S Jones

Hey all thanks for all the responses. It seems I just don't have the proper materials to get this thing done properly. I thought I could get it done with just some bricks mud and some clay (and some flexible ducting) but there is definitely more involved. I plan on trying it again soon when there isn't such a mad dash for warmth. For now it will just be a regular fire place on the side of my hut. It may not be the most efficient but at least I'll get to watch a fire. Till next time! And thank you again

I am wondering if there is a difference in performance between the RMH systems that use a cylindrical heat riser rather than a square heat riser

I have constructed and deconstructed my RMH system twice because of poor performance. I thought I had a good draft, and the fire burned realyl well, but the barrel never really got hot. I mean of course it got warm, but never to temperatures that can radiate heat and heat up a space. ( a small space, I have, maybe 100 sq. ft) After burning the system for several hours I could still touch the sides of the barrel for ten seconds or so. So I decided to take out some of the variables and test out my J-tube core. Here are my dimensions

Feed: 15" high
Burn Tunnel: 22.5"
Riser: 45"

following the 1:1.5:3 ratio. All components with a 7.5" x 7.5" CSA

Mine is made with bricks and all is insulated with clay.

So after testing just the J-tube core I noticed that my fire does not really get very high. The highest it has gotten is just about halfway up the riser. I am wondering if something is wrong because I have seen videos online with the fire blazing out of the riser and also have seen videos of people with fire vortexes in their risers. Mine just doesn't seem to be doing that and I'm not sure if it should be. In both the videos that I've seen they used cylindrical risers, and I know the designs have evolved from square to cylindrical.

Also as a bit of side note - the hot coals build up so much during my burning that they begin to clog the burn tunnel. Is this a common thing or a sign of something going wrong with the burning.

Any tips or help is greatly appreciated!

I am using flexible aluminum ducking for the exhaust and flue. I can put it directly in the bottom of the barrel and seal it in with more clay. I have it running along the floor and exiting through the bottom of the wall where where it extends upwards vertically about two feet. Mind this is not in a home in the traditional sense but in a temporary winter shelter in the woods.

Ok - so I rebuilt my system changing some of the measurements. I know have a system that has a 15" high feed, 22.5" long burn tunnel and 45" high heat riser. This goes along with the 1:1.5:3 ratio. My openings to my feed and riser are 7.5". I attached the barrel with my exhaust and it worked! I was so thrilled. I checked the flue and steam was coming out. Hurray! So I waited for the barrel to get hot and it did a little, but after hours of running it I could still touch the sides for about ten seconds. It just wasn't getting hot enough to radiate any decent heat. I'm wondering if it has to do with the draft. Sometimes the fire starts to climb the logs and burns upwards rather than sideways - is this a thing that happens? Also I'm guessing if all goes well there should be no heat coming from the top of the feed? I thought my draft was good but maybe I am wrong?

My heat riser is made of bricks insulated with clay/Cob

Thank you all for the replies - I have to work the numbers out a little bit with the ratios that you've given me. The heat riser is sealed with clay although the feed is not so maybe that is part of the problem. Hopefully I will triumph!

Hello everyone, I'm trying to understand why my heater sometimes gets a draft and sometimes just duds out. I've been trying to toy with the measurements but nothing seems to be giving me a consistent draft, and I can never actually burn wood consistently with it (The only draft/rocket sound has been with paper) Could my measurements be wrong? My system is made out of firebricks. Here are my dimensions:

The opening of the feed box and heatriser are both 7.5"
The feedbox is 13" high
The heatriser is 44" high

Following is where I think the problem might be:

The bridge (the row of bricks that connects the heat riser and feedbox) Mine is 10" long and the burn tunnel below has 6.5" of space heightwise until of course it reaches the heat riser.

I keep messing with the length of the bridge, but I'm still not getting consistent results. I am making this outdoors so the whole thing is usually very cold which I know can be a problem.

Frustration is consuming me.

I know there are a lot of variables involved when making these and I need to keep tinkering, but any help is greatly appreciated!