RMH,double barrel stove hybrid

I am starting a new thread on my build as it is no longer bell heater. I have changed it to a RMH double barrel stove hybrid with large horizontal batch burn box. The burn box and riser were tested outside and worked perfectly. I am using 3 water tanks for the heat exchangers. The vertical tank doubles as a support for the top 2 tanks. The burn box will have a glass door. Above the burn box will be an oven. The burn box is 14 x 15 x 23. The finished dimensions will be 28 x 53 x 74. There will be 3 clean outs for the tanks on the end opposite the burn box.

More pictures of the build

Today I laid up the brick work inside on the raised hearth. The burn box arch top is not on yet as it's too heavy for me lift alone. The water tank that will act like a vertical bell is shown and will be cut off lower than the riser top. The two small holes in the burn box sides are air inlets. The air will come in from the outside behind the water tank. The steel air channel will go under the middle of the water tank and then split off to both sides. There will also be an air intake at the bottom of burn box door.

Interesting idea Alan, Looking forward to seeing more!

I have seen some water heaters at a dump. Do you just peel off the cover and insulation to get the tanks?

Would all the tanks out there be the same size or what should I look for?

Miles, I got my tanks at the dump. The 2 top tanks are 16" diameter and will end up about 51 inches long after the ends are cut off. Flat plates will be welded to the ends. The vertical bell tank is 14" diameter and will go inside the upper tank and be welded to it for a support. It will be easier if this lower tank is less round than the upper ones. Propane tanks may work also. The metal work should be done next week some time. I can test it then without the cob covering.

You will need a crow bar to pry apart the outside cover along the seam. Then the insulation comes off in almost one piece.

Alan

The arch top is now in place. I have changed the side air intakes to come from the front instead of the back. I have one side intake pipe in place. Air will also come in through the door. I am looking for a metal box to use for the oven.

I added cob over the the arch to create a flat base for the oven box shown. I hope to get all the tanks cut today.

This is the finished heat exchanger assembly of 2 water tanks. The vertical tank needs to filled with rocks and or gravel so I cant put the heat exchanger in place yet. There were 6 holes cut into the tanks. 3 - 6" for flues, 2 - 8" on the ends for clean outs. and the square hole for the riser. It was very hard cutting these holes with a scroll saw. I broke or wore out many blades. The best blades were made by craftsmen with 21 teeth per inch.

Today we put the heat exchanger and oven into place. The vertical tank holds most of the weight of the heat exchanger. The vertical tank is filled with 3 to 4 inch rocks with good air flow through them. There will be a hole at the top and bottom of the vertical tank to allow for a natural air flow through the rock and into the room. There are 8 inch diameter holes in both tank ends for clean outs. For a burn test I need to install the clean outs, seal the hole around the riser in the bottom tank, and add a short piece of flue pipe between the 2 elbows. This has worked out exactly as I envisioned it. I am going to put brick around the whole thing for a typical masonry heater look. I will gradualy raise the brik outside wall and back fill with cob as I go along.

Right now is a super stellar moment as my first burn test is taking place. We put a piece of tin in front of the burn box opening since I don't have a door yet. It back drafted out the gaps between tin and bricks for about 5 seconds. Then it started to rocket strongly. In 30 seconds the whole lower tank was too hot to touch. The upper tank is now the same. We lit a lighter in front of the side air inlets and they were sucking air in very well. The main fire was happening where those pipes enter the rear of the burn box. The fire is barely going and it's producing tremendous amounts of heat. The top of the oven box is as hot as the tank. I can touch the top of the riser but not the tanks. All I have to do now is the outside brick work, remainder of cob, and doors for the burn box and oven. Simply stellarr!!!

Update: The temperature rose 10 degrees in 30 minutes with a window and sliding glass door all the way open. This is 650 sq feet with a vaulted ceiling. I had to put a fan in the doorway to cool things down. I'm in perfect awe as to how much heat those 2 tanks are putting out and what was being lost with the wood stove I was using. The top of the riser is now too hot to touch and the cob on the sides of the burn box and riser is now getting warm.

conjecture: Water tanks should be used in bench style heaters instead of flue pipes.

I laid up 3 rows of bricks around the base. You tube vids and library books were a big help having not done brick work before. Don't get your hands in the mortar like I did!

I took out the metal box that was going to be used for the oven and will make a brick lined oven instead

I will let people who attend the Sandpoint workshop come up here and view this heater and see it working. The brick work should cover the cob already in place and a burn box door should be installed by then.

I have 8 rows of bricks in place as of yesterday. I am laying them up with the large faces out to save on bricks and I like how it looks better. I placed a few fire bricks to show where the brick oven will be. The door opening is 13.5" x 14.5". I'm going to make a 2" wide metal flange to go around the opening for the door mount. In order to not make a typical arch pattern above burn box I spanned across the arch with 1/4" flat bar. I need to clean the mortar off of the bricks.

I have been trying to find a cheap wood stove on Craigs to get a door for my heater. I almost had one for $50. Today I got a Vogelzang barrel stove kit at our L.H.W.S. I will use the door and sell the legs and damper. I just have to make simple flange to mount it.

There is one small error in my build. The top of the smoke exit in the back of the burn box is lower than the top of the burn box so smoke can come out the front when opening the door. I need to drill a hole through to let the smoke into the riser.

Alan Mikoleit wrote:
conjecture: Water tanks should be used in bench style heaters instead of flue pipes.

Hey Alan. This looks incredible! I don't have the welding skills or apparatus to do what you've done but it's a great take I think on a hybrid Russian/masonry and rocket stove.

Would you elaborate more on what you mean about water tanks being used in bench style...Would you stretch out this system rather than stack it?

Also it would be interesting to see a diagram of the exhaust flow...It's not exactly clear to me how it goes.

It must be exciting to have it all working as you had envisioned.
Best,
Sally

Sally,
Nothing was welded, the tanks are just bolted together with the 4 braces. The pipe connecting the 2 horizontal tanks was a very close fit and sealed with black masonry cement. The clean out pipes and exit flue pipe where dog eared with half of them on each side of the hole, then screwed on and sealed this masonry cement. The bottom horizontal tank is just sitting on top of the vertical one. The hard part was cutting all the holes in the tanks.

The vertical tank is filled with 3 inch rocks. There are 2 holes in side of the tank for heat flow one at the bottom and one at the top. The smoke does not go into the vertical tank. The smoke goes up the riser into the bottom horizontal tank, then into the top tank at one end and exits the top tank at the other end. There are 8 inch clean-outs on the ends of each horizontal tank

For bench style systems I would put a water tank over the riser and surround it with a brick wall to hide the tank, leaving space between them. The tanks on the floor could be inline or side by side or both.
Alan

Yesterday I installed the burn box door so my heater is operational even though the brick work is not finished. Yesterday around 5pm I put 2 half logs in the heater. This morning it's 75 degrees inside. Oh the " warm feel" of success!

I have been using my heater for a week or 2 now and am ecstatic and raving over it's stellar performance! Over 24 hours ago I made a small fire just using cutoffs from a friend who is building a shop. It quickly went up to 80 degrees and maintained that for 24 hours! Now it's 75 degrees and will not start another fire until tomorrow. It's amazing how long the brick work stays warm. This radiant heat feels so much better than a wood stove.

I did some temperature measurements with a digital laser device. Burn box on the fire - 925, burn box door - 525, middle of bottom tank - 385, middle of upper tank - 285, flue exit out of the upper tank - 145, on the roof exiting the flue 124.

The burn box arch top turns the flames into one huge vortex. They go up on one side, along the top, half way down the other side and then out the back.

A friend is also quite impressed with it and wants to copy it before snow falls.

Others are waiting for the first pizza made in the oven LOL.

Cost so far with a lot of free materials around $400. I just need to finish the brick work and back filling with cob.

Nice work alan , i'll have to get over that way sometime to see it in person !

Alan, 145F° out of the last flue, that's prety much bang on.

Now, time to find someone with a testo, to get a sniff at it!

With current fall temps. I am burning 1 or 2 small pallet wood fires a day at 12 hour intervals. A friend is going to copy this for his greenhouse. I would make just one small change now on the second time around. I would make the opening from the fire box to the riser taller and have it go from the floor all the way up to bottom of the fire box arch. Then I would put a removable brick in the bottom of the hole for access to clean out the bottom of the riser. This will aid drafting and keep smoke from building up at times at the ceiling of the burn box. Otherwise very awesome. Very mild and even heat distribution in the whole room. Its a totally different feel from a metal wood stove.

Hi Alan,
  This is really exciting for me. I built a RMH this summer for our greenhouse, and I love it. But now I want to build one for a small cabin, and wanted one that has food prep capabilities.
  What's also exciting is the small footprint, and the use of the old water tanks.
  What I don't understand is the point of the vertical tank. Does it actually let air flow into the system?
  Also, did you ever finish it with the cob, as in your drawing of the "finished" version?
Thanks,
Andy