I have an 8 inch J tube and I want to convert the front of it to be a batchbox. But I am unclear on how it will benefit me . Firstly, what is the definition of a batchbox and what are the benefits and drawbacks?
I have seen some posts which sort of answer these questions, but it is still unclear to me.
As for comparing one against the other, this is something I've been mulling over myself. So far, these are my thoughts between the two combustion units. A I'll add that while some folks get by with the exhaust simply stuck out of a wall with a J-tube rocket, having a good naturally drafting chimney system is mandatory for the batch-box. Personally, I'd argue the same for the J-tube RMH when installed in the USA industry standard stick frame house.
* simplicity in construction
* open fire box to tend, look into, listen to
* wood loads in higher up off the floor than a typical batch-box
* not friendly to big chunks and or gnarly non-uniform wood
* works best with equally sized and or finely split wood
* requires more fire tending than a batch-box
* a little more difficult to construct
* requires a firebox door (that usually gets really hot)
* more or less no fuss no tending, just load and burn
* wood loads in lower to the floor than a J-tube
* accepts larger less finely split wood than a J-tube
* able to take larger gnarly wood pieces that would hang up in a J-tube
I would second everything Byron said, and add that a major difference in use is that a batch box is going to deliver its full load of heat to the system, fast - no deciding you have burned enough and stopping halfway, but also no babysitting. If you are using a barrel top for cooking, you can't control its temperature. A J-tube burns at a measured pace, takes longer to deliver the same amount of heat, but you can control exactly how long you burn and to some extent how hot the barrel top gets. But you have to be there to tend it.
I am building a J-tube bell system with cooktop insert on my main floor, and plan a batch box bell system for my lower floor (secondary living space).
Interesting projects you've got going on there Glenn. I'll pass this on FWIW.
There are some really interesting cutting edge batch-box design developments over at Donkey's site, that allow the PvdB batch-box to be slowed down and achieve several hours burn time, with a shortened approximately 1/2 height heat riser (handy for cook stove height systems I'm thinking), and the stove maintains its very clean combustion performance nonetheless. However, the mass/bench/chimney requires careful consideration as a unit in order to maintain a not-to-fast, yet not-to-slow, flow rate through the system, primarily to keep the after-burn low in the shortened riser. I'm in process of constructing my own 6" batch-box test unit with the shortened riser, tapered P-channel, and chet (EGR) portal.