First rocket build.. I think I have a problem.

[rantinraven]

We have been looking into rocket stoves for some time now. We primarily heat with wood now but our pot bellied cast iron stove doesn't do such a great job. It gets really really hot and then when the fire goes out we are back to freezing again. So this year we decided to build our rocket stove. We are building in the basement attaching to a chimney that runs outside of our house, by a 90 degree elbow that is in place already. Here's where our problem has come in. We laid our brick for the heat riser and had planned to attach to a hot water tank that had the insides cut in two, one we planned to use for the burn chamber, the other we planned to use for the heat riser insulation holder. when the brick was laid we thought we did a wonderful job, all was pretty and level and went up with no problems. We gave ourselves a pat on the back and 10 thumbs up from all standing around. After reading posts on the board this morning I realized something is very wrong with our heat riser. It is rectangle and not in a square shape. On the inside it is 6 and 1/2 inches by 4 and 1/2 inches. Is this going to be a huge problem?? All the exhaust pip is 6 inch pipe, and we are piping out about 12-15 feet after the 55 gallon barrel. I have lots of pictures of the work done so far but I am not sure how to put them in a slide show on the site yet. so I guess my question is Are we going to have a problem with air flow with the heat riser being rectangle instead of square? Thank you so much for your time and I look forward to posting pictures here of what we have done. Raven

[canyon]

The area with your rectangle is not much different than the 6" exhaust pipe. I don't see the shape being a problem. Fire it up and see!

[Donkey]

Shape matters little.
Looks like yer riser is slightly larger (about one square inch) than 6" pipe..
Better slightly larger than slightly smaller...
Go for it. It's probably just fine!!

[rantinraven]

Thank You for your imput. I got the stove fired up and actually used it for about 6 hours tonight. I was origionally only going to test fire it but it worked so well that I just kept feeding wood in. I figured I might as well be warm in the basement while mixing cob. (I piped out from the heat riser to the chimney to make sure I was ok with everything) Tomorrow the outside barrels will go on and be filled with insulation and sealed a bit to see If I got everything right. I am still very confused about how this whole things going to work, I understand the theory I just need to "see" it happening. Something interesting to note, (Ill post pictures as soon as I get them off the camera) my firebox is made from teh inside steel chamber of a water heater we had. when we began to fire up the stove we realized that we didnt have anything to cover the fire box with yet, kinda oversight on our parts. Anyway we used the "top" of the water heater that still had a pipe attached to the inside of it. I don't understand the workings of a hotwater heater so I cant tell you what that pipe is for. Well upon tring to light the stove and get it started I saw some smoke come out of that pipe so I capped it with a vegtable can, I know not so great but it was close by. Well we forgot about it in our enthusiasm to see the stove working well. In trying to understand how the fire was feeding itself we got to looking around and realised that the pipe coming out of our lid was taking cold air down it and basically throwing it into the fire for lack of a better description. Putting your hand over it you can actually feel cool air being sucked around your hand. Was pretty interesting so I thought I would note what I found by accident and see what you all made of it. Again thanks for helping me along this journey, Raven

[johnjmw]

Raven, Like you I could not figure out how this thang worked. I went out and bought the fire brick to build one in the yard. Even with out the mortar and insulated burn tunnel and riser it burned fantastically. Now if I can only get my Cabin built to properly install it.
John