Ok. I have a few minutes to spare so I will share some photos and a description of our "Rocket Mass Brooder version 0.7" experiment. Tony and I knew we would be moving to Mastodon Valley Farm around May 3, and had a batch of 100 Freedom Ranger chicks arriving on May 8. We also knew we wouldn't have electricity. So we did a little research and learned about "hay-box brooders" or using kerosene lanterns. At first we thought we'd try building a "hay-box" but still wondered where we'd get a heat source. Hot rocks? Hot water bottles? After spending last winter in the rocket mass heater tipi, I began to imagine a Rocket Mass Brooder. In my first imaginings, I thought we could build a structure made entirely of cob, so essentially build a round cob basin that would have ducting in the walls, and would return to the barrel and exhaust from there. But then we thought it would be good to have a cool area as well, instead of encircling the entire enclosure with warmth. We also had limited time, so we decided not to build a 25 square foot cob basin, and instead opted for a quick wooden insulated box. There is a sawmill on the property and plenty of scrap wood so we slapped together a wooden box and attached some purple insulation that was lying around with a R4-R5 insulation value.
At first, we also wanted to build the Rocket Mass Heater core with 4 inch ducting. We though this would make the project quicker, and would provide sufficient heat for the chickens. We even spent a day searching for a smaller steel barrel. But after contacting Erica, we felt we better not waste time tinkering with a less optimal system. But we did go with 6 inches. We felt 8 inches would be too big of a mass.
We then decided we would send the ducting through one end of the box to create a warm mass on one end of the 8 ft by 4 ft box and leave plenty of space for a cool end. We did debate whether or not we should have the ducting return back to the barrel so that the exhaust would be heated up by the barrel, but with trying to keep materials cost down, and wanting the exhaust to be as far away from us as possible, we decided on sending the ducting through the box once, from the core out to the other side and up. This still left a giant mass for the birds. We filled the bottom 4 inches with perlite, then set the ducting on top and surrounded it with another 4-5 inches of thermal cob.
We also decided to build the core entirely out of cob (heavy on perlite for the burn tunnel and heat riser). Unfortunately, we were in such a hurry that the manifold and heat riser collapses on us the night before the chicks were to arrive. But we decided to buy two more pieces of stove-pipe that was filled with perlite-cob to replace our heat riser and after a week or so of burning the heater, it was dry and ready for our chicks!
OK, I will add some pictures now: