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Okay, so I've made BOOH V. It's a lot like BOOH III and IV, except neater. Same chimney, but with a new cage. As it stands, it's an end loader now, but I will eventually install a vertical fuel inlet and cap the end. You can't easily see it in this picture, but the burn channel is three layers.



It incorporates about 36 sq. ft. of the 1/2" blanket and 27 sq. ft. of the concrete reinforcing mesh. The whole thing weighs in at 17 lbs.

Some of the construction details are worth a glance.

I'm now using the inner part of a wire mesh roll, rather than cutting up and rerolling a tomato cage. This part of the roll is already in a nice cylinder shape, needing only a little circumferential compression to fit the chimney. There are a lot of ways to achieve this. I'm mostly using hooks bent from heavy copper wire, as it is easier to work with than the even thicker steel wire.



The two wire cylinders are held in place in the wire channel by a combination of gravity, friction and mechanical interference. Good enough for now, and easily undone. I've also loosely attached this handle:



It is slightly below the center of gravity, so it takes a second hand on the chimney to keep it stable. It felt surprisingly solid, carrying it from my workshop to the garage, but I wouldn't want throw it into the back of a pickup.

The burn chamber is still joined to the chimney by just jamming them together and stuffing cracks. Still ugly, but tighter than before.

It's raining today, so I don't think I will get a chance to run it. At this point, I would be very surprised if it doesn't run up to 900˚ pretty easy. Aside from working out these incremental improvements in my construction methods, I want to use this BOOH to run some tests on how various things survive in the burn tunnel and how they affect the batt material. Plus fuel and air intake geometry.

Wow, it's really starting to look like a core. 17 pounds! I truly believe you are on to something. Nice work.

Looks like a very nice unit Nutcase. I like the handle for easy carrying, that is a nice feature. I see that the metal cage around the unit looks very sturdy. The handle is a good addition and will make it much easier for you to move the unit around as you experiment. I was wondering if you have thought about using an inner metal wire support for the inside of the burn chamber as well as the upright chimney section? It might help prevent the insulation from collapsing or sagging and give you a better test burn. I know that these units are experimental for you and you may have a good reason why you do not want to support the inside of the burn chamber. I was just curious about your thoughts on a metal wire support for the inside of the unit.

Thanks, Matt.

Guy, I have indeed thought about it.
Steel cans burn out in days, if not hours. cast iron would of course defeat the whole purpose. Some sorts of stainless steel may be useful though. The electric burner elements are sheathed in some sort of nickel chrome alloy. people use nichrome wire in furnaces, though not necessarily exposed on the hotface. This is one of the things I want to play around with a bit. Mainly though I expect to use some sort of refractory ceramic to hold things in shape and protect the inner surface.

Yeah, steel won't last long inside. Even stainless will lose the ability to add much support after a couple burns, in my experience.

That answers that question, Thanks.

Matt, have you used high temp stainless or something more generic? My impression so far is that the stove burners are holding up so far.

My comment is from destroying a double wall stainless flue pipe when using it as a temporary riser. I think your grates may be okay for a while. They are still upstream of the hottest part of the stove, although I've melted glass right at the bottom of the feed in a hot stove.

The burners were a great idea for a Grate. I was impressed by your ingenuity in making them into a grate for your unit. They are fairly thick and designed to heat up and get hot and stay hot. I think the metal in them should last for a good while. In addition the max temperatures are up the burn tunnel and into the heat riser, not at the base of the fire. Keep testing them, but I think you have a winner with that idea. They may burn out in time, I have burned out the grate in my fireplace, but I let the ashes build up around it, and it took 30 years.