It's approaching mid December and I'm already sick of hearing my forced air furnace kicking on every 5 minutes! I can see my money going up in smoke!

In my latest attempt to, if not get off the grid, at least be ABLE to, if need be, I just finished my bare bones rocket stove space heater and it works even better than I had hoped! The thing is pretty ugly, but it does exactly what it's designed to do -- produce a lot of great radiant heat and burn wood (or whatever) at near 100% efficiency.

'Ive just done a test run for a couple hours using TWIGS I picked up in the yard (I have about an acre with lots of tall old trees that constantly shed small branches). I really can't stressenough  how cleanly this contraption burns. There is absolutely NO smoke coming out the exhaust vent.  After I pretty it up a little, I'll post pictures of my own, but here's a guy's completed rocket stove that looks almost identical to mine:



If you are curious about the way they work, you can see his video here:

How does a Rocket Stove work? - Construction explained

This is a pretty ugly design, but there are actually some beautiful ones.  Maybe with the money I save this year, I can build this next year!

These things really do kick ass, super clean, very little ash left behind.
But the one in the pic using a 55 gal drum won''t last long, it will actually rust out rather quickly.
Because they heat and cool so quickly, condensation becomes an issue and they rust, then when reheated, it sheds a little metal.. Rinse/repeat till gone.
I'd go to a local sewer pipe company and see if they have some scrap you might have for cheap.

Can't think of what they call the pipe, but it looks like Terracotta, might be the perfect solution, in that it absorbs heat somewhat slowly, it also releases it slowly, alleviating the issue of relighting the stove every 30 minutes.

The innards are  firebrick and the stack is supposed to be within 2 inches of the inside top of the barrel. I need another 9 inches. I'll pick up more fire brick this weekend, plus I have it exhausted out the window. It'll be that way all winter, but I have to at least make it a little more permanent.  I was thinking, originally, of using 8 in chimney liner but I had a few fire bricks from before and just bought more.

I've heard problems with degradation if you use metal pipe for the insides and everybody recommends fire brick which should last forever, so that's what I used. I haven't heard complaints about replacing barrels, but I can see that happening. The top can get 700 degrees, while the base is below 200!  The exhaust measured 140! That barrel works great at capturing the heat.  I used a fan over the top of the barrel to keep it from getting dangerously hot. I think it helps it to run more efficiently too.

What I like about this thing is that it is designed to use twigs you can pick up anywhere rather than expensive logs if you have to buy those.

I talked to a guy at Lowes and I'm hoping to get a good load of sawdust this weekend to try making a sawdust stove (they're really simple) to burn inside the rocket stove.

Quote from: carlb on December 07, 2014, 06:08:24 AM
The innards are  firebrick and the stack is supposed to be within 2 inches of the inside top of the barrel. I need another 9 inches. I'll pick up more fire brick this weekend, plus I have it exhausted out the window. It'll be that way all winter, but I have to at least make it a little more permanent.  I was thinking, originally, of using 8 in chimney liner but I had a few fire bricks from before and just bought more.

I've heard problems with degradation if you use metal pipe for the insides and everybody recommends fire brick which should last forever, so that's what I used. I haven't heard complaints about replacing barrels, but I can see that happening. The top can get 700 degrees, while the base is below 200!  The exhaust measured 140! That barrel works great at capturing the heat.  I used a fan over the top of the barrel to keep it from getting dangerously hot. I think it helps it to run more efficiently too.

What I like about this thing is that it is designed to use twigs you can pick up anywhere rather than expensive logs if you have to buy those.

I talked to a guy at Lowes and I'm hoping to get a good load of sawdust this weekend to try making a sawdust stove (they're really simple) to burn inside the rocket stove.

Glad you posted this, I think I'll put one of these in my shop, because of it's ability to generate heat immediately, and if you aren't staying long, you don't waste wood.

This thing has me excited. But like I said, mine is bare bones. I'm giving up a ton of valuable heat by just exhausting it out the window. The permanent rocket stoves are actually called Rocket Mass Heaters because they run the exhaust duct through a thermal mass such as clay (seems the preferred method), stone, concrete, or water.  The weight seems too much to add to my stick frame house.  I was thinking of using a water tank in the basement. It would only be 4x4x5 feet high (748 gallons). I calculated that that could store enough BTUs to get me through most 24 hour days without needing the furnace.

To do that creates another problem. I have heard others who use the heater to heat their hot water too. They do this using a coil of copper tubing inside the barrel.  I want to store hot water to be released later for heating (thermal storage).

I know NOTHING about boiler systems. Is there a CHEAP and quiet way to pump water between a water tank in the basement up to the heater. Are their special pumps designed to stand up under constant 180 degree hot water?

I want the heater in the living area to take advantage of the great radiant heat, but if it were in the basement and the water storage was above, I could use thermosyphoning (no pumps), but as I'm building it now, I have to find a way to circulate the hot water.

The goal is to run the heater for only a couple hours a day and store the excess heat in a large thermal mass.


Here's a diagram of an efficient Rocket Mass Heater for those who don't understand th concept:

Here's a super-minimalist version of the same principle:

http://www.youtube.com/watch?v=ffldYo4EVCg#t=767

Quote from: carlb on December 07, 2014, 07:08:19 AM
This thing has me excited. But like I said, mine is bare bones. I'm giving up a ton of valuable heat by just exhausting it out the window. The permanent rocket stoves are actually called Rocket Mass Heaters because they run the exhaust duct through a thermal mass such as clay (seems the preferred method), stone, concrete, or water.  The weight seems too much to add to my stick frame house.  I was thinking of using a water tank in the basement. It would only be 4x4x5 feet high (748 gallons). I calculated that that could store enough BTUs to get me through most 24 hour days without needing the furnace.

To do that creates another problem. I have heard others who use the heater to heat their hot water too. They do this using a coil of copper tubing inside the barrel.  I want to store hot water to be released later for heating (thermal storage).

I know NOTHING about boiler systems. Is there a CHEAP and quiet way to pump water between a water tank in the basement up to the heater. Are their special pumps designed to stand up under constant 180 degree hot water?

I want the heater in the living area to take advantage of the great radiant heat, but if it were in the basement and the water storage was above, I could use thermosyphoning (no pumps), but as I'm building it now, I have to find a way to circulate the hot water.

The goal is to run the heater for only a couple hours a day and store the excess heat in a large thermal mass.


Here's a diagram of an efficient Rocket Mass Heater for those who don't understand th concept:

I love this stuff, but for me it comes down to cost vs payback. How long would you have to use it for it to pay for itself and pay dividends?
And yes, they make pumps for every application, but one fitting your requirements probably start around a grand, and it's not something you'd want to skimp on, so figure 3 grand at a minimum, then there's the cost factor of running a pump X amount of hours a day.

Stupid question but what is the ignition source? Does it ignite the first time every time? Are you sure it burns super clean rather than having the ash and smoke being pushed out of the exhaust pipe?

Quote from: Dr. Meh on December 07, 2014, 09:45:08 PM
Stupid question but what is the ignition source? Does it ignite the first time every time? Are you sure it burns super clean rather than having the ash and smoke being pushed out of the exhaust pipe?

Most of the articles and videos I've looked at showed pretty simple ignition procedures, generally a cotton ball or some lint impregnated with Vaseline and lit with a match as an ignitor. Also what I've read is universal claims of "practically no ash," though that hardly seems possible. I note that the cross-section of a rocket stove mass heater shown above features two ash pits. I haven't seen or read anything about those ash pits or how they might be cleaned or emptied.

One video I looked at showed a simple rocket stove in operation, burning sticks and producing heat, and a girl put her face in front of the flue outlet for a considerable period of time. There was no visible smoke, and she claimed that she could smell a smoky smell and feel warmth from the pipe, but it wasn't enough to cause her to recoil.

Quote from: Dr. Meh on December 07, 2014, 09:45:08 PM
Stupid question but what is the ignition source? Does it ignite the first time every time? Are you sure it burns super clean rather than having the ash and smoke being pushed out of the exhaust pipe?

Initially there will be smoke due to the fact the venturi effect has yet to kick in, but once it does, the process begins increasing heat and airflow exponentially.
The process is kind of like pellet stoves that have little ash, with the exception that pellet stoves require the assistance of a fan, where this process does not require any assistance.

What takes place, as the fire gets hotter, it requires more oxygen, more oxygen creates yet more heat which requires more fuel, and the process exponentially feeds upon itself while sucking ashes up and out the flue due to the increase in airflow from feeding on yet more fuel.

I had a stove a few years back I'd had for 30 years, most efficient stove ever, but this efficiency too a toll on it, in that it would get too hot for it's own good.
What happened, was it worked along the same principle, but had way too small of a fuel box, so for it to work efficiently, you'd stoke the box, fire it up and basically it would get so hot, it began to melt/droop, causing it to draw air where it was never intended, though it lasted 30 years.

Point is, it was so efficient, I only had to clean it once a season, unlike the POS Wolfgang stove I replaced it with, where I have to clean it out twice a month or it builds up with ash.