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Post by permaculturebob on Jan 29, 2020 20:49:16 GMT -8
It was only with the reduction of primary air and a port design in the batch box that secondary air became advantageous. Hmmm... Maybe, just maybe, you've got the wrong end of the stick here? The original p-channel was the one in the j-tube and although the benefits aren't that obvious, the Testo clearly proved it has a positive impact. More hydrocarbons are burned this way, plus the first brick bridging the tunnel won't crack as easily due to heat stress. I did the experimentation as early as 2011, you joined 6 years later. Maybe you've missed the thread about this development completely? See donkey32.proboards.com/thread/355/small-scale-developmentYou were right, the thread where the first p channel was created had escaped me. That puts a totally different take on what I thought was meant by the P channel mentioned in this post, too bad I didn't know about it when I was still running a j tube rocket. Trying to balance burn efficiency and having the fire climb out of the intake box was an ongoing problem after about the third batch in a hot firebox.
thanks for the link
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Post by permaculturebob on Jan 2, 2020 15:56:33 GMT -8
It's interesting that you say you have a strong suction at the p channel, perhaps the outside air at that point is cooling the rising gases rather than combusting them. The J tube was designed originally without any secondary air to the riser and burned quite efficiently,
It was only with the reduction of primary air and a port design in the batch box that secondary air became advantageous.
I would try blocking or removing the P channel for a burn and see if that helps your temps
I was always fascinated by the idea that the j tube was supposed to have enough oxygen to combust the fuel completely, but not so much it burned away the steel drum top too quickly.
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Post by permaculturebob on Dec 31, 2019 7:26:05 GMT -8
Bill Mollison described a wood distillate recovery system in ancient China using the final horizontal flue of the "Kang" by simply locating containers at different sections of the pipe which would have had different temperatures, and the condensing liquids simply ran out a hole in the pipe.
So the stove not only cooked the evening meal and warmed the sleeping platform, but recovered various wood distillates.
I tried searching Kang for more detailed reference to this, but so far have not found the details of this recovery, only the cooking and heating aspect. I would guess this grew out of observation, trial, and error, using consistent types and quantities of wood/biomass over a long period.
If anyone has any references to this it might be interesting to study.
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Post by permaculturebob on Dec 25, 2019 17:39:34 GMT -8
I'm not sure what can be said here to suddenly bring you up to speed on the many years of experience represented in these threads. I came on this forum about three years ago and learned about the batch box first, then came horizontal risers, DSRs, etc. I'm still trying to understand it all. It can take a week to read through some of the lengthier threads, and even longer when you start to read the reference links included in them. I'm guessing you are getting ready to start winter in earnest, so unless you have a place outside to do experimental builds it's likely a little late for hands on, but a perfect time to start reading and familiarizing yourself with the different things that have already been tried, and the ones that might apply in your situation. I'm going to guess you put a p channel in a normal J tube, no batch box or port. It would probably not have much effect since there is no serious pull on the secondary air supply , J tubes are designed to be used with unrestricted primary air, and metal in the firebox may interfere with burn temps, reducing efficiency. If you don't have a firm understanding of J tube dynamics, that's certainly going to be another prerequisite to understanding some of the more recent designs. I'm guessing you already have some of that reference material If you only need to run two fire box size loads each day maybe the J is all you need, if like me you run more fuel through your stove, then you will likely want to know more about batch box dynamics-- I would suggest you start with donkey32.proboards.com/thread/1998/batchrocket-eu-information-siteThen there is the DSR donkey32.proboards.com/thread/2341/different-batch-core-riser-all which ultimately fell out of favor, giving way to the DSR2 donkey32.proboards.com/thread/3503/double-shoebox-rocket-mark-iiAlong the way you will be introduced to many innovators and experimenters and perhaps be able to make a little more sense out of the science and art of stove building My own experience on this site has dramatically increased my knowledge base as well as giving me some great tools and designs to play with, but they come with a fair amount of reading and rereading trying to make sense of everything just so I know what questions to ask. As far as insulation for your bench, that's a huge question, and a topic all it's own. built on the ground like that you are probably losing half of your heat to the earth. It's impossible to say long distance without looking at it, put a thermometer in the earth under the bench right after a fire, if the temp is higher than surrounding soil away from the bench you have your answer. As far as the dynamics of managing the burn box on a J tube, it seems you already have some techniques, using the brick to restrict air flow and avoid smoke. leaning the fuel against the leading edge of the burn box can also help keep the fire down in the box, and giving the thing a rest to cool down in between fires can help improve manageability. I also found that ashes can accumulate in the tunnel and obstruct free flow of gasses so if you think you have too much smoke, reach in there before lighting the fire periodically to clean it out. One thing I noticed is your temps seem a bit low for the top of the barrel, at least compared with mine. My top could glow so bright it scared me. I used to have 1/2inch water pipe coiled around the barrel and one time when it ran out of water it melted the solder on the pipe joints about 1/2 way down the barrel. You reported 230C as your high temp on the barrel top which to my way of thinking is less than 1/2 what it should be, and while your J seems to be ok enough to use by your report except for some minor smoke issues after longer burns, There must be something else going on reducing it's performance.
I feel a bit pretentious commenting with so many more experienced people on the forum, but maybe the links I've offered can answer more of your questions.
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Post by permaculturebob on Dec 21, 2019 5:15:23 GMT -8
I have been using a forced /assisted draft since my first BB conversion of a j tube.
Just a simple 12 volt fan, gets a little sooty after a while, but cheap enough to replace.
I would make sure that you do have enough mass to keep exhaust temps real low, and a regulator/ potentiometer to control the speed of the fan.
I am also noticing that with my exhaust at ground level, care needs to be taken regarding the carbon dioxide, monoxide , etc. I am extending the exhaust pipe to at least get it farther from the house, and may bury it underground in a loosely sealed chamber of some sort where it may get some biological processing before going into the atmosphere
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Post by permaculturebob on Dec 21, 2019 4:47:10 GMT -8
Thanks for the links Karl, both will come in quite handy, And thanks Sksshel for commenting on my post and documenting your build process and conversion to DSR2. I will also probably be doing that, although at the rate I'm going that will be a build for next years heating season.
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Post by permaculturebob on Dec 18, 2019 16:28:18 GMT -8
Hi Scott,
This is likely not the place to comment on cook top glass removal, but since I don't know how to rearrange posts I'll leave that to the experts. I recently used a propane torch along with various metal scrapers, utility knives and occasionally one of those multi tools. The saw blade on the multi tool saw blades seem to be at a perfect angle for getting down perfectly flat against the glass. So far it has been tedious at best, but I did think the torch made it a little easier.
Also, the braces and rubber putty on each cook top are different, although the glass is all about the same dimension, and while the tops are pretty rugged, I did break a corner off one at the very last minute after separating all the glue except for one spot on the corner. I thought it was small enough to pull free without cutting it--it wasn't--don't take any shortcuts.
Also I was pleasantly surprised that a diamond bladed wet tile saw cut the glass without incident--but keep a steady hand and go real slow
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Post by permaculturebob on Dec 18, 2019 16:10:54 GMT -8
that has several pictures and more thorough analysis.
I think the main observation about efficiency and burn characteristics is the idea that the "riser" is the horizontal upper batch box and as such I started to apply the other principles of the original rocket stove riser. Primarily that meant greater insulation to help the burn be more efficient. I was told there is some insulation in the stove glass top,but adding ceramic fiber on top of the stove top increased the temps there by a couple hundred degrees.
I also noticed that putting a pot on that hot surface could create a sooty place under some conditions which runs counter to the whole idea of a heat riser as a place where as much as possible heat is allowed to build and not deliberately extracted.
The 2018 stove had a second chamber where I tried to include an oven, so top temps were not as intense as they are on the 2019 build which substitutes a simple insulated bell under the second half of the glass top. Temps on this part of the cooktop are now plenty hot. I have measured them at 600 F when the top shoebox has ceramic fiber board on top as an insulator.
The front viewing glass of the top shoebox frequently tops 800F with this arrangement.
The other observation is about the door , and the pyrex and neoceram pot lids that have been used by many. My experience has not been good Perhaps my door opening wasn't molded right, perhaps it was too close to the working part of the bb, but those lids have all failed. I can't really blame the visions cookware as far as temperature stability, but manipulating those hot lids eventually has led to disasters.
I'm working on a design, and will elaborate more if it works, but even a neoceram glass pane will need a frame of some sort- eventually.
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Post by permaculturebob on Dec 17, 2019 16:39:35 GMT -8
Hi sksshel, it's been about a year since you put up this thread, what were the results of your castings? Any tips on things to look out for?
I'm planning to do 4 basic molds, half a shoebox at a time, split horizontally, with some sort of overlapping joint where they come together. Any thoughts?
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Post by permaculturebob on Dec 6, 2019 1:08:04 GMT -8
Thanks for the answers to those questions Karl, I'm almost cleaned up from my new DSR install, so the GP experiments will begin soon.
Funny though how sometimes the simple things (like reducing particle size) can take more time than working out the whole rest of the process.
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Post by permaculturebob on Dec 5, 2019 7:17:43 GMT -8
Thanks for that clarification Karl, I questioned that when I saw it, as the process I remember was relatively quick as far as mixing and applying, with no wait time/ I also remember somewhere that multiple thin layers over a form were better than a single thick one. Is there an optimal time interval between layers? Does the finished piece accept hardware--screws or bolts?
Which would be the better aggregate, clay or sand?
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Post by permaculturebob on Nov 30, 2019 15:47:38 GMT -8
While I do appreciate, and even have some aptitude for the chemistry of some of these other processes, for the time being I mostly just wanted to get a little success with the easiest most direct process making a geopolymer. Like many new concepts, seeing the process first hand can be a powerful incentive to going deeper into the many variations.
No, I haven't yet taken my zeolite out of the bag (sweet PDZ) but I do anticipate the possible need to grind it to a finer powder. Also, it seems the NaOH needs to be a fine powder also, so maybe part of the dry mixing process can be taking both through a grinder together.
That won't happen for another week or two, but with some luck when I do start playing with the GPs I'll have enough alternatives to get a happy conclusion/
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Post by permaculturebob on Nov 30, 2019 4:25:00 GMT -8
Hi SLT, Your description of the process seems to indicate the "binder mix being created in two steps rather than one, mixing 1-1 first, then adding the rest of the zeolite,creating the correct binder proportions, I assume the aggregate is added next.
Unless I'm reading your description wrong, this is a third way to make the binder.
My original understanding was that the dry mix was done in one step--1-4 and boiling water was added- (just enough to dissolve the mix). The boiling water added some heat and the NAOH dissolving added some more heat to expedite the initial reaction (dissolution) creating the binder. Particle size was important to make the reaction happen at a quicker rate with less need for mixing while the reaction was going on thus preserving the heat needed for a thorough "dissolving" of the zeolite making the binder.
I think your analogy of the acetone and pvc is a very good one for me, it helps with my visualization of the process.
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Post by permaculturebob on Nov 29, 2019 4:30:40 GMT -8
Thanks for your comments, I'll likely try it with a dry mix first, then if I have problems I'll try your method. It's good to know there's more than just one procedure that will give results.
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Post by permaculturebob on Nov 26, 2019 20:09:17 GMT -8
Hi Berend, How did your final GP turn out? All the directions I've seen call for the dry mix first
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