Horizontal rocket stove design

Hi there, I ran into a video with a horizontal heat riser essentially, running parallel to the combustion chamber. It seems to work, I’m just curious if anyone has any insight into whether or not this is actually an efficient design. If it is fairly efficient it would sure be a space saver. Here is the video.

Hi Justin; Welcome to Permies!
There are riserless rmh stoves being produced at Walker stoves.  Here is a link  http://walkerstoves.com/index.html
Matt has some very cool stoves he sells detailed plans for.

What your video is showing is a rocket stove , looping the heat to allow a larger cooking area.
However it is not a Mass heater only a cook stove.
A mass heater takes up room and heats either a long low mass (bench) or a hollow brick bell.
Rocket stove's are small and they normally cook on top of the riser, (very hot very fast)
The stove in your video looks like a nice little camping stove. But it really is not a true rocket stove.

Hi Thomas. It’s funny I actually stumbled on Matt’s heaters shortly after posting. I do realize the video I posted is not a mass heater, I just could not find any other source that depicted what I was trying to describe. Any diagrams out there of Matt’s flue flow? Are his cores just as efficient as conventional rocket cores? Looking at the video I posted, if I built a core in that fashion, out of proper insulated materials, would it be as efficient as a conventional J tube? The reason I am asking is because I would like to build a mass heater but I am very limited for vertical space, and if a system like this could potentially be close to the efficiency of conventional designs it would sure save a lot of headache and head scratching.

Hi Justin;
Well to start , although it appears to work fine. In my opinion, what they have built would not be anywhere near J tube efficiency.
To reach super hot temperatures. A rocket stove needs certain size requirements and to be run wide open. No extra bends allowed, slow the gasses at all and your efficiency drops, as well as the ability to flow horizontal thru a mass.
As far as Matt's riserless plans. Yes they are super efficient, but I think you would need to purchase plans to get a detailed description of the flow path.

What are you trying to do ?
Were you hoping to use a similar design "flat stove" as in your video?  
And maybe you could run the exhaust from that stove thru a low mass?

I would like to build an 8” system to maximize heat capacity, but height constraints will not allow me to get even 3ft tall, so curiosity got me wondering if the “riser” could be routed above the combustion chamber running horizontally back toward the feed side and then from there running horizontally through a mass. At the end of the flue I can possibly put in a short (12”-16”) vertical riser before heading into the mass to possibly add more draft. Unfortunately for the 8” system I would like there is no way I would even come close to fitting a 48” riser plus a barrel overtop. I will try to make up a quick sketch of what I mean and upload it.

Here is my horrible drawing. 8” diameter all the way through, no choke points. Possible to add 12” to 16” riser afterward to increase draw? I am curious how Matt walker accomplished his design with no vertical riser. My thinking is that by placing the flue horizontal yet still above the combustion chamber the flue gases are still rising. But please correct me if my thinking is flawed.

Hi Justin;
I do know a few things about Matt's stoves.  They are not a J tube design.  Nor are they a Peter Berg batch box design. Although closer to a batch than a J tube.
Matt's stoves are built with ceramic fiber board throughout. Surrounded by red clay brick.  So they lose no combustion heat when starting or running. Every btu is traveling towards the chimney.
I do know that his stoves use a bypass startup arrangement to heat the vertical chimney, prier to heating the oven and or mass.

So your not so horrible drawing.  Your showing it in a J design.  Matt's riserless is not a J.   You have your exhaust turning 180 degrees and then again 90 more degrees. At that point you have slowed the gasses down considerably.  Draw will not be nearly as good as it would in a conventional J tube with one 90 degree turn.  Flow thru a horizontal mass will also be compromised,  how much is the question...
If a rocket stove loses draw then it all starts flowing backwards... into your building.

So having told you all that.  We call ourselves rocket scientists , we learn by experimenting.  If you are determined ,then give it a try. Just be prepared for it to be "finicky at best and belch smoke /fire into your house at the  worst .  

I am curious where you are trying to put a rmh in only 36" of room?

No, your thinking is not flawed about heat rising. It does have a limit and it will stall.  

You could look at a riserless system such as the double shoe box 2 which then dumps to a stratification chamber.

Hi Thomas. The core part of the rmh would have to be located under a stairway next to where my chimney is. I actually went down and did some measuring, and figure that if I position everything just perfect (although not in the most convenient of spots) I could squeeze the height to a little over 50” tall. I know the 1:2:4 ratio means my riser would have to be 64”, which is definitely a no go, but I just came across some older posts saying that 1:1.5:3 is another common ratio, which means I could potentially squeeze a 48” riser in there. However, how efficient is this ratio compared to the 1:2:4? Is the difference noticeable or negligible?