Gregg L'Oeuf

shilo kinarty wrote:yes/
but you can more easily do a bigger barrel.

bigger how?

taller, which would affect the gap at the top of the riser?
or wider? which would affect the csa of the exhaust part of the barrel (the outer downdraft part) - assuming the heat riser stays the same diameter.

I'm guessing you mean surface area of the barrel - so either? - in which case it won't work for me as I only have a limited area in which to build the heater part. ie, an area 44in tall x 38in x 36in

I've just changed a CPU in one of my PCs, and that got me thinking about heatsinks...

I'm wondering whether a large heatsink placed on top of the heat riser barrel, and perhaps bonded with thermal paste, and a fan blowing across it would extract more heat from the gases

I'm thinking I could cast a heatsink [1] the same size as the top of the barrel, with 4" (6"?) ribs and give it a go.

Anyone done anything similar?




[1]or half a dozen smaller ones.

Glenn Herbert wrote:So your alcove is all masonry? How thick is the masonry on various sides? You may be able to use that as part of the mass that stores your heat, with a bell built as a liner for it.

Interesting...



this would be how the bell would be built?


I've discovered an issue unfortunately - the steel chimney liner which I was going to leave in the chimney to use as the exhaust is only 3.5inches in diameter, so I'm going to have to remove it, and use the original chimney for the exhaust - bit of a pain, because that means i have to climb onto the roof to disconnect the cowl so i can pull the liner out.

Glenn Herbert wrote:If you have limited space, you would be better off just replacing the barrel with a hollow masonry box, as tall as you have space for. There are formulas for the correct internal surface area of a "bell" as these are called, to get full heat absorption without taking so much that you lose your draft.

Bells work by letting the hottest gases rise to the top and stratify; the coolest gases after they have given their heat to the masonry fall to the bottom and go out the exhaust.

I was looking at these, but I want to fit the heater into an alcove (which used to be a fireplace) - it is only 44in internally, but 38 inches wide and deep - so enough floor space for the double barrel, but not enough headroom for a tall bell

I'm wanting to build a heater for my workshop - something along the lines of a rocket mass heater, but without the cob bench - so just a rocket heater I suppose?

The biggest issue is keeping it "stealth", to which end I want to remove as much heat from the exhaust gases as possible before allowing them to exit the chimney.

I don't have enough room in the shop to build a cob bench, but I was wondering whether a second heat riser in a second barrel would work.
basically take the horizontal outlet from a normal rocket heater and where it would enter a cob bench, put another "L" bend and run the gases up another insulated chimney and then down a second barrel and then out the roof(wall actually)something akin to the attached image.

Has anyone done this? Did it give a significant reduction in exhaust temperature?did it work at all?
I'm going to give it a go with a 6" system,but there's no point in me duplicating work, if someone's already tried it and it didn't work.

The shop is quite well insulated, so I'm hoping that a fire for an hour or so in the morning would take the chill out of the air until the sun rises (it's quite mild in UK, usually around 25-40F in winter), then again on an evening if I'm working late.

Unfortunately, the area i have to build the shed is only just 8ftx12ft, and obviously I want
as much space inside as possible.
I'd much rather build 4"-6" thick wattle and daub walls than 12"-18" (?) thick cob walls, then lose another foot
each wall for the roof overhang (I realise that I will need overhang to protect w&d as well)

If I had unlimited space, I'd just build an "earth bag" structure, since I have access to a pretty much unlimited supply of
1 tonne sand/gravel bags which I could fill will "urbanite"[1]

[1]urbanite - we don't really use as much concrete in the UK.
Most buildings are made of brick or stone which tend to be cleaned and reused (and sold at a high percentage of "new price"),
and our roads are "tarmac", or asphalt.
"road planings", which are a mixture of sand, gravel, small (up to 2") rocks and tar are quite abundant
and cheap to obtain (as in 1/4 to 1/2 the price of quarry scrapings or crushed building rubble)
The road planings are quite useful, as in winter they can be poured onto/into an area and rolled flat or compressed, they will
then reconstitute into a waterproof, not quite self-supporting solid mass during the summer.

I have lucked onto about 5ft of 8" square box section steel about 1/4in thick.
I also have about 20ft of 5" diameter round steel pipe.
I want to build a "rocket mass heater style" heater for my workshop.
I'm planning to build it inside a couple of scrap 47kg (100lb?) propane cylinders and fill the gap
with vermiculite,with a 200l (55 gallon?) barrel over the top, then some sort of heat exchanger -
maybe from the 20 or so LARGE (6"x4") aluminium heatsinks I have in my scrap pile.

The "rocket stove book" says that each part of the heater, from fuel feed to
exhaust should have equal cross-sectional area.

Can someone more knowledgeable tell me what problems I will have if I make the fuel feed
and exhaust from 5in pipe (about 20 sq in cross section), with the fire box and riser from 8"
box section?

I want to make the heater portable if possible, as I am in the process of building a new garage.

The machines don't so much crush and pulverise - more a turnover/squeezing action, which I'd've
thought was perfect for mixing cob?

I'm thinking that I can add sand, clay, straw and water to the mixer, and save myself the labour
of mixing the cob "by hand" so to speak.

I usually work as a two-man team (with my son), and would like a machine that could keep us supplied
with cob, same as a cement mixer would keep us supplied with render on a conventional construction
site.

Has anyone ever used one of these to make cob?

http://www.youtube.com/watch?v=r-fUMqtQ5L4

http://www.youtube.com/watch?v=mgP1cwyw44M

http://www.youtube.com/watch?v=RdabqoUK3eg


it's a machine to "mull" foundry sand (which is basically sand with about 8-10% clay added).

The sand is given a sort of squeezing/mixing action which seems ideal to mix cob.

I'm planning to build one - I do some aluminum casting as a paying hobby - and it would
be relatively simple to adapt it for cob mixing; perhaps a toothed roller, rather than smooth,
and a heavier squeeze?