John Adamz wrote:Well I had to get something together quick a few days ago for a very cold spell, but now it's time to try again to get it working optimally.
I had used the mortar in a tube initially but it didn't hold together so I'm going to re do the fire brick with refractory mortar I got at lowes.
Firstly I have 1 variable that cannot be changed namely 40ft of 6" duct under the gravel floor. 4 90deg L's 1 45, and 1 90deg L turning vertical at the end for the exterior stack. (which I had to use a booster fan on for the previous burning). I suppose this means I might have a problem if I have a 8" J tube trying to pump in to a 6" exhaust??
The pics show what I hope to use as a starting point with on the combustion core. It has a CSA of 26.56sq in (Just shy of a 6" pipe CSA) Original J dimensions were (not 100% sure where to make these measurements) measured at inside corners of the J- 9" feed, 17.25" burn, 34" riser.
I'm going to remove the first 90deg L and redo the barrel transition area with cob, and cover the combustion chamber as well.
Perlite gets you a lot further. Vermiculite loses some of its insulation value in cob, and sand just becomes thermal mass (it gets totally dense when stuck together with clay).
Thoughts on whether to use perilite, vermiculite or sand to increase insulative properties of the cob. Any ideas how many 50# bags of fire clay mix I would need to use to cob the core and make a transition area? I would like to retain the barrel lid for the bottom so as to make for easy removal and inspection.
Another issue is the riser. Right now it's just the 1/2 thick fire brick stacked on it's side. I am going to further insulate it but how big (or small) of a diameter pipe/tube do I use around the riser? I guess the limit is to leave enough area between it and the inside of the 55gal barrel. bigger is better for more insulation?
Also need to make an ash pit in the feed tube.
I'm on a short time table as well as a very limited budget but any ideas would be helpful.
Erica Wisner wrote:p.s. That's a new way to handle the manifold. Looks interesting. I might have to try it sometime.
You may want some gasket or refractory wool around the edges of the steel hole at the heat riser, so the thermal expansion doesn't wriggle things out of place over time. Definitely insulate this area between the bricks and the metal with something relatively flexible.
Cindy Mathieu wrote:What is your chimney situation? Maybe that is your problem and not that transitional area.
I'm just wondering if the opening in the transitional area may be to wide at the opening? Please keep in mind that I am so far from an expert it's not funny! It funnels down to a 6" pipe into the ground correct? Is there any way you could possibly temporarily reduce the opening a little just as an experiment to see if it makes any kind of difference?
The cross-sectional areas should be consistent between firebox and exhaust, no big jumps up or down in size except that the barrel area can be larger.
allen lumley wrote:I would like You to share how you are going to seal the part that is open at its bottom
and extends over the top of your Transitional Area ! More hardware cloth and cob? You would need to roughen up the area where the two patches should bond, perhaps all the
way back to the Transitional Area's hardware cloth ?
Kevin Davis ; I am sure that this whole area will be sealed off and in fact, filled with ether perlite with a Clay slip and perlite Cap at the top of the Heat Riser, or perlite and cob, or
just rock wool stuffed in between the brick inner and outer metal shield, like the filling in a sandwich ! Big Al !
John Adamz wrote:I would really appreciate some thoughts on the thermal mass aspects of my system.
I have the 6" pipe in a 10"+ wide trench in the dirt (very black former garden soil). I have covered the pipe with ~2" cob so far and filled in on either side with cob mixed ~15% small gravel well compacted to avoid air voids. I liken it to a sort of claycrete I estimate a total of 1050 lbs of cob for the entire project of the combustion core/barrel transition area and 12' of new pipe.
I'm now considering 2 alternatives to cover the duct up to surrounding floor level. 1) to just use the gravel that was there making it ~3" over the cob covered duct, or 2) go and buy solid concrete cap blocks (2x8x16 or 4x8x16) to go over the top of the cobbed duct (sort of "setting"the brick in a bed of cob over the duct). They would span the duct trench which is the path most traveled in the greenhouse. My concern is that with just 2-3" of gravel over the cobbed duct unless the cob is really set up it might tend to crush it from walking on it. The duct being crushed under the ~4"+ gravel floor wasn't a problem before.
So bottom line would I get more heat off the duct covered with gravel or with cap blocks?
pics of the progress so far.
Jennifer Charlton-Dennis wrote:Hey John,
Just wondering if you had the chance to try out any drier wood to see if it reduced the ash problem as it did for ours. Keep us the great work and keep up posted!!
allen lumley wrote: YOU are just feeding the wood in so that only the lower tips of the wood is burning right, not dumping in chunks like you were throwing your dirty socks on the floor next to
your shoes ?! for the good of the Craft ! Big AL
Jennifer Charlton-Dennis wrote:John,
Hey just wondering if you had any success with the rest of your modifications. The low tonight is 18 where we are in Ohio so I know it's cold there too!! Hope it's working out!