Yes, I finally built a small rocket stove. I know, it's ghetto and has many flaws, but it still works!
I wanted my first experiment with this to be on the cheap, so I just bought a 4" galvanized steel duct T, a cap, and a 5' straight section. I capped the bottom of the T, cut off about 1' off the straight section to fashion both an 'extender' for the side of the T and a tray to hold the wood, and slapped it all together. Nothing is very secure, but I wanted it that way for now because I wanted something light and easily movable. I placed the whole setup inside my chiminea in order to stabilize the chimney portion of the rocket stove.
Attachment 102297
Attachment 102298
I gave it a test run last night, and I was shocked at how well it worked. I used pieces of lumber that I've scavenged from nearby construction sites (see my "400 lb. of free firewood" thread in the "Disaster Preparedness" section) and cut down to about 1"x1"x8" pieces. It's pine and some fir, so it burns fast and requires fairly constant tending, but it burns hot. The backside of the combustion chamber glowed red-orange hot, so my guess is it reached about 1,000F.
Attachment 102299
You can't see it well in this picture, but it's definitely yielding a good secondary burn. It's easier to see at night. The flames from the secondary burn came out the top of the 4' chimney (surprised me) were unlike any other flame I've ever seen, very soft and 'slow'.
I made some notches at the top to let me set a pot on top for cooking. It took a pint of water about 6 minutes to boil, which isn't fantastic for rocket stoves, but considering how little fuel it took, I was pretty happy. That's about as fast as my propane stove on medium-high. I could have had it hotter too.
Compared to my chiminea, the amount of wood it will take to cook food is ridiculously small. I would estimate that we could prepare enough rice for three people with about 1 lb. of wood. Considering that I now have close to 500 lb. of free firewood and more coming in all the time, I think that's pretty awesome. And of course, you can always burn twigs and such.
Now before anyone starts ripping on me, I've already researched it, and the zinc coating on galvanized steel is not a health hazard at the temperatures where this stove will be operating (http://ift.tt/1g7L0MA). For my initial burns, it's been outside on a couple of windy days anyway, just to be extra safe.
And yes, I know that I would be more 'efficient' with insulating the burn chamber, but I wanted to do a small scale test first. I might place the whole stove in a metal trash can and fill it with perlite or even just sand. But right now, it's very lightweight and mobile.
Besides being able to cook with little fuel, this was also my first step in a closely related project: an indoor rocket heater. By bringing the whole thing inside and venting the chimney out a window, I could easily heat my 400 sq. ft. living room in the winter. I've seen a couple of similar instances of this already on the web. I would obviously want everything to fit much tighter, and I would definitely want a 'J' shaped combustion chamber rather than just an 'L'. That way, the wood would drop down into the combustion chamber rather than needing to be constantly pushed as it does now. For the ventilation tube, I would run it through a piece of wood made to fit the window opening and wrap the tube where it meets the wood with either fiberglass insulation or just crumpled aluminum foil.
I know this would be less efficient than a rocket mass heater, but I would only be using it for emergency purposes as a tertiary backup to my natural gas fireplace and my propane heater. As hot as the combustion chamber and chimney get with this, I would think that would supply plenty of heat for a mid-sized, well insulated space.
And of course, if I did this, I would only bring it inside after I had burned it very hot and thoroughly outside, and I would definitely keep a carbon monoxide detector going nearby the whole time too. I know that it would represent a fire and burn hazard, but again, this would be only a last-ditch effort to keep our living area warm if we couldn't go elsewhere.
Thoughts?
I wanted my first experiment with this to be on the cheap, so I just bought a 4" galvanized steel duct T, a cap, and a 5' straight section. I capped the bottom of the T, cut off about 1' off the straight section to fashion both an 'extender' for the side of the T and a tray to hold the wood, and slapped it all together. Nothing is very secure, but I wanted it that way for now because I wanted something light and easily movable. I placed the whole setup inside my chiminea in order to stabilize the chimney portion of the rocket stove.
Attachment 102297
Attachment 102298
I gave it a test run last night, and I was shocked at how well it worked. I used pieces of lumber that I've scavenged from nearby construction sites (see my "400 lb. of free firewood" thread in the "Disaster Preparedness" section) and cut down to about 1"x1"x8" pieces. It's pine and some fir, so it burns fast and requires fairly constant tending, but it burns hot. The backside of the combustion chamber glowed red-orange hot, so my guess is it reached about 1,000F.
Attachment 102299
You can't see it well in this picture, but it's definitely yielding a good secondary burn. It's easier to see at night. The flames from the secondary burn came out the top of the 4' chimney (surprised me) were unlike any other flame I've ever seen, very soft and 'slow'.
I made some notches at the top to let me set a pot on top for cooking. It took a pint of water about 6 minutes to boil, which isn't fantastic for rocket stoves, but considering how little fuel it took, I was pretty happy. That's about as fast as my propane stove on medium-high. I could have had it hotter too.
Compared to my chiminea, the amount of wood it will take to cook food is ridiculously small. I would estimate that we could prepare enough rice for three people with about 1 lb. of wood. Considering that I now have close to 500 lb. of free firewood and more coming in all the time, I think that's pretty awesome. And of course, you can always burn twigs and such.
Now before anyone starts ripping on me, I've already researched it, and the zinc coating on galvanized steel is not a health hazard at the temperatures where this stove will be operating (http://ift.tt/1g7L0MA). For my initial burns, it's been outside on a couple of windy days anyway, just to be extra safe.
And yes, I know that I would be more 'efficient' with insulating the burn chamber, but I wanted to do a small scale test first. I might place the whole stove in a metal trash can and fill it with perlite or even just sand. But right now, it's very lightweight and mobile.
Besides being able to cook with little fuel, this was also my first step in a closely related project: an indoor rocket heater. By bringing the whole thing inside and venting the chimney out a window, I could easily heat my 400 sq. ft. living room in the winter. I've seen a couple of similar instances of this already on the web. I would obviously want everything to fit much tighter, and I would definitely want a 'J' shaped combustion chamber rather than just an 'L'. That way, the wood would drop down into the combustion chamber rather than needing to be constantly pushed as it does now. For the ventilation tube, I would run it through a piece of wood made to fit the window opening and wrap the tube where it meets the wood with either fiberglass insulation or just crumpled aluminum foil.
I know this would be less efficient than a rocket mass heater, but I would only be using it for emergency purposes as a tertiary backup to my natural gas fireplace and my propane heater. As hot as the combustion chamber and chimney get with this, I would think that would supply plenty of heat for a mid-sized, well insulated space.
And of course, if I did this, I would only bring it inside after I had burned it very hot and thoroughly outside, and I would definitely keep a carbon monoxide detector going nearby the whole time too. I know that it would represent a fire and burn hazard, but again, this would be only a last-ditch effort to keep our living area warm if we couldn't go elsewhere.
Thoughts?
