Great build, I cut my tank in half at the bottom, I like your idea better. I use a sliding tray to start the draft and it also works to clean out the little ash that collects.
I ignorantly built my stoves with incoming air adjustment for controlling the burn rate, like PainterD has mentioned. Then I read "Designing Improved Wood Burning Heating Stoves" by Dr. Mark Bryden, Dean Still, Damon Ogle, and Nordica MacCarty on the Rocket Woodstove Forum. What an education!! It's definitely a must read for anyone playing with any type wood stove. Their recommendations for introducing incoming air to achieve more complete combustion are as follows: "Warming and increasing the velocity of the cold air entering the fire- Air is warmed as it passes through a small opening into the combustion chamber. For systems without a fan, make enough small holes under the door into the combustion chamber so the holes have as much cross-sectional area as the chimney exiting the stove. Position the holes so that primary air is sucked into the coals and up into the combusting wood. Do not allow the user to block the holes reducing primary air. Blocking the necessary amount of air will create pollution. *The* *rate* *of* *burn* *in* *a* *heating* *stove* *should* *be* *determined* *by* *the* *amount* *of* *fuel* *in* *the* *combustion* *chamber*, *not* *by* *shutting* *off* *air* *to* *the* *fire*." Of course if one doesn't care about creating a cleaner burning fire then throttling down the air will certainly throttle down the fire.
comment ; put your air entry in the outside of the pellet supply and try to embed your exhaust [not radially 90 degrees from center] but on the wall like a vacuum cleaner drum. this will promote swirl along the wall and boundary layer adhesion will keep the hot gasses in contact with the chamber wall extracting more heat. also the outside air should be piped in to your fire box to stop parasitic air loss from the combustion thus removing you hard fought for hot air from the room. most other users who claim toroidal burning at the top, do stop the collector or riser pipe about 1.5 to 3 inches. generally this gap promotes a super rotating toroidal gas mass. this is the place you would engineer secondary outside make up air to promote complete combustion of all consumable gas and particulate matter, leaving only fly ash.
You will find eventually the steel riser with start to chip little pieces off inside and then start to warp if you run 600 degrees or more. I found out after I built my 4" system. I'm making my next riser out of refractory cement and perlite and going with a 6" instead of 4" to make it burn a little hotter (I can always turn it down with the air controls) Good luck with your build!
Randy Barstad Yes and no. If I do nothing before I light it, then I can have issues with back draft. But I usually cheat. :-) While I'm dumping the previous days ashes, turning on the radio, etc. I turn on a heat gun on high and shove it in there, pre-heating the air in the tank a bit and creating some flow out the chimney before I get started. It doesn't take much.
Painter D, that's my next summers project to make this same thing, basically, out of fire brick and cement. The only steel parts will be the pellet feeder and tray.
If you are using 3" tubing then the stack inside the bell can go as close as 1 1/2".The one I made is similar to yours. I made one out of a large ammo can and 4" square turning. The stack is 2" from the inside of the top. I maxed out my temperature Guage.
It seems like the ashes will flow in the direction of the sidedraft, so a chute down just past the fire grate with a little door on the bottom comes to mind. Another thought would be two side doors swinging on a top pin and a push-through clean-out. It is well on the way.
clear cool exhaust = success. What is your shutdown procedure? just let the fuel burn out? do you get backdraft in the final embers? at what point to you close the intakes to prevent smoke in the shop? (have I pelted you with enough questions? ;-)
How many lbs of pellets will fit in the hopper at one time? How many square feet is this stove able to heat without added biomass on a day that is 32F or below?
Mine is similar to yours, except mine is 4" square tubing instead. Mine will burn 600 degrees, no problem. My next step is to wrap the tank with this sheet metal, 2" away from the tank all around it and use a squirrel cage fan to blow the heat out the top of the stove into my heat ducts to heat the house (eventually) At 600 degrees, it should be no problem heating my home and I will probably have to turn the air intake down to control the heat output. My burn-pot for the pellets is 3" X 4" and burns much like yours. My next step is to see how long a 40 lb. bag of pellets lasts, then I can calculate the cost of using my rocket stove vs my wood furnace (which I also built) Good luck with yours!!
Painter D , Pellets I buy come to about $3/lb. It can become expensive to heat with pellets in a rocket stove! Burning a log in the regular stove is considerably more thrifty. Even at $100/cord of wood you pay 0.64$/cubic ft of dried wood. Adding another 36 cents per cubic ft for transportation, It's still cheaper to buy a cord of wood than an equivalent weight of wood pellets.
nice build. I like the pellet feeding system. I am building a stove now to heat the water in my aquaponics greenhouse. If you have a chance check out and let me know what you think. thanks, Von
you can always put the reserve feul on the side ,fill the basket treu a tube ,have a look at zerrofosilfeul's channel for inspiration ;-) stay hot and burn savely
Kind of, maybe. The Wiseway is a little different but similar. The Wiseway uses a really neat draft system and also has kind of a second burn chamber that catches the smoldering pellets that fall through the first grate. The Wiseway is pretty slick and if I had a couple grand laying around, I'd probably buy one.
Randy Barstad There's an outer tube around the bottom half of the stack. The insulation is about 1" thick and in between the tube and the stack. I don't get a lot of fly ash in the tank. The stack actually extends about 4" below the place where the burn chamber enters it and there is a door on the bottom of the stack. I get a bit in there and clean it about every 12-15 hours of burn.
I did a little more tweaking with the intake and the burner basket and am now getting up to 650 on the top of the tank. Still a little more work to do as after an hour or so I'm getting some plugging up of the ash drop and that is effecting the pellet feeding.
Feeding the basket of pellets needs attendance every so many minutes. This increases fuel consumption and subsequently heat production. Placement of the lower level of pellet basket just below the top edge of the opening into the firing chamber would reduce the amount of pellets consumed per hour and still give off a comfortable level of heat production. Otherwise, somebody has to check the amount of pellets in the basket frequently to avoid restarting the stove when the fire goes out!
nice build. I like the pellet feeding system. I am building a stove now to heat the water in my aquaponics greenhouse. If you have a chance check out and let me know what you think. thanks, Von
Edgar Harris The pellets are sold here for people using standard pellet burning stoves. I don't know of any small, manual pellet making machines, but I have built a manual press for making my own bio-logs and sticks. I've not had a chance to make any yet or burn them to test them. My press is based off one I found here, though mine is made of steel: leehite.org/ewb_project.htm
