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Post by peterberg on Dec 16, 2020 3:42:16 GMT -8
peterberg How are you doing at the moment? Work in progress? Could you enlighten us with a small update? I don't think I am the only one being extremely curious. Please excuse me  OK, you are right, it's time for an update. Luckily, there's some progress to report and also a change of target users but I'll come to that later. Since the Testo was sent away for calibration I couldn't measure anymore. So it looked like a good moment to leave the slowly desintegrating ceramic fibre board in the top box and the far too massive 5 cm (2") cast refractory walls of the firebox behind. I opted for firebrick slabs of 30 mm (1.18") thickness for all of the core, because of the relatively low mass. It wasn't cheap, since I had to order it through a webshop and had it shipped to me on a 1/2 pallet. I had to hire a wet saw in order to cut it accurately enough and in the course of a couple of days it was done. As I probably mentioned earlier, during cold startup the top window tended to get dark brown and burned clean during the rest of the burn. With the higher mass of the top box this was much more pronounced, it didn't look good at all. About some struggle and a week later I decided the way forward should be lowering of the mass. The obvious solution seems to be by using hard firbrick(ish) material that is much thinner. By browsing the internet I stumbled across refractory slabs of just 10 mm (0.394"), used for stacking pottery in a ceramic kiln. Those are available in the Netherlands and while ordering through a webshop I discovered this shop has an outlet about half an hour drive from where I live. Suffice to say, I cancelled the order and drove there to pick it up in person. Initially just for the shelf and the support of it, being the parts that are receiving the greatest heat stress. Those plates are specified as 1300 ºC (2370 ºF) and uptil now there's no sign of degrading or visable hairline cracks. Running it like that seemed to improve things but I couldn't measure since the Testo wasn't returned yet. What I got was a quotation for replacing the aging CO cell and minor reparations together with the yearly calibration. Needless to say, it would cost me an arm and a leg to have it usable and up to date again. While I was pondering the possibility of giving up real testing altogether something else came along. In the shape of a friend who's selling as a one-man-band the Bulgarian Gamera rocket heaters in the Netherlands. He wanted to know what the new experiment was about and asked to see it working. Suffice to say he was really impressed with the sight of it, seeing the double vortex spinning through the glass. Some days later he phoned and asked whether it could be turned into a commercial appliance, of course complete with European certification. I honestly think it could and I told him that. This might be a commercial adventure, costing a lot of money (and time!) up front with the potential to generate a profit through a couple of years or not at all. The guy from rocketstove.store won't be able to cough up that kind of money on his own but when doing it together it might be doable. So now the goal is different: not a simple do-it-yourself heater but one that is a sellable appliance, initially without any mass at all. Actually, a core that can be built without too much fuss and a bell-like housing about the size of one and a half barrel, specifically non-circular. Preferably easily serviceable, working right out of the box, dry build-up, possibility to add mass later and last but not least: released under the same CC license as the original batch box rocket. Two weeks ago the Testo arrived accompanied by a hefty bill and I started to run test burns again. By this time all of the top box was built differently: two slabs of 10 mm with 12 mm Superwool in between. Simply put: all walls and ceilings are sandwiched, even the support of the shelf is. I switched the shelf from kiln plate to Neoceram glass which is holding up well so far. The stumbler or block in the top box is skipped for now, space above the shelf is about the same as in the afterburner area. And last week I experimented with secondary air in different guises, ruling out air intruduced into the sides of the port itself. Six different configurations and none of those were like hitting the pot of gold. More on all this later. |
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Post by josephcrawley on Dec 16, 2020 5:30:31 GMT -8
I would be happy to contribute to your research efforts. Let me know how I can send you funds.
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Post by peterberg on Dec 16, 2020 13:08:57 GMT -8
I would be happy to contribute to your research efforts. Let me know how I can send you funds. This is quite unexpected, I won't say no to such a generous offer. You could send money through PayPal or directly to my bank account. Details in a separate private message. Thank you very much! |
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Post by josephcrawley on Dec 16, 2020 14:15:06 GMT -8
I would be happy to contribute to your research efforts. Let me know how I can send you funds. This is quite unexpected, I won't say no to such a generous offer. You could send money through PayPal or directly to my bank account. Details in a separate private message. Thank you very much! Don't mention it. Hopefully other folks on here that have benefitted from your hard work and keen intellect can pitch in a little as well. I've been out of work for most of the year otherwise I would have given more. |
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Post by skywalker on Dec 16, 2020 14:53:30 GMT -8
I would be happy to contribute to your research efforts. Let me know how I can send you funds. Yeah thats the way! We al benefitted enormously from Peters efforts and expertise didn't we? We always say: honour and feed the source that you are tapping from. So everything can exist and continue. I hope more folks will follow this example. |
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Post by martyn on Dec 16, 2020 23:36:47 GMT -8
That all sounds very exciting Peter!
Will the commercial product be sold purely as a heating device or will it have any cooking potential ?
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Post by peterberg on Dec 17, 2020 1:28:04 GMT -8
Just a heating device, no cooking facilities unless one would use the firebox for that purpose. In fact a stout metal bell stove holding the 120 mm core.
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Post by martyn on Jan 16, 2021 4:43:53 GMT -8
Peter has there been any more developments or news with your design model?
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Post by peterberg on Jan 16, 2021 6:19:55 GMT -8
Yes, in the sense I've been fooling around with different port sizes and shapes of the afterburner area. No luck so far, Trevor might be right in recommending an insulating afterburner. I've been trying what could be done with superwool that's soaked in pottery clay slip and shaped around a mold. Just clay won't work for me, not rigid enough after a week of drying, pottery clay slip and (very old) waterglass seems to do better. Coming week I'll try newly bought waterglass and clay and a separate one with a slip of a special refractory mortar. This mortar is called Moviset, made in the Netherlands, and consists of bauxite, clay and... waterglass! Stoneware clay powder, waterglass, Moviset and Superwool are lying around here so let's try what it does.
When succesful, I'll produce a mould to shape the afterburner chamber around. When dried for a week it could be de-molded and made to measure in the development core. It's not that I want to produce this part commercially, there's a company in Belgium that is capable of producing these type of parts in quantity using a vacuum process. Mold costs initially and then a price for each item, depending on numbers.
Before outsourcing this particular part it would be best to make sure it'll do what I expect of it, don't you think?
Times are still interesting, that's for sure.
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Post by martyn on Jan 16, 2021 7:13:51 GMT -8
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Post by peterberg on Jan 16, 2021 7:58:41 GMT -8
Castables could be done. I've used one before, Golite 135 from Gouda refractories. Rated to 1350 ºC, specific weight 1.4 kilogram per liter. Much lighter than others, that's true. Using bare Superwool like in the 5 minutes riser is a route I won't go because of loose fibers.
The riser in my heater is made of the Superwool vacuum tube and is much, much lighter again. And thinner than the 30 mm minimum thickness of castable refractory. My best home made sample to date is just 14 mm thick and already strong enough. And it's sort of fun in itself to try out recipes.
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Post by martyn on Jan 16, 2021 8:35:18 GMT -8
Will your design variation still be using an exit in the roof of the top box rather than the side and if so have you have you settled on a size for the opening?
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Post by peterberg on Jan 16, 2021 13:52:46 GMT -8
Yes and no. The top exit is required for the plans of the commercial version. The size of the opening isn't settled on yet, both the stumbler and exit can be altered quite easily without taking the whole thing apart.
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yasin
New Member
Posts: 33
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Post by yasin on Jan 17, 2021 10:49:23 GMT -8
Hello peterberg I wish you the best in your new commercial venture ! Development is costly and I'm very glad to see you taking that road.. I'm sure you won't regret it and that it will open you up to more possibilities ! If you need any help, please let me know. Regards, |
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Post by peterberg on Jan 25, 2021 12:56:56 GMT -8
The past two weeks I experimented with making a rigid but very insulative liner for the afterburner chamber out of superwool/clay/waterglass. The more waterglass the least impregnated the wool will be, and it did stick to the makeshift mold as nothing else. I don't want to go the route of bare superwool or vermiculite board in a spot where a client could reach in easily.
Yesterday I was thinking about implementing an old idea where the port was tilted in a 45º position. This would require the whole of the thing be taken apart plus I would need some more kiln shelfs and hire a wet saw. Both stores are closed because of the pandemic so it seemed I got stuck.
This morning I realized the problem is this: to get the afterburner hot as quick as possible in order to avoid a situation where the fire ramps up while there's not enough heat available for clean burning. I noticed while fiddling with the stumbler earlier that the top of the upper door tended to get quite hot. The lower the stumbler, the hotter.
So I grasped the idea I could do something along that line with the afterburner. There has been two pieces of ceramic glass as the ceiling of the afterburner for two months, both completely opaque by now. I took those out and replaced it with a 10 mm kiln shelf I used before that. Of the two possibilities, the glass performed best although not good enough for certification. In front of the kiln shelf I mounted a strip of the same material of just 30 mm wide, hanging down 20 mm under the shelf. Theoretically, part of the heat would be trapped under the ceiling and hopefully would ramp up the temperature quick enough. And to my surprise, it did.
The moment that the afterburner area is getting black and CO is going through the roof was much less pronounced this time, even the glass wasn't stained. Most of the runs that event happened about 10 to 15 minutes into the burn. I'm inclined to say the results are comparable with an afterburner area made of insulative materials. Too early to sell the bear's skin but it certainly is encouraging!
I can't show a diagram since the Testo stopped during the burn due to a loose USB connector. But the burn as a whole was good enough to be certified like that. I have to tune it down a bit because it is racing through the fuel now. Tomorrow I will cut a new strip, twice as wide this time, and see how it influence the burn. Next step would be reintroducing the glass and try to tune the thing back with the end port. As it is now, there's no stumbler in the top chamber's ceiling and the end port is larger than system size.
Interesting times again.
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