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gusmus Wallace
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Hi folks. I've been a lurker here for a few years now and thought that maybe it was time to actually post something. I started building an RMH about 5 years ago and have enjoyed myself immensely tweaking, modifying, coughing, and generally filling the house with smoke on a regular basis ever since. Alas,, My darling head chief order giver has handed me an ultimatum in that either I stop fidgeting with the damned thing or she is going to fill the burn tube up with my tools and set fire to them. I therefore present my humble efforts in the hope that you will preserve them for posterity just in case she turns up with a small excavator one of these days.
I started this from some internet plans of a standard burn tube and barrel idea and gradually changed a few bits like having a half and half steel/fire brick lined bottom burn tube with a few lumps welded to the top and sides for added turbulence. I later added the vertical feed tube for ease of burning longer wood (less cutting) and pellets. A full gas outlet manifold was then added with an inspection and clean-out door. The manifold is quite high and allows any ash to drop before it enters the mass heater tubes and also allows me to get my arms fully inside for any repairs that need doing. You will notice that I've done away with the heated bench idea and replaced it with a solid concrete block of approx 1 cubic metre which has roughly 6 metres of 15Cm Dia flue pipe embedded in it. From the beginning it worked quite well but now it is starting to teach me its moods and foibles. So long as I listen to it, it just keeps getting better. It will burn rubbish wood like a champion. This helps a lot as I have a source of free wood from an orange box factory who burn tons of waste "cottonwood" because no one wants it, even for making sawdust. Then again, my frugal rocket burns so little that I could probably carry a weeks firewood home in my shopping bag. Anyways. That's enough waffling. Here are some photos of my drunken brickwork .
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The Beast
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Vertical feed tube
 
Glenn Herbert
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Location: Upstate NY, zone 5
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To give useful advice we need to know more dimensions of your system. You say 6 meters of 15cm duct; at approximately 20 feet of 6" duct, that may be past the standard 30' limit for a 6" system when counting each elbow as 5 feet. How many elbows do you have? What are the dimensions of your feed tube, burn tunnel, riser and barrel/gaps? (And describe where you take the measurements, like burn tunnel ceiling length or full length end to end.) What is the configuration of the manifold where the gases enter the duct?
 
gusmus Wallace
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There you go.
I haven't shown them in the drawing but at the join between the steel tube and the firebrick I have welded 5 small bits of steel (1 x 2 or 3 Cm) quite randomly to the roof of the burn tube. The difference to the turbulence is quite noticable and the barrel temp was noticablyhigher. I really must get a decent thermometer for the barrel top. The other detail I forgot is that the mass tubing rises in a spiral covering all of the block but it was a bit difficult to show that. Also, the flue from the mass to the chimney top is approx 4 metres. I was told that this was too long when combined with the 6 metres inside the mass but it seems to work just fine and it throws any gases away over the roof instead of wafting them into the house when you open a door or window. I don't care how clean a burn you get. It still ain't Chanel Nº5.
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Best I can do for now.
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Burn tube view from bottom.
 
Garry Hoddinott
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Love it! And thanks for posting. You seem to have a bit going on here - to the left (in the kitchen pic) appears to be an oven. Is this part of your RM(S)H?? or separate incendiary device altogether? I'm staggered by how LOW the heat of the mass block is. Shows it must have a huge capacity to take up heat. Gas guff Gus!
 
gusmus Wallace
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Garry Hoddinott wrote:Love it! And thanks for posting. You seem to have a bit going on here - to the left (in the kitchen pic) appears to be an oven. Is this part of your RM(S)H?? or separate incendiary device altogether? I'm staggered by how LOW the heat of the mass block is. Shows it must have a huge capacity to take up heat. Gas guff Gus!

No Garry. There is no oven. Those are just clothes rails for when the washing won't dry outside. The reason for the low temps is that the mass is almost 1 cubic metre of pretty high density concrete. I didn't choose this for its "green" credentials as a material. I actually chose it for its "Green" credentials as a heat retaining mass which leaves just about every other material by the wayside so by my way of thinking, what carbon credits I spent on the material I will get back in abundance by using less fuel for more usable retained heat. An eight hour burn is now giving me a "mass" core temperature of about 48-50ºC which will slowly dissipate to about 24-25ºC after 4-5 days. Strange thing is that it seems to keep a stready core temperature even when not in use. I was away last winter for almost 2 months and the core temp never went below 18ºC according to the guage whilst the ambient room temp went down to 12ºC (according to the same guage).
 
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