Batchrocket icw barrel and bench (as a bell)

Hi all,
After a lot of reading I decided to register since I believe I can use some advice regarding the construction of our RMH. This will be our first build ever.
At first I looked into the "classic" J tube design. The thing I don't like about this is the open feed tube. After going further down the rabbit hole, i ended up on Peter Van Den berg's batchrocket site.
I like the core that peter designed, with the floorchannel sec. air supply and square riser (150mm/ 6") (number 7: "A simpler core design" under the Design section). This design seems pretty straightforward, and I would only need to cast the cover of the core.

Combining this effective core with a barrel over the riser would give (according to my humble opinion) the best of both worlds.
In the bottom of the barrel I'd make a channel to a bench: I still haven't decided on whether to go for tubing covered with cob, or use bricks (single brick bell).

Option1: a bench as a bell: According to Peter's site, the ISA should be max 5,3m² for a 150mm riser. For a bench of 3m in length, 50cm high, and 50cm deep, I would end up with 4,5m² for the 3 long sides + 2x0,25m² for the ends, all in total 5m². I only found a picture on his website of a similar design, but with a "classic" bell. Unfortunately no plans available.

Option2: covering 150mm channels with cob.

My questions:
- do i keep a 2"/ 5cm gap between the top of the riser and the top of the barrel, just as one would do in a J design setup?
- is it correct to state that the maximum length of the channels (in option 2) is 10,5m/ 35ft?
- how does the inside look of the bench (bell): is it only the 4 wall with a cover plate, or do I have to divide it into multiple chambers? Is 50cm high enough to properly work, or is it better to build a narrower but higher bench?


Our homestead is located in South-Africa, temperatures go as low as 4°C in wintertime. There is currently no wood stove installed yet, hence the need for a solution before winter

Hi Fred;
I'll try to answer your questions.
#1)  No, a Batchbox riser requires a 12" clearance.
#2) No, 35' would be for a 6" J-Tube, 6" batch works with 8" J-Tube numbers, so 50'.
#3) A bell is open, no dividing walls.

Using a barrel will give you a large amount of instant heat.
Perhaps, it might be more than you would like.  
Your barrel can be covered up to 2/3 with cob to mitigate how much instant heat you need and how long your bell will hold it.

Hi Fred, exciting times for you then.
The old style batchbox is a powerful stove but it has a few restrictive aspects from my perspective.
The riser it’s self, is what makes the stove work so well but, it is a tall component and you would need more than one barrel to enclose it.
Another issue for some people might be the internal metal work that will deteriorate quite quickly although Tom (who made the above post) can sell you a few components that will help your build……
There are more up to date models that don’t use a full size riser but rely on a good, ideally straight up, tall chimney.

I don’t think the riser less stoves are quite as powerful but, they might offer more options to make them fit into your home.
One of the benefits from my prospective with Peter’s latest design, called the ‘shorty’ is you can re load the fire any time you like without causing any problems with smoke or reducing the stove clean burning aspect.

Now that you mention it, I didn't think about the deterioration of the barrel.
You don't happen to have a link to his "shorty" model? I don't believe I came across it.

The only thing that's holding us back to build a J type is the "fear" of having smoke inside the room at startup.
And perhaps that I'd need to make our fire wood smaller: length of our wood blocks is 30cm.

Hey Fred.
I don’t think Fox is talking about the barrel. Barrels usually last quite a long time as they quickly shed the heat that’s coming in from the riser.
Smoke back can happen with any wood fired stove. But if you prime the riser and maybe even the chimney you won’t have that problem with a standard J-tube.
A way to close off the feed tube is having a tile or something ready to be put over the feed.
So if that’s what you want to build after reading up on all of the types, go for it!

As for the length of the firewood, the last one I built had a 35cm feed tube height. That would be enough to fit 30cm wood.

Hi Fred, no as Ben points out the barrel (s) can last for years, it is the  secondary air supply feed that will degrade!

Personally I love J tubes, they are very simple to build and use, one  disadvantage is the need to keep topping up the fire box with fuel.

I have my own design J tube that has a glass door and a viewing window, it also only requires a fairly short riser that easily fits inside a single barrel.
If I were you I would spend a few days looking at the builds folk have completed on this forum, there are quite a few choices.
A lot might depend on your DIY skills or your budget.

Benjamin Dinkel wrote:Hey Fred.
As for the length of the firewood, the last one I built had a 35cm feed tube height. That would be enough to fit 30cm wood.

You don't happen to have the dimensions of that setup?
I found this one in an old topic, but was never build, and is for 40cm wood.

Edit: I noticed in the construction example of "The Rocket Mass Heater Builder's Guide" that it has a 16" (40cm) feed tube, being ideal for our situation. The bench in this setup, has the correct dimensions for the room as well.
So most likely I go for this one: easy to build but more importantly most components are easy to find.

Fox James wrote:Hi Fred, no as Ben points out the barrel (s) can last for years, it is the  secondary air supply feed that will degrade!

Personally I love J tubes, they are very simple to build and use, one  disadvantage is the need to keep topping up the fire box with fuel.

I have my own design J tube that has a glass door and a viewing window, it also only requires a fairly short riser that easily fits inside a single barrel.
If I were you I would spend a few days looking at the builds folk have completed on this forum, there are quite a few choices.
A lot might depend on your DIY skills or your budget.

Oeps, almost missed your post.
DIY skills are ok, regarding the budget: we'd rather spend something more instead of regretting it later, and having to start over.
I'll take a look at your build (and the other ones).
The only problem now: there are so many different builds/models/options, that choosing is really difficult 😀