Another Green house RMH

[careinke]

Hi All,

I am in the process of building a RMH for my small (15' X 14') green house. Here are two time lapse videos of us building the stove part. The second one has some boring parts where I was off mixing cob, sorry about that.

www.youtube.com/watch?v=NtX0B00qIeA

www.youtube.com/watch?v=W3cs4uZpufc&feature=mfu_in_order&list=UL

I also am posting still pics on my facebook page if anyone wants a look.

www.facebook.com/photos.php?id=1007803355

When the stove is fully running, the barrel top temp is around 600 F. I guess that is a good temp. I can place my hand on the end of the exhaust tube and estimate it is around 140 F.

I am now putting a two inch cob wrap (sand and Clay only) around the exhaust tube. Next will be cob with straw in it.

Since this is in a green house and the bench will be used to warm my soil block starts, moisture is a concern. I am not sure what to use to seal the cob bench from water. It seems a product like Thompsons water seal might work but I am not sure about the chemicals leach out in the green house. I'm open to suggestions!

Cliff (Start a rEVOLution, grow a garden)

[Donkey]

Umm..

You could try a lime plaster.
Or maybe paint it with waterglass (sodium silicate).

Linseed oil WILL make it waterproof (or very nearly so) but I'm not sure how that will do with the heat.

[careinke]

Thanks Donkey. After some research I think I will go with water glass.

What is a "normal" temp for the top of the barrel? I am trying to keep it at 450 F most of the time. I got it up to 800 F last night, but then the fire wanted to climb the sticks.

At the exit point for the exhaust I am running about 90 F no mater the temp on the barrel top. It is very clean.

I managed to get the whole 8" exhaust pipe cobbed with 2" of clay sand cob (no straw). It is cool enough that I feel comfortable for using straw cob on the next layers. I will also add a lot of bricks as fill.

So far, things seem on track and I am pleased with the project.


Cliff (Start a rEVOLution, grow a garden)

[northriver]

How are you measuring the temperatures?
I want to start taking my own measurements, and am curious what you are using.

Thanks,

Chris

[careinke]

I am using a $10 magnetic thermometer I bought at home depot. That said, I think I may buy one of those temp guns that you just point at the surface and read the temp.

[Donkey]

I don't know if there is a "normal" temperature..
Depends on too many factors and at this point, there ain't really a standard.

[careinke]

Dec 11, 2010 11:31:18 GMT -8 Donkey said:

I don't know if there is a "normal" temperature..
Depends on too many factors and at this point, there ain't really a standard.

You are probably right. But I would still like to know what everyone else is getting for a barrel top temp. Mine seems to run best at 450 F

Cliff (Start a rEVOLution, grow a garden)

[Donkey]

The bench in the "Myrtle" (the common house and library) at Cob Cottage likes to run somewhere between 350 F and 400 F..
It's a 6 inch rocket with about 30 feet of bench.. Temp is measured towards the top of the barrel with one of those household, magnetic stove gauges.

[careinke]

Thanks Donkey,

This Rocket Stove for my greenhouse is a lot more labor intensive than I thought it would be. Anyway, here is a video of my progress so far:

www.youtube.com/watch?v=w5hNIvnZ51I

It is pretty amateurish, sorry about that, but it also shows a little of the main garden area.

Cliff

[Donkey]

I've got a dial up connection to the net..
Can't see yer video, nor LARGE images as I ain't got the bandwidth.

[careinke]

Well don't waste your bandwidth on it. You know all about rocket stoves. I posted it so other people just starting to think about RMHs could have another video to look at. I know I must have watched them all before I started. So it is kind of like payback for all the ones I watched.

I also put stills on my facebook page. The link is at the start of this thread.

Cliff

P.S. This is a very useful site, thank you.

[careinke]

My son bought me a Ryobi laser thermometer for Xmas. I am having so much fun with it as I slowly add the cob. It does not work on shiny metal, as my burnt fingers can attest to! It also only gives readings up to 650 F (+/- 5 F), so I can not measure the burn tunnel.

Anyway here are some numbers from my 8" system covered with a standard 55 gal drum:

The top was around 600 F over the burn tube and was as low as 500 F towards the edges. On the side of the barrel it was around 400 at the top and 450 four inches down, then tapered off to around 250 at the bottom of the barrel.

The pot stuck in the clean out tube next to the barrel was around 180 at the bottom of the pot. The exhaust was 83 F.

I have not been to a store to get PH strips yet.

[hpmer]

Dec 29, 2010 0:07:22 GMT -8 careinke said:

The exhaust was 83 F.

Wouldn't an exit temp below 212 F mean that the water in the wood would condense back from steam to water and therefore be an issue in the stove? Though I suppose you measured the temperature of the pot and not the actual exhaust. Not sure if there would be much difference or not.

[josephjcole]

Though I suppose you measured the temperature of the pot and not the actual exhaust

I would be curious about this too. I would have thought 83 F would have been too cool to even effectively rise out of the vertical chimney. Though maybe the heat riser is powerful enough to actually push this vertical column of air...
Is the outside of your chimney pipe 83 F or is that an actual measurement of the air inside the chimney?
Joe

[hpmer]

It has to be the outside of the pipe. I built a cooking stove with a 6" burn tunnel/heat riser and put a bbq thermometer to it. The rising gas is above 700 F (though not sure how much higher as that is the limit of the thermometer).

My heat riser is only 32" I believe. So my guess is the gas is much hotter than either the barrel or the flue, and at least for the barrel the difference is many hundreds of degrees.