Kirk Mobert’s California Batch Box Rocket, Autumn, 2016

November 22, 2016 by les@well.com

: Laying out the stove, planning for space and usefulness

: The base

: First course

: Soft, high temperature insulating brick can be cut with a handsaw

: The heat riser must be built with care

: Making sure it’s all square and plumb

: The riser grows

: We were short, just one insulating brick.. That’s OK, way at the top, it’s not so important.

: The form for pouring the firebox top

: Filled

: We cut ths barrel in half, to act as the void(s) in our heated benches

: Line it up, mark it up and prepare for the skin

: Chimney exit at the back

: We notched these bricks up, so that gasses would flow to the benches first, before finding the chimney.

: The combustion unit complete and the brick portion of it’s bell begun.

: This opening is for a secondary air injector, called a P-Channel. After Peter van den Berg

: Here you can see how the barrel gets used.

: Making cob

: It’s closing in nicely

: We left a space, between the main parts of the stove and the wall, into which we poured sand, which will have an insulating effect.

: And here is where we left it for a couple of months.

: Building the form(s) for the cap of the bell

: Lining it in plastic wrap works to prevent refractory cement from sticking to the form.

: Dealing with the plastic wrap after it comes out of hte form sucks! I can’t reccomend it. Yes, it works, but it’s hard to get off and is nasty on the first burn or two.

: We came back to finish the stove, the metal fabricator had the door for us. Of course, we HAD to try out the stove, right away!

: Ram’s horns! Nice burn characteristic, exactly what is called for.

: The cob we made cracked badly while drying, and our bridging over the empty spot (where the barrels meet the main bell body) was a fail.

: The sheet rock crew, being careless, fell into the stove, knocking over it’s heat riser.

: There was a little damage, but in this state, it looked a LOT worse than it actually was.

: We cleaned the bricks and carefully inspected them,

: The wire mesh that we used as a temporary support for holding up wet cob did little to nothing.. It probably contributed to the failure here.

: So, we pulled out the wire, which gave us access to the inside of the works, which was really helpful!

: Ready to rebuild

: Heat riser going back up

: And we’re back to where we started

: We wired the door on, using metal brackets to protect the brick work.

: Door on

: Installing the door was a bit of a chore. I wish now that it was made to sit on the floor.

: Laying out the next course

: Carefully building over the door and air channel.

: The bricks, pretty much done, just wiping off excess and double checking everything.

: Then for the lid

: The lid was cast in two pieces, otherwise it would be too heavy to deal with.

: Now to patch over the openings in the benches

: First, some clay slip to make it all sticky

: We used a bunch of different pieces to add strength. First the barrel ends..

: Then layers of hardy board.

: Then cob over it all.

: Then, of course, TEST!

: Even unfinished, the thing looks great.

: The first firing of the stove, began with the lid off. We let it heat up a bit, then closed it up.

: OH! Cracked!! The glass is rated to take the heat and the heat shock (sudden change in temperature), so my guess is that the frame is a little too tight on the glass in one spot. Heat expansion might have pinched it.

: Looks like we made a hole in the lid gasket, while putting on the lid.

: The gasket slipped here, leaked a bit. When the lid went back on, we fixed this.

: On inspection and re-measurement, we discovered that the exit to the chimney was oversized. So we took the opportunity to increase the vertical distance between the openings to the benches and the opening to the chimney.

: We were able to shorten the chimney exit by 3 inches, giving us a total of around 6 inches of difference between the bench ports and the chimney port.

: This made a BIG difference in how much heat is retined by the system.

: More testing.. ALWAYS!

: We didn’t have the chimney parts, nor was the ceiling ready to accept them if we had them. We ran the stove like this.. With the upstars windows open, we could hardly tell that there was a fire, exhaling into the room with us!!

: Notice how in the rest of the images here, you will see no smoke in the room, even though there is a fire raging in the stove and it’s exhausting directly into the room.

: Adjusting the shapes of the benches

: Cleaning the bricks before plastering

: Plastering the lid

: Checking that it’s flat and regular.

: The first coat on the lid puffed up with steam, as we fired the stove while plastering it. We poked holes in the first layer, so it would not bubble so badly and rather, sit flat.

: I love how earthen plaster can be used to define shapes.

: Nice!!