sauna rocket stove progress

Tel, when I get back from my trip on the 14th or so can I come sauna? btw, I might have some chickens for ya if'n ya likes. loans or keeps. i have some travel to attend and cant keep them here....

Deston Lee wrote:
Tel, when I get back from my trip on the 14th or so can I come sauna? btw, I might have some chickens for ya if'n ya likes. loans or keeps. i have some travel to attend and cant keep them here....

if it's done, and I hope it will be by then, you'll be more than welcome to try it out.  and I hope you do.  may have to have a party to celebrate.

any tips on how to face the ends of the 16-inch pipe?  the initial cut with a torch wasn't exactly precise, and I've already spent rather more time than I would have liked with an angle grinder.

tel jetson wrote:
any tips on how to face the ends of the 16-inch pipe?  the initial cut with a torch wasn't exactly precise, and I've already spent rather more time than I would have liked with an angle grinder.

Um... I'm an infrequent metal-worker at best, it sounds like you've identified the main problem and tried the standard solution already. 

Is the 16" pipe the one that's substituting for a barrel?  If both ends are open and jagged, might need a better welder than me to advise on how to get a good seal for the top of the 'barrel.'

Among your options for ordinary edge-smoothing...

1) Thor: heat it again (assuming you can set your cutting torch for a slightly more diffuse flame), and when the burrs get red-hot, round them down with a hammer.  Could also shape the seat for a gasket this way, possibly.

2) Loki: Wrap foil tape around the edges for current handling, then bury it in cob so nobody notices.

reasonable ideas.

I don't have a cutting torch.  I could probably drag one over from across town, but I don't have the steadiest hands.  the welder who cut the thing is 200 miles away, so I don't think I'll be dragging it back to him.

the problem isn't just the burrs, though.  the cuts on both ends are pretty crooked.  between 1/4 and 1/2 inch between highest and lowest points.  I guess I'll spend some more time with the grinder to get it to a point where I can just hide it.

tel jetson wrote:
any tips on how to face the ends of the 16-inch pipe?  the initial cut with a torch wasn't exactly precise, and I've already spent rather more time than I would have liked with an angle grinder.

get a metal cutting blade for a circular saw, any big box store should have them

http://www.lowes.com/SearchCatalogDisplay?storeId=10151&langId=-1&catalogId=10051&N=0&newSearch=true&Ntt=abrasive+saw+blade

wardd wrote:
get a metal cutting blade for a circular saw, any big box store should have them.

I think that would work, but I would probably go through several of those blades getting it done.  this is .255-inch steel pipe.  I figure it would take me roughly the same amount of time as the angle grinder, and I've already got the grinding discs.

in case I do decide to go that route, though, how would I draw a good line to cut?

tel jetson wrote:
I think that would work, but I would probably go through several of those blades getting it done.  this is .255-inch steel pipe.  I figure it would take me roughly the same amount of time as the angle grinder, and I've already got the grinding discs.

in case I do decide to go that route, though, how would I draw a good line to cut?

take a piece of sheet metal that will fit around it and draw a line

wardd wrote:
take a piece of sheet metal that will fit around it and draw a line

any other ideas?  I don't have a piece of sheet metal large enough.

tel jetson wrote:
any other ideas?  I don't have a piece of sheet metal large enough.

perhaps a roll of paper or cardboard

most anything that could be made to lie flat on a cylinder might work

I'm still not sure I've got anything that will work for that, but I'll have a look around.  I'm a little embarrassed that I didn't think of such an easy solution.

duct tape?

duct tape is too flexible.  wouldn't make a good line.  I ended up using some butcher paper.  probably wasn't perfect, but I think I got both ends to a place that was close enough.

did some other boring stove work today.  coated the big pipe with walnut oil.  mixed some ceramic stuff in with the oil for the side that will face the wall for some extra insulation.  painted that same mix on the wall side of the exhaust duct and the stove side of the heat shields I cut out of a cement board.  they'll need at least another coat, and the walnut oil doesn't cure terribly fast, so I could be waiting a good while.  I really like that there aren't any solvents involved, though.

You can use a 25' metal tape measure to mark your cut line. I use that for marking PVC pipe when doing drain work. I've only gone to 8", but it should work.

I suppose I should say, you wrap it around the pipe, pull it taught and then mark with a sharpie or similar.

I thought of that, then didn't do it.  don't know why.  probably just needed one more hand than I have.

I've also got some aluminum tape hanging around that would probably work, too.  at this point, I'm satisfied with where the ends are.  I could change my mind, though, and these ideas will help.

I wasn't thinking of using the duct tape to draw a line. I was thinking of the tape as being the line.
But maybe it won't stick to the pipe.

ronie wrote:
I wasn't thinking of using the duct tape to draw a line. I was thinking of the tape as being the line.
But maybe it won't stick to the pipe.

ah.  that could have worked.  duct tape wasn't sticking very well.  too much metal dust on the pipe, I think.

disaster!

well, maybe not disaster, but certainly the first major setback.

the walnut oil was taking far too long to cure, so I ended up using some high-temperature paint for the wall side of the big pipe and the two tile-backer heat shields.

today, my sister and I tried to set up the pipe assembly.  we got the 8-inch pipe inside the 16-inch pipe laying down next to the stove without too much trouble.  standing them up caused all sorts of problems.  the smaller pipe kept sliding out of position, and then bricks started shifting all over the place.  rather than continue screwing things up and becoming more frustrated, we set the pipes back down and called it a day.

so now I'm stumped.  maybe we just didn't have enough hands there to help out.  I haven't weighed them, but those two pipes together are probably well over 300 lbs.

I considered ditching the 16-inch pipe and going with a 55-gallon drum, but there just isn't enough space for one.

so: any ideas?

Im assuming the 16" pipe is to big to simply lift over the top of the burn chamber? Or too heavy to lift, but you have enough height?

if you cant lift due to size constraints, an internal collar assembly- i think you could make it out of wood, and it would burn out.

mmrg. sorry my travel fairies are going rouge.   IM busing out post haste, I just got together a trip to see a friend of mine whose been moved into hospice. Ill be back after the fat man burns. 

Deston Lee wrote:
Im assuming the 16" pipe is to big to simply lift over the top of the burn chamber? Or too heavy to lift, but you have enough height?

if you cant lift due to size constraints, an internal collar assembly- i think you could make it out of wood, and it would burn out.

mmrg. sorry my travel fairies are going rouge.   IM busing out post haste, I just got together a trip to see a friend of mine whose been moved into hospice. Ill be back after the fat man burns.

both too tall and too heavy.  the collar idea might work.  there's a third element in there: some stove pipe to contain the insulation around the 8-inch pipe.  seems complicated to work around all that, but maybe.

and you'll get down here sometime.  I'm not worried about that.  have good travels.

im back in pdx the23. 9pm. prolly stay the night there. whats yer plan for the christmas eve? youd be a good one day or overnight layover on my weary wendt home. We could lift heavy stuff and grunt in archaic fashions.

I'm not absolutely sure, but chances are pretty good that I'll be around.  your help would be great.

working through some more ideas for setting up the pipes.  I'll repair today's damage in the morning before we get out of town, and see if what I'm thinking of makes any sense.

progress has been slow, but we finally cleared a major hurdle.  probably won't be the last problem before the project is over, but I'm feeling good for now at least.

finally went with the block and tackle to lift the pipes into place.  I climbed in a very small space to have a look at the stoutness of the ceiling, and determined that Erica's suggestion at the beginning of the project would work just fine.

climbed in here:



probably isn't obvious without any scale, but it was a real tight fit to climb in there, even for my fairly slight frame.

then I crawled over to the other side to set up this:



again, no scale, but that space is less than 18 inches tall and full of cobwebs and other sundry nastiness.  I wrapped a cable around a 2 x 6 and set it across two of the 2 x 6 rafters and drilled a hole in the tongue and groove.  ended up looking like this:



the block and tackle:



and the whole mess:



either there was an awful lot of friction in those pulleys, or those two pipes are seriously gd heavy.  I'm no He-Man, but I do work for a living, and it took just about everything I had to lift those things.

anyhow, we knocked another brick lose in the process, but that was easy to fix.  next step is setting the riser properly and insulating it.  stay tuned.

set the heat riser today.  there wasn't enough room to see a spirit level in there, so it's only as plumb as my eyeball.  cobbed around the base to seal the joint.

I imagine that's going to be a fairly hot part of the stove, so please let me know if there's a better material than cob before I bury it in insulation.

coming right up is the insulation for the riser.  my plan is perlite and clay slip.  Ernie mentioned going light on the clay, which I'll try to do.  beyond that, is there a good technique for mixing up the perlite and clay?  previously, I've just dumped them all in a plastic basin and mixed it all up with my hands.  seemed to maintain a fairly light mix.  is that a satisfactory method?

The way you describe is pretty much what Ive done with the p/c mix in the past. I should be able to come the third of jan. after the turkey oven fun.

Deston Lee wrote:
The way you describe is pretty much what Ive done with the p/c mix in the past. I should be able to come the third of jan. after the turkey oven fun.

sounds good.  what do you think about cob for the junction of the pipe and bricks?  will that stand up to the heat there?

it looks like you have straw in that mix? cant tell exactly from the photo, but I'd suggest no straw in contact with anything above @250f. itll just char out and leave voides and then you ll get crumbles. if it is straw, get rid of it and make a clay and jagged sand stiff mix- something that is so thick and gritty you dont want to mix it in bare feet. no fiber. the mix should be a stiff one. use that and it wont burn voids into the seal, it'll turn to brick.

right.  there is definitely straw in there, so I'll tear it out and try again.  sharp grit is the ticket, then.  check.

tel jetson wrote:
right.  there is definitely straw in there, so I'll tear it out and try again.  sharp grit is the ticket, then.  check.

next question: where do I find sand like you're recommending?  hardware stores and contractor supply in town are no good.  rock/sand/bark place in town is no good.  ready mix plant has sharp sand, but it isn't very coarse and I don't need a ton.

I've got a bunch of oyster shells.  would smashing those up make a passable substitute?

MAybe. oyster shell wont burn, calcium carbonate has a higher  temp tolerance than cement. I tpicall get unscreened sand from a landscape supply in longview and screen it myself for that kind of grit. I pull about 1/5-1/6 of the volume per load that way. kept me chugging on stuff last summer. tsugawa's is probably spendy. you shouldnt pay more than $12 a load for unscreened. youll need some fiber free course cob (ffcc in the house!) for packing the burn chamber walls as well, eh? and the rest can go to whatever. Itll be about half and half 'regular' grit and fines. If you go that rout well take some of my screens down when I come next week  so you dont have reinvent the wheel. or the sifter, as it were.

Question:  I remember reading a "how-to" on making your own firebrick.  The process involved mixing straw with the clay before firing.  The straw would burn, leaving air pockets in the brick.  It was these air pockets that both gives firebrick its insulating properties and also let it float.

Shouldn't you be mixing straw with your cob in order to create firebrick?

First post here.... I've been researching for a stove for our pottery studio, leaning toward some kind of rocket/bell configuration, probably all cob.

I just wanted to tell you though that even though oyster shells will not melt at the temp your stove will be running at they will (this applies to limestone sand as well which is also calcium carbonate) remain somewhat porous and can expand and shrink with water.  This might lead to cracking in the long term.  I don't have any personal experience with this exactly, and I imagine it would depend a lot on the properties of the clay you are using.  Don't mean to scare you, and it might be fine if your clay body is somewhat porous already.....
Joe

Muzhik: from http://www.1911encyclopedia.org/Firebrick

I bolded the stuff that I felt might lead to an answer for your question. nice catch, tho not quite the same use for the low fire (pourous) bricks.


The proportion ... depends on the nature of the clay and the purpose for which the material is required, but generally speaking the more plastic clays require a higher percentage of a plastic material than the less plastic clays, the object being to produce a clay mixture which shall dry and fire without cracking, warping or excessive shrinkage, and which shall retain after firing a sufficiently open and even texture to withstand alternate heatings and coolings without cracking or flaking. For special purposes special mixtures are required and many expedients are used to obtain fireclay goods having certain specific qualities. In preparing clay for the manufacture of ordinary fire-grate backs, &c., where the temperature is very variable but never very high, a certain percentage of sawdust is often mixed with the fireclay, which burns out on firing and ensures a very open or porous texture. Such material is much less liable to splitting or flaking in use than one having a closer texture, but it is useless for furnace lining and similar work, where strength and resistance to wear and tear are essential. For the construction of furnaces, fire-mouths, &c., the firebrick used must be sufficiently strong and rigid to withstand the crushing strain of the superimposed brickwork, &c., at the highest temperature to which they are subjected.

(note: frit (when it goes granular and can be rubbed back by hand, crumbles) starts at about 600, spall (when it flakes off in sheets) at 1200. the base of the burn chamber is @600 on the ouside once fully ramped according to the notes Ive read. never had a fancy toy to take its fever reading tho. the further up you measure the hotter it gets. I wouldnt fiberclay myself, but I do amit that it seems to be a grey area/borderline)

The wearing out of a firebrick used in the construction of furnaces, &c., takes place in various ways according to the character of the brick and the particular conditions to which it is subjected. The firebrick may waste by crumbling - due to excessive porosity or openness of texture; it may waste by shattering, due to the presence of large pebbles, pieces of limestone, &c.; it may gradually wear away by the friction of the descending charge in the furnace (spall), of the solid particles carried by the flue gases and of the flue gases themselves (also spall); it may waste by the gradual vitrification (the silica starts bonding to itself, alumina flakes out and your get glasspebles and alumina flakes) of the surface through contact with fluxing materials: in cases where it is subjected to very high temperature (1600f) it will gradually vitrify and contract and so split and fall away from the setting. It is a well-recognized fact that successive firings to a temperature approaching the fusion point, or long continued heating near that temperature, will gradually produce vitrification, which brings about a very dense mass and close texture, and entirely alters the properties of the brick. (bricks intentionally made this way are very heavy and used in refractory, which Ive built some of, they weigh about3x a normal firebrick that we use for RMH. I used these in glass and metal shop furnaces and kilns where we hit 2400-2800f, typically for glass, and one that ramped to 3200f, used for forging low carbon steel.)

Where firebricks are in contact with the furnace charge (1200f +) it is necessary that the texture shall be fairly close, and that the chemical composition of the brick shall be such as to retard the formation of fusible double silicates as much as possible. Where the furnace charge is basic the firebrick should, generally speaking, be basic or aluminous and not siliceous, i.e. it should be made from a fireclay containing little free silica, or from such a fireclay to which a high percentage of alumina, lime, magnesia, or iron oxide has been added. For such purposes firebricks are often made from materials containing little or no clay, as for example mixtures of calcined and uncalcined magnesite; mixtures of lime and magnesia and their carbonates; mixtures of bauxite and clay; mixtures of bauxite, clay and plumbago; bauxite and oxide of iron, etc....

more than you asked, but i thought it was interesting

Yes, it was VERY interesting!  Thanks!  I especially liked it because the "how-to" I read was part of a series on making a forge.  If I'm understanding this right, the home-made firebrick could be used in making a kiln for making charcoal, but would be next to worthless in making a forge you could use to (for example) make a sword or a plowshare.

Tel, you present a problem that may not have a simple solution. You are making a connection of dissimilar materials at the same time you are changing the shape from cuboid to cylindrical. To compound the problem you are doing it at a place that will be changing temps from cool to very hot in a short period of time and be subjected to direct flame for long periods.

The steel will expand much faster than the firebrick and any high temp joint material that i can think of.

I suggest a design change where you don't change materials right there or at least don't change shape right there.
(Actually i suggest neither a material nor shape change right there.)

With all the work you have done to get to this point, I hope someone can think of a material that would work there for you. (Might pm Erica, Ernie and Joel.)

ronie wrote:

With all the work you have done to get to this point, I hope someone can think of a material that would work there for you.

A wrap of ceramic insulation such as this:
http://www.axner.com/superwoolfiber-1thicksoldpersqft.aspx

which is then coated in a very thin layer of cob.  if you allow this to harden then more cob can be added later with out compressing the fiber.  I've never used this in a rocket stove as I've yet to build one, however I've used this in other application the fiber works well as a expansion joint, though it can be expensive.  There is other fiber out there that is cheaper which will still stand up to the temps reached in the stove.... I'm just too lazy to search for them...

Joe

ronie wrote:
Tel, you present a problem that may not have a simple solution. You are making a connection of dissimilar materials at the same time you are changing the shape from cuboid to cylindrical. To compound the problem you are doing it at a place that will be changing temps from cool to very hot in a short period of time and be subjected to direct flame for long periods.

it's a good point, but I'm not sure it will end up mattering that much.  I'm not sure if you can see it in the photographs, but there's a piece of 12-inch sheet metal pipe around the 8-inch pipe.  the space between them will be filled with perlite and clay slip.  I believe that will seal the junction adequately even if thermal expansion of dissimilar materials causes cracking.  it probably won't be a perfect seal, but I don't think that will be a problem.  I could be way off, but that's the assumption I'm working on.

the cob, which I'm planning to remove, is really just to fill the large gaps at the corners so that the perlite and slip can set without falling into the burn chamber.  it's possible that I could just leave it and not even worry about it, though.  it might not even be a big deal if the straw chars and the cob crumbles away, so long as I get the perlite slip mix right and the whole thing vitrifies into one piece.

josephjcole wrote:
A wrap of ceramic insulation such as this:
http://www.axner.com/superwoolfiber-1thicksoldpersqft.aspx

that looks like a handy product, and I may use something like that for wrapping around the triple-wall section of stove pipe passing through the wall at the end of the exhaust.  I don't think I'll need any inside the guts of the stove, though, for the reasons above.  I could be completely wrong, though, and I hope folks will let me know if they believe I am.

I’ve attached a photo of a two-room sauna we built last year.  Took 12 days start to finish;  raw logs to fire-up.  Had a sawmill on site, one logsmith who knew what he was doing and 4 men who know how to move logs and pound nails.  Took about 8000 board feet of logs and lumber.  This is fired with a good-sized steel wood burning stove, buried in several hundred pounds of rock. It takes about 3 hours to get to somewhere around 200 F.