Thanks for all the ideas and encouragement folks, gives me lots to experiment with
Pat, The height of the inside back of my firebox is around 9 or 10 inches. I finally got those temperature figures for the firebox / 'bake chamber' for you:
The stove was lit at 10am this morning with a full load (Firebox is 15.5" deep at the moment). At 2pm the Firebox/Bakeoven: was 420*C Cooktop: 172*C Stovepipe: 35*C Sides of stove 120*C/31*C 5pm the Firebox/Bakeoven: was 222*C Cooktop: 92*C Stovepipe: 32*C Sides of stove 90*C/31*C 6pm the Firebox/Bakeoven: was 181*C Cooktop: 72*C Stovepipe: 29*C Sides of stove 68*C/31*C 8pm the Firebox/Bakeoven: was 138*C Cooktop: 58*C Stovepipe: 25*C Sides of Stove 50*C/31*C
The Firebox temp was measured in the middle left side wall. The Stovepipe temp was measured just below the damper. Cooktop was measured at the hottest area above the throat. The outsides of the stove were measured at the hottest and coolest areas I could find). Hope that covers what you were looking for.
I've never actually been sure what a trip wire refers to in a stove, I'm guessing it's something that sticks out and creates turbulence in the flow? I've looked for a picture of one on here before but couldn't find anything clear.
Edit: Note* The stove pipe temps above were inaccurate because of the emissivity of the stainless steel stove pipe.
And the chamber size is just fine for the big roasting pan.
Thanks you so very much for sharing your works
Man, i am all giddy with enthusiasm because i recon you have manifested an evolutionary quantum leap in the hybridization of masonry/rocket fire chambers. The anecdotal information and basic temperature readings you shared in earlier posts indicated that this is a very good design. Simple. Compact. Steeped in a long history of masonry heating.
And now, with the results you are getting from optimizing secondary air feed... An aesthetically pleasant 4+ hour burn that increases overall efficiency... This is huge! And funny to boot that a leaky door top was one of the key ingredients to the discovery...
The trip wire idea comes from Peter Van Den Berg's empirical observations as he experimented in optimizing j-feed systems. He also led the evolution of the back sweep and of course, P-channel. You can view much of the history as tracked in 'small scale developments' And get a good visual of how they work together at www.dragonheaters.com
It could be that your existing set up is already offering just the right turbulence at the elbow. But chances are there could be ways to enhance it somewhat. How best to inject the air is a question in amidst all that.
I've no doubt now that this fire-chamber is to be at the heart of my next few builds (at least). I don't have a testo (yet) but i will give some thought to how i can experiment with the turbulence/mixing variables in a way that sheds clear results. Laying up trip wires with bits of finish plaster might be done and un/redone with relative ease... we shall see.
One modification to the layup i am considering is to 1/4" to 1/2" of ceramic fibre around the sides and back with an inch or so of cob plaster over it. This is to help buffer the expansion and contraction, concentrate more heat in the burn chamber/riser, and begin insulating from nearby combustibles. And, if we can cajole Satamax into agreeing that the riser is insulated... it could officially be called a ROCKET!
One question for you. Can you lead me towards any information on the history of the design? I am presently drafting up plans for our local code officials to review, so tracking the records of this sloping firebox might (understandably) enhance their willingness to trust this technique.
After a lot of thought I realized that my stove with it's deep dead-end firebox, (with both the air inlet and exhaust at the front,) is perfectly suited to wood gasifing and so shouldn't actually need the Walker port. (The PB Batchbox rocket has the primary air inlet at the front and exhaust port at the back, which creates a cross flow that isn't ideally suited to gasifying. By filling the primary air port with the metal tube of the Walker port, it's creating that super hot dead-end, heating the air in the tube and feeding it into the fire at the right spot to mix with the wood gasses and burn them.)
Vortex, I feel that the rocket stove's cross flow design would be better at gasifying than a stove with the intake and throat on the same side(such as yours). The incoming air would have more opportunity to combine with hydrocarbons to keep the temps up.
It's excellent that your stove is running so well in gas-mode. I would think that you end up with char at the far end of your stove. Is this correct?
Pat, If we can identify the principles of what's going on then I'm sure it can be improved upon.
My stove design was mostly out of my head. I built metal box woodstoves from all sorts of junk for many years before I started on this, and it was a combination of my experiences from that and what I'd read in a few masonry stove books.
The area above the throat is insulated now, a few years ago I mixed up a bucket of fireclay and pearlite and filled in all around the edges to make it into a nice insulated tubular curve below the cooktop, instead of the angular firebrick box that it was before.
Thanks for the links Eric, I see now in this picture that it is what I was thinking.
Hi Terry, I think the stove in this mode is working like a Camping Wood Gasifier Stove. The stove in that video when it's burning properly is the closest I've found to what the fire in mine looks like. My stove has a small amount of heated air coming into the burn chamber through the grate and from a few of the joints between the firebricks, which I think are acting like the bottom holes in the video. I see the small tell-tale jets of white flame when it's at it's hottest. And the air being drawn in all around between the hot metal door and frame is behaving like the top jets of the stove in the video.
I'd expect my stove to be full of char at the end of the burn like this but it's not, there's no soot, no charcoal, just fine white ash. This is it a few minutes ago, from this mornings burn. (The bricks stacked in the back are part of my experiments with different depths of firebox)
Regarding clean burn in slow gassification mode - maybe the airstream elbow at the back of the fire box scurries up some extra turbulence. Particularly later in the burn.
Pondering the increase in heat harvesting efficiency in slow gas mode… could be the system is moving flue gasses thru the thermal battery a little fast in masonry batch feed mode. Could be that a bell or longer runs can bring that closer to optimal. The nice thing about a flue bypass is, all things considered, that you can build ISA on the large side and then tweak it back if/when necessary. A point that will vary with varying burn magnitude, durations and atmospheric conditions…
This is a very beautiful stove… so simple and versatile...
Pat, regarding the baking, i cooked a chicken in the firebox of the green machine once. Works all right. I overcooked it tho! But even the insulating firebricks and the vermiculite refractory mortar mix held the the heat quite well.
Last Edit: Feb 16, 2015 23:57:45 GMT -8 by satamax
Figured it is about time i shared some photos of the vortex-inspired heater i am building of late.
The fire box is tweaked out to 13" x 13.5" tall by 18" deep, which enabled me to use a combination of, two castings, and 4.5" x 9" with a few 4.5" x 13.5" fire bricks involving only three cuts (one 13.5 brick in half, and another shaved down 1/2").
Also, much to my pleasant surprise, 3 such fire bricks on edge came out to exactly the same height of 5 common red bricks on flat… so the merging of bell to downdraft was smooth. Of the 180 red bricks involved I cut only about 15 of them in half. Hooray for less cutting
I have built the front lintel (above opening) with a 1.5" slope upward towards the throat and am planning to add a metal plate below that to create a plenum chamber thru which warmed air can be injected into the throat just below a series of trip wires going round the bend. The cardboard form has some trip wires carved into negative space and is sacrificial to burn away in the first fire and leave the clay-vermiculite casting behind it. I'll probably also treat that surface with sodium silicate and fine sand.
Repurposed from an outdoor kitchen i demo'd a couple of years back. It is a classy 'Victoria Foundries' cast iron. Always wondered when i'd get around to applying it.
This has been an interesting build. Every time i have gone to tweak the design with the intention of getting it to burn a bit cleaner, i have to ask myself: Is this going to make an improvement?
With your riser-less batchbox charting promising numbers, i have to wonder if Trev has already fully dialled things in. Without the test we cannot tell.
One thing for sure - I certainly don't want to lose the 5 hour gassification burn that he is achieving.
So i am glad that i have done little other than fiddle with the turbulence and air feed in the throat.
Whether or not the air plenum across the top is a good idea is up for evaluation. The original design has about 10sq" of secondary air creeping in around the sides, top and bottom of the door frame; coming in contact with 52sq" of hot metal on its way in. I am considering reducing that to 6sq" (12"x1/2") gap along the top contacting 36sq" of hotter plenum metal. This may have the effect of ramping up the throttle in the throat which could diminish slow burn mode. At least, i will try to build the door lay up with adjustable ceramic gaskets. Maybe leaving the gasket out of the upper sides to achieve the same secondary CSA.
Ya please upload them to your server and post as you see fit. Dropbox is freeware, but i understand if people would rather not tie into yet another service... I switched to it after my photobucket account started getting hit with nasty adware popups.
TexasGonzo: Sooooo glad I found this site! Its always rewarding to find such a super group of folks! To any and all, feel free to PM me anytime. Thanks for having me!
Mar 11, 2019 18:56:41 GMT -8
jlmtech: GADGET: CONSIDER USING A JET PUMP INSTEAD OF A BLOWER FAN TO INDUCE DRAFT; NO CLOGGING.
Mar 26, 2019 8:19:28 GMT -8
michaelegan: i am unable to open the sketchup files on my mac. I used sketchup a few years back but apparently the company now requires a subscription. does anyone have any advice/instructions on how to use the program or how to view pictures without spending money?
Aug 20, 2019 18:41:48 GMT -8
mannytheseacow: michaelegan: download AutoCAD student version for free... import .SKP
Aug 23, 2019 13:33:44 GMT -8
topbaza: hi everyone, been searching all over net and this is were i need to be i think!!
Sept 28, 2019 6:16:25 GMT -8
anounaki: Hi, why I cant upload photos when I make new tread to this forum?
Feb 28, 2020 2:09:40 GMT -8
ahansen: photos under 1 mb not possible?
Jun 4, 2020 0:09:21 GMT -8
belgiangulch: Photo's are possible. They must be downloaded elsewhere and the image url (adress) is copyied.
Sept 14, 2020 7:26:15 GMT -8
belgiangulch: While creating a thread click on the small picture in the banner above the reply. A box pops up, paste the image url in the box. Pay no attention to the huge list of numbers and such.When you finish and hit reply your post with pictures will come up.
Sept 14, 2020 7:29:27 GMT -8
deadstarsstillburn: Hi there. I was directed this way by folks on the Permies.com website and am hoping I can get some information on how a total newbie can get started designing, siting, building, and not-dying-in-a-horrible-house-fire with a new RMH in a 160-year old home
Oct 21, 2020 6:52:10 GMT -8
deadstarsstillburn: The people over there recommended either a 6" batchbox or an 8" J-tube. I don't know what those are but am going to try to figure that out. What I need is a blueprint that I can scale to fit the need for my house. I have something likne 5000 square feet
Oct 21, 2020 6:53:00 GMT -8
deadstarsstillburn: but I do not need to heat all of it by any means. probably only need to heat half of that, maybe less.
Oct 21, 2020 6:53:15 GMT -8
deadstarsstillburn: moreover, the house has 3 storeys (large attic) so I assume if I get very efficient heating on the ground floor, that will go a long way toward heating the upstairs as well, no?
Oct 21, 2020 6:53:59 GMT -8
BenAlexanderT: Happy new year everybody. I wish you the best
Dec 31, 2020 15:06:14 GMT -8
Solomon: Anybody in Southern Oregon, in Jackson or Josephine counties?
Jan 16, 2021 21:54:43 GMT -8
gnomedome: i realsie this is from 2009
Apr 14, 2021 8:30:44 GMT -8
gnomedome: i realize this is from 2009 id love to see the photos from this ..as im looking to build a sauna soon similar to this .... if anyody sees this post firstname.lastname@example.org..... the photos in this post did not show up
Apr 14, 2021 8:32:00 GMT -8