I think I came up with a novel idea, the rocket mass forge. It is a combination of a side blast, side draft forge and a rocket mass heater. I can do my smithing and heat the garage at the same time!
I built a side blast forge – one who puts air in from the side instead of from underneath in the hopes that it will direct the smoke towards the hood. This is the older style, it’s simpler, and works better for charcoal.
It’s a side draft forge, meaning that the chimney sits beside the forge fire and not over it. It draws the smoke in sideways.
It’s going to be a rocket mass heater, with the insulated inner burn chamber, the outer barrel chamber, and the horizontal ‘chimney’ that dumps heat into the room.
So far, I have… ~ $20 invested in the forge, discounting gasoline used to pick free stuff up. The block is retaining wall block and the fire brick is recycled red clay brick. Most of the ductwork was free, but I bought a few pieces of it. My dad gave me the blower, it was brand new – about 25 years ago. The barrels will be free. Oh, I did buy the perlite.
2 weekends ago I visited a local blacksmith for a few hours, and that really got a fire under my butt. When I got home, I built the base of the forge. I used probably 2/3rds of roughly 160 retaining wall blocks that will be used for a pond next year.
They are stacked in a circle with room for a 6 inch stove pipe to do down the back and out the bottom. It is infilled with a mix of block and brick to support the brick top. The brick top is layered in 2 different patterns and 90 degrees offset so I don’t have any seams that overlap. Less likely for hot coals to fall through down to the floor this way.
The brick burn chamber did not work at all. Too ‘open’, the smoke poured right out of it. It felt good to get a fire lit there though. The next thing I did was hook up my old pocket rocket to vent out the new rocket mass heater chimney system. This worked a little better. I was able to get it to burn in the right direction.
So I grabbed an old 5 gallon metal bucket of killz paint that had dried up – or so I thought, under about 2 inches of crust was white goo, not quite paint – that was in the weeds in the back yard when I bought the house. I cleaned that out, burned out the goo, it burned OK once lit with a torch.
The forge didn’t really get hot enough for me, and the rocket mass heater didn’t want to draft for crap.
I need a 55 gallon drum so I have room inside to make a proper insulated heat riser. This should help it draft better. I need a different hose for the forge blower, as what I am using now whistles something obnoxious. I need to make a cold air intake for the forge blower and a mixing box so I can pull some smokey air as well if needed. I need to make a heat exchanger to pull more heat from the system before it leaves the building. I need to make the thermal mass yet too.
Lots of things to do for the next iteration. The important thing is that I got it working, if poorly.