Jim, sounds like you've got a good plan of action there. BTW, when these stoves are running full tilt it will be uncomfortably hot within 3 feet of the barrel. Needless to say, the intense radiant will heat up the stovepipe that's angled above the barrel, so there is really no need to insulate the first (lower) three feet or so of that 45° run, if any at all. And it goes without saying, it's a good idea to closely watch the temperature of the tent's ceiling directly above the blazing hot barrel.
As far as priming time, typically only a few minutes is required with the torch, as Max mentioned. Once the stove is run consistently for a time, the thermal mass bench will dry and warm up. Then daily start up will become much easier and exhaust priming should no longer be needed. To get a bit more heat from the combustion unit into the mass, you may want to consider insulating (Rockwool, CFB, etc.) the half barrel manifold, at least from the base up to the barrel clamp.
If you have any sections of 6" dia. HVAC duct left over, with insulation added, that would serve as a quick and light weight way to test the draft improvement of adding chimney height. Because it's very lightweight, none guyed support could be done indoors using something like sections of inexpensive TV mast pipe, running from the floor up through the same ceiling opening as the stovepipe, and extending above the tent's roof. You will be amazed at the draft strength improvement that a few feet of additional chimney height makes.
Another suggested area to improve upon is J-tube's wood feed. Build up the area around the wood feed entrance with several courses of brick (fireclay/sand mortared in place) to form a vertical wood feed "tube". I'd make it exactly the same measurements square as the current opening, and tall enough so the depth of this vertical wood feed channel (measured from it's opening down to the burn tunnel floor) is about 16 inches (common firewood length).
It's been awhile, but I've not been idle. I took all of the comments posted and went back to the drawing board.
I stayed with the six inch system, (thinking now I should migrate to 8"). The foundation consists of 1 inch of marble, 1 inch of dura-board rated at 2300 degrees and then a layer of 2.5 firebrick.
During the first trial I noticed the dura-board didn't stand up to the fire inside like I thought it would and scraping out the ash damaged it. So I went with #2 firebrick to line the firebox. As you can see from the pictures, the main changes I made are I made the riser 48 inches instead of the 32 I had before. I thought this would help with the draft. On the manifold I started with an 8 inch outlet for two feet then reduced the ducting to 6 inches the rest of the way. I modified the ducting so that I only have three bends instead of the previous 5 and increased the chimney to 23 feet (its all I can support).
I fired it up, and draft is no longer an issue. The problem now is I'm not getting any heat from the barrel. The temp in the firebox will reach up to 1850, but thus far the best I can get at the top of the barrel is 450 - 500. Now I'm really confused. The temp above the Tee in the chimney never got above 100, and the burn is so complete that after a day of burning wood, all that remained was less then 3/4 cup of ash. There is no smoke appearing at the top of the chimney when it got to 500. So the question to be asked is where does all the heat go from the firebox to the top of the barrel. Surely and extra foot of riser would not dissipate the heat that fast.
Measurements: 2 inches from riser to top of the barrel
4.5 inches from the foundation to bottom of 8 inch outlet.
4 inches from the firebox to the edge of the 8 inch outlet
23 feet chimney height
Hi Again Jim;
6" systems just don't get as hot at the barrel as an 8" would. 450-500 is not bad and it may get better as you add your mass, and things dry.
My 8" system with 2.5" clearance at the riser to chimney, regularly runs 800 , I can push this configuration to around 1000, my previous core could hit 1100. Now those temps are with a completed dry mass.
You mention, wondering about switching to an 8". I really prefer them over the 6". For the size of the feed tube. That extra 2" makes for larger wood and longer burning.
Dispite all the very nice work you have done, now would be the time to modify if you wanted . After all its summer solstice today, there is certainly time!
EDIT) Sorry Jim , your wife's (LuAnne) account fooled me.
I do believe upgrading to an 8 inch system is the new requirement. What I don't understand is, on my first effort burn, on my original 6 inch system I reached almost 1200 degrees. I understand the cold plug issue now, and hence the rebuild, but to only get 500 degrees with a higher riser is just baffling. I apparently do not understand the cause/effect issue here. But 8 inches its going to be. I'll update when I get that done.
Glad to hear your still at it LuAnne.
I have a 6" stove and the top of the barrel above the heat riser can get to 930 degrees when I'm consistently feeding it small stuff continuously for about 1/2 hour to 45 min.... Averaging around 700 though with regular size wood.
Perhaps because you extended your riser with more mass (cause) which helped make the draft is so much better (effect 1) and the heat is getting sucked up the chimney and not having enough time to be extracted as effectively (effect 2)... or all your extra brick is sucking up the heat (initially) but will eventually equalize and then not do this. Are you running it for a few hours and still not getting higher temps?
I have run the RMH continuously for 18 hours (still attempting to figure out how to keep it going during sleeping hours lol) and the average temp hangs around 530 once it gets going.
Quick question. Is the riser measurement from the bottom of the burn tunnel to the top of the riser, because I started from the top of the burn tunnel to the top of the riser. Maybe I don't need to so much riser then.
I am using a combination of anywhere between 1x1, 1x2 and 2x2 lumber and usually I can get between 5-6 pieces going at any one time.
If you're correct and the extra riser height is robbing the heat .... I do know the Chimney is not that hot. I can always place my hand on that and its warm but never hot.
Jim, 18 hours! Wow! Your one hard working dude! Of course, once you get some mass on those horizontal pipes, you won't need to worry about feeding it all night with the heat storage.
I've always been a top to bottom measurement kind of guy but some people like to take their measurements to the center of the burn tunnel. As long as your consistent with your measurements throughout (center to center or edge to edge) on the feed, burn tunnel and heat riser and roughly keep the ratio: 1:1.5:4 your golden.
Do you have your heat riser insulated? It could be lowered by a brick to see how it performs.
The gap between your heat riser and barrel will affect how hot it gets too. The minimum gap is around 3" but there is not much of a limit (many feet). The bigger the gap, the more cool the top of the barrel - not as good for cooking but better for heat extraction. Depends on what your looking for.
Is your wood good and dry? Even dampish wood will reduce the temperature significantly. Maybe try some different wood (species also) and see if that makes any difference.
Your description of the chimney temperature sounds about right but could get hotter once your mass goes on. I think you'll find those horizontal pipes radiate heat much quicker bare than when covered.
Have you considered a bell bench?
I can’t really see but does your fire sit directory on top of full size fire bricks?
From my own personal experiences using one inch of high mass lining the firebox then a min of 2” insulation surrounding the box seemed to work the best.
I have experimented with riser hight and settled on 42” from floor to top of riser but this may vary from one system to another.
Location: Southern alps, on the French side of the french /italian border 5000ft elevation
The goal is to heat a 20 by 48 foot space as efficiently as possible. There is no insulation along the walls. (this is a temp tent situation)
So I'm looking to extract as much heat from the barrel as I can - the hotter the barrel the better. The riser is insulated, but I could remove a layer of brick without too much effort. The wood I'm burning is as dry as your granddaddy's scalp, so that is not a concern.
I think I mentioned earlier that I measured the riser from the top of the burn box level of brick and went 48 inches up from there. If I've over done it, that would present a situation where I'd have to adjust (possible) the height of the manifold barrel to get the right height of the barrel assemble correct, given any changes to the height of the riser and the gap between the rise and the top of the barrel correct.
One more thing, I've noticed the Wisner RMH guide calls for a 2" gap but assumes a 25 inch circumference on the barrel. Standard 55 gal barrel has a 22.5 inside diameter. My presumption now is I'll need to increase to 3" to accommodate te difference. Correct?
Location: Southern alps, on the French side of the french /italian border 5000ft elevation