12" ID system

I have a bunch of 12" pipe and a couple old doors off wood stoves and was wanting to make a batch feed RMH. I am planning on casting both the firebox and the riser. I have been collecting used firebrick and want to make a oven on top of riser. my question in about spacing on sides of riser and if a barrel is big enough if I use a 12" ID for riser. So that would make the OD about 16" . I want to get the book but haven't been able to yet...
I have a "salvage yard" of stuff on this property from previous owners so am trying to use whats here as much as I can... I have been inspired by some of the work of others here!!! TIA Julie

A 12" batch box system would probably be big enough to heat a gymnasium. The common batch box size is 6", and the 8" batch box Peter van den Berg built at the innovators event last fall was reportedly scary huge and hot. My impression is that an 8" system is twice as powerful as a 6", and a 12" would be much more than twice as powerful as an 8". It would use a lot of wood at each loading, and you would need a huge storage mass to hold all that heat for later.
What size and type of space do you want to heat, and what is your climate?

1.1.3.6 that would create a 6 ft bell or barrel. No go. Look into rocket castle builds. No reason why you can't store thermal mass behind that

WOW! Chad, would you "dumb down" the 1,1,3,6 for me? are you really saying I would need a 6ft. diameter barrel? I guess I will go dig around and see if I can come up with smaller pipe. I just didn't want to have to babysit it so often. I am planning on heating a greenhouse/sauna. but need the large mass storage cause I live in Interior AK zone 2. I have unlimited wood supply even if I just use downed trees on our property... I will look at the castle build thing. Thanks for being patient and answering my questions!

Julie; Matt Walker told me that an 8" J tube will push thru six 1/2 barrels (55 gal) long, possibly more. Suggested that the outlet pipe could be slid up or down depending on how warm your bell ,barrel tunnel, mass is. My greenhouse has 8" pipe buried in the mass, I hope to build either a J tube or a batch, this summer in my shop using the 1/2 barrel system.

Julie; Matt Walker told me that an 8" J tube will push thru six 1/2 barrels (55 gal) long, possibly more. Suggested that the outlet pipe could be slid up or down depending on how warm your bell ,barrel tunnel, mass is. This summer I hope to build either a 8" J tube or a 6" batch in my shop using the 1/2 barrel system.

Julie, i would say, try a mockup, with no barrel, a stacked brick box and port. With your 12" metal pipe as a temporary heat riser.
And see if you like it!

Something like this




The one above is a six incher. With the metal tube outside, and refractory clay and grog chimney liners on the inside.

But i think Thomas is on the right track. You could use your pipe a bit like the half barrel system from Matt. http://s65.photobucket.com/albums/h228/mremine/NYC%20Rocket%20Stove%20Build/

You could either open your tubes, to make domes. But myself i just would use the pipes burried in mass, as a bell, and forget about it.

We know that a 6 incher can come with 6m² of ISA (internal surface area) for the bell. And that for pipes, you don't take into account a bottom quater to a bottom third; to make the same calculation.

And 8 incher can cope with 9 m² safely, 12m², IIRC theoreticaly.


Hth.

Max.

Julie, that needs a correction. 1:2:3:6 which means.... 1=system size, in your case 12in. Now plug in to the previous ratio, 1, system size, 2, j tube height 3, burn tunnel length, 6, riser height. Which puts you at 2 ft x 3 ft x 6ft, approximately of course. So your barrel would be be a hypothetical 6 ft tall 3 ft wide. To make this more accurate.....this is the math for a batch system...


1. Decide what system size you want and name your DIAMETER of chimney flue.

2. Then use equation to calculate the Cross Sectional Area(CSA) of a chimney flue:

The formula to calculate cross sectional area of a cylinder is pi (a constant value, approximately 3.14) multiplied by the radius of the cylinder (half the diameter, so half the distance from on side of the circle to the other) squared (multiplied again by itself) So if the circular end of the cylinder is 12in across then the diameter is 12in and the radius is 6in. The cross sectional area would be calculated as: 3.14 x 6in x 6in = 113in sq.

3. Now solve the following equation (insert CSA of chimney flue and calculate)

Y = square root of (CSA OF CHIMNEY FLUE) * 2 / 3

4.Based on Y you can derive the dimensions of firebox (without slopes - these you will add in the end)
FIREBOX:
WIDTH= 2 * Y
HEIGHT= 3 * Y
DEPTH or LENGTH= 4 * Y

HEAT RISER:
HEIGHT= 6 * Y
CSA: if SQUARE, then one side of a square is the same as the DIAMETER of a chimney flue!
---------------------------------------------------
EXAMPLE:
1. I want the system for a chimney flue with DIAMETER of 12in.

2.
(CSA OF CHIMNEY FLUE) = PI times the square of the radius
(CSA OF CHIMNEY FLUE) = 3.14*6^2
(CSA OF CHIMNEY FLUE) = 113in sq

3. 
Y = square root (CSA OF CHIMNEY FLUE) * 2 / 3)
Y = square root ( 113 sq. In * 2 / 3)
Y = square root ( 75in)
Y = 8.5in (roughly)

4.
FIREBOX:
WIDTH= 2 * Y = 2 * 8.5 = 17in

HEIGHT= 3 * Y = 3 * 8.5 = 25.5in

DEPTH or LENGTH= 4 * Y = 4 * 8.5 = 34in

HEAT RISER:
HEIGHT= 6 * Y = 6 * 8.5 = 51in

So with a 12 inch build, the system would top off at 6'4 just as a box and riser.

Since you're in Alaska, an 8" batch box sounds appropriate. 12" pipe would be just big enough to act as a bell for a 6" system, but not for an 8" system. You would need the half barrels at least. If you can cut or open the 12" pipe to make a half circle, that would work fine as a bell for the 8" system.

But it would be exciting to see a 12" combustion core in action If you do test something that size, please take video and share!

Hey Chad; I'm guessing here but are you a school teacher ? college professor ? Your math is flawless. Sure is confusing before coffee tho...

Ok, WOW! Chad Thanks! (still had my head spinning but I can get it! (I'm a simple sort) I will play with some mock ups when I can and will post pictures/Video. Ok, I will plead mercy again... Seems like I have seen several systems where the Burn box size did not match the exhaust chimney. That's a no-no correct? you can increase the CSA in the middle (bells) but the exit/exhaust chimney needs to be the same as burn box and riser? and If I use half barrels in the middle do I open them up the whole way or use off set holes to vent from one to the other? seems like it would need to be the second... Thanks so very much everyone you all are a great help!

Nope, thomas, not a teacher. Calculator. Thanks though.

In regards to using the 12 in pipes as bells or exhaust...not a terrible idea.

I did more math for that: If you build a 6in system you should use around 12.5ft of 12in pipe whole, or 15 ft cut in half.
If you build a 8in system you should use around 16.5ft of 12in pipe whole, or 20 ft cut in half.

But like levar Burton said, "don't take my word for it. Go to your local library"

Edit: yeah exhaust should be the same size. Plus it's just easier.
The system could definitely push through more, but it lends itself to a risk of loosing some draft on the coldest days, or chilly mass. I would rather reclaim some heat from the exposed flue if your loosing too much heat, rather than tear the whole system apart, later.

Oh yeah, based off of heating 3 ton of mixed mass.

For 12 inch cut in half, I'm not a fan, I would like to see examples to how people could flip them flat side up, for better contact, but keep it cheap, smooth enough to clean, and still hold the mass above it. My idea is an internal wall in the mass on each side of the half pipe, sheet metal cap, some cob skreeted level and then flat urbanite over the metal, urbanite bridging wall to wall, then fill on top.

Glen, i know a 12 pipe can't be a bell for the 8 incher, but it can slow down the gases enough to have a better heat exchanger. Followed by a reduction and a 8" vertical, it could work nicely.

Chad, i don't think anybody talked about cutting the pipe in half. Just one cut and open it like a half barrel. But it would be weak i think!

Agreed, the initial post was for a mass heater, and all my comments referrer to using a bench-like mass. My apologies if I implied using the 12 pipes as a bell. For cutting the pipe in half, I was thinking of this type of setup: http://s65.photobucket.com/user/mremine/media/NYC%20Rocket%20Stove%20Build/P1030300.jpg.html?sort=3&o=19
Cutting and spreading the pipe open...sure but we are starting to get weak (like you said), too big, and in my opinion, undesirable contact surface area. It's sometimes hard to keep on track, and simplify explanations.

Chad, i was kind of saying the same

https://permies.com/forums/posts/list/46176#368468


But, Glenn and i were talking of splitting the pipe once, and open it to form half barrels. Tho, without the ridges, the pipe won't be as tough. But a half barrel and a 12 pipe open have aproximately the same width of metal, if flatened.

I agree completely. Cutting in half was just my proposition. If one really wanted to make use of that 12 inch pipe, I stick with whole round, no loose fill. A cob like mass will hold its own. IF the 12in cut and spread pipe was strong enough, I would still stick to 12.5ft for a 6in, and 16.5ft for 8in, since that flat bottom doesn't really count when factoring in surface area contact. Only hypotheticals. But based on size, an estimated btu out put, exhaust surface area contact, and the masses heat storage capacity at 3 ton dry earth/stone.

Julie; When using the 55 gal barrel cut lengthwise, you trim all but a small bit across the ends , (helps hold the 1/2 barrel shape) No holes just wide open between the barrels.

Thanks!!!