reyh
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Post by reyh on Nov 24, 2018 2:02:49 GMT -8
Hello everyone, I'm back with a new project: With a friend we decided to make some serious molds in order to purpose parts of batch-box fireplace. We desire to make the first pieces before the end of the year. So this time i'm doing plan with sketchup and i will be happy of any kind of advice. It's the first time i use sketchup and there is still a lot to improve but the global idea is already done, I believe it's time to show it here, and hope you could give me some advice. Skp 2016 version skp8 version It's a ø150mm, side exhaust. The fireplace is 600mm long to receive 50cm log. There is some notable differences with Peter van der Berg's version: - The floor chanel is deported on the side so there is no obstacle in the fireplace (When re-using the mold of a previous ø150 fireplace i've made, it happend to be this way because the mold were not initialy done for a sided-stove, and i think it's interesting and probably not a problem. My friend's stove seems to work very well). - I tried to make a minimum of pieces, and that most of them can be used for a right-sided as for a left-sided stove. A this point, only one piece is not symmetric. - The exhaust has a "half octagon" shape. It's the "turbuleur" concept from Yasintoda who seem to authorize very short chimney size. This fireplace is also design to be compatible with his batch-bloc concept. - Plus, I started with Peter's casted stove sketchup for inspiration and seen some strange points: The port height is the same as with P-channel although this model has a floor channel. Yasin as myself have done it 16mm shorter to compensate the lack of P-channel part who obstruct the upside of the port. I'm curious to know what is the best way to treat this part. Thanks for your attention. I hope you appreciate and could help me a little to not make big mistake in this project.
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Post by peterberg on Nov 24, 2018 9:34:25 GMT -8
It's a ø150mm, side exhaust. The fireplace is 600mm long to receive 50cm log. I had a close look at the drawing and there are some comments to make. Such a large depth of the firebox in a 1500 mm system is essentially an untested variant. May I suggest you could enlarge the system size to, say, 160 mm or more? In that case the firebox depth is within specs. Yasin said at some point he likes a larger firebox in order to burn bigger logs. The French market seem to prefer high-performance stoves anyway. - The floor chanel is deported on the side so there is no obstacle in the fireplace (When re-using the mold of a previous ø150 fireplace i've made, it happend to be this way because the mold were not initialy done for a sided-stove, and i think it's interesting and probably not a problem. My friend's stove seems to work very well). This is a real deviation from the design, I am sorry. A lot of people has done something similar, most of the time just rounding off or chamfering the corners of the port at the firebox' side. The first one I am aware of was done in 2013 in the USA as an attempt to create higher gas velocity. The result of such attempts has been lots of smoke and/or CO most of the time. I strongly advice against such a modification for that very reason. I discussed that failure point with Larry Winiarski a couple of years ago and he agreed it has something to do with fluid dynamics being very different with sharp corners as opposed to chamfered in that particular spot. - I tried to make a minimum of pieces, and that most of them can be used for a right-sided as for a left-sided stove. A this point, only one piece is not symmetric. You are right, for production purposes it would be indispensable to use symmetrical parts. I counted seven different parts showed in the drawing, in my view that could be six and perhaps even five. - The exhaust has a "half octagon" shape. It's the "turbuleur" concept from Yasintoda who seem to authorize very short chimney size. This fireplace is also design to be compatible with his batch-bloc concept. The lower part of the riser is the right half-octagon shape for that, the higher parts doesn't need to be octagonal. - Plus, I started with Peter's casted stove sketchup for inspiration and seen some strange points: The port height is the same as with P-channel although this model has a floor channel. Yasin as myself have done it 16mm shorter to compensate the lack of P-channel part who obstruct the upside of the port. I'm curious to know what is the best way to treat this part. In general, I did that because I feared the ashes at floor level would block the port partly making it shorter. Having used my own heater for three full seasons now tells me that isn't the case. Air velocity is high enough to blow most ashes away, even the (flat) bottom of the riser won't accumulate more than a bit over a season. So I'd think you are right in bringing the port size down to 70% of riser csa. I would applaude to a new commercially slanted initiative, that's for sure.
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Post by travis on Nov 24, 2018 23:34:47 GMT -8
This is an idea I have heard many talk about abd rarely seen happen. What are your goals for a market, shipping weight and cost for a full core?
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reyh
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Post by reyh on Nov 25, 2018 4:07:08 GMT -8
Thank you very much Peter. As I said, it's the first time I use Sketchup, and I started drawing without thinking about a lot of details. I made a ø150mm just because it's the dimensions of my prototype from last year... I have redraw it instead modifying your's cause I wasn't able to, and if there is a lot of piece it's only cause I had trouble modifying the parts around the heatriser. I realy suck with sketchup! I realize that I have to think a lot more about the dimensions. And many other things! So, I took your plan and just made some modifications (Now I'm able to do it, a little bit) to have only one part to modify according to the direction of the port:
I have draw an octagonal exhaust but the final shape will depend the way i will build the molds. With things like wood, octagon is easier. But it also could be round. About the deported port: I took a look at the pictures I took of it and noticed something I think is important. There are about 2cm of 90° walls around the port. The same configuration is found on one side of your stove. My friend's stove really looks like it's working well. Yesterday I watched his chimney as he started a fire. It smoked for about a minute before there was nothing visible left. The fire in the foyer is very hot. It's not worth an analysis, but from what I've seen, everything seems okay. I would really like to test this configuration. My goal is to make fireplaces user-friendly and I think this is a good thing if the yield remains good. Travis, I understand your skepticism. At this point, I have no precise idea of the cost price, weight and many other things. Some of my friends are enthusiastic about these stoves, but have trouble understanding that if mine have cost so little (less than 150€) it is because they are prototypes, made with cheap perlite or vermiculite concrete, without joints other than an earth mortar and I do not intend to use it more than one season with care. It worries me to see them more confident than me when they barely know the concept. First of all, I want to be able to make them safe, efficient and cheap fireplaces. This may then be of interest to self-builders if it does not cost much more than a brick fireplace and is easier to install. I think I can make the fireplace, and maybe the door, for less than 500€. With barrels, this will make it easy to make quality stoves for a very low price. And since I'm not looking to become rich, with a design that takes little time to make a home, it should be able to be at a very interesting final price and allow me to earn a little money.
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Post by peterberg on Nov 25, 2018 11:56:44 GMT -8
Reyh, it seems to me the distance of the vertical part from the edges of the port is quite large. My best results were obtained having a distance of no more than half the port's wide from both sides of the vertical stub.
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Post by Dan (Upstate NY, USA) on Nov 25, 2018 13:27:46 GMT -8
You should mass produce the molds instead of the parts. The molds could be lightweight plastic or silicone and the cost of production could be low with low cost of shipping. Then you sell them to people and they buy the heavy castable and make the parts with your molds...
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Post by peterberg on Nov 25, 2018 13:45:47 GMT -8
Wolf, the same thing could be done with sturdy cardboard or even a plywood flatpack. Problem arises when people start to cast the things whether the mold is strong enough to withstand the outward forces of the refractory castable.
I, for one, made quite a few experiment molding out of extruded polystyrene with minimal reinforcement on the outside. That means a lot of plastic waste when mass produced, might be the wrong way forward...
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reyh
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Post by reyh on Nov 25, 2018 15:57:48 GMT -8
The molds might interest some people here, although I think many will prefer to do their own experiment. People who are a bit of a handyman will find it long and complicated to get and install refractory concrete. And it is very expensive to make a single part, not just because of the molds. I'm not sure it's that interesting. Anyway, making stoves is fun for me, and if I can sell them it would be great. Selling mussels doesn't excite me at all and if it's worth it I leave the initiative to others. For now I would be very happy to have made 10 stoves. If it gets any bigger, maybe I'll reconsider. Reyh, it seems to me the distance of the vertical part from the edges of the port is quite large. I totally agree, and it's certainly not the only imperfection. My friend is the kind of person who, when he wants to do something, starts by doing it and then after thinks about it.... I was very worried when he decided to make this stove, and I did my best to make sure that at least he didn't put himself in danger. This situation is not for nothing in my motivation to make these molds. But I must also point out that the boundless motivation of this friend, who is my accomplice in this adventure, is largely causing fact that I am embarking on this project, which I have been thinking about for several years. He has the "advantage of his disadvantages". Me too, but on the other hand, let's hope we can achieve a good average! One last question, I can't find out again which power corresponds to which size of fireplace. Does anyone have a link to a relevant page?
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Post by coastalrocketeer on Nov 27, 2018 10:32:34 GMT -8
You could sell your stoves more locally and sell molds worldwide... Much cheaper to ship 5lb's of plastic. And I expect the waste is made up for in the rediced oetrochemical usage from the casting of just one stove, if it replaces oil, natural gas, propane, or electricity sourced from fossilized sunlinght.
I would want molds, ans would be using one set of molds to make as many cast cores as I could sell or give away in my part of the world.
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reyh
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Post by reyh on Nov 28, 2018 18:43:27 GMT -8
Hi, I have taken the time to think about this project and I think I have made enough progress to come back for your advice. First of all, because you don't necessarily have time to load and look at a stranger's sketchup plan, I made a screenshot of the modification I made to Peter's plan, which allows you to change only one part to make "left", "right" or "back" fireplaces. If I plan to improve the plans as much as possible before making the first molds, I think that's the best I've done so far. Then, I decided, as Peter recommended it to me and because it is a dimension that Yasintoda also adopted (precisely to eat 50cm logs), to make the first fireplace in ø160mm. declined with the normal depth, it will take 33cm logs and with the maximum depth, it will accept 50cm logs. All compatible with 150mm pipes. Last night I made a new plan that has some modifications designed for "Mr. Everyone": the excrescences that keep the parts in line are made so that all the elements of the fireplace are kept in the right place. I also planned a recess of the front triangle because I am trying to design an integrated system to fix the door. I consider this to be a crucial and delicate point in the assembly of the stove and prefer to spare it to future customers. At last the back is made in such a way that by rotating it 90° the fireplace can be "left" or "right" with the same parts and there are only 4 parts for the fireplace without the chimney. But this is certainly not the last plan I would make before building molds. I am not convinced that it is so relevant to want to avoid making several molds so much, or to reduce the number of parts so much, because that poses other problems. Before talking about these problems, here are two overviews and the skp file of this plan: (skp 2016)It's time for the questions I ask myself and the problems I'm trying to solve. peterberg will probably be the best person to answer me, because this work is only a variation of his own and is very strongly inspired by it, but any help is welcome. I also assumed that you didn't do things randomly and watching your plans led me to a lot of thinking. - For the assembly notches, I saw that you made the inclined edges and I guess it's to allow the whole thing to move a little rather than break the connections if the holder is too rigid, is that right? If I am right, I have to change the form I have adopted a little more, and if not, totally. - When I molded parts that close on themselves, such as chimney sections, they tended to crack. I think that these shapes do not withstand the expansion due to thermal shock, this creates a tension between the inner part and the outer part which has no escape. I'm all the more convinced because there's none in your plans. Is it also a problem if both sides of the fireplace are made of a single piece with the bottom? I think so, especially since the bottom does not heat as much as the edges, and so it is necessary to do this in two pieces. - To assemble and hold the castings, I think I saw somewhere that you use a steel strapping. Is it a reliable and robust technique? Or do you have any other suggestions? - I am considering the possibility of drowning the entire fireplace in perlite-based insulating concrete, which is less expensive than hard refractory concrete. This would allow even thinner walls of hard refractory concrete, to reduce cost while being more efficient, and to offer a one-piece fireplace in the end. But I fear that this insulating concrete will peel off or crack with thermal shocks. What do you think of that? - If I put this insulating coating on, is it possible to leave a steel strap on it or will it cause expansion problems, or worse, rise to temperatures that could deteriorate it? Or will it be protected by the absence of oxygen and other reactive gases? - For the fixing of the door, I have not yet found a satisfactory solution. The only one that comes to me would be to drown metal legs in the insulating mortar, but that brings me back to the fears expressed above. Do you have any ideas or have you ever seen anything effective for this point? - Enfin, depuis le temps que tu as fait ce foyer et que tu travail dessus, tu as peut-être d'autres suggestion ou point d'amélioration à me suggérer. Je serais heureux de les connaitre. That's it, this post is quite long. I thank all those who have had the patience to read it to the end, and even more those who will answer it. coastalrocketeer and those who ask me to sell molds: I'm sorry but my project is above all to make Batch-Box stoves for the general public, because I'm convinced by this technology and want it to come out of its confidentiality. There is already a lot to do to make the batch-box "user-friendly", a lot of work to launch my project, so I'm not saying no, but selling molds is not one of my priorities. Give me time to run some fireplaces and we'll talk about it again.
Personally I don't understand why making molds seems so difficult to you, I'm more apprehensive about the idea of bricklaying bricks so that they don't move for more than ten years... Try it, test it, perlite concrete comes back to less than 100€ for a fireplace and holds out at least two years being delicate, and you can then make a final casting with a better concrete. Translated with www.DeepL.com/Translator
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Post by peterberg on Nov 30, 2018 8:12:48 GMT -8
- For the assembly notches, I saw that you made the inclined edges and I guess it's to allow the whole thing to move a little rather than break the connections if the holder is too rigid, is that right? If I am right, I have to change the form I have adopted a little more, and if not, totally. Two reasons: casting sharp (less than 90º) edges lead to problems, they'l break off very easily. Second: in case the notches doesn't fit exactly it's easy to grind some material away or use refractory caulk to seal it all (like I did). Try to avoid 45º thin edges like the plague, those will give you severe headaches. - When I molded parts that close on themselves, such as chimney sections, they tended to crack. I think that these shapes do not withstand the expansion due to thermal shock, this creates a tension between the inner part and the outer part which has no escape. I'm all the more convinced because there's none in your plans. Is it also a problem if both sides of the fireplace are made of a single piece with the bottom? I think so, especially since the bottom does not heat as much as the edges, and so it is necessary to do this in two pieces. Casting larger pieces isn't a problem, having different temperature gradients in the same cast is. Even my latest firebox (in my own heater) design displays some very thin cracks in one of the sides. In general, the hotter areas will expand more and earlier, the areas that stay behind will be teared apart. The same goes for your riser and port piece, I expect it to crack badly because of temperature differences. - To assemble and hold the castings, I think I saw somewhere that you use a steel strapping. Is it a reliable and robust technique? Or do you have any other suggestions? Yes, strapping is a good way to hold the pieces together. The casting will expand as pointed out, but the steel strapping start to expand at a lower temperature so there won't be a problem. This method has been used for quite a long time now, personally I used it in 1983 for the first time as construction metod at the outside. The simple steel wire has been in use since 2003 in another design which is still being commercially produced. - I am considering the possibility of drowning the entire fireplace in perlite-based insulating concrete, which is less expensive than hard refractory concrete. This would allow even thinner walls of hard refractory concrete, to reduce cost while being more efficient, and to offer a one-piece fireplace in the end. But I fear that this insulating concrete will peel off or crack with thermal shocks. What do you think of that? Minimum wall thickness that is still workable with refractory castable is 30 mm. I tried 25 mm once and I found it very cumbersome. Casting a mantle of insulating concrete around the core sounds good, but I would prefer a lighter and still strong castable myself. Once I did an experiment using Gouda Refractories GoLite 135, a 1,4 kg/liter insulating refractory. It ended as quite strong and surprisingly light weight. - If I put this insulating coating on, is it possible to leave a steel strap on it or will it cause expansion problems, or worse, rise to temperatures that could deteriorate it? Or will it be protected by the absence of oxygen and other reactive gases? Can't answer that, sorry. No experience with such a construction. - For the fixing of the door, I have not yet found a satisfactory solution. The only one that comes to me would be to drown metal legs in the insulating mortar, but that brings me back to the fears expressed above. Do you have any ideas or have you ever seen anything effective for this point? I've seen a very pratical solution for this problem. Someone welded a rectangle out of angle steel so the core could be placed in there. The door frame was welded to that rectangle with a 45º brace left and right of the firebox. This way, the door assembly was held in place by the core itself. Such a solution lends itself nicely for placing it on legs so it would be elevated from the floor. While the bell could be built around it.
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Deleted
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Post by Deleted on Nov 30, 2018 9:40:23 GMT -8
Casting larger pieces isn't a problem, having different temperature gradients in the same cast is. Even my latest firebox (in my own heater) design displays some very thin cracks in one of the sides. In general, the hotter areas will expand more and earlier, the areas that stay behind will be teared apart. The same goes for your riser and port piece, I expect it to crack badly because of temperature differences.
One needs just to select the right materials for the task.
Cordierite based refractory has very low thermal expansion coefficients [x10-6 K-1 ] , about 2,6 for about 12% MgO and about 3.7. For high alumina refractory it is about 8 and for lower alumina contents still around 6 however it may be around 10 for some mixtures. Thermal expansion coefficients up to 200°C may reach 150% of the higher ranges in non cordierite based refractories, while ther is only a small difference in cordierite based refractories,.
The thermal resistance of cordierite based refractories is lower but still in the range of 1400°C. Cordierite based refractories may be 150% to 200% of the cheaper refractories.
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reyh
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Post by reyh on Dec 3, 2018 18:24:07 GMT -8
Thank you for your answers. I didn't have time to work on new plans, but I would take all your advice Peter. The idea of the metal frame, do not make sharp corners, fix with wire.... I'm all remembering that. For light but hard concrete, I prefer to use the hardest concrete despite everything, because some people are not at all delicate with their stoves. I would test my idea on a first prototype, and if not, I would be satisfied with fibre insulation where it is necessary.
Karl, I am very admiring of your experiences on geopolymers, and I regret very much that my level of English does not allow me to better understand them. For the moment and probably for a long time still, I remain on "common" refractory concretes that are already quite difficult to find and expensive. But I hope one day to be able to benefit from your experience and everything you have shared on this forum.
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reyh
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Post by reyh on Dec 20, 2018 8:50:54 GMT -8
Hi Here's the last plan. It is not quite finished but I will take care of the final details in the workshop as I am more comfortable with a piece of wood than with "sketchup". But I would like to have an outside opinion before starting the manufacturing process. I like the fireplace, for me it only needs the protrusions to hold the parts together, and a more realistic internal chimney. I would like to have an outside opinion before starting the manufacturing process. The port is offset by a few cm, it is the only originality. I really want to test it, and the result at my friend's convinced me that it's not something that will significantly affect performance. The metal cladding also has defects, but the idea is put forward. It will be filled with perlite concrete or simply clay soil depending on whether it is equipped with cans for instant heating or equipped as a batch-block. Here is the skp file (sketchup 8). Only the coloured parts are the right ones, the others are my previous attempts.
Hope you enjoy.
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Post by peterberg on Dec 22, 2018 3:00:15 GMT -8
The port is offset by a few cm, it is the only originality. I really want to test it, and the result at my friend's convinced me that it's not something that will significantly affect performance. I had a close look at the drawing yesterday, the port being situated in a recess bugs me. You really want to test it as you say, but tested using what? Just by looking and sniffing at it? Also, the results of your friend's heater is by looking etc only, the real truth will come out using a gas analizer. And besides that, what other heaters do you know of to compare the one of your friend's with? My point: you aren't in the position to really test it, just by running it and calling it perfect, 99% of novice stove builders are doing exactly that. The little nooks and crannies in your design will prove to be the "devil in the details", in my opinion. There's a 45 degree angle in there too, creating a very sharp edge which will break off easily. The riser seems to be done in one piece, that's a problematic thing to do as well. Just my five cents.
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