O.k., so I'm not much of a techie. However, I CAN follow good instructions. Loved the vids on the moveable RMH done in the wooden box. I've been reading the threads, looking at books, purchased and watched the DVD set, and am a bit overwhelmed at this point. I know there are detailed plans for RMH that aren't portable, but I live in a rented home and when I go, it will need to go. I don't care if it means taking it apart to do so, it just needs to go!
Talked with my hubby about it and he said we could probably put one in the attached garage. However, he's no more a techie than I when it comes to RMH so he needs detailed plans as well. Do you happen to have any detailed plans for a total newbie available for barter or purchase? Thanks!
I don't think they are looking for "portable" so much as "can be taken apart enough to move once or twice".
I would go for a cast core (maybe in a metal box to hold it together securely when moving) placed in a pebble bed with well-sealed ducting. I might even use some sort of concrete block for the outsides with pavers for the top, so it can be reconfigured for the next place you live, if necessary. Using fireclay for mortar on the exterior shell would give stable fsces which would be easy to disassemble (the fireclay could be washed off if you didn't want it on a surface later).
These construction methods all have detailed documentation and instructions available, so you can combine them into a project.
J. D. Ray : I have to follow-up here because of the future happiness of new members who find this Thread !
Yes the link you have sent us to shows a beautiful, Well built, Rocket (Cook) Stove that someone has carefully crafted by hand out of iron or steel.
The problem is- because of the high working temperatures of this model, it will fatigue and fall apart within 6 months of operation ! Iron and/or steel
can not withstand the effects of "High Temperature Hydrogen Attack'' and ''Hydrogen / Steam Embrittlement '' You can do a google search for these
terms, the Articles are fascinating !
For the Good of the Crafts Big AL
Success has a Thousand Fathers , Failure is an Orphan
Several areas of greatest concern / challenge come to my mind:
Isolation of the extreme heat generated in the fire box (feed tube, burn chamber, and fire riser; which I am collectively calling the "fire box" so I don't have to type all that out).
Controlling heat transmission to ceiling above barrel / drum.
Proper draft from the exhaust/chimney.
Heat Isolation of Fire Box
I have a test build going right now. I am not yet certain what I think of the heat isolation, and I monitor it very closely. In fact I bought a digital thermometer that accepts k-type plugs and high temperature probes to go along with it (these are quite affordable: the digital reader/display itself was only $20 or so, and the thermocouples range in price from a few dollars on up; I believe the 700 F cost about $5 and the 1400 F cost about $35).
I am testing this above a wooden floor. I used 3.5 inches of perlite, stabilized with fire clay, as the insulation under the fire box. I am measuring the temperature about 3-inches under the spot where the coals get piled up, just inside the entrance of the burn chamber. From my outdoor tests, I know this area reaches it's maximum temperatures several hours after the fire burns out. (Also, a close temperature relationship exists, between this maximum and the maximum measured during the burn, immediately behind the fire brick on the far wall, where the burn chamber and fire riser make their 90-degree turn - this is where the flames hit against the back brick, so it makes sense it gets hottest burning the active burn; likewise, it makes sense that the area under the coals gets hottest some time after the coals have sat there, completing their burn cycle).
So anyway, so far I have measured as high as 170 F to 175 F 3-inches below where the coals are piled up to finish the full burn cycle. And that happens about 3 or 4 hours after the flames die off.
I also note that it takes longer than 24-hours for this area (170-175 F) to return to room temperature (which in my case is on the order of 55 F). Thus my concern that if I burn twice a day, I may over-heat this area, which I do not really want to rise above 200 F. I also have noted, that from the point where I decide I no longer want to add wood, and just let what is in the feed tube burn up, I see about an additional 40 F rise in this area 3-inches under the coals (in the perlite-clay insulating mixture). These numbers and rates of change I would expect to vary from one built to the next, but I would also expect there to be some normal range of temperatures observed, as the heat from the fire box moves into the insulating material surrounding it.
Thus, my suggestion would be to use 6-inches of perlite-clay insulation under the fire box -and a foot or so beyond this to all sides- so as to maintain safer temperature build up.
Below this, of course, there is an air gap of a minimum of 1-inch (mine is about 1.5-inches), because any space of 1-inch or more readily allows air movement, which in turn carries away any heat transferred to the surface exposed to the open air space.
I need to keep weight low due to the floor, so I did not build the decking and support with masonry materials, but rather 2x6s. This is my concern and attention to monitoring the heat so closely. 170 F seems to be quite safe for stud walls, floors, ceilings, etc. So that would be my ideal high temperature limit. But I'm willing to run that up as high as 200 F, with the information I've seen so far (I'm open to changing my mind on this point).
Just so you have the build details, which I am not recommending, I'm just saying this is what I have done (and plan to change, increasing to the aforementioned six inches of perlite-clay):
deck of 2x6s laid side by side 2x4 laid across floor deck, at 90-degrees, to form air space channels (roughly spaced 12 to 18 inches apart, as best I recall)
another deck of 2x6s
layer of aluminum foil, shinny side upwards (facing the heat of the fire box; also facing the inside and top of the 2x4s in the next step)
2x4 screwed on top of deck (to help hold the fresh, damp perlite-clay mix, and give a level guide; a simple "fix" would have been to use 2x6 or 1x6 for these sides, and fill that with 5.5 inches of the perlite-clay insulation mixture)
Then I filled this in with the perlite-clay mix.
Then I double checked the level, paying extra attention to the area upon which the fire box would sit.
Then a layer of aluminum foil below where the fire box is to be built.
For a test, I then laid down three 12x12-inch ceramic tiles, 1/4" thick. I'm curious if they are going to shatter. They should be able to take the heat, but I'm not sure they can take the rate of change.
Then another layer of aluminum foil, under the fire box area.
Then about 1/2-inch of perlite clay, mostly for leveling the fire brick floor (I could have used sand too; but the perlite clay mix was lighter in weight).
Then a full thickness fire brick floor, and build the rest of the fire box on that.
So that's what I've done.
I'd suggest two potential changes. I'm considering both modifications, but since mine is built, I will closely monitor the heat building up under the fire box and decide if I need to do this now, on this build, or if I can wait to make the modifications on the permanent build I plan next summer/fall.
One I've already mentioned, which is increasing the perlite clay insulation under the fire box from 3.5-inches to 6-inches.
The other, is inserting pipe through the perlite-clay insultion layer, where it meets the wooden deck upon which it rests. These would be hollow tubes, and sized so that I could use a dowel or electrical grounding rod (or other properly sized stiff rod) to clear out any perlite-clay that may get into the hollow pipe as I drive it through the perlite clay (temporarily capping the pipe might be a smart idea, heheh).
Once the pipe has been inserted between the perlite-clay and wooden deck, I'd make sure it was uncapped and clear, so that air would move through it. To encourage this, one end could be angled down toward the floor and the other end angled upwards toward the ceiling, although I'm not certain that would be required, I suspect it would encourage air movement. This would carry away heat build up in the insulation.
The other observation I would make about the idea of adding pipes under the fire box to carry away built up heat, is that if they are located a minimum of 3 or 4 inches away from the fire box, I think the temperatures there will be low enough, and reach that depth in the insulation late enough, that removing heat build up at this depth will *not* inhibit the needed high temperatures inside the fire box. One might even be able to locate them a little closer, shallower, but that would require some more measuring of temperature movement through the insulation mixture to determine.
In my above post, the build I am describing is in my living room. It is a temporary build and is planned to only last through this winter. Unless I see a safety concern and modify it before UN-building it
My plan is to take what I learn from living with it this winter, and making perceived corrections, when I make my permanent build next summer/fall.
This build has no thermal mass. Too much weight for the floor. But the fire engine and build isolating it's extreme heat from the building structure, and the draft, and the feed and care of the fire are all relevant points.
Furthermore, because I am going to completely tear it down and move it after this winter, I felt the specific points I addressed were relevant to this thread.
Yes, I believe those plans would serve as a reasonable point of departure.
I would also emphasize to point of making outdoor test builds. Maybe s garage test if outdoors is impossible, adding several fire extinguisher units at hand, and familiarity with using them in this kind of a fire risk.
Once one is comfortable with the basic build, as per those plans, I would anticipate modifying them for one's specific site, with some advice and discussion on this forum and , or donkeys, one will devise a workable solution.
Off gassing safety
Portable or semi-portable thermal mass
Those are the big points that come to my mind. Then hands on details, like getting the
feel for the various clay mixtures, which I at least cannot learn by reading or videos. I have to get my hands into and fail and adjust.
Use fire brick. At least 2200℉ rating. And buy them from a brick yard not a box store like Home Depot or Lowe's and you'll save a lot of money. Plus they'll actually have 50-75 fire brick on hand
Mortar for s portable build, I would just use fire clay. You should be able to get that at the same place that sells the fire brick.
Otherwise you may need to ask around and find out who builds fireplaces and masonry heaters in your area. Then hope they will tell you where to buy material.
I would not use the vermiculite and refractry mortar, and if I did, I'd prefer Perlite to vermiculite.
Perlite is said to hold up better, and it insulates better. But I don't think I'd pay twice as much to get Perlite either, so there are a variety of points to consider.
Straight fire clay is a nice building material for sealing the fire brick. I like it. Easy to work with, easy to take apart with water and patient prying, easy to clean with water and brush. I like
Fire mortar seals are thin. Like 3 mm maximum. One old hand at it actually said he prefers to set the brick by feel to the point he can feel one brick touching the next. That's what I shot for and it seems to have worked well.
Regarding the earlier mention of:
"Iron and/or steel
can not withstand the effects o"High Temperature Hydrogen Attack'' and ''Hydrogen /steam Embrittlement '.
This applies respectively to steel exposed to over 400°C and copper exposed to heat. If your building an all masonry heater then it wouldn't apply. If your going to build a typical metal rocket thing, then using either a pre-made core, or diy ceramic, or diy ceramic fiber with or without a coated refractory metal lining, for the "heat riser"/ secondary combustion chamber.
Personally I wouldn't build one of these, but that's me. Having the skills and materials needed, I'd prefer to build a unit something like one of epa certified dual combustion wood stove/heaters. At about 400 lbs they're semi portable and burn longer and passed polution and efficiency tests.
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