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Post by jgreen on Oct 25, 2011 21:44:29 GMT -8
I'm glad the pics were helpful. When I built this stove, the people I was living with & building the stove for were into experimentation and open to trying different things to see if they worked. So we broke a lot of the "rules" and have found, at least in this specific case, that you can make a fine stove by just doing what makes sense and being willing to play with things if something doesn't work right at first.
They haven't had any issues (thus far going into the third winter of use) with smoke escaping, excessive cracking or problems due to the straw component of cob being too close to hot gases. There are 6 different clean-out "ports" in the system, all with the same construction (cob sealing around a metal cap) and they've had carbon monoxide detectors positioned in different places around the room and directly next to the clean-outs and never set one off. They did end up using the stove for the first winter with just a rough plaster on the combustion unit because we finished it just in time for the first fall frosts that year. We then put a nicer finish plaster on it the next summer, which ended up looking a lot better and covered up superficial cracks from the initial drying.
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hpmer
Full Member
Posts: 240
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Post by hpmer on Oct 29, 2011 14:10:36 GMT -8
Does the same principle apply exiting from a bell, or can one use the same csa exiting as entering?
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Post by mudpacker on Oct 31, 2011 11:57:59 GMT -8
This thread is so helpful! Thank you for sharing. I have been "paused" at this part for a few weeks, and busy with other stuff too. But still, I wasn't sure how to move forward. I am building a 8" system. It has a 7x 7(49sq") feed tube, 7x6 (42) burn tunnel, 7x7(49) heat riser and then 1.5" negative space between the barrel and the insulated heat riser (50?) So to be clear, 33.3 is the circumference length to leave as a vent to the first primer/ashpit for the third option illustrated above? And if the gap was 2 inches then I would only need 25 inches open around the barrel. As a visual learner, the pictures and photos are so helpful. Thanks again..
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Post by peterberg on Oct 31, 2011 12:23:11 GMT -8
Does the same principle apply exiting from a bell, or can one use the same csa exiting as entering? According to the theory, the area of the entrance should be larger. The exit hole could be the same as the chimney cross sectional area. |
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Post by peterberg on Oct 31, 2011 12:50:29 GMT -8
So to be clear, 33.3 is the circumference length to leave as a vent to the first primer/ashpit for the third option illustrated above? And if the gap was 2 inches then I would only need 25 inches open around the barrel. You are absolutely right, the gap is playing a very important role in this whole setup. The circumference length should be measured in the middle of the gap, averaging out the length difference between outer barrel and insulation canister. That last one is not very important, only to see what quantities you are working with. To make matters complicated, try to calculate the minimum gap between inner and outer barrel. You're in for some surprise there. Don't try to follow that calculation, it'll create an unworkable situation. For example you'll have to have a channel all around the barrel which is impossible because the burn tunnel is in the way. |
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Post by mudpacker on Nov 4, 2011 23:36:39 GMT -8
Thanks peterburg! I decided to go with a combination of option 1 and 3 from the diagram. I reconfigured the insulation chamber to remain 1.5 inches from the top, but 2 inches around the vertical side instead of an 1.5". We cut a half moon out of the barrel, as well as, have a third of the bottom open, or exposed. There should be plenty of room for a combustion love festival to still take place with the dome and the ash pit included. The flow of gases should happen smoothly wil the round shape. If it works well, I will post pictures, after I catch my breath. Mixing cob can wear a girl out! Question. I plan to mix plaster, gypsum, to set the barrel. I read it is more durable to the thermal heating and cooling. Does anyone have experience, for this to be true? Or am I just over-doing it?
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Post by hippiebuilder on Nov 17, 2011 9:02:58 GMT -8
Hey JGreen...
Your pics really helped, my stove is begining to resemble yours..... I was wondering, wouldnt it be better physics if the stove pipe came out of the roof of that cob chamber as opposed to the side as you have it... Just a thought... Im no "rocket scientist" but I thought it might be a helpful tweak... what do you think...
For all of you others: Im referring to pics Jgreen posted earlier in this thread....
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Post by jgreen on Nov 17, 2011 17:38:07 GMT -8
hippiebuilder -- I'm glad to hear that the pictures are helpful. I don't count myself as a person who understands most of the physics involved in a good rocket stove, but your observation about the location/orientation of the flue pipe makes good sense to me. I'm not sure why it ended up where it did to be honest... I may have had a reason at the time, or I may have just overlooked the possibility of having it come out vertically. Perhaps you should try it on your stove and see how it works? I recently visited the folks that I built the stove for and took some pictures of it "finished" (ie. nicer plaster and oil on it) and with some subtle modifications. Thought you might like to see, so I uploaded some more to that same picasa album. Also a picture of the bench that the pipes go into. Would love to see photos of your stove  -Jay |
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Post by hippiebuilder on Nov 30, 2011 10:34:47 GMT -8
This is a lot of work and Im building it by myself but tons of progress all the same...The combustion chamber is just about done... I had my first testfire and it went really well... I have a ton more cobbing to do for the thermal battery but we shot a little video... Check it out www.youtube.com/watch?v=l3GigBm8awQThanks again to everyone who answer my questions and posted pics and replied to my posts... You helped ALOT! Attachments:
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Post by waynem11 on Dec 9, 2011 13:56:41 GMT -8
Donkey, I have a sinking feeling you have hit on what is wrong with my stove. It seems to burn fine at first then slows down and starts back drafting. Is there a way to post a picture?
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Post by waynem11 on Dec 10, 2011 4:27:46 GMT -8
Are there any symptoms that might confirm a too small barrel exhaust chamber? I would hate to bust up my cob and masonry work if I don't have to. Actually I'm mistified the stove can push the gasses through the flue and up the stack. It seems to me the system can't overcome the cold air that wants to come down the stack. Especially near the end of a burn, as the system cools, there is a point when the flames go out and there is just coals, the cold air, being denser, over powers the warm air in the flue, and the system flows backward. I have included a picture of the exhaust area, its about 2 1/2 wide, collects at bottom and flows through a 10" to 8" reducer. Does it look too small? Attachments:
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Post by Donkey on Dec 10, 2011 17:10:30 GMT -8
The symptoms you've described indicates a constriction somewhere. The MOST common one is right under the barrel.
It's difficult to really see it from the images, but (IMHO) if you gotta ask.....
I'd be inclined to just dig it out as much as possible no matter what. It can be a pain in the hiney, sometimes leaving enough for the barrel to have a solid seat is difficult. If you need to, you can cheat the barrel one direction or the other, which has the added effect of concentrating more heat towards the wider part of the gap.
While yer at it, might as well move the barrel up just a smidge as well. They seem to run a little smoother with a larger top-gap than indicated by system size (per the book). When placing the barrel, I get the stove running with the barrel off, let it get hot, then place the barrel on and move it up and down till it sounds "right". You'll need to experiment a little, move the barrel beyond the sweet spot in both directions as you go, feeling out where the failure points are and where yer out of the sweetness in both directions, when you've got it have a helper wedge it up with spacers, etc. and cob to it.
Also, I enclose the stove WHEN IT'S RUNNING! If something happens (cob falls in or a pipe gets crushed) you will know it instantly if the stove is running while you work. Otherwise, you've got to guess where the problem might be after the fact.
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Post by waynem11 on Dec 14, 2011 0:39:27 GMT -8
LO and behold. Resized the exit chamber and Resized the fresh air intake from 3 inch to 4 1/2 inch and now it burns hot and doesn't smoke. Thanks for the tips Attachments:
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Post by canyon on Dec 14, 2011 7:58:56 GMT -8
Good news! Thanks for sharing that. Looking at your picture I see an elbow leading into a tee (with the condensate drip collector) and would like to offer the suggestion before you go any further to replace that elbow with another tee so that you can clean out both legs. Way easier now then later! |
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Post by willowways2 on Dec 29, 2011 16:36:06 GMT -8
how does this transfer into a 3" duct heat riser and a heineken mini kegs (3 total) for the out barrel? there are so many little things in this just like in electrical engineering that i know i am missing.
thank you.
FYI i am an electrical engineer as far as my education goes.
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