Author Topic: Rocket Stove project  (Read 129512 times)

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glenn-k

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Re: Rocket Stove project
« Reply #25 on: January 01, 2007, 02:55:23 PM »
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I hope nobody minds, but I broke this off from the underground house thread and started a new "Rocket Stove" topic for this thread.

John

Sure - make more work for me, John.  Now I'll have to do something on the underground house to get some readership there. :-?

Actually I was thinking that would be a good thing to do anyway. :)

glenn-k

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Re: Glenn's Underground Cabin Update
« Reply #26 on: January 01, 2007, 04:19:21 PM »
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I'd really like to see those plans, you guys.  Glenn, thank you for all the experimenting you do, and then for telling us all about it!  I'd sure like to actually see the stove -- haven't quite figured out how you are cooking on (or in?) it.  I have been thinking about building something like that in our attached garage for emergency heat, since Grandma doesn't want a wood stove in the house.

Kathleen

Thanks, Kathleen.  I enjoy playing with things like this and figure it would be a waste to keep it all to myself.

John is working on more information on the plans - Note that aside from a few critical things needed to make it work - same cross sectional open area throughout - burn tunnel to heat riser ratio is about 1/2 length -- a lot of this can be made of other things.  Bricks, adobes, mud bricks, fire bricks, clay tiles, cob, water heater tanks - etc.  Shapes can be different as long as the cross sections are correct.  

There are other variations -all use the principal that air flow is pre-heated but fire does not flow over unburned fuel.  The fire is what releases the gasses to burn.  If released before there is sufficient air or need for more fuel, it just goes up the chimney and builds up as creosote -- this is some of your best hottest burning fuel just going to waste --sitting in the chimney waiting for you to start a big fire - then chimney fire then  danger of burning your house down besides wasting 1/2 to 3/4 of your wood.

jraabe

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Re: Rocket Stove project
« Reply #27 on: January 02, 2007, 09:25:02 AM »
We just went through another storm and power outage on Whidbey Island. Four times between last night and this morning the power has gone down and then come back for up to an hour. The first hit came with a bang with sparks coming out of a nearby outlet (not a good sign) ....

Now that I can test the outlets and appliances I find that a surge blew out half the circuits to the office and fried the microwave oven and an electronic instant hot water pot. Computers and things on surge protectors seemed to fair alright. So today I will be an electrician (and a purchaser of electrical products!)  >:(  ...and I think I'll get a few more surge protectors!

However the wind is still blowing hard, trees are flapping around and this grid could go down at any time. (Better post this while I can!) Maybe I'll wait awhile to start grabbing wires.  :-/?

Ah... the laid back life of a country gentleman.  ;)
« Last Edit: January 02, 2007, 09:34:13 AM by jraabe »

jraabe

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Re: Rocket Stove project
« Reply #28 on: January 02, 2007, 10:03:36 AM »
While I can, I'll post a follow up on the concepts and history of the rocket stove.

In the 1980's we designed several versions of the Russian masonry wood stove that were built here in the Northwest. The rocket stove is, in many ways, a simplified and downsized version of the long chambered masonry stove that burns a hot quick fire and then takes flue gases on a roundabout adventure through a high mass heat exchanger.

Such stoves have been built in almost all cold winter climates. I visited a 300 year old mountain chalet in Switzerland where the feed door for the stove was in the kitchen (under the big chimney hood such kitchens always had) and the masonry mass was in the sitting room. This low temp radiating mass had boot warming niches built into it and steps up to the top where someone needing extra warmth could sleep. This kept the ashes and smoke out of the main living area.

The main problem we had with the Masonry stove in the NW climate was the timing of the heat release. In any climate a huge storage mass takes hours to warm up. In the NW we often need heat in the morning and things will warm up in the afternoon.

In really cold climates the heat-load is large and constant throughout the winter. A high mass stove is perfect for this.

In mild climates you are often getting fooled by the heat release. In the 1980's I went to several open houses where the owners had fired up the masonry stove in the morning only to have it be too warm by the time most people got there in the afternoon.

It will be interesting to see how Glenn uses the Rocket stove after it is no longer a building project but an everyday heating appliance. I expect the lower mass of the Rocket stove will probably make it a better choice in milder climates such as Glenn's (and mine). On the other hand the low firebox capacity will mean much more attention than the firebox of a masonry stove which is often only fired once a day.
« Last Edit: January 02, 2007, 10:13:29 AM by jraabe »

Freeholdfarm

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Re: Rocket Stove project
« Reply #29 on: January 03, 2007, 04:31:36 PM »
You have some good points, there, John.  But in planning heat for a small cabin, I would also be using the stove to cook and heat water, so it would be fired several times a day anyway.  I have plans for a masonry stove (from the state of Missouri, I think), and had trouble envisioning cooking in or on it.  But wood cook stoves aren't usually very good heating stoves (and new ones cost a mint).  I've lived with barrel stoves in several houses, grew up with them, in fact, and they use a lot of wood and tend to overheat a small cabin even in really cold weather.  The rocket stove seems to have a lot of advantages, if I can figure out how to build it.

Kathleen

glenn-k

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Re: Rocket Stove project
« Reply #30 on: January 03, 2007, 05:19:34 PM »
There are a lot of ways to do it as long as the critical guidelines are followed to make sure it works.  It will be necessary to follow the book recommendations and maybe more to be sure there is no fire danger in the burn tunnel area.  The steel one gets red hot and will ignite wood on the outside - granted this could be insulated more there but it is a area to be sure is right.  Note that this stove has not been tested for code compliance and with the outrageous testing prices a stove you can build for free never will be.

As far as cooking on it goes, I think this one is great - the center over the heat riser gets really hot.  Another feature is that when fueling stops so does the high radiated heat then the lower stored heat is all you have to deal with which may be enough.  There are moments you will deal with a bit of smoke - lighting or unattended burnout or burning up the sticks - more during a lower fire time.  It likes to be tinkered with but when hot and running does not take as much attention.

I used to build stoves that were certified - bought parts kits  from a friend.  He spent thousands on testing - seems it was over $20000.00 in 1976 or so.
« Last Edit: January 03, 2007, 05:26:01 PM by glenn-k »

jraabe

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Re: Rocket Stove project
« Reply #31 on: January 04, 2007, 02:04:47 PM »
Instead of trying to do actual scaled drawings of this Rocket Stove project, what I think might be best is to evolve a PDF booklet of Glenn's narrative and some marked up photos to make the stages easier to understand.

To get this started I have sketched over some of the photos to show names and how things work. See if it is easier to understand this way and if I have it right.

Here are three preliminary marked up scans.






glenn-k

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Re: Rocket Stove project
« Reply #32 on: January 04, 2007, 02:23:44 PM »
One thing not correct above is the burn tunnel is entirely closed on the bottom so that heated air only comes in through the front feed tube - this pre-heats the air to get fire temps up to help ignite all wood gasses.  Ash will collect in it clear back to the back of the burn tunnel which is where the bottom of the heat riser starts.  The heat riser, whether metal surrounded by clay sawdust insulation, or brick goes up to 2" under the inside of the barrel.

So the area marked ash cleanout does need to be cleaned out but it must be done from the front of the burn tunnel or possibly by removing the heat exchanger barrel or the top of it if one with a removable top is used only to get to the bottom of the heat riser.  

The fireproof clay in the tin surround is insulating type masons clay, sawdust and wood ash as described above - this helps to keep the temperature up to completely burn the high temperature gasses.  The burn tunnel must be tight and well insulated all around also.
« Last Edit: January 04, 2007, 02:27:05 PM by glenn-k »

jraabe

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Re: Rocket Stove project
« Reply #33 on: January 04, 2007, 02:43:29 PM »
I understand that the burn tunnel is a solid square channel, but I understood that the bottom of the heat riser was not welded shut with a metal plate but is open and would allow ash to drop below. I assumed the feed tube to have openings at the front and back so that the ash in the chamber under the burn tunnel to the bottom of the heat riser could be vacuumed out. No? Is the feed tube only open at the front?

Now that I think a bit more on it I see it can't be open at the back, otherwise the fire would not be totally contained in the burn tunnel and might just as easily travel the lower road to the heat riser (which is much more dangerous!)  :P

The bottom of the heat riser must be sealed with something fireproof, or be sitting on fire brick.
« Last Edit: January 04, 2007, 02:52:01 PM by jraabe »

glenn-k

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Re: Rocket Stove project
« Reply #34 on: January 04, 2007, 03:36:19 PM »
You got it- I extended the bottom plate of the fire tunnel under the heat riser then put insulating clay/sawdust/ash mix under it.
« Last Edit: January 04, 2007, 03:36:37 PM by glenn-k »

Freeholdfarm

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Re: Rocket Stove project
« Reply #35 on: January 04, 2007, 04:53:03 PM »
Okay, I think I have most of it figured out with the help of John's sketches.  And I went back to Glenn's post #13 where he showed the pizza cooking, and I can see where the upside-down barrel is sitting.  But where is the flue opening on the stove?  

Kathleen

glenn-k

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Re: Rocket Stove project
« Reply #36 on: January 04, 2007, 05:11:48 PM »
The flue opening is on the other side of the cob bench.  Heat is absorbed from the flue gasses into the deck channels John labeled above - it is covered with cob which stores the heat.

This picture shows a view toward the flue which then goes outside.



The flue pipe has always been cool enough to hold my hand on - maybe 105 or so.

That is why the primer is necessary also.  It is to start the draft in the cold stove and suck it down the inside of the heat exchanger barrel, across under the cob bench -(the heat storage) then send it up the chimney.  With out lighting it first when the stove is cold, the fire wants to burn up instead of down.
« Last Edit: January 04, 2007, 05:15:15 PM by glenn-k »

jraabe

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Re: Rocket Stove project
« Reply #37 on: January 05, 2007, 08:45:51 AM »
I'm still working out the best way to show this. Here's one that might help.


glenn-k

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Re: Rocket Stove project
« Reply #38 on: January 05, 2007, 08:59:37 AM »
Outstanding, John - that should help. :)

glenn-k

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Re: Rocket Stove project
« Reply #39 on: January 05, 2007, 01:50:40 PM »
Curiosity got the best of me today.  Decided to take the barrel off the rocket stove and do an inspection while I was cleaning out the ash.  Probably around 20 hours burn time.

I removed the cob seal around the bottom of the barrel in large pieces like bricks so I could put them back with very little problem.  I next lifted the barrel off of the stove.

 

There was some carbon-creosote coating the tin surround around the heat riser insulation.  I think this may have come from the time the clay was wet.  The inside of the heat riser is totally clean - no creosote as seen in the next image..  Note that there is about 1/2 inch of ash in the bottom of the heat riser area and up to about 1" in areas of the burn tunnel.



The cob layer - about 2 inches over the insulating clay is undamaged.  In one place where I could feel some of the insulating clay at the bottom of the barrel the clay was soft but intact.

The area John has marked "Future Cleanout" above has very little ash in it so I won't bother with the cleanout at this time.



The area below the primer at the end of the heat storage bench is very clean with just a few scraps of ash probably from the priming paper.  Note that excess priming paper can plug this area causing burn problems - info from the book.



This is the biggest revelation from this tear down.  Ianto mentions in the book that if using steel for the burn tunnel, use 1/4 inch or so which I did.  He mentioned that in the presence of oxygen, steel burns -- true -- I used an oxy/acetelyne torch to cut the steel -- the steel is actually on fire when being cut.  

In this photo I am holding a magnet that is holding one of many large flakes that came from the steel inside the burn tunnel.  The oxygen seems to be used up before the heat riser so I will probably replace the burn tunnel with a fire brick or cob one when this steel one burns out.  At this rate I would give this 1/4 inch steel  a year.  Save yourself some trouble - use the clay tile, brick, castable refractory  or fire brick recommended in the book.  You will not want to use this on a combustible floor without adequate protection.




 The book mentions a way to do it.  I would spend some real time evaluating the recommendation to make sure I am safe.  A wood house would make one heck of a heating fire.  Note that my floor here is all dirt - no fire danger.
« Last Edit: January 05, 2007, 01:58:46 PM by glenn-k »

Freeholdfarm

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Re: Rocket Stove project
« Reply #40 on: January 05, 2007, 04:32:31 PM »
John, thank you for the additional sketching -- I think I understand that now.  

Glenn, it's really helpful to see what is going on inside of the stove!  And to have the tip about using clay tile or firebrick -- I do plan to get the book before actually trying to build one of these, but it's good to have another voice of experience here.

Kathleen

glenn-k

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Re: Rocket Stove project
« Reply #41 on: January 05, 2007, 05:23:42 PM »
Thanks Kathleen.  I like to know what's going on in there too, and at this point it is no trouble to experiment - change things or whatever is necessary.  This stove burns so much hotter than a normal stove that it has different problems than a normal stove.  It would take years in a chunk burner to eat away that steel - here due to the high heat, it looks like a form of brick is the way to go.

After cleaning out the ash from the fire tunnel, I was able to start and keep the stove burning better than the last time I burned it.

Amanda_931

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Re: Rocket Stove project
« Reply #42 on: January 06, 2007, 07:15:29 PM »
Very glad indeed to see that report, Glenn.

I was thinking that steel mightn't be good for a burn tunnel, but I wasn't quite sure why.  Glad to have an answer.

Now all I have to get is a building to put that in!

jraabe

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Re: Rocket Stove project
« Reply #43 on: January 06, 2007, 07:45:08 PM »
Very good work Glenn:

You're doing real leading edge owner-builder science here.

Science in the very best most practical way:
- Build it, -Test it, -Tear it apart, -Learn from it, -Rebuild it, -Repeat...

The photos are great and a ideal learning/teaching tool. 15 years ago we would have had to publish a book to get this much information to this many people.
« Last Edit: January 06, 2007, 07:47:35 PM by jraabe »

jraabe

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Re: Rocket Stove project
« Reply #44 on: January 06, 2007, 07:55:25 PM »
Glenn's caution is well taken. When built in a standard wood frame house, the Rocket Stove should be placed on a fireproof slab or hearth such as is built for a masonry fireplace and chimney. These are poured slabs supported on masonry all the way down to the foundation. The concrete footer is also oversized and reinforced to take the weight of the masonry above.

Because of both weight and fire considerations I would not suggest building a Rocket Stove on top of a standard wood framed floor.
« Last Edit: January 06, 2007, 07:57:57 PM by jraabe »

glenn-k

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Re: Rocket Stove project
« Reply #45 on: January 06, 2007, 09:12:06 PM »
I really have the urge to add a regenerator to this thing - pick up some hot flue gasses and send them back through to superheat this thing- then fire brick would be required for sure and some of the other research Ianto talked about in the book - More heat and storage for less tinkering around time.

glenn-k

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Re: Rocket Stove project
« Reply #46 on: January 06, 2007, 09:18:27 PM »
This stove, as it is right now would run you out of a small house in a short time.  I have it in the middle of a 61 foot x 16 to 24 foot room with average 12 to 16 foot high ceilings so  I would like to see more but most people wouldn't need it.  This room is not well sealed or insulated yet either.

The cob bench is pretty slow to warm - we have about 9 inches of cob over it.  Less would warm faster but cool faster also.

desdawg

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Re: Rocket Stove project
« Reply #47 on: January 07, 2007, 06:07:36 AM »
Outstanding Glenn. Keep up the good work. Who was that that said "It ain't rocket science"? Little did they know.

Amanda_931

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Re: Rocket Stove project
« Reply #48 on: January 07, 2007, 12:23:31 PM »
How long is your flue?

Currently wondering what the short end of that length is--long is 25 feet or more--my copy of the book isn't in yet.

glenn-k

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Re: Rocket Stove project
« Reply #49 on: January 07, 2007, 06:02:12 PM »
Lengths - from bottom of hot air or gasses plenum about 10 inches below the barrel- 6 feet of triple 3"x6" channels under decking then to transition piece under primer -12"

Section of pipe and stove pipe primer is in is about 4 1/2 feet, -- about 9 feet through pipe and stove pipe to flue outside then about 8 or 10 feet vertical after the elbow.  Probably will add more later outside - it's a bit short.  All together from the stove to the outer end of the flue is about 30 feet.

Temp at the elbow above  the primer is just warm.