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Post by peterberg on Jan 27, 2017 1:50:09 GMT -8
So, if this turned out to be a winner, would you consider vacuforming both halves of the mold and making them available? Or is there a better way to mass replicate this design? You mean, vacuum formed ceramic fibre? That would be a tempting business model, clear from afar that it would be work though. Running a business and making the design open source at the same time do sound very incompatible to me. Apart from that, I will be 71 years old within a couple of weeks, retired and all. Frankly, I was thinking about the possibily to make a flat pack design out of rigid waxed cardboard and sell this to the general public as a DIY package. Could be done, both of the ideas, but not for me. Any takers?
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jono
Junior Member
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Post by jono on Jan 27, 2017 3:57:13 GMT -8
is the cardboard flat pack a mold? that sounds like a fantastic plan. There are examples of successful businesses with open source designs, like Arduino or the all power labs GEK gasifier. I have a flat pack eco-house project and a lightweight electric farm vehicle project in the pipeline both based on that business model, so I hope it works, but I'm going way off topic here.
just finished demoulding. a cardboard whiskey tube is strong enough to hold a concrete form, and it softens by absorbing the moisture from the concrete to the point where the next morning it will fold up and pull out in seconds. I found that this lightweight insulative refractory concrete was not strong enough in the fire box, so I'm going to try a design with a metal firebox and a refractory secondary combustion chamber on top of it.
So, the smaller port size is creating a more vigorous burn that is producing a greater pressure drop, that is creating a more vigorous burn. fantastic.
I would wait until you have the design all worked out, but I need to feed a hundred people with this thing tomorrow, so I better get welding
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Post by keithturtle on Jan 27, 2017 9:40:10 GMT -8
So, if this turned out to be a winner, would you consider vacuforming both halves of the mold and making them available? Or is there a better way to mass replicate this design? You mean, vacuum formed ceramic fibre? That would be a tempting business model, clear from afar that it would be work though. Running a business and making the design open source at the same time do sound very incompatible to me. Apart from that, I will be 71 years old within a couple of weeks, retired and all. Frankly, I was thinking about the possibily to make a flat pack design out of rigid waxed cardboard and sell this to the general public as a DIY package. Could be done, both of the ideas, but not for me. Any takers? With this potential for high heat (runaway) I'm not sure I'd be comfortable with ceramic fibre. The rigid cardboard form is what I was referring to; DIY one-off build available to the willing builder. Alternatively a fibreglass mould could be made from the pattern and production parts from that. I will be 71 years old within a couple of weeks, retired and all
Done properly you could license the idea and add to the retirement income; how open source is this? After all, you have decades of experience with this sort of thing, might as well reap a reward if one is available IMO Turtle
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morticcio
Full Member
"The problem with internet quotes is that you can't always depend on their accuracy" - Aristotle
Posts: 371
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Post by morticcio on Jan 27, 2017 11:08:53 GMT -8
this port is a smaller percentage of the riser and consequently the pressure drop is larger as compared to the original design. So there's a firebox full of fire with an atmospheric pressure opening at one end and an lower pressure opening at the other. Add the notion that the combustion is ramping up, seemingly without a limit, speeding up the combustion rate and the level of underpressure in the port. The net result is a blown fire, much more so than the straight batch box, easy to see why it is effortless running out of hand. Widening the port could be a solution but I like the wildly turbulant environment in the riser. I'll try the tight door first, maybe incorporating the main air inlet in the secondary air duct could be an alternative. The air feed will be coming from the top of the firebox by doing so, might be a better way to calm it down. Just thinking out loud... Peter, Is an 'adjustable' port an option here. Open it to calm the beast; narrow it to unleash it! Similar to how the throttle valve works on a carburettor albeit in an opposite effect. Not sure how this could be implemented though!
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Post by peterberg on Jan 27, 2017 12:06:20 GMT -8
Morty, as a first thought I would say no, not possible because of the refractory nature of the port's surroundings. But on second thought maybe, just maybe it could be done with sliding in or out the secondary air channel. I need to think about this more, not sure it can be tried with this core because it isn't meant for such a sliding action.
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Post by pyrolyse on Apr 2, 2017 4:09:39 GMT -8
Any news on the new core, Peter?
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Post by peterberg on Apr 2, 2017 5:41:32 GMT -8
Not sure this existing core will ever make it to a real heater, it has been running out of hand almost everytime I've tried it. So experimenting with this core is on hold, I'm in the process to try out another idea which is far more simpler to implement.
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Post by pigbuttons on Apr 2, 2017 6:23:49 GMT -8
Peter, if I might offer some advice on this beast. As a fireman, we are taught to recognize backdraft conditions. What you are describing is exactly like what you might expect because the feed box is heating up so much that the wood is off gassing too much and the burn is happening too early in the air flow and it cannot vent out the small venturi fast enough. This causes it to "gulp" air into the feed area which has now become a "pre-burner".
One way to reduce this without changing too much would be to glue a layer of vermiculite board inside the feed box area to reduce the heat of the upper combustion area from overheating the wood through induction from the true combustion areas. You seem to have more than enough heating going on to keep the pyrolysis efficient.
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stoker
Junior Member
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Post by stoker on Apr 30, 2017 15:29:45 GMT -8
In one of the pictures it looks as if there's a horizontal ram's-horn pattern inside the firebox itself!
Pigbuttons, what you said makes sense to me, about pyrolysis being too fast because too much of the heat is reaching the wood.
How can that be fixed? The suggestion from pigbuttons was "to glue a layer of vermiculite board inside the feed box area" to protect the wood from the heat of the hottest parts, but I'm not sure where that would go.
Alternatively, having more of the intake air flowing around the wood (rather than through the secondary tube) might help keep it cool. Maybe.
As for restricting the total airflow, would it be better to do that at the port rather than the intake? It would be putting all the restriction (and hence pressure drop) at the place where it can do most good.
I can imagine the port might be made adjustable by having a tough refractory rod or bar in the firebox just before the port, with a way to move it closer to the port to partly block it... a bit like some of the pre-port tube designs. Perhaps one of those cylindrical kiln-shelf supports would work?
Finally, a simpler shape to build would have the port in the horizontal ceiling of the firebox, with the "riser" leading horizontally towards the front of the stove and then turning upwards:
# # # # # ############## # # #############port# # # ################## Has anyone tried that?
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Post by peterberg on May 1, 2017 0:12:12 GMT -8
Finally, a simpler shape to build would have the port in the horizontal ceiling of the firebox, with the "riser" leading horizontally towards the front of the stove and then turning upwards: # # # # # ############## # # #############port# # # ################## Has anyone tried that? Not yet, this was the simpler layout I was hinting at on April 2nd. It is similar to the idea DCish tried, suggesting that the double vortex could be coached in a number of directions. I worked out a layout with firebricks but the exhaust opening is a bit troublesome. This opening could be at the side as well, opening up even more possibilities. Lately, I have great difficulties to kick myself into working mode after being ill for some time. The material is there, I watered the clay more than a week ago and I prepared a spot in the garden. Now waiting for a nice day with temperatures above 15º C.
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terry
Junior Member
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Post by terry on May 1, 2017 15:18:20 GMT -8
Peter, after seeing the initial photos (the metal plate experiment/throat), how much of the induced turbulence/rams horn was due to the very narrow size of the slit (ie only a mm or two thick, the thickness of the metal)? When they are made from refractory, they are necessarily much thicker, many orders of magnitude thicker.
Is this an area where you have done much research?
(hope the question made sense)
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Post by satamax on May 1, 2017 18:41:56 GMT -8
Yep Terry. You might be onto something there. For records, here is what happens un the case of a sharp orifice plate. youtu.be/KS-GSLrkf30With a thicker plate, i think, there's a wing shape depression or turbulence, forming on the edge. If only i had time to make a small wind tunnel. Hth.
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terry
Junior Member
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Post by terry on May 1, 2017 22:49:25 GMT -8
good find satamax
looked through the rest of his videos in the (vain) hope he had a corresponding 'flow through a deep orifice', no such luck. Sadly he did not link to a program to generate flows through varying thicknesses.
That would have to be some sort of program like that out there, god knows what to type into the search engine though.
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Post by peterberg on May 2, 2017 1:23:53 GMT -8
Peter, after seeing the initial photos (the metal plate experiment/throat), how much of the induced turbulence/rams horn was due to the very narrow size of the slit (ie only a mm or two thick, the thickness of the metal)? When they are made from refractory, they are necessarily much thicker, many orders of magnitude thicker. Is this an area where you have done much research? I've done some research on this, in that the thinnest back wall happened to be 30 mm and the thickest 150 mm. It didn't make much difference until the depth of the port exceeded 100 mm. Chances of overfueling did increase with a deeper port, keeping the other parameters, fuel etc., the same. The difference between a 30 mm deep port and one 60 mm deep wasn't noticeable at the time, in my experimental model of 150 mm system size.
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terry
Junior Member
Posts: 128
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Post by terry on May 2, 2017 14:43:40 GMT -8
it seems that your gut feel does not tell you that the extreme thinness (is that a word?) of the throat is much of an indicator.Probably plenty of other things more important to pursue.
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