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Permsteading.com • View topic - Batch Box vs J-Tube

Batch Box vs J-Tube

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Batch Box vs J-Tube

Postby 4seasons » Mon May 26, 2014 2:36 pm

I finally finished my head to head comparison that I started about a month ago. Both the Batch box and J-tube are built from a 1:1:1 clay:sand:wood ash mix with some straw mixed in. Both are 4 inch systems with P-channels, and kick tails. The J-tube also has a trip wire. I used the same wood from some pallets that I broke down and I cut them short for the batch and split them smaller for the J. I used a toilet paper roll stuffed with dryer lint as a fire starter for each. Here is the videos for anyone interested:



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Re: Batch Box vs J-Tube

Postby 4seasons » Mon May 26, 2014 2:43 pm

After fiddling with the J-tube for a few minutes I got it to take off by rolling a piece of paper up and sticking it as far into the burn chamber as I could. Once the paper started I blew down the feed and it started drawing. Just to keep things as even as possible I stuck a piece of paper in the batch box too although it did not need any help getting going.


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Re: Batch Box vs J-Tube

Postby 4seasons » Mon May 26, 2014 2:47 pm

After 12 minutes both cores were up to speed and burning well.


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Re: Batch Box vs J-Tube

Postby 4seasons » Mon May 26, 2014 2:52 pm

This first video I shut up so you can see and hear just how much more powerful the Batch Box is.


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Re: Batch Box vs J-Tube

Postby 4seasons » Mon May 26, 2014 2:58 pm

After 30 minutes the Batch box had used all its wood and the J-tube didn't get fully loaded until 33 minutes in.


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Re: Batch Box vs J-Tube

Postby 4seasons » Mon May 26, 2014 3:18 pm

Over an hour into this experiment the J-tube finally ate as much fuel as the Batch box went thru in under 30 minutes.


Other things that I observed that are not in these videos:
1. J-tube is much easier to build as the mold is simpler to design and pack your mix around.
2. Batch Box is much more fragile with it's large roof on the firebox. I actually built the Batch 4 times before I found a way to keep the top from collapsing as soon as all the clay was dry.
3. Since I used the same amount of wood I would assume that the same amount of heat was released. The Batch just put it out over a much shorter period of time.
4. I can not speak to the efficiency of either design as I have no fancy testing equipment.
5. The J- tube core is actually pretty solid even when built from free materials. While I can't speak to the long term durability the J-tube has held up much better than the Batch in the short time I have played with them. I would think that a J-tube build like this encased in cob, indoors, and not abused would hold up very well. I would not recommend building a Batch Box using free materials for the firebox as it is just to fragile.
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Re: Batch Box vs J-Tube

Postby TruGrit » Tue May 27, 2014 11:25 am

.. wow, great job 4seasons .. I hope to do my RMH build later this Summer, so this was really good info .. thanks!!
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Re: Batch Box vs J-Tube

Postby Rhett » Tue May 27, 2014 12:26 pm

What about relative ash production? Did one or the other leave a larger ash mound that might be an indicator of a less thorough burn?
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Re: Batch Box vs J-Tube

Postby matt walker » Tue May 27, 2014 2:03 pm

Nice side by side comparison man, very cool. I concur about free materials and the different cores. The large span of the roof in the batch requires more substantial construction for sure.
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