Emergency quick and small batchbox for the 400 sq ft wofati (0.7)

We have an emergency need for heat in the 0.7 wofati as soon as possible or the kids are going to freeze or have to give up and move down to the house. I thought that maybe a four inch batch box might be the answer for something quick, all radiant no mass. I thought that "four inch" systems were what our system was scaled up from but couldnt find much information after a bit of looking. Seems like most people have done 6". Looking at the donkey threads for a little bit it seems the four inch was square tube and a few people have experimented with 4" round systems.

The wofati is 400 sq ft and the walls and ceiling are the mass. What I'm hoping for is that you could point me in the direction of an approved design or details of a similar build so I could throw something together in a couple of days to get them warming up.

The smaller the system the better due to a couple of factors, but need to radiate a decent amount of heat and am thinking not any mass. We would then chimney it up and out similar to the 0.8 design. In any case, what size do you think could get us by on radiant alone and how many 55 gallon drums could we use to shed the heat?

Any and all feedback will be greatly appreciated.

Using the batch scaled formulas, the riser would be 29" and the box only 5.76 wide, 8.64" high and 11.52" deep. The port would be 1.44" x 6.34" and the p-channel 1.44" x 1.37"
this seems small but if just as powerful, maybe enough heat can be shed.
Still maybe 2 55 gallon drums one on top of the other and the riser black stove pipe that will eventually burn out but wrapped in 2 layers of 1" durablanket that would hopefully get us through this season, then we can pull the riser and refit with something more permanent. this could just as easily be done with 5" and 6". at some point height will be of concern for heating the ceiling members but we can attach shielding.

From what I gather, the "normal" 6" batch box is finicky- it has to be just so in order to run well. The 4" batch box is much more finicky, and very challenging to get to run at all.

It it were me, I'd build a 6" batch box and figure out how to shed the excess heat, rather than taking my chances on something that might take a few rebuilds to get working.

Rick, I'd say just do a bone stock 6" into two drums, either stacked or side by side. 6" will be much better output, fuel handling, not to mention chimney parts availability.

Dimensions and pertinent info here:

http://donkey32.proboards.com/thread/734/peterberg-batch-box-dimensions

You guys should still have lots of castable refractory. Use my ghetto casting tech and you can whip one up in a couple hours. Jesse should have a handle on how to do the casting, he went through it pretty thoroughly for the J.

I agree with Mikes diagnosis of the situation, right now the ONLY 4'' system i would trust would have to come from Dragon Heaters, wwwdragonheaters.com.

Seriously, a very small misalignment of internal connections could easily result in a low working unit that might take 10 days two weeks to trouble shoot !

This might be one of those the problem is the solution moments, There is a type of box wood stove called a laundry stove and its main purpose was to be

a supplemental source of hot water for laundry !

We brag on how much more efficient the rocket mass heater is over a conventional wood stove, put a very small conventional wood stove that will require
that it be fed with small Very dry fine split wood, and keep track comparing the two wafati's off against each other ! Even a trial of 1 month would be very
instructive !

I realize this is not an optimum solution, and many would never consider this as an option, but you may well have run out of time, and then the only
remaining option is just to move them out!

Sorry this is not a more positive message ! For the Good of the Craft ! Big AL

Mike Cantrell wrote:From what I gather, the "normal" 6" batch box is finicky- it has to be just so in order to run well. The 4" batch box is much more finicky, and very challenging to get to run at all.

It it were me, I'd build a 6" batch box and figure out how to shed the excess heat, rather than taking my chances on something that might take a few rebuilds to get working.

2nd on the 6". If height is a concern, perhaps 2 separate barrels as lower in-line bells instead of one tall one would be an answer. Peter or Matt are the ones to consult.

Edit- 2 posts above appeared while posting this...

Ok, so now it has been decided to go with a 6" standard j tube rocket engine. Any ideas on the best radiant after riser setup.

I thought regular barrel over the riser with inch and a half gap. Then port that into another barrel low as if going into a bench then chimney comes out of the top of that barrel.

Bigger top gap on the first barrel. Second barrel inlet and outlet should both be about 3" or so from the bottom, opposite sides from each other.

How much gap you thinking?

Then chimney up and out after second? Or can it do more? Two might be all we can fit anyway.

Short baffle in middle of second barrel so no gasses can cheat and shoot straight through or is this unnecessary?

Two is max for a 6" J. No baffle necessary, it won't shortcut. If you have to you can couple from the first to the middle of the second like Peter's auditorium heater. Better if you can get down low though.

Oh, top gap...as big as possible. 4" minimum I would say.

What were you thinking of when you said 2" max for gap. And we are talking about the gap between the top of the heat riser and the top of the first barrel correct?

I thought it was supposed to be small to work well, or is that if optimizing for a mass?

Sorry, my first sentence should have said "Two barrels is all that a 6" will drive" with regards to the radiating surface, so as not to cool the exhaust to the point of stalling. Still might be close, but you will have a good chimney so it should work.

I don't personally believe in the small top gap theory. I think bigger is always better. I've built 'em in just about every configuration from close top gap to a whole second barrel up there. Smaller can cause problems, bigger never seems to. Yes it does change how much heat follows afterwards, as the taller gap usually equates to more radiating surface. In that case, it's not the size of the gap but how much surface area of exposed bare metal. More exposed bare metal, more quick heat and less heat for the mass. That's my opinion on the matter. There are others with different opinions.

Thanks all. This has helped a lot. Tomorrow we can start work.

Matt, how do you know my chimney is going to be good? Just cuz you love me doesn't mean I'm always gonna do the best job.

Could something like dragon heaters' derrick build masonry stove be used? You did something similar with the 8" batch box stove. A brick lined barrel could soak up the extra heat from a 6" system and still be easily(?) disassembled.

Rick,
I rather would like you to use a 6" batch box, even a quick and sloppy one will work and besides, a 4" is too small for that purpose. The same chimney style as in the wofati 0.8 means there's a quite long stretch of bare pipe inside the space. So I'd think the maximum you could do is a double 55 gallon barrel, on top of each other or side by side. Please don't use a steel pipe for the riser, that will fail miserably when it's coldest outside and the heater is pushed hard. A sloppy 6" batch box will still deliver more power than a J-tube which has been built really well. You could leave out the insulation of the riser entirely and the thing will still run. Not optimally, but you are asking for speed.

I'll delve into old drawings or make a new one of one core that's entirely made of fire bricks. You are 8 hours behind time wise, it's now 12:30 hrs middle European time and a drawing should be ready before evening. You've got fire bricks and kaolin clay, do the bricks with clay and sifted sand in a 1:1 ratio and with thin seams you'll be alright.

Thanks Peter, eagerly awaiting.

Peter and Matt are acting much like fine cooks discussing a recipe, and considering carefully exactly what ingredients are in the pantry ! Even if cooks with
a little less experience have to prepare and serve-up this dish -My only comment should be a willingness to serve as a Sou-chef if only I could be there !

Remember:

Think like Fire! Flow like Gas! Don't be the Marshmallow! For the Good of the Crafts ! Big AL

OK, drawing is ready. For good measure: every dimension inside the 8" one is 1.77 times larger as compared to the 6" version. So the volume of the 8" firebox is 1.77x1.77x1.77=5.545 times larger. The auditorium thingy is shorter, so I'll guess it's a 5 to 1 ratio. The 6" firebox can hold about 13 pounds of soft wood species.
Construction: bricks and clay/sand. Barrels stacked as drawn, lowest barrel front cut out in order to accomodate the firebox. Riser not insulated, exhaust opening 8" to 6" converter when available. P-channel not implemented yet, can be run with a simple door or none at all. Not sure about how the chimney stack will work, when very good maybe a 3rd barrel with stacked bricks inside could be added.

There's a choice how to arrange the barrels. When used side by side the 1st barrel need to be mounted on top of the firebox like the 8" thingy in the auditorium, the 2nd one at the side. In this case you need to make a support frame for the barrel otherwise it's too unstable. I'm not sure you have access to SketchUp so in addition to the drawing itself here are 7 pictures showing most of the brick layout.





And last but not least the drawing itself.

As you can see, the biggest problem is the cutout of the barrel and the sealing against the fire bricks. I'd suggest to make the cutout a little smaller, make a flange around with that ball/claw hammer and stuff the space between steel and brick with superwool. In addition, the bottom end could be cobbed in.
The installation of the chimney and hauling all the materials plus tools to the wofati would be the largest part of the work, I'd expect.

After the second barrel, can the exhaust go up to 8" if we have more of that laying around?

Peter. Thanks for the plans, most excellent.

Rick Edwards wrote:After the second barrel, can the exhaust go up to 8" if we have more of that laying around?
Peter. Thanks for the plans, most excellent.

Yes. Chimneys can be larger diameters as the heater, not smaller.
You're welcome, I do sincerely hope it will solve the heating problem.

Chimneys can be larger diameters as the heater, not smaller.

If I may, just a slight addition, alteration...

A chimney within a wood burn system for a given combustion shaber for a given run of horizontal, and Up down radiant passages should fall within certain parameters depending on multiple factors of location, elevation location of build, and general design of system...These chimneys are meant to match the system...definitely not undersized, yet too large will also cause inefficiencies, and/or failures.

Regards,

j

Jay C. White Cloud wrote:A chimney within a wood burn system for a given combustion shaber for a given run of horizontal, and Up down radiant passages should fall within certain parameters depending on multiple factors of location, elevation location of build, and general design of system...These chimneys are meant to match the system...definitely not undersized, yet too large will also cause inefficiencies, and/or failures.

Agree. In these specific circumstances I'd think it will work.

Thanks also for the brick layout Peter. I have also been thinking about building a brick 6" batch burner, but thinking about substituting for the steel barrel(s) a small brick/masonry bell and brick/masonry bench of some sort. Nothing fancy of course, just a small cabin heater of sorts. Has this been done before?

Byron Campbell wrote:Thanks also for the brick layout Peter. I have also been thinking about building a brick 6" batch burner, but thinking about substituting for the steel barrel(s) a small brick/masonry bell and brick/masonry bench of some sort. Nothing fancy of course, just a small cabin heater of sorts. Has this been done before?

Yes, this has been done quite a couple of times all over the world. Beware though, a well running batch box is delivering about twice as much power in any given time frame as it's J-tube counter part. So it's a surprisingly big heater in a small package.
A well built 6" batch box in an all masonry heater can serve 6 sq m or 64 sq ft of internal surface area, not counting the floor of the bell and/or bench.

Rick,
Forgot something... The sloped sides of the firebox and the back sweep in the riser can be made with clay and perlite. Make it really stiff like dough, so you have to knead into place.

We are moving forward with Peter's plan and I'm considering a P-channel as well so it can have more push hopefully.

1. could you remind me the csa of the primary air intake? I'm thinking 20% system size.

2. also using these dimensions I'm going to start cutting brick to size Could you double check for me please.

System 6" diameter or 5.3" square riser.
riser height 43 3/16"

box width 8.64"
box height 12.96"
box depth 17.28"

port width 2.16"
port height 9.5"

P-channel W 2 3/16"
P-channel H 5/8"

Primary air intake 20%?

3. there will be a door of duraboard like the auditoreum for better draw.

4. Was thinking of duraboard top for ease of install.

Any problems let me know and thanks for the sloping tips.

also when using a square riser could it be better to rotate the riser 45 degrees to help the rams horn?

Sorry also,

when you say clay to sand 1:1 do mean dry clay to sand or clay slip to sand?

and what are you referring to as the kaolin clay, our local clay or one of the purchased clays we have around the shop.

Also i was going to wrap the riser areas with durablanket for insulation and better push.

As always any and all feedback is welcome.
Thanks to everyone here throwing in their two cents.

Rick, it's ram horning in square risers too!

P-channel should be 1.41"sq.

Is it better slightly bigger or slightly smaller.

I can get easy 1.3125"sq or 1.53"sq

Progress. All but one brick cut.

Riser can be 40 or 42.5 or 44.5.
Any thoughts?

Radiation option will be the barrels stacked like in the sketch up.

We have slip warming and clay soaking. Tomorrow we'll burn the barrels off and maybe get them cut.

Well Rick, we should wait for Peter to wake up, but I'm just going to throw out this assumption in case you are cutting more bricks after dinner. He will probably want that riser to be 6"sq. rather than the 5.3" you list. CSA is right with the latter but the corners tend to drag so it's best to make the square so a 6" circle can fit inside it. Otherwise it's a restriction.

I'd go with the taller option. Are you measuring from firebox floor?

Good point Matt. I've been going through so many threads the last 48 hours. Now I remember reading that in the forums. Had my head in J-tube land. Already cut them but only need to cut three more at 6" to fix. Thanks for the heads up.

We're looking at trying your mix from the video for a later shippable attempt. Any thoughts on how to gauge the amount of pulled fiberglass proportions?

My mix there is a good diy option for folks who don't have access to industrial refractories. It won't be a good option for a shippable type core. It's fragile and needs much thicker sections than the refractory so it's a lot heavier than a similar refractory core. You guys should still have some bags of insulated castable refractory left over. Use that and reduce wall thickness to 1"-2" throughout. I used 1" for all the cores I made during the event, mostly to conserve material, but it's enough.

That said, my mix is good for any cob based type stove you guys might build that you don't want to use the good stuff on. It won't handle a lot of moving around though, needs to be wrapped up in good cob to keep it all together. To answer your question, you want to use enough that there are hairs evenly distributed throughout, but no clumps or strands. I think I used about 2 sq/ft for that 8" J.

Thanks again Matt. Good input on your ghetto mix.

I also wanted to thank my new partners in crime , Derick and Olenka. Olenka has experience in casting cement, plaster, bronze and resins. Also mold making. Derick attended an RMH workshop and knows the barrel burning process to help me with that tomorrow.

Rick Edwards wrote:We are moving forward with Peter's plan and I'm considering a P-channel as well so it can have more push hopefully.

Good plan.

Rick Edwards wrote:1. could you remind me the csa of the primary air intake? I'm thinking 20% system size.

20% is fine.

Rick Edwards wrote:2. also using these dimensions I'm going to start cutting brick to size Could you double check for me please.
System 6" diameter or 5.3" square riser.
riser height 43 3/16"

box width 8.64"
box height 12.96"
box depth 17.28"

port width 2.16"
port height 9.5"

P-channel W 2 3/16"
P-channel H 5/8"

Primary air intake 20%?

All dimensions are correct, except the riser size. Thanks Matt, for pointing that out. Remember, all the dimensions does allow some tolerance, especially the depth of the firebox. This can be oversized as much as 8", but don't overdo it when not necessary.

Rick Edwards wrote:3. there will be a door of duraboard like the auditoreum for better draw.

Can be done, but I don't know how it will hold out for a season. Best to fabricate one in reserve.

Rick Edwards wrote:4. Was thinking of duraboard top for ease of install.

Same as above, monitor this closely.

Rick Edwards wrote:Any problems let me know and thanks for the sloping tips.

also when using a square riser could it be better to rotate the riser 45 degrees to help the rams horn?

The rams horn will swirl anyway, the only thing is it will take higher temperatures to work.

Rick Edwards wrote:
when you say clay to sand 1:1 do mean dry clay to sand or clay slip to sand?

Dry clay to sand.

Rick Edwards wrote:and what are you referring to as the kaolin clay, our local clay or one of the purchased clays we have around the shop.

One of the clays in the shop. I think the word Kaolin is on the bag, it's a white clay, very fine powder.

Rick Edwards wrote:Also i was going to wrap the riser areas with durablanket for insulation and better push.

In that case, watch out for the manifold side where the exhaust opening is, which can be on either of the three side by the way. You need at least a distance of 2 inches everywhere when the exhaust opening is 8". When the opening is 6", you need 3.5 inches minimum. These numbers are presuming heart of the exhaust opening is at least 8" above the barrel's lower rim. Insulating is a good choice when you have the space.

Rick Edwards wrote:P-channel should be 1.41"sq.
Is it better slightly bigger or slightly smaller.
I can get easy 1.3125"sq or 1.53"sq

Better to have the depth as close as possible to the proper dimension, wider doesn't have much effect. But it all depends on what you have at hand so 1.53" would do.

Rick Edwards wrote:Riser can be 40 or 42.5 or 44.5.
Any thoughts?

I'm not sure, the 7 layers as per the drawing should be adequate. Higher risers tend to add more mass to the core.

Keep us posted, this is a very exciting development!

More pictures ! Please and thank you ! Big AL

Thank you again Peter. Most helpful.
I was just starting to get into all the history and knowledge of the RMHs and batchboxes in the forums when this came up. So I just want to reiterate how grateful I am to Peter, Matt, Satamax, Big Al, Mike, Joe, Andrew, j, and last but not least Byron for letting me lean on you guys pretty heavily to get me up to speed. All of you are making the world a better place through learning good things and moving them forward.

That being said:
1. The clay perlite ramps should be kaolin clay? I'm assuming the local clays of a site shouldn't get used for the burn areas or the fire brick unless their properties are investigated.

2. The riser height dimension came from the formulas and spread sheets on donkey 32. Sounds like that is if using optimal materials, yes? The 7 lifts of brick give me only 31.5" from burn chamber floor.

2a. Peter is thinking shorter for mass, Matt is thinking the taller the better, both of you know it's built out of fire brick. I think it would be great if the two of you had a little collaboration here on the whys and hows and ins and outs of the pros and cons to the shorter vs. taller height. I'll install whatever seems most appropriate.

2b. Just realized I can make the riser out of split bricks for less mass and more room inside bell for insulating the riser. Seems this would be better in all ways, yes?

2c. Matt, steps for casting a round riser with your goo? Peter, And if using something like that, then take riser to the chart height? Was thinking 1"thick and could wrap with 1 layer durablanket and wire for sealing any cracks and extra insulation.

3. My P-channel will be 2" x 1" o.d. And the slot gap is 2.3" should I narrow the gap to 2" so air can't go around the sides of the channel?

4. Can I offset the barrels from center for better manifold spacing or does this have negative effects on the bell radiation and downdraft qualities.

5. Al, I'm workin' on it!

6. Satamax the link please to your video or the title. My brand new "smart" phone can't do anything with an embedded video.

Going up to the wofati now to look at space and figure chimney lengths and stove position. Also decide box length, might go longer for longer fuel pieces.

Can't wait to stop being the marshmallow.
R.E.