

Lighting: I make a small pile of DRY wood varying in size from minute twigs to 1/2 inch splinters about the size of the fire box(kindling). I fill the bottom of the fire box with DRY crumpled paper and cardboard. Light the paper, wait till it really catches then blow hard toward the J tube. After the flames steadily head that direction, I drop a pile of mixed size kindling in the chamber and away it goes. The colder the outside air the faster the rocket drafts if it is built right. The draft is better because the difference between the barrel inside temp and outside temp is greater (rapid heat dissipation).

This is my lessons learned drawing:

I am sorry the temperature readings are in Fahrenheit. The detailed reports are PDF files as soon as i can get them to upload i will. The small pictures are hard to interpret.

The short burn tests:

Rocket stove: 1/2 pound oak log split into 8 parts burned in 25 minutes. Picture taken at 30 minutes. Little or no thermal mass stove exhaust designed to fit into picture to show exhaust heat
Barrel was tuned to a light rocket sound with no smoke in exhaust. exhaust temperature averaged 80 degrees F. Outside air temp 38 degrees F (stove is outisde)

Buck stove: 1/2 pound oak log split into 8 parts burned over 45 minutes. Picture taken at 30 minutes. After ignition, dampers tuned till the exhaust was around 80 degrees. very little smoke leaving exhaust. auto blower disabled to minimize heat leaving metal shell of stove. Outside air temp 38 degrees F (stove is inside 62 degrees F)


It is hard to compare the two images. It looks like the Buck stove got hotter in the flu and the rocket stove is really hot in the burn chamber and dissapates that heat to the large barrel fairly evenly in a short burn.
Anyone have any ideas? I can keep trying to get better images of longer burns if it could help.

Is anyone doing detailed testing of RMHs? I think that if the data was collected and shared supporting RMHs many more people would jump into the innovation cycle. The cycle should be performance and user based. Many thanks to many people for uploading videos of rocket stoves designs, problems, and re-designes.
Here is an infrared of a short burn test of my Proto RMH.