mass catering

[jono]

Ill do that, thanks

[peterberg]

Jan 15, 2015 9:59:24 GMT -8 jono said:

Peter, did you put the testo on your institutional stoves? Did you make any changes to the combustion chamber?

Yes, I've tested one of those but to my mind the oxygen level was far too high. That's why this type of stove yield very good results, the exhaust gases are greatly diluted.
No combustion chamber changes, though.
Don't hold your breath, a 4" J-tube would be probably all you need for this application. And those are notoriously difficult to get right.

[jono]

I did some testing with a 3" j. The ratios change (much longer riser relative to burn tunnel length and system size compared to a 6" system) but the thing burnt twigs at a ferocious speed with a mighty roar and no start up issues. I'll redo my experiment and post some pics and dimentions over the weekend

[jody]

Hi my first post after following the forum for a while.

I wonder if this type of stove would work better if the gasses first go up the insulated outer cavity and then come down the inner cavity in contact with the cold surface of the cooking pot. Is it not true that when hot gasses cool down they become heavier and that as much as possible we want to be using this to help drive the stove?

[satamax]

Jody, that effect is not proved yet!

Every time comeone puts a barrel on a rocket, without making a chimney to be fitted at the same time, it stalls the stove.

[jono]

That a piece of 3" ducting, bent into a shape which is about 3' x 1'. Below is what it looks like with a fire in it. Quite smokey when used like this, but lights without much bother and draws well.

[jono]

Here it is wrapped in a ceramic quilt. I didn't want to cut the ceramic for the test. The draw is better, lighting is even easier and it burns clean almost instantly. Here i have opened up the insulation to show the glowing red pipe within.

[jono]

Next experiments: how well does it cope with the resistance of a heat exchanger with a resistance similar to the institutional stove? How much wood does it burns in how much time, (to get an approximation of its power)?

[jono]

Im not sure if i can find a good way to cast it. I was thinking of doing it donkey style and using that pipe as a sacrificial former, but i might have trouble getting shards of metal out once it does fail. Cardboard tube would probably work better, and if i think the ridges are important, wrapp the former in string

[satamax]

Jono, do you have an angle grinder? If you buy a little diamond blade for it, you could make ledges on firebrick splits, assemble that with wire.

Not realy to scale for a batchbox. But here's a quick sketchup i've done for somebody else, which shows the details.

www.permies.com/t/38889/a/20390/heatriseresteban.skp?download_attachment=true

Or in video.

youtu.be/7RyvsZD1_CU?t=2m39s

[jono]

Yes, i don't know why i had dismissed using bricks. Maybe I'll try and set up a quick test with the old house bricks that i have. I'm guessing 3'x1' with 4" square system size, and if i have trouble with it i can shorten the fire chamber. Bricks like this i guess would be ideal

shop.vitcas.com/insulating-fire-bricks-vitcas-grade-23-216-p.asp

[jono]

There is a quick sketch of how this thing might be implemented with insulating fire bricks (no attention given to the number or size of bricks). When i drew that i was imagining the fire box being made of metal, like a can riveted to the outside of the barrel in which i could drop a piece of kit paper then a handful of sticks. Thinking about it, that can would both lose a lot of heart from the fire, and get very hot. So here is the redesign


A big advantage of brick is that it will support the weight of my pot

[satamax]

Yep, forget the metal feed tube. Thoses have proved to be lousy.

3 squids for an insulating firebrick? You'd be better off buying in France!

www.prosiref-boutique.com/-classe23--171--a.htm

[jono]

Ah cool, I'll ask them about delivery costs. Falling that, my fiancee was talking about sending her parents to France to buy wine for the wedding.

I know I'm getting a bit ahead of myself, but this is a drawing of my fantacy cooker.

It's not just for my wedding. I'm part of a group of permaculturist types taking over a veg box farm, so as we have a captive market of 100 veg box customers it would be good to be able to make jams, pickle, bread and beer to expand the business, so a wood fired commercial size range would have many uses

[jono]

I am worried that peter has suggested that a 4" j probably wont work, but i dont understand why it wont work. If i can make these little j's work in these systems i think the fires will be easier to manage, will burn hotter, and do a better job of controling excessive airflow through the system to make for a more efficient heat transfer. On the other hand, theres a lot i dont know, and no doubt aprovecho spent a bunch of time on the design of their L shaped combustion chamber, and designing their whole stove to work well with it, so i would probably be wise to abandon this 4" j idea and just follow the aprovecho design as accurately as i can