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Post by invention1 on Jul 22, 2018 20:01:27 GMT -8
Completed basket sides. Both were drilled while bolted together to make uniform hole spacing between them. I had to use cobalt drill bits and cool them with a dribble of water to keep from burning them up. All holes drilled on a drill press so they'd be straight.
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Post by invention1 on Jul 22, 2018 20:04:20 GMT -8
Assembling the pellet backet, ceramic rods in place, sides insulated and held in place with 3/8"-16 stainless steel carriage bolts. On the backside of the steel plates, there are thin sheetmetal pieces that serve to trap the ceramic rods so they don't fall out. The rods are trapped, but loose in the holes so if there is any expansion or contraction they shouldn't be under any stress. Every part of the basket is replaceable, however the steel sides took several hours of drilling and countersinking, so I'm hoping I've designed it so these steel parts don't get hot enough to burn out.
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Post by invention1 on Jul 22, 2018 20:06:07 GMT -8
Pellet feeder, pellet basket and some pellets ready to fire up for a test run.
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Post by invention1 on Jul 22, 2018 20:11:19 GMT -8
Pellet basket running, with an electric fan behind it to simulate draft. Almost smokeless.
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Post by invention1 on Jul 22, 2018 20:13:10 GMT -8
Touching the sides of the pellet basket with a roaring fire inside. It was warm to the touch. Didn't bother with a thermometer, it was plenty cool to prevent burnout.
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Post by invention1 on Jul 22, 2018 20:15:34 GMT -8
Chimney-eye view of the firebox/pellet basket. Note that a few pellets are falling through into the area that will become an ash pit/primary air inlet. I'll construct this area of firebrick in case there is a fire down there.
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Post by invention1 on Jul 22, 2018 20:17:10 GMT -8
After the fire had burned down to coals, almost nothing left in the pellet basket. A whisk with a soft brush might be needed, but nothing hard, in order to prevent busting any ceramic rods.
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Post by Vortex on Jul 23, 2018 1:17:49 GMT -8
Nice work. I'd imagine once the fire is going properly and you have a bed of hot coals that new pellets entering would not be able to fall through, so it would only be an issue at startup. If that's correct then it just means sweeping a few up and putting them back on top when you light it.
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Post by invention1 on Jul 23, 2018 3:16:22 GMT -8
Nice work. I'd imagine once the fire is going properly and you have a bed of hot coals that new pellets entering would not be able to fall through, so it would only be an issue at startup. If that's correct then it just means sweeping a few up and putting them back on top when you light it. Correct. Once a few pellets are in the hopper, no more fall through. It's probably a minor problem, but if I ever need to build another basket (likely as this is a prototype) I'll adjust the spacing. Today I'm using grilling pellets, because regular fuel pellets aren't available int he summer, so we'll see how the real thing works. I think grilling pellets are the same size, but cost three times as much. I'm building it so there is an ash pit or secondary firebox underneath. Even if I take out the basket and burn firewood, the ash pit seems like a handy feature.
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Post by invention1 on Jul 23, 2018 17:32:10 GMT -8
So in order to test out some mortar, I built a little 4" J-rocket, with some of the firebricks mortared with my test mortar and the rest just dry-stacked. The stuff was made out of clay, mason sand, and a bit of commercial refractory cement. The mortar - essentially mud - was basically worthless and worked about was well as you'd expect mud to work. My other experiments with these mixtures have also had limited success. My brother, not afraid of being blunt, looked at a half-charred puck of one of these mixtures I was testing, and said "Why don't you quit being a dumbass and just go buy a jug of refractory mortar?" So, can someone explain to me like I'm 5 (ELI5, as the Redditors say) why we insist on making up mortar out of basic materials, despite the fact that battalions of brickmasons have made refractory brickwork all over the world for generations with commercial refractory cements and mortars? (Quoting from the manufacturer) "The compositions and methods of preparation of refractory mortars have been developed through extensive laboratory investigations to develop the particular combination of properties each bonding mortar should possess". Should I really be spending time trying to duplicate years of effort by pros in well-funded labs? Are these home-made recipes actually "better"? Is there something about these commercial refractory mortars that won't work? I'm sure folks have had success with the recipes here, after long experimentation, but really is it necessary to reinvent the wheel, when the wheel comes in a bag that I can just go buy? For instance this mortar from Sheffield Pottery
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Post by smartliketruck on Jul 23, 2018 18:23:14 GMT -8
A brick mason sells the materials on a separate line from his time, time for the most part is his only real cost.
Premixed refractory cement ain't cheap. If I'm building something for myself everything costs at the very least 50% more from taxes etc earning that money elsewhere.
From what I've seen here, most of the experienced experimenters here use a tight fit with a simple clay slip and sand for their own projects.
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Post by invention1 on Jul 23, 2018 18:41:50 GMT -8
A brick mason sells the materials on a separate line from his time, time for the most part is his only real cost. Premixed refractory cement ain't cheap. If I'm building something for myself everything costs at the very least 50% more from taxes etc earning that money elsewhere. From what I've seen here, most of the experienced experimenters here use a tight fit with a simple clay slip and sand for their own projects. Well, I'm getting a bag of the stuff for $32.50. Enough to set 250 firebricks, more than I will need. That's a lot cheaper than the time I've invested in something that has yet to work. I'm glad these folks have found something that works, but so far, despite sitting on essentially a kaolinite mine (there is literally a kaolinite mine down the road, at my place the layer is 18" down) I've had zero success in making anything resembling mortar or withstanding high temperatures, but have produced some pretty good mud pies that I'd have been proud of when I was about 8 years old, that fall apart when heated and won't stick bricks together. I'm tired of being frustrated, $32.50 for a product developed specifically for this purpose sounds pretty good to me right now. Change my mind. [EDIT] there are several kinds of pre-mixed refractory mortar. Ignore what the label says and look up the MSDS which lists the major materials. If the mix is sodium silicate and sand/quartz/silicates, it will not withstand the temperatures in a rocket stove. If the mix contains kaolin or clay and is rated 3000F, it has a half a chance.
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Post by smartliketruck on Jul 23, 2018 19:43:01 GMT -8
1/3 the $ cost of at my supplier, so no not gonna try to convince you so long as it's on label application is for firebrick.
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Post by invention1 on Jul 25, 2018 14:46:37 GMT -8
After having zero luck with various clay mixes, I built a little 4" J-rocket with commercial refractory cement, let it cure 24 hours and fired it up to complete the cure. Joints are strong, adhesion to brick is perfect, works first time without an experimentation. I am going to go so far as to break with the opinions of the majority on this board, recommending to not screw around with digging up stuff out of your back yard and just buy some purpose-made stuff. With the caveat that it must be rated for the temperatures in these stoves, which are hotter than most hardware-store refractory cement can stand. Of course, someone will soon chime in, and recommend that if my soil isn't right for one of these mixes, then I can buy some fireclay and start with that. I'd counter argue that now that I am buying all of the ingredients, I might as well just buy something that already works instead of more experimentation. I'm spending hundreds on ceramic insulation, firebrick, steel bell, etc. The cost of mortar is actually insignificant. The time, however, spent futzing around with clay sand mixes was significant. I need to have this thing prototyped and working by heating season. I really don't have more time for experimenting with homemade mortar mixes which so far have always failed.
Not gonna be disassembling this prototype though, the bond is stronger than the adjacent firebrick. Trying to prize it apart just results in the firebrick cracking.
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Post by wiscojames on Jul 26, 2018 13:54:25 GMT -8
I'll chime in, but not to advocate fireclay. I have only used sand clay mixes (with wood ash, occasionally) with great success. Pretty strong, easy to work with, and i don't need to be careful about storage. If it saves you time and hassle, by all means, buy a bagged refractory product. I think the attraction to clay sand mixes is that that are nearly universally available around the world, that can be undone without much trouble, and they are free, or nearly free.
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