Hooray for the learning curve. This iteration of a mass heater weighs in at just over 100lbs, and took a day to create.
simplicity. Mold form is a plaster hardy-backer board that is an aspect of the form, rather than the previous pop-away mold form. An external frame holds the thin board in place and will absorb the liquid pressure against the form. The seams are sealed with drywall paste.
The stovepipe ends are added in with AL tape and drywall paste on the bottom, and a salvaged board with a routed hole holds the top pipe in-situ. AL vent pipe taped together makes an “S” in the stove, using two straight flexi pipe connected to the stove pipe ends, the straight flexis meet at a short flexi forming the bottom curve of the S.
The drywall screws poking into the interior will help anchor the walls and the aircrete. This is my maximum size possible with a 3’x5′ panel; 14″ x 36 “floor, 13″ x 14″ front/back, 16″ x 36” sides.
Two days of curing in 75 degree temps, an inch or two of shrinkage at the top- and so I poured an un-airated concrete & perlite backfilled with cured aircrete “stones” from the demo’d mass. This will make a nice hard top for the form, and I may grind it flat for a reveal of the red aircrete backfill stone and white bits of volcanic perlite.
Rolled up in the old rubber pond liner to retain moisture in the desert wind, and build heat for a better cure. This form I can easily move into the studio for the weekend snowstorm, and has about 1/4 of the footprint and 1/3 the weight of the demo’d mass- so the trip to the ranch will be easy. Now I just have to weld up the little bench it will sit on to align with the J-Stove.
First, lets remember the J-Stove / Rocket Stove project:
To capture the heat from the J-Stove, a secondary stove pipe connects into a separate mass, the pipe then exits the mass and rejoins the main J-Stove stove pipe to flow out the chimney. This is the mass form I designed and made. It will warm to a few hundred degrees durning a 40 minute burn of the J-Stove and radiate heat for 8 to 12 hours.
The side vent of the stove fits into the hole pictured below- the mass form is upside down and will have a welded metal platform to align it with the side vent.
This is the mass heater form / mold, inverted for pouring in the mass. It will have stove pipe connections and tubing added, along with rebar and expanded metal to add strength to the mass of aircrete (foamed concrete). This form provides a large mass and a bench for warm seating.
The holes are where the tubing will enter and exit, and the L shape is the bench. The form is made of one 4×8 sheet of Laminated 3/4″ MDF. It is screwed together, then hot glued, then silicone sealed along all edges and some exposed MDF was taped over as well to create a water tight form that could hold hundreds of pounds of aerated concrete.
The fins under the seating ledge provide support for the concrete weight it will bear.
It has to live through the pour, holding hundreds of pounds of liquid concrete, then after the concrete cures it has to be able to come apart and knock free of the internal mass.
The form had to wait a bit on the order of two 6″ long sections of 4″ diameter double-wall pellet stove vent that fit into the enter/exit holes. I thought I had the right pieces already…then tape on the flex tubing and add in a rebar cage with expanded metal to carry heat through the mass.
Another layer of expanded metal is added to bolster the seating platform (remember, the form is upside down / inverted for pouring.
All connections have to be secured from the outside, and water tight.
Hats off to the Honey-Do Carpenter for the aircrete cannon and aircrete recipe- just add warm water and a bit of shampoo (and my air compressor) for foam too thick to shave with. Then I use a “barber-pole” drill bit to lift the concrete mix from the bottom of the bucket into the foam laid over it, until all the concrete is suspended in the foam. It seems impossible, but it works.
The aircrete mixing station: 17 five gallon buckets will fill the form- at about 1/3 the weight of concrete. So about 300lbs, should have been 275 but the first three buckets were a bit off. Nora is next to the drill with the concrete mixer attached (black), the silver spiral between Nora and the drill is what I used to blend the concrete into the foam.
The main mass of the form is more than half full. I’m using a red dye in the aircrete.
This is all very tiring, and I’m only half convinced it will work- the form could blow out at the sides/bottom, the aircrete might not set, and even if it does the thing is a lot more massive than I had conceived.
4 hours after the pour is finished and not even beginning to cure out.
I wake up with a dread that the form has popped overnight, and the concrete never set, and it all flooded into the pond and killed all the fish and ruined the pump and waterfall. Now, 5 days later, and after 3 nights below freezing wearing a foam cap, it is solid and curing toward a respectable hardness.
I’m letting it cure into next week. There has been some small shrinkage/settling that will need another round of pouring- I may use a fast setting concrete to make a stronger platform for the mass, then I will remove the form. If all that is successful, I’m going to cut it down in size quite a bit. This is designed as the ideal form to have at the ranch that can fit into the back of the pickup, but it is too heavy to move without at least two more strong guys and a bit much for a 500 mile trip in the back of the little pickup. I’ll remove the bench and bevel an angle into the body of the mass, dropping around 100lbs. If all that works out, it will travel up to the ranch sometime this fall for installation and testing.
I found this armoire for free, just a few blocks away. It had seem some hard use, but two days of Danger tinkering and she is ready to travel to the Montana ranch (she’ll nearly fill the bed of the truck).
3 Part Armoire. Mirrored Door. The biggest triage was making new interlocking boards between the drawer section and the closet section. Simple in theory, but it needs to align perfectly so when they seat together they seal tight. I had to wait for E to come home to help lift the closet on and off to set the pieces.
Steel wool carrying beeswax with orange-oil loosened black grime and paint splatter. It wiped away with a sacrificial microfiber towel cut into sections for degrees of yutz.
Both inlay panels are intact and cleaned up nicely.
Fleur de Inlay with flaming grail.
The door hardware is intact. Twist the hoop and now the latch catches and releases. I have an old skeleton key at the ranch that will likely fit the lock.
The center rear panel is new birch, still debating whether to stain it. The side panels just needed their tops and bottoms trimmed to fit and lots of fresh staples. A piece of oak is just behind the bottom edge of the door, securing the wall to the floor. The weight and pressure of the door had shattered the old bit of wood holding things together there. It was a few hours of fiddling to get that one detail to come together.
Also added in; a clothes hanger rod. This took some new supports for the walls.
The bottom of the drawer needed reattaching, and a side wall dovetail connecting to the face board had split out and needed glue with a long clamp overnight. The lateral runner bars needed resetting, and I added a back bumper strip to act as a stop.
Last week’s triage was repainting a portion of the bathroom door. First, removal of hardware.
I stripped the door down to the wood, removing old stinky lead paint. Then repainted and reassembled and rehung. This was necessary after using Costco’s mild bleach cleaning wipes around the door handle for a few years- it melted the binders in the paint.
There is a blizzard at the ranch, and here it will drop into the 30’s with rain and wind- so we moved all the deck plants back into the sunroom. The fig tree is blocking half the room, and I can hardly open the door. The sliding glass door is completely blocked as well. Things got big this summer!
The pair is cleaned and waxed.
All welds, road rash & dings, car paint & rubber bumper transfer have been turned back to fish skin and stream stones with grasses.
After adding in new patina at welds and dings, the sculpture is left to warm in the sun. Once toasty, I paint on a layer of clear wax, let it cool, and buff it off. Then warm it in the sun again. This view shows the rear fin’s weld to the hoop, and the front fin’s weld to a stream stone.
Another view of the front fin connected to a stream stone. A tan stone behind the fin is making it a bit visually confusing.
The rear fin from the opposite side. This weld is the only connection to this stream hoop, so it is hefty all the way around.
This fin had been ripped nearly off, and was clapped against the fin on the other side.
The third main anchor weld is the fin connection to the front hoop. A section of the stainless pipe is visible under the rear hoop, it’s weird angle shows the force of the impact. It will be cut away and replaced.
Happy to be clean and waxed, the pair will return to the studio to wait next to their stainless steel poles.