stand alone mass

I want to build a mass for my rocket stove, its one of the propane tank standalones and the exhaust is piped up the properties chimney.
I cant build a normal mass of brick and mortar so im thinking a long coffee table type coffer, 4 inch pipe runs up it and back, filled with brick, sand and topped off with a slab of slate.

feasable? im living a bit of a hermit lifestyle here so dont get to meet many people to bounce these ideas off, so your thoughts and ideas are greatly appreciated, thanks

Bongo O. : Welcome to our PERMIES site, and a big welcome to the Rocket Stoves Forum threads! So you have a working Rocket Stove now ?!
I have to ask because the outlet discharge size of your Rocket Stove should be continued throughout your build, so you are looking at using the
same diameter stovepipe for your Thermal Mass. A mix of clay and sand Somewhere in the range 30%-70% to 70%-30% will work well, better
than lite brick or insulating sand, and a slate top will work fine if bedded into the top of your thermal mass with a little clay slip ! Any questions,
feel free to ask them here, Many builds are started and finished here and we always like lots of pictures !

For the good of the Craft ! Be safe, keep warm, PYRO Logically Big AL

Bongo, it's perfectly feasible, but don't use sand.

Alen, clay's all right, but not the best. For storing heat, and releasing it, concrete is better.

Bongo, One daft question, do you have a chance of moving, or a need of moving the table every now and then? If yes, forget about the concrete, exept if you plan to leave it behind, or have the proper equipement.

There's another solution i've thought about, not the best thought, but movable kind of easily.

Check my post #12 here http://donkey32.proboards.com/index.cgi?action=display&board=experiment&thread=560&page=1

And the following sketchup file.

The idea now is to use the half barrel system, bottom of the barrel embeded in a little two inch concrete layer to seal it, and then, above the barrel, use fist sized or a smidge bigger stones to fill the box. And then put a top on all this, either raised so air can pass and escape, or tight so it heats up the top, and slows the release. So why fist sized rocks? To allow for the air convection to happen to "charge" the rocks. Gaps need to be bigger than an inch and a half to allow for convection. Don't use a wooden box in this case, it would be prone to scorching. I think any kind of metal box of the right size would do. May be a modern metal travel trunk. What we call "une cantine" over here.

http://www.google.fr/search?q=cantine+m%C3%A9tallique&safe=off&hl=fr&rlz=1T4ADFA_frFR472FR472&tbm=isch&tbo=u&source=univ&sa=X&ei=eemJUeuOGamQ0AXniYGIAQ&ved=0CE8QsAQ&biw=1491&bih=622

Even, with thoses metal boxes, you could either close the top for slow release, or open it for faster release of the heat. Then, the day you need to move, you can remove the stones with a bucket, and move the metal box with half barrel in it easier than a full mass.

Hope this helps.

thanks guys for the welcome and food for thought here then
so my rs has a 4inch outlet, continue that through the mass - check
im thinking about using oak for the coffer, this shouldnt be a problem with scorching? what sort of temps do your masses get up to?

rocks sounds like a good clean option, how about beach pebbles?

Hi Bongo.

Well, if you use a half barrel and rocks, using a wooden box would be asking for trouble. But if you do a concrete or clay mass, no prob with scorching imho. Realy, do a bell type mass, enlarging your flue tube means the flow slows down in that part and releases more heat into the mass. This is what is the half barrel, a bell. But you can use all sorts of metal containers, surounded by monolithic mass or bricks in contact. One i'm planing to use, is fuel tanks. Like small ones to hold fuel for tractors or else. Rectangular in shape, you can just pile up bricks around, and put slabs of stone or concrete on top. Toolboxes can be used too. And aplenty of other things.

Bongo : Now would be a great time to tell us a little about your build,and its location. A simple sketch or pictures if we can get them, showing where you want
to place your Thermal Mass and your exit out the chimney, so we can follow the path you think will work best for you, like is your house plan all on one level?

Take every bit of our advice as being worth exactly what free information is always worth, you are the one that has to live with this, not any one here, it would
be nice if you wanted to share something of yourself so we don't propose to grossly over or under build something you will have to live with. Where are you
located, and tell us about any major solar gain !

For the good of the Craft! be safe, keep warm! PYRO Logically- Big AL - As always all comments are solicited and welcome!

Thanks for the replies, been marshalling my thoughts. Tried using a computer program to draw, results were awful, will draw on paper and try to upload. My rocket stove is a standalone type like this http://www.youtube.com/watch?v=yDDla5AdNvk now at the moment it is sat in the kitchen with a pipe leading out and up to the registry plate of the chimney, my thoughts s to just divert the exhaust pipe through the mass placed in the center of the room. At the moment the exhaust pipe runs through the softwood strips that the fire gets fed with so im not worrying overly about scorching.

Im not putting a steel box in my cottage, it would look awful. I also dont have one, I do have slate and oak, some cast iron piping and the beach has the pebbles. I dont have money, i have to work with materials I already have or can scrounge/find in skips.

Tell you what, lets be blunt, im an incredible bull headed chap, im going to build my wooden oak box filled with pebbles and well see where it goes from there, Ill be documenting stuff as I go along. If scorching is a problem I can insulate the base and sides with rockwool roof insulation, then put a layer of pebbles down, then the pipe surrounding that with pebbles, fill to the brim and then lay on my sheet of slate. The rockwool should keep the heat from the sides and base and it will then slow release through the slate. Hopefully, probably, maybe... I made a start today by cutting the oak for the legs, sides and ends, next step is routing the legs and putting together the carcass.

Well, metal boxes can be hiden, covered. Vintaged or whatnot. I don't care if my idea didn't tickle your fancy. There's plenty of other ways. Thought it was cool for standalone, moveable mass.

Now, i'll be blunt, your rocket is doomed, all metal rocket work only for a while. then end up spalling badly before colapsing. I think, you should go back to the drawing board.

Look, that's the innards of one, after only 14 burns.




Well, with the fireplace you have in your lounge, you could do something far better with an horizontal batch rocket. And may be use the fireplace and chimney, with the surounding wall as mass. Tho, it won't be easy nor fast.

http://donkey32.proboards.com/index.cgi?board=experiment&action=print&thread=113

http://donkey32.proboards.com/index.cgi?board=experiment&action=display&thread=511

Your metal box idea was appreciated and did merit serious thought and consideration. I looked at large ammunition boxes and some old trunk styles but both required financial outlay unfortunately.

When I 1st had a look at rocket stoves i read about spalling, thats the metal flaking and breaking up right on the inner? I used very thick steel which was then insulated. It will happen eventually and then Ill change to either cast iron or ceramic riser. Im lucky in that I have a lot of very thick 4inch box section and a good supply of cast iron floating about. Im hoping it will last 2 years, its done 6 months already and still looks and works well. If it doesnt then its a small matter to replace and start again, im pretty quick at making one of these so replacement cost v wood cost isnt so much of an issue.

I cant work out from the pic what Im looking at, thats the internal?

Thanks for the link to the horizontal batch rocket, thats something Ill look at again. Unfortunately im in a old listed(protected by law) house so building modifications are tricky which is why I went down the standalone rocket system. The previous woodburner a franklin was very wood hungry and inneficient in comparison.

Well, unburnt part, feed tube, then short one at the elbow was the burn tunel, entering the gas bottle circumferencialy, then the gas bottle acted as the primary part of the heat riser, which was meant to induce a cyclonic movement. Rocketed madly that thing, despite being too small. Was a 4 incher. I even managed to melt the top of the gas bottle to the point that it dipped under it's own weight! This is to tell you it was hot. All of this was in the barrel below, filled with vermiculite.

Satamax A. : I am with you, that the nearly all-metal system here is not going to be a long lasting build, however if Iorweth wants to run this system
and give us a report on how it works for him, thats great! He gets to learn on a system that by failing early will more effectively help him with his next
build , as compared with one that lasts so--- long he forgets why he did part of it that way, and how he was going to change it on his next build !

We have not dealt with the difference in sizes between Iorweths 4'' square steel tubing in his Rocket Stove, and his interior dimensions within the bench
that he is building. I would personally go to a round 5'' pipe to get a Cross Sectional Area only slightly bigger, as the only other way I can see to do it
would be a 4'' square brick tunnel, exactly where we want smooth walls. Iorweth, I only noticed this after I re-read everything (!), Sorry I hope this has
not set you farther back !

For the Craft! Be safe,keep warm! PYRO - Logically Big Al ! - As always comments are solicited,and welcome ! A.L.