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Post by iambeeman on Dec 23, 2011 23:08:40 GMT -8
I'm new and haven't found this yet so I hope I'm not asking an already answered question. Has any one tried to build an auger fed rocket heater? I'm attaching a link to very quick (and crude) drawing of kind of what I mean. I haven't figured out how to post pics yet. s1116.photobucket.com/albums/k563/iambeeman/?action=view¤t=stokedrocketburner.jpgYou can see there is a standard lay out except for an auger and a micro switch with a fuel sensor. The stove would get it's air same as any other and the fuel would be augured in through the side until it pushed on the fuel sensor and through the push rod de-activate the micro switch shutting off the auger, until enough fuel has been burned to take the weight off of the sensor thus turning the auger back on. such a system could be setup for pellets or wood chips. The reason I'm asking is I have access to a virtually unlimited supply of hard wood scraps from a local cabinet manufacturer (to give you an idea of their size, they employ in the ballpark of 300 people) and if I could build such a system to heat a hydonic system the could heat a 30'X40' shop as well as a 2000 square foot house I could feed it for free. But I might be asking a little much of my skills. |
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Post by Deleted on Dec 24, 2011 3:10:05 GMT -8
I have not, but among other things I was trained as a mechanical design engineer.
As a general advice: Never place mechanical parts in a hot area if it can be avoided.
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Post by iambeeman on Dec 24, 2011 6:41:44 GMT -8
As a general rule I agree, but a self feeding stove sure is nice. The reason I ask is when I was growing up my grandparents had a similar system to what I describe but for coal and it worked for about 40 years, until the fire box burnt out. The real difference in the feed aspect of the stove was that it was temperature controlled and not controlled by the presents of fuel on a sensor paddle.
The reason why I think it should work is the old heat riser butterfly valve on the old carb'd V8s, they lasted for years under very high heat situations. If one where to keep the one joint loose so that it won't tighten up under the heat of the burn and the push rod only has to move very little bit to work correctly.
It would be quite an advantage to be able to have several days worth of fuel ready to be augured in as needed.
But I'm rather new it this so I could be completely mistaken.
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Post by Deleted on Dec 24, 2011 7:58:48 GMT -8
Of course it is nice.
But there is no need to feed on fire level, where the fire could back burn into the auger.
At the extremely hot and dirty place you have drawed it your sensor paddle is poised to fail.
The work environment in the old carb'd V8s is not nearly as hot and dirty.
I would recommend to place the auger above fire level, the feed sensor in the feed tube,
and additionaly a temperature sensor in the fire chamber.
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Post by machinemaker on Dec 24, 2011 9:57:04 GMT -8
just a suggestion or two. put your screw conveyer across the top of your feed tube so that the bearing on the discharge end is out side of of the feed tube. This will keep things out of the heat and let the fuel drop into the feed tube. rather than use a limit switch inside the burn chamber as a fuel sensor it would be easy to set up the auger either on a timer or to put a thermal couple in the burn tube or in the heat exchanger to activate the motor on the auger or screw conveyer. I would also advise using a fairly slow gear motor to drive the auger. using a fairly slow gear motor you will also not have to cycle the motor on and off as often. I kind of think that a control circuit activated off of the temp of the heat exchanger may be a better option. you may want to use an "off timer" so that the when the temp drops the auger comes on for only a set time and shuts off. you could adjust this time so that the feed tube does not fill too full.
kent
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Post by iambeeman on Dec 24, 2011 10:10:03 GMT -8
My grandparents never had a problem with burn back and I've seen a whole bunch of similar systems on yard boilers that burn coal with no issues. And all of them feed from the fire level or below. But all the hoppers had a lid with a air gasket of some description.
That is my fear, and it would make an ash drawer rather challenging.
Dirty I agree, hot I don't. I've seen the exhaust manifolds glowing cherry red and 3-4' of the exhaust pipe as well (don't forget the butterfly valve goes between the manifold and the pipe) and the ones off of these vehicles lasted better than the ones off the ones that didn't get worked that hard.
I thought the fuel would block off the air supply and give an incomplete burn, especially if one where burning wood chips, pellets wouldn't flatten out as bad and block air.
That was kinda my plan but I didn't mention it, sorry.
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Post by Deleted on Dec 24, 2011 10:48:39 GMT -8
It is your choice.
That starts at 977˚ F (525˚ C, 798 K)
If there is not a lot light, even at lower temperaures.
The burning temperature in a wood stove is a bit higher.
Only feed slowly.
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Post by Donkey on Dec 24, 2011 11:43:12 GMT -8
iambeeman, You might want to go look at the pellet burner thread. He doesn't use an augur, though the stove is all about burning pellets, some kind of active feed could possibly be added to it. 'Course, yer not talking about burning pellets and any scrap wood you use would need to be made into little chunks and dried out COMPLETELY before use. I tend to stay away from moving parts and such.. It's a personal failing I suppose, my intent is to make these stoves MORE accessible and simple.. Moving, powered bits tends to work at cross purposes to that.. Not to discourage innovation, just stating my personal path, which I suppose makes me somewhat useless in conversations such as this..  |
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Post by iambeeman on Dec 24, 2011 21:42:57 GMT -8
I will, looks interesting.
My scrap is kiln dried hard wood I get free from the local cabinet factories, so dry isn't an issue.
For mechanical stuff, I'm a beekeeper so building mechanical stuff is a in the job description. But accessibility isn't an issue, folks who want to build one, go to a farm auction. You can pickup the old augers that won't reach the top of the new big bins for scrap price, and one if you cut it right should be all you need plus you get a good axle for other projects. but it does add a layer of complexity.
One of the reasons I would like a self feeding rocket heater is out here a lot of farm yards have the yard boilers and most of them are GROSSLY inefficient, mine being one of them. You shovel in as much wood into them as will fit 2-4 times a day and see 1/2 of your wood go out the chimney or get stuck to the inside as soot thus reducing the efficiency further. Mine cooks all the wood to charcoal then burns the charcoal. So I said to myself there HAS to be a better way, which led me to this forum.
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Post by Deleted on Dec 25, 2011 4:30:24 GMT -8
An underfeed burner would be the most efficient. www.heizungsfinder.de/images/pelletheizung/pelletbrenner.jpgWell, that is not a rocket, but the picture shows how the fire is feeded. The feed tube needs to be long enough to make it self-extinguishing for lacking air. The auger needs to be driven precisely and stoped if the storage runs empty. |
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Post by iambeeman on Dec 25, 2011 8:29:11 GMT -8
My grandparents was very similar to that pic but the fire feed auger was, rather that fed by a secondary auger direct fed by the hopper and had about 3' between the fire and the hopper and an air seal in the door for the hopper fill. I think the long auger and air seal was to prevent burn back.
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Post by canyon on Dec 25, 2011 22:48:34 GMT -8
There has been plenty of work done on this stuff already. I am not at home to pull out the references to share but will post it when I return. The key is a "fluidized bed". Pellets are way easier to deal with but chips of reasonable range of particle size can work with the right equipment. Donkey's point of moisture content is important. Larger scale wood scrap/chip boilers have a hot air conveyor or other style driers before the burners. One could certainly batch pre-dry on a mass bench or however first (you really don't want that going on in a living space though). I have been interested in this as there is a lot of small alder growing along roads in my area that needs cutting anyway and could be chipped. It is not a priority of mine that I can put effort into currently (kind of a pipe dream) but I will stay tuned and am ready to glean from ya'lls experience if shared! |
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Post by iambeeman on Dec 28, 2011 17:37:58 GMT -8
I was watching some youtube vids on variations of boilers/rocket stoves/home built bio mass heaters. For those who can watch here are the links www.youtube.com/watch?v=Iqnka8nzkYQ&feature=mfu_in_order&list=ULwww.youtube.com/watch?v=xGckIOGSp38Those are the two must interesting ones from a feed perspective, the first one because of the simplicity and the ease of production of the feed, the second because of the scale that one could preload the stove for extended use. Canyon - I wait with giddy anticipation. |
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