portable rocket mass heater

Do I just watched the potable rocket mass heater video and am wondering, is that book now outdated considering the innovations described in the video i.e. the pea stone and updated combustion chamber? Or are those innovations in the book?

Paul talks with Ernie and Erica about rocket mass heaters in this podcast: rocket mass heater podcast

They talk about Pauls portable rmh.

a picture of my portable rmh made it into the rmh article! thanks, paul!

So...

What about an RMH that's really-really portable? AKA, disconnect the exhaust (as you would with the lint-duct of an electric clothes-dryer-machine) and then pick up the RMH by its handles and carry it out, all in one piece? Excuse me, but I do not think that I saw that this question had already been asked.

Two potential problems:

1) "It's too hot!"
nah, just kidding.

okay

1) "It's too heavy!" How much does the Paul's-Portable-Way weigh? If it were sturdy and fully contained, how many college students would it take to screw in that lightbulb? AKA, lift it into a truck? Would it smash the truck?

B) "The wooden-containing-box is only a frame: it has no floor! If we lifted it up, everything would fall out the bottom!" The Wheaton-Porta-Rocket has a wood-walled frame, but the frame has no floor, correct? Now this problem reminds me of the forum-posting about placing an RMH on a wood-floor (https://permies.com/t/17183/stoves/wood-floor). Since the burn-tunnel is so close to the bottom of the whole contraption, placing wood down there is risky business, eh? So there'd need to be an insulating mass beneath the burn-tunnel-- that is, between the burn-tunnel and the wood-floor of the containing frame. Adding this insulating mass would add... more mass... causing mo problemo for 'potential-problem 1' (see above.)

Nonetheless, all of this sounds possible? Is it really too heavy to be lifted by 10 strongish people?

According to this website http://www.simetric.co.uk/si_materials.htm , 1 cubic meter of common red brick weighs 1922 kg .

So, 2 ft (0.60959998049 meters) x 2 ft (0.60959998049 meters) x 6 ft (1.8287999 meters) = 24 cubic feet (0.67960423754 cubic meters).

Finally, 0.67960423754 cubic meters multiplied by 1922kg/cubic meter = 1306.19934455 kg (2879.67319898 pounds).

So, a 2ft by 2ft by 6ft mass entirely of common red brick weighs about 2880 pounds (1306 kgs).

Divide that amongst ten people and each person is trying to lift 288 pounds.

Sounds great!

Sounds greatly stuck to the ground and going nowhere!

Some problems with these calculations:

Firstly, 2x2x6 is too big: the portaRMH is smaller than that?

Secondly, the portaRMH has significant hollow-space.

Third, there is a giant metal barrel on top of it.

Fourth (and most important?), it's not necessarily primarily filled with common red brick.

Here are some interesting numbers from that website (see top of this post).

(numbers are in kilograms per cubic meter)

Ashes - dry 570- 650
Cinders, furnace 913
Cement - clinker 1290-1540
Cement, Portland 1506
Cement, mortar 2162
Cement, slurry 1442
Cinders, Coal, ash 641
Clay, dry excavated 1089
Clay, dry lump 1073
Clay, fire 1362
Clay, compacted 1746
Earth, loam, dry, excavated 1249
Earth, dense 2002
Earth, soft loose mud 1730
Earth, packed 1522
Flue dust 1450-2020
Gravel, loose, dry 1522
Gravel, with sand, natural 1922
Sand, dry 1602
Sand with Gravel, dry 1650

And, sorry but the website doesn't say anything about cob. ... But it does say Cobaltite ( cobolt ore ) 6295 !!!

And... Gluten, meal 625

Guys, for a portable RMH, i think the best bet, if room is not a problem, is a bell. Either concrete or brick. And a sack troley.

Here you can see concrete and brick ones.

http://www.google.fr/search?q=boisseaux&hl=fr&rlz=1T4ADFA_frFR472FR472&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=fIpVUNX1D4bF0QXW84HgBg&ved=0CCkQsAQ&biw=1280&bih=553

The euro hollow wall brick type should be filled with clay or concrete in the walls.

Another possibility for the bells, suage elements. All sorts of size and shapes.

http://www.google.fr/search?q=regard+b%C3%A9ton&hl=fr&rlz=1T4ADFA_frFR472FR472&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=t4tVUITBFqif0QX_54DQDQ&ved=0CCYQsAQ&biw=1280&bih=553


So brick we already have the weight. Concrete is usualy in the 2700kg range for a cubic metre.

So a water boiler and J tube on one side, and one or two bells on the other. Nothing should weight more than 250kg. That's manageable with two persons and a good quality sack troley.

According to a French supplier, the big ellements to make a bell weight 42 kils.

http://www.robert-thebault.fr/images/Boisseaux.pdf

And i was planning on fitting two bells of 7 500x300 blocks. That's more than 300 kilograms with the J tube, top and bottom plate etc. By the way, J tube could also be inserted in the bell, instead of using a barrel. The bells could be done in halves, and jointed with clay slip/mortar Or even the whole lot of blocks could be dismantled. And That's manageable in weight and size. 600 or 700kg, in terms of portable RMH, that's not negligible. Transportable in a car, may be in two trips if you have a tiny one. If your burner is one piece. the taking appart could be done in aproximately 20 trips to the car, less than two hours.

Well, that's my research so far.

Would this kind of design work if connected to a 30ft tall standard chimney?

Bob Carmellio wrote:Would this kind of design work if connected to a 30ft tall standard chimney?

That depends

Each RMH is different and so it is dependent on the particular unit and the designer's aim. With a portable RMH, the mass is likely to be less that a permanent unit. As such less of the generated heat will be trapped by the the mass and more will make it to the exhaust. As there are some permanent units that flow to a standard chimney fine, I suspect a portable unit would too. The real thing is the temperature of the exhaust. So long as it is still steam things are fine pretty much. So how well it works with a flue can be fine tuned by removing/adding mass to adjust the heat retained to match the exhaust temp.

Sorry to dig up an old thread, but I have read the whole thing and either no one said or I missed it But.

What is the foot print of the Portable RMS?

And how small can you build an RMS and still expect it to work?

I have an 10' X 12' Green house and want to put one of these in. I am thinking I could fit in a 2'W X 8'L X 2'H.
Would that be too small for a 6" system?

Thanks for this site its great I have learned a ton of stuff!

R Hansen.

Ron Hansen wrote:Sorry to dig up an old thread, but I have read the whole thing and either no one said or I missed it But.

What is the foot print of the Portable RMS?

And how small can you build an RMS and still expect it to work?

I have an 10' X 12' Green house and want to put one of these in. I am thinking I could fit in a 2'W X 8'L X 2'H.
Would that be too small for a 6" system?

Thanks for this site its great I have learned a ton of stuff!

R Hansen.

Favourite reply:

"It depends"

My first try was about 24inchs diameter and around 4ft tall. That was with all the mass right on the barrel, but then I was allowing good usable heat hit the flue too. With the bench I added mine is still within the 8ft length, but is 4 ft high. I don't think it could still work with only 2ft high and any length of burn tunnel. I also think a "J" style would not work. I don't remember the ratios, but the riser has to be taller than the length of the burn tunnel and height of the feed together.

Is the green house on a concrete slab? or on earth? If it is on earth it should be possible to put at least 12 inches of it below grade as a 3 ft riser sounds more do-able. In a green house situation I would want the barrel to have mass on it as well as the bench so that there was no direct hot radiation that might fry the plants (others feel that at least part of the barrel must be bare for it to work, but I have not found that to be so).

By the way.... portable does not mean able to be moved in one piece, able to be disassembled and moved and reassembled. We are still looking at over 1000 lbs. The RPCH I was talking about (in another thread) is yet to be built and tested, but could work size wise.... being about the size of a pot bellied stove.... but having a CSA of less than 6inch which wouldn't work well in a RMH. ( may not work for my own idea for that matter )

Sorry, I meant the bench part would be 2' high, I was going to try to use one of the small 36 inch tall
barrels like you can get from the quick lube places for my riser and build a standard burn tunnel
under that. I was also thinking I could get some Refractory cement and make the bottom part for the
burn tunnel over some 6 inch corrugated tube to get the shape then fill in the ridges after the tube
was removed from the molded piece to make the chamber smooth for better flow.

Hope that makes sense?

Ron

Ron Hansen wrote:Sorry, I meant the bench part would be 2' high, I was going to try to use one of the small 36 inch tall
barrels like you can get from the quick lube places for my riser and build a standard burn tunnel
under that. I was also thinking I could get some Refractory cement and make the bottom part for the
burn tunnel over some 6 inch corrugated tube to get the shape then fill in the ridges after the tube
was removed from the molded piece to make the chamber smooth for better flow.

Hope that makes sense?

Ron

2ft high for the bench is not a problem I would think, mine is 16inch or so. If I was using it in a green house I think I would just add more mass till it was the right height. Most plants will enjoy less warmth than humans (even tropical plants) as the heater is for night time mostly. Even with clouds solar radiation will add to the heat of the stove during the day. So more mass is better in this case. The quick radiant heat from a bare barrel is nice for humans in a house, but probably a bad thing for plants in such a small green house. I would add cob or brick around the barrel with brick being my first choice as it will conduct the heat away from the barrel better and be less likely to crack. The other reason for the mass around the barrel is that it keeps the temperature differential from the stove surface to the outside temperature smaller so your heat will not radiate to the outside as fast as glass is not a good insulator.

For a short bench like that I would use a hollow chamber to make a bell out of it because that will make the best use of the heat. The long, long exhaust tube is great for long runs in long benches (30 ft run sometimes), but the bell is better for shorter in my opinion. My bench is only 4 ft long, the hot flue gas goes in at a higher level (though it could be lower) and the exhaust takes away the coolest gas at the bottom.

Guys, i think i've found a trick. For portable, i gonna make elements with the half barrel system, embeded into concrete, and make two lengh of bench which can atach to each other.

Here's the skp file.

http://donkey32.proboards.com/index.cgi?action=downloadattachment&board=experiment&thread=560&post=5514&key=aibTimMeeDJExHl4iAWe

Satamax Antone wrote:Guys, i think i've found a trick. For portable, i gonna make elements with the half barrel system, embeded into concrete, and make two lengh of bench which can atach to each other.

Here's the skp file.

http://donkey32.proboards.com/index.cgi?action=downloadattachment&board=experiment&thread=560&post=5514&key=aibTimMeeDJExHl4iAWe

Why did you put the round part of the barrel up instead of down? I found that with the open part of a half barrel up and using 24x24inch patio blocks to cover the top, I get a nice even heated surface... even still, the 3 inches of the concrete that over hangs the side is cold at the edge when sitting on it. With the round part up it would take even longer for the edges to get warm. There would be a warm area right in the middle of the bench at first... it might be many hours before the bench felt good to sit on. I am moving the sitting edge back for less over hang and will increase the thickness of the top.

I am also thinking that the warm flue gas takes more room than the cooled gas and so less room is needed at the bottom than the top of a bell. (making it less "bell" shaped ) The volume at the low end could be 50% of the top end volume. This is also why I am putting my mass on top and making the bottom more insulative. If I was using the floor as a mass for heat storage I would not worry about that though.

Hi Len.

Yep, i didn't think about the surface area being heated etc. I just followed Matthewalker's idea. Thought if i do a monolithic concrete mass, it's easier to put them that way. So they cope naturaly with presure. I have to think about stratification of gasses etc. I'll go back to donkey's site and ask.

Len, thinking about it, with the half round up, there's more surface in contact with the mass, for a longer time, as the flue gasses cool down. 8432cm² of steel on the half round, against 5368cm² for the cut side of a steel barrel.

Satamax Antone wrote:Len, thinking about it, with the half round up, there's more surface in contact with the mass, for a longer time, as the flue gasses cool down. 8432cm² of steel on the half round, against 5368cm² for the cut side of a steel barrel.

You have to look at the whole top half not just the upward surface but the sides as well. With the round side up and only looking at the parts that are more than half way up the surface area is less than with the wide side up. The surface area is the same either way, the idea is to get the hottest surface area to do the most work.

Second, because most of the volume is at the bottom, there is the risk of the outlet being high enough to exhaust warmer gas than if most of the volume is higher than the outlet. We want to keep as much of the heat as we can... in my books, the flue gas exiting downhill of the feed at a temperature lower than the air intake would be ideal... though I don't know how practical. I am thinking that in a PAHS home the flue could be directed under the insulating layer of earth, downhill to an exhaust that is mostly a rock pit (to collect water) and the CO2 would make it's way down the hill into some CO2 hungry plant life.

Ernie and Paul. From what I can tell, you guys know the most. I wish I was alot closer, so I could learn directly from your expertise. I have recently become self aware of my enviornmental impact, and I am dicussted with myself. I've been recycling and planning shopping trips to reduce my impact, but my use of fuel to heat my home is crazy. So I began a quest to find alternatives, which lead me here. The problem is , I can't find any one plan, that says "here is the tried and true measurements". I've spent alot of time over the last 2 weeks looking. I'm sure I've overlooked it somewhere. I'm also dealing with a space issue, but I really want a RMH because I can get lots of free fuel ( broken pallet slats from my job). But, the space thing...... I was wondering what you think about the possiblity of a verticle mass section? Zig-zagging back and forth, but on an incline and going up with each zig and zag. Make sense? Hope so, because my drawing skills are really bad. Thanks For Yor Time.
Joe

Joe, massonery bell instead of mass, it's what you need. Check my SKP files at Donkey's site.

HTH;

something similar is my plans for emergency heat should something major happen in winter.

you could put a small fan in the exhaust before it exits the house to draw for a short time to get the pipes warmer and start the draw....then take the fan out.

Just wondering if anyone is still on this thread?

Jennifer Charlton-Dennis wrote:Just wondering if anyone is still on this thread?

https://permies.com/t/30006/rocket-stoves/pebble-style-rocket-mass-heater

Thanks Satamax,

I'm going to check out that thread!

Jennifer

There are people on this board experimenting with water-mass RMH, isn't that the most portable of all? Easy-ish to unload [probably via siphon] and ridiculously easy to load. Of course if you don't want to add extra moisture into the room being heated an additional 'chimney' type object is required to vent through the ceiling.

Were the plans ever made? I would like to build this. Does it weigh a lot? Would I need to shore up the floor? My house is old on a dirt crawl space without a lot of good support under. I have a chimney outside my house with a hole into the wall can this work for exhaust? The hole's about 6.5ft up from the floor. I guess it's a 6" hole meant for a woodstove but it has plaster over it now. How far from the wall do you need to put this heater? It's a wood and drywall wall. What size is your barrel it looks smaller than a 55gal. Is there other insulation to use besides vermiculite? I don't trust it because of possible asbestos contamination. Thank you.

Kyrt, water mass certainly would be the most portable. It would require more careful construction and handling, though, as leaks would be a major problem. Gravel etc. needs no special care. A portable water mass system would be a very interesting experiment.

Ian, I don't think formal plans were drawn up, but the original system is so simple that you could build it yourself from the description. If you are not confident about building the J-tube core on your own, you could get Ernie & Erica's "Annex" or "Daybed" 6" plans which give brick by brick instructions.
http://www.scubbly.com/item/75761/
http://www.scubbly.com/item/76710/

It would probably weigh between 500 and 1000 pounds, depending on the final dimensions you make it and the type of fill you use. It would probably be alright if you put it near a wall rather than in the middle of a big floor span, and sitting across several floor joists, not just two or three. If the place you want to put it is weaker than that, you could add a cinder block pier in the crawlspace to help support it.

Your existing chimney would work as long as you inspect it and make sure it is clear and sound. The box could sit right next to the wall with a few inches of air circulation space, but the barrel would need the same clearances as a woodstove, generally 4' or so unless you have a heat shield on the wall.

You can use any size barrel that will fit around your insulated heat riser with 2" clear all around. 30 or 35 gallon barrels can sometimes be found - check craigslist if you don't know a source.

Perlite is a very common insulation material; it's a completely inert mineral which will not settle the way vermiculite can. You might find it at building supply or garden supply stores. Get the biggest bag you can (2 or 4 cubic feet) as it is expensive in smaller bags.