portable collapsible rocket stove heater/stove/pizza oven

[briank]

Hi folks,
I started designing this stove last August and I finally built it this month, a (somewhat) portable collapsible ceramic fiber board rocket stove deck and patio heater / stove / pizza oven with a vacuum formed ceramic fiber 6" riser. This is designed to be easily taken down and moved (but the 2" low density ceramic fiber board insulation, while being easy to cut on a table saw, is a bit too brittle for frequent assembly/disassembly.) I built this in my garage in PA, took it to a camp out with about 40 friends in Michigan and fired it for the first time, dissembled it and came home to PA, then took it to a friend's in New York to experiment with the pizza oven.

The barrel is cut from a standard 55 gallon barrel at 25" and the pizza oven on top is about 12". The 25" barrel sits on the 2"x4" frame with casters for transport/storage, and the ceramic fiber board pieces fit in this barrel when disassembled. Riser stands about 12" into the 25" barrel on top. I used a USSC barrel stove door and flue collar and 6" elbow and black stove pipe for this build. The door is hung on 2/16" mild steel.

Barrel top temps hit around 740 degrees F via infrared thermometer, and pizza oven (uninsulated) hit 500 degrees on a Bacharach flue thermometer.

Secondary air is introduced via a 2" x 1" channel I made with a router in the bottom ceramic fiber board under the firebrick liner and introduced with a 2" black iron pipe that goes through the firebrick about 1 1/2" from the riser, similar to Matt Walker's. The bottom, left and right sides of the firebox are lined with firebrick splits. A thin plate of stainless lays over the secondary air groove under the firebrick to seal it better. I haven't weighed it but I figure total weight is 100-120lbs.

It has satisfactorily survived about 1500 miles of traveling and being assembled and disassembled three times now but again, I don't think the ceramic fiber board would hold up to repeated assembly and disassembly.

This could be used as a deck, patio, backyard, cabin, hunting tent, ice fishing hut, or emergency heater / stove / oven.

[icarus]

Nice job. Lightweight, fairly small footprint, and easy to relocate. Any plans to insulate the oven?
Maybe just to slow the heat loss. Lots of food cooks well at 500F and below. Cooking pizzas at temps above 500F starts to require serious
skills. Again, great work.

Did you find a good source for the ceramic fiber board?

[briank]

May 2, 2017 10:43:36 GMT -8 icarus said:

Nice job. Lightweight, fairly small footprint, and easy to relocate. Any plans to insulate the oven?
Maybe just to slow the heat loss. Lots of food cooks well at 500F and below. Cooking pizzas at temps above 500F starts to require serious
skills. Again, great work.

Did you find a good source for the ceramic fiber board?

Thanks. I'm going to be insulating the oven this week, including a door or a more permanent insulation block for the opening and also incorporating a pizza stone in the top to hold/reflect some of the heat. 

I found cases of 2" ceramic fiber board locally with three 2'x3' sheets for $160. I thought that was very reasonable.

[Daryl]

Nice. You could easily slow down the burn to bake or cook at lower temps in there. Good job.

[briank]

May 3, 2017 10:29:51 GMT -8 Daryl said:

Nice. You could easily slow down the burn to bake or cook at lower temps in there. Good job.

Thanks. Yes, I was able to keep it around 350 degrees indefinitely just by adding one small split at a time.

[briank]

This firebox held heat for a very long time. As I was disassembling it about 8 hours after the last fire last weekend, I literally burned my gloves on the firebrick as I took it apart. It was very difficult just to add wood to this firebox while the fire was burning because of the intense heat inside the firebox. 2" of this ceramic fiber board insulation is extremely effective.

[patamos]

Nice build briank

one suggestion to increase durability of the CFB would be to coat its surfaces with sodium silicate (aka 'waterglass'). Should be available at pottery supply stores. two or three coats (one after the other while still wet) of a fairly thin viscosity blend with a paintbrush will soak in well add considerable strength and resistance to abrasion…

[briank]

Hi folks,
I finally got a chance to do some more controlled tests with this stove. I sealed around the door frame with black carbon felt as a gasket and used 8' of six inch chimney pipe. For fuel I used a twelve pack of small compressed sawdust firewood bricks. I started the fire at 4:15pm. It stopped smoking and the flue gases were clear within 5 minutes. The barrel top hit 760 degrees within 25 minutes and the pizza oven (still un-insulated, unfortunately) hit 600 degrees (during prior burns the pizza oven only got to 500 degrees)..

Interestingly, using regular firewood in the past, it was burned down to ashes within an hour and a half.

I walked away and made dinner after an hour, but when I came back after two and a half hours the barrel top was still 300 degrees. I opened the firebox to find the compressed sawdust logs still burning and only half consumed.

In retrospect, I think my black carbon felt gasket around the door frame may have limited the primary air entering the firebox, slowing the burn, because I noticed some smoke when I walked away after the first hour. I'm going to have to take a closer look at that tomorrow.

After two and a half hours:.


I threw in a small piece of cherry firewood and barrel top temp got back up to 470 degrees.

[briank]

May 28, 2017 5:25:17 GMT -8 patamos said:

Nice build briank

one suggestion to increase durability of the CFB would be to coat its surfaces with sodium silicate (aka 'waterglass'). Should be available at pottery supply stores. two or three coats (one after the other while still wet) of a fairly thin viscosity blend with a paintbrush will soak in well add considerable strength and resistance to abrasion…

I actually picked up a bucket of their ceramic fiber cement. It turns out to be the same product as their rigidizer, but in a more concentrated form. You just water it down more and paint it on as a rigidizer.

[briank]

I opened up the primary air path and tore apart the burn chamber today. I created an expansion chamber where I had previously had the vertical riser. I then moved the vertical riser to the left front of the box and cut the side of the vertical riser out next to the expansion chamber up 6" from the floor.

This is vaguely similar to the Walker Riserless core. This sort of creates a combination expansion chamber/ horizontal riser then immediately a true vertical riser. I forgot to take a picture so I have to wait till it cools.

I already got 15• hotter in my pizza oven, 615• after 45 minutes. Stove top temp was increased, up to 776 •, an overall improvement of 36• from the initial tests.

Burn times are definitely longer with the compressed sawdust fire bricks. After one hour and ten minutes pizza oven was still 500 degrees without any insulation and the door still open. At two hours it was still 400 degrees, and stove top temp still 575 degrees.

About half the compressed sawdust fire bricks were still burning.

[briank]

It's now 3:15 since I lit the stove. Amazingly, the open door pizza oven temp is STILL 350• and stove top barrel temp is 386•.

[briank]

Firebox at three and a half hours after lighting up:

[briank]

At four hours after light up and with only the original load of firewood bricks, the pizza oven is still at 315• and barrel top temp is still 386•.

What kind of temps are people seeing on the barrel top after 4 hours without reloading? I didn't think this thing would still be heating this long.

[briank]

At five hours, open door pizza oven temp is 260• and barrel top temp is 256•.

[briank]

Last observation for today. At six hours pizza oven is cooled down, barrel top temp is 177• and there are only a few red coals remaining in the firebox, which I drug forward: