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Post by Karl L on Jan 16, 2023 6:54:28 GMT -8
Hi Trev, I'm doing a careful re-check of various things before going any further with my 125mm design. Looking at the Sketchup and notes on page 1 of this thread, the basic firebox for a 150mm system is 305mm wide and 305mm tall. But looking at the photo in this post, it looks significantly taller (from the top of the box to bottom of 'V') than it is wide: donkey32.proboards.com/post/36830/threadIs that just distortion in the photo? Thanks, Karl |
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Post by Vortex on Jan 16, 2023 12:11:59 GMT -8
It's camera distortion.
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Post by dcoyte on Jan 16, 2023 12:40:09 GMT -8
Trev,
I am making forms to cast a firebox for the gasification model. (I like that the stove can be transformed to the rear top throat that you are working on now, with just casting a new top.) Wondering if you have any suggestions about that earlier gasification design. Did you ever experiment with the size of the throat? The 3" X 12" throat seems large given the throats in the current design and j-tube systems.
Thanks,
David
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Post by dcoyte on Jan 16, 2023 14:23:02 GMT -8
Trev,
I was also wondering if you had any second thoughts about the slanted roof of the firebox leading to the throat?
Thanks,
David
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Post by Vortex on Jan 16, 2023 15:37:01 GMT -8
No never experimented with different size throats, all of them that I built were 3" x 12", but as you noticed the second one had those slanted sides into a 3" x 9" 1 CSA secondary burn tunnel. The idea was to create a reverse vortex, but as I never had a glass window on the secondary burn chamber I don't know if it actually worked. The secondary air jets seemed to help a lot though.
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Post by martyn on Jan 20, 2023 9:37:01 GMT -8
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bibo
New Member
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Post by bibo on Jan 21, 2023 9:15:55 GMT -8
I made moulds for castable, and pour half of firebox walls. Now, while waiting that I can reuse moulds for other half, I am preparing for iron part of stove.
Trevor, I can't find in posts nor in any photo.. How is door frame attached to stove? Is it connected to firebox walls (castable) or just to metal plates (stove's skin)? If to castable, what kind of bolts can be used that castable don't brake when bolts expand due to big heat?
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Post by Vortex on Jan 21, 2023 9:58:56 GMT -8
The stove door frame is attached to the front metal plate. I made it so the top of the door frame has a couple of bits that slot inside the steel plate, the bottom of the frame is held in behind the hearth which is bolted on.
On my previous stoves I drilled holes through the inner sides of the door frame and used self tapping screws into holes filled with aluminium foil as a fixing, that allowed some expansion and didn't break the casts but tended to get loose and need repacking about once a year.
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Post by martyn on Jan 23, 2023 9:08:27 GMT -8
I was hoping to enlarge the viewing window but it is not working for me so far…..
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bibo
New Member
Posts: 14
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Post by bibo on Jan 23, 2023 12:27:12 GMT -8
Trev, if I understood good, the door frame has screws what goes trough metal plate, and nut goes behind metal plate to fix it? Or some more simpler way?
I cast 2 pieces do far just, and I wanted to check with you fellows is it good casted.. First try I made it as little water as I could, and that block has more air bubbles. Second block I used little more water, and it turned out better. However, siggestion is to use as little water as possible, so I wonder are these bubbles problem, or it won't affect the performance? Which mix should I continue with?
Ups, now I see I don't know how to upload photos😅
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Post by Vortex on Jan 24, 2023 1:53:54 GMT -8
Hi bibo, This is an old sketch of how I made the door and frame on my original stove so ignore the rest of it, it just saves me having to redraw the whole thing. The black part is the metal plate that forms the front skin of the stove, and the white part is a short piece of threaded bar through the top of the door frame that holds the frame in place. I originally made them as grub screws but they rusted in place, but I found if I put the top of the frame in first at 45 degrees to the front of the stove then I didn't need to remove the grub screws to get it in and out anyway.  I take it you're vibrating the molds to remove the bubbles? Because of the consolidation when vibrating a cast, the denser material tends to be at the bottom and lighter at the top with any bubbles that didn't pop because of surface tension. This seems to make one side more durable with a harder longer lasting surface and the other more dusty and more easily abraded, so I always make my casts so the bottom of the mold is the inside surface of the firebox. The forums picture hosting quota is long since full so you have to upload your pictures somewhere else and link to them here like this: [img]https://www.vftshop.com/images/others/Stove/doorframefix.jpg[/img]Trev |
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Post by Vortex on Jan 24, 2023 2:06:35 GMT -8
I was hoping to enlarge the viewing window but it is not working for me so far….. Hi Martyn, With the holes that small in the sides of the port I didn't notice a lot of difference, try taking out the whole sides so you have at least 5% csa, and regulate the flow from the front then you should really see the effect. Trev |
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Post by martyn on Jan 24, 2023 9:08:58 GMT -8
Trev, on pages 77-78 Victorlt talks about directing gases directly from the fire box to the exhaust stream, did you manage to decipher exactly where the holes are situated?
There are 12 5mm holes for the secondary air, I could try 8mm holes that should give me around 7.5%
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bibo
New Member
Posts: 14
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Post by bibo on Jan 24, 2023 12:29:06 GMT -8
Trev, I feel ashamed for how helpfull you are. Thank you so much! Here are three photos. On first one is mix with less water, on second one mix with more water. On third photo both of blocks, left one is with less water. I vibrated it following advices that when "oil" starts to collect on surface, it need to be stoped. I am not sure should I vibrated it more or not, but I hope you csn say from photos is it good. paste.pics/L5Y20paste.pics/L5Y5Wpaste.pics/L5Y6OConsidering the smooth surfaces.. How is best to turn firebox top plate? What is more abrasive, vortex, or burning wood in firebox? I made mine with smooth surface oriented to firebox, but still didn't cast it, so I can easy change if it is better that smooth side is on vortex.. |
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Post by Vortex on Jan 25, 2023 1:41:27 GMT -8
bibo , First one looks like it could have done with a bit more water or vibration, second one looks fine. I put the top cast with the smooth side facing down into the firebox, though the last year I have been running with vermiculite board on top on the afterburner floor. Trev, on pages 77-78 Victorlt talks about directing gases directly from the fire box to the exhaust stream, did you manage to decipher exactly where the holes are situated? There are 12 5mm holes for the secondary air, I could try 8mm holes that should give me around 7.5% , If my math is correct 12 x 5mm holes would only give you about 20mm2 of secondary, to get 5% csa on a 100mm/4" system you need about 400mm2, so a 2mm slit down both sides of the 100mm long port would be about right I think. I have no more info on his use of Kuznetsov principle of free gas movement than victorlt posted in his reply: Hi Trev, Yes, I have two vertical holes (10% CSA in total) from the firebox directly into exhaust stream bypassing the afterburner. Reading this forum I was wondering that nobody are not using this theory in rocket stoves. Actually it's not my idea - I took it from the theory of Kuznetsov, which is named: "the principle of free gas movement". These holes helps to separate ballast gases from the hot ones and let them exit system in a short way without pushing them with hot gasses over the afterburner. This allows to keep very high temperature in firebox and afterburner even after you are adding cold bunch of wood. As I mentioned, all my wood I'm feeding the stove now is outside, under the sky and not in a shelter with roof. Wood has remnants of snow and ice and when I adding it to the firebox, I can see how this snow and ice melting and squealing till becomes water vapor. But despite that Vortex in afterburner recovers very fast after the fresh load, because water vapor and other ballast gasses have easier path to leave the system and allows to keep high temperature in afterburner. These holes have a name "dry seam". They are located in the back of firebox left and right sides in the bottom - each hole is around 1,5 cm wide and around 1/3-1/4 of firebox height. In Kuznetsov design stoves these holes goes vertically over all firebox height, but this design was not suitable in my case because through the holes gasses appears directly in to the exhaust channel where chimney traction is very high. So when I tried to make them full firebox height, I saw that big part of flames was simply sucked through these holes and high chimney temperature indicated that with ballast gasses I throwing out and some hot ones. You can find more details about Kuznetsov theory here: eng.stove.ru/stati/chto_takoe_pechi_ivkuznetsova_sokraschennoTrev
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