Michael Graham

Glenn. Thanks so much for taking the time to share your guidance. Appreciate it.

Got it. The whole mathematical deciphering leaves my head spinning but if a six inch duct is 28.27 inches and a three inch duct is 7.06 inches wouldn't the air flow be more even with a four rung ladder in three inch as opposed to six?

Thank you kindly sir for your thoughts. A ladder configuration hadn't occurred to me; do you think just a loop with entrance on one side and outflow on the other achieve the same result? I'm curious to find out just how hot the floor will be with a couple of inches of crusher run ( i.e. melt a ground tarp ). The total length from stove out flow to chimney rise is approximately 20 feet. If I added a second chimney for warm weather use it would amount to a straight run of about 15 feet. Do you think dampers are needed or could I just cap off one chimney when not needed? I don't have the option of running the out flow back towards the barrel, plus it would add about an additional twelve feet or so but I like the thought. I have a fire pit/ cooking area about four feet from the MHRS and it is backed by a granite drystacked wall four feet tall. My plan was to continue this behind and around the stove although I may use hypertufa over metal lath for that area. I was aware of the heat deteriorating the portland. As an old mason it just did not feel right to leave it out and I am fairly confident with the ratios I used the fire clay/ vermeculite will stand on its own. I will examine after a time and evaluate. I've worked on a couple of historical log cabins and was always amazed at how well the lime and aggregate mortar of yesteryear held up in the fire boxes of the chimney but am aware the relative temperatures were much lower. I will use the kaolin as the coating for the barrel over lath and am interested to see how well it performs. I would enjoy being able to use a local resource as part of the build. So far it has been a fun project and I am keeping my fingers crossed it will all come together. I will be down there soon and will take some photos to share. Namaste.

Greetings all. I have currently completed the construction of my MHRS at a semi permanent campsite. It has performed well during test fires and I have just mounted the barrel and am ready to install exhaust piping and seek the collective wisdom. Specifications: 6 inch metal duct - 16 inch feed tube, 20 inch burn chamber and 40 inch updraft with 2 inches of vermeculite/ fire clay/ portland cement/masonry lime in a 9 inch sonotube. In ground portion is layer of heavy foil then bottles with vermiculite/fire clay masonry mix in which duct was embedded. Outer perimeter of stove base is granite and field stone. Barrel is heavy steel 55 gallon with 1 3/4 inch gap. I will top this with a mixture of portland cement/ fire clay/ masonry lime and sand and will also use this around the barrel half way up supported by metal lath.
My primary purpose for building this was to heat the floor in my tent. Heated area is 8 feet x 8 feet. From stove outflow the run is 7 feet to a 90 degree elbow and 1 foot into tent area. My original plan is to snake 6 inch flexible duct in the floor area. I will excavate approximately 7 inches, lay down welders blanket, install pipe and cover with granite crusher run. I am concerned the flex duct will have to many sharp turns. Is it possible to, say, run two 3 inch ducts from the six and then back to six and out to chimney? Also, since I would conceivably like to use the stove portion during hot weather for cooking purposes without heating the tent and I was thinking of using a tee in lieu of the 90 degree elbow and installing two dampers as cut offs and adding another straight run to a second chimney. Would simply blocking one chimney serve this purpose? How much crusher run should be above the heated floor duct to avoid too much heat? ( sleeping on floor ) Also, I have an abundant supply of high quality kaolin nearby. Can this be used instead of fire clay. Any insight/ suggestions are warmly appreciated.