Len Ovens wrote:
Do you have a specific application in mind? What size/weight are you designing for? I have thought of small scale rocket heaters, but have not had the materials/money/time to try my idea out. Personally I would try to include some mass in the form of soapstone or cast iron if nothing else. These are denser materials than cob or even fire brick and so would store more in less space.
A couple applications. One would be any type of livable vehicle from small to large motorhome.
Another would be anywhere one might set up temporary camp, such as fishing expedition, gold panning, etc. Small lean to situations. Occasionally there is a need to spend some time in a small one room cabin. etc.
One of the ideas I had was to fill an 8 foot, two inch diameter tube, laying horizontally, or slightly diagonal, with pellets/twigs and figure out how to make the fuel burn very slowly along the entire length of the tube, so that about only 1 inch of the metal would be getting hot at one time. The entire tube would either sit horizontally, or diagonally, and function as the feed tube, burn tunnel, and riser ALL IN ONE straight pipe. Or it could have an additional 3 foot riser on one end to create draw. One could bury this in dirt under a sleeping bag or cover with dirt on the side in a lean to. But now I understand rocket heaters better, so I know there would be no way to get hot enough burn to be efficient this way.
But that's just to give you an idea of how radical some of the directions I am exploring are.
Possibly if I could figure out how to burn the resulting woodgas at the end of the system with a small chamber it might work. Either way, I would not want it to accumulate wood gas and create a pipe bomb right next to me.
maybe I could start a fire at both ends of the 8 foot tube, and the at least the woodgas from one end would have to travel through the fire at the other end to exit the system.
Len Ovens wrote:
(Re)movable mass is another interesting idea.
on the 8 foot tube stove I had an idea to have semi-circular cement drain tile underneath the tube, then cover the tube on top with several pieces of the same material to complete a cement jacket around the entire burn tube. Because it would quickly get too hot, then the cement jacket would simultaneously block the extra heat, while storing it for later.
Or when the space got warm enough after initially starting the fire, I could cover with dirt and rocks.
Regarding the normal 4.5 to 6 inch RHM with small mass such as over an existing fireplace hearth. For portability I wanted to try 5 gallon cans filled with water, stacked very close to the barrel and vertical exhaust. I figured for a small space they would block some of the initial heat that would be too hot for small space, but would absorb plenty. I could get 10 5 gallon cans stacked two high around a 20 gallon barrel and vertical exhaust leaving the front of the barrel exposed to direct heat. The cans could simply be emptied of water, and with lids off they would stack and be very light and take up very little space. I would either leave holes in top to vent if they got to hot ( which I doubt they would, or create a system of tubing to vent outside if it was creating a steam problem in the space.
Len Ovens wrote:
I was going to suggest using a gasifier set up next... it turns out that is what the Kimberly is
I am starting to think this is the only way to achieve a very small volume fire, and at very slow speeds, and have complete burn.
That is another one of my objectives to meter the fuel out VERY SLOWLY. It does not take much heat at one time to take the edge off in a very small space. And metering out heat very slowly is contradictory to a complete, efficient burn rocket style. But since gasifying works by INTENTIONALLY making a very slow, cold burn, one can achieve a much smaller btu per hour, while simultaneously extending burn time.
Which for small spaces is perfect. Because if one does not have the MASS to accumulate the energy from a very fast, hot burn, the only other option is to slow down the burn to achieve a the goal of not having to constantly put fuel in.
Unfortunately the gasifier setup seems a lot more scientifically complex. Where as I got my mind around the physics of a rocket heater very quickly, I am not certain what is required to build a kimberly type of gasifier.
The guy in the video with the motorhome did mention that at the top of the stove was a "honey comb" thingy, which I can only assume is a catalytic converter, which would make sense, seeing as how the fire is being metered out so slowly and with such a cold burn, that the exhaust is mostly wood gas.
I have to admit, that playing around with woodgas in chambers, seems a lot more technical, and critical, than achieving a quick clean burn based on the simple physics in a conventional RMH.
But there cant be that much to how the kimberly stoves work, and at $4,000 there will probably be a lot of motivated people trying to figure out how to build a reasonable facsimile.