Hi all;
As many of you know. This last year I upgraded my two rocket mass heaters from J tube to batch box.
Our one J tube, we have been using for over seven years! It was not an easy decision dismantling it .
Liz in particular, was very concerned. Her perfectly working 8" J tube, that she had come to count on . Was about to be dismantled.
She also didn't like the thought of me creating dirt and dust on all her art work!
Sorry Dear but Progress has a cost... You'll get over it and love the new rocket even more!
Yeah right...we will see!
Now a month later, construction is finally complete, she/we couldn't be happier!
Her studio/ greenhouse was always comfy with the J tube. No problems. Even over a Montana winter night with no fire. Next morning always found the plastic uninsulated building well above freezing.
You did need to go restart that fire relatively soon in the morning or it would start dropping towards freezing.
The big catch with a J tube is the one hour reload time. Yes you can luck out and get 1.5 hrs and yes they relight super easy when hot.... But your still messing with a fire quite often.
It does become a habit, to note the time and plan on a trip out to feed the dragon. Not really a big deal.
Now that the new Batchbox Dragon is up and running... OMG! Why did I stall all these years in building these!
No comparison! Hands down the batchbox is superior in every way.
This morning it is 13 F outside, The studio was 51 F at 5:30 when I got up, now 3 hours later its a whooping 14 F outside and the plastic studio is 48 F
The J tube would have been 40 F or so at 5:30 and 3 hrs later it would have been 37 F and falling steadily.
So what makes this batch so much better than the J tube it replaced ?
To start, I have more brickwork than before. My barrel with the J had a thick cob covering. It was great, held heat, you could lay your hands or body up against it and not get burnt just soak up the heat!
My batch has the original brick base that the J tube was made from. All filled in with cob.
The new batch sits on top of that. The batch firebox is made from heavy firebrick, surrounded by insulated firebricks and then covered by red clay bricks.
With the heavy steel door and the insulated bricks that fire box is one hot puppy. I encased 3/4 of my barrel with red brick backed with cob.
That is quite a bit more mass than I had with the J plus the fact that the fire box is insulated and closed off with a door means I can easily go 2.5 hrs before needing to check the fire.
I had always heard that a 6" batch burned around an hour or so... with my J going almost that long I thought why bother? Well let me tell you that its true. The load of wood might be burned into coals in an hour or so ... but that glowing pile of coals will be there for a long time!
Another difference "so far" is exhaust stack temp. I use a candy thermometer inserted directly into the stack after it comes out of the mass. We call this a T&G Dragon breath monitor.
My J tube after it was running for a few hrs would get exhaust stack temps of 250 F to 350 F Recommended running temp is 200 F Minimum is 140 F
So far the hottest my batch has gotten the exhaust is barely 145 F that,s hours later that it might get that high and promptly cool off as soon as the fire coals out.
I still have moisture that I am drying out and these temps may rise as the water evaporates ... Or this batch and mass are absorbing the massive heat that this puts out and is keeping it & not sending it up the chimney! Time will tell!
Of course another benny to a batch, is larger wood can be burnt. It lays horizontal so it is much more conventional than a J.
One particularity of a batch is it needs air space on both ends of the wood. The secondary air stub creates an "end iron" to keep wood off the back wall but you must leave air space on the door side as well.
This mean a 6" batch with an 18" firebox really needs 14-15" wood although longer can be used at times. My 7" batch box in the auto shop is 20" long it is much more forgiving on long wood.
I discovered a specification variance on batchbox's that Peter Berg has approved.
The only spec on a batch that can be safely changed "by a few inch's" is the length of the firebox. Had I know this ahead of time I would have increased my 6" by 2 inch's or so!
One issue with building these stoves is the metal work involved. This is more than the average person feel's comfortable doing on their own.
To make this more available to the average permie. I am starting a rocket stove store. It will be called Dragon Technology. It is not online yet.
I have secondary air tubes built and available for sale now. I am also making all steel doors for batch's as well. Matt at Walker stoves will be reviewing a door on line .
I also hope to offer
superwool , T&G monitors , Ceramic boards, Bypass gates and anything else that builder's are looking for.
I want to make batchbox's available to all.
So I am now a convert! These batchbox's rock! Our fellow rocket scientist Satmax has been telling us this for several years now...
He is completely correct! I wish I had taken his advice years ago!
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