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General => Owner-Builder Projects => Topic started by: glenn-k on December 26, 2006, 02:49:51 AM

Title: Rocket Stove project
Post by: glenn-k on December 26, 2006, 02:49:51 AM
I got started on the rocket stove today. Best is fire brick but I didn't have any so I did the heavy steel alternative.  Its experimental so we'll see what happens.  I'm building from the plans in Ianto Evans book, "Rocket Mass Heaters."  

Here is what I got  so far..

(https://i35.photobucket.com/albums/d184/glennkangiser/P1010352.jpg)

Feed tube, burn tunnel and heat riser.

This shows the bottom half of the tin retainer for the insulation.  Not good to use galvanized but I'll hold my breath for the first few burns. It's internal so should go outside anyway.  Behind it is the heat exchanger barrel.

(https://i35.photobucket.com/albums/d184/glennkangiser/P1010354_edited.jpg)

I put it inside - now for insulation options - I think maybe clay and sawdust to make insulating clay -- we'll see what happens.  Gotta study more.

Title: Re: Glenn's Underground Cabin Update
Post by: Amanda_931 on December 26, 2006, 10:44:35 AM
Don't remember if it's vermiculite or perlite (similar, expanded rock stuff).

Is that what is recommended for insulation?

Might have to--oh-my-gosh--buy some.

Be sure and get Mason's type, not Gardener's.  The latter, I'm told is open cell, and sogs up badly if you mix it with cob.

Those things go up to 1500 (but only F) degrees pretty easily.

Don't think you have to take as much in the way of care for earth ovens as the rocket stoves.

I want one.  And I'm glad to see you are motivated to build one.
Title: Re: Glenn's Underground Cabin Update
Post by: glenn-k on December 26, 2006, 11:29:59 AM
I know this is one of your favorite projects.

Don't tease me about being a tightwad, Amanda. :)  You know I would never spend real money on a project.  I think I will buy some stove pipe instead of using well casing though.  Easier to change and I'm not ready to do the cob yet.  Trying to work this into the Roman bath as heat storage.

Perlite, vermiculite, wood ash but also clay and sawdust.  I have sawdust -- fine sawdust as they call for. :)  Also a bag of fire clay I bought several years ago.  The sawdust burns out leaving insulated clay - KiKo did some and said it was good until he rebuild.  I was hoping it would hold up against the fire in case the pipe burns out.  Also thinking of dropping a stainless steel liner in the riser as the pipe I used is oversized and would take it.  Experimenting is always fun --- sometimes it's fun anyway. :)
Title: Re: Glenn's Underground Cabin Update
Post by: jraabe on December 26, 2006, 08:07:20 PM
Lots of action over here. I go away for a couple of days and Glenn has built a rocket stove and made a movie.

(Glenn - I use Sony's Vegas Movies Studio - understand I'm no expert! - but it does allow you to do a narration track and replace the audio after you've assembled the video tracks. Might cut down the cacophony  :) a bit.)

Title: Re: Glenn's Underground Cabin Update
Post by: glenn-k on December 26, 2006, 09:38:02 PM
This movie program will do a bit more too - It was the one that came with the computer and I never tried it before --- I hope to improve the next one -- maybe even get rid of the that automatically composed one - or de-composed one. :-/

I read the instructions after I did it and there are ways to improve things quite a bit.  Always time to do it over -never time to do it right.  (Or read the instructions ahead of time).  

Title: Re: Glenn's Underground Cabin Update
Post by: jraabe on December 27, 2006, 11:45:29 AM
Glenn:

You got me to start playing with video.  ::)

I took a few short videos with my Nikon Coolpix S3 while on a beach walk and produced this using Movie Studio to add titles. I found that reducing the quality (compressing) to about 25% of the normal WMV file gives decent download times and OK (for web) video.

http://www.countryplans.com/Downloads/beach-foam-256.wmv - this on my site.
http://www.youtube.com/watch?v=t955EmHGwXk - the same video at Youtube

I've also uploaded another short video to Youtube (this was a straight upload from the camera - no edits):

http://www.youtube.com/watch?v=SD0kQ8Cy1eU
Title: Re: Glenn's Underground Cabin Update
Post by: glenn-k on December 27, 2006, 02:40:59 PM
See - I'm good for something -- got you to play with videos. :)

I didn't think about  You Tube -- the whole reason I went to the choppy edit program was because I was about 28 seconds too long for Photobucket.

Well - checking that out I still have a problem - It is to large a file - so start from scratch and do it right I guess.  Photobucket is 5 minute limit(or pay extra)  You Tube is 10 min -100 mb -I was over 100 mb


Title: Re: Glenn's Underground Cabin Update
Post by: jraabe on December 27, 2006, 03:08:59 PM
Can you save it in another format? I had the option of saving in WMV formats (varying compressions) but any of them reduce the file size considerably. Seems like Youtube isn't too fussy about the format you upload from. See if you can compress into a tighter format and then try to upload. (The beach-foam-256.wmv was 92 mb.)
Title: Re: Glenn's Underground Cabin Update
Post by: glenn-k on December 27, 2006, 07:45:01 PM
I'll have to give that a try.  It will have to be with the edit program as my camera puts out Quicktime only.

Now - progress on rocket stove testing continues.  Here is a test of the sawdust- fire clay insulation mixture.  I used 10 fine sawdust 5 wood ashes w/ small pieces of charcoal as from the stove, 5 fireclay - mortar clay it is called -$5.08 for 50 lbs dry powder for masons.

(https://i35.photobucket.com/albums/d184/glennkangiser/P1010357_edited.jpg)

Now before anybody asks, no I do not have a dog and no-- he was not eating asbestos.

The mixture held up remarkably well even under the torch flame.  This may not be the best insulation but it was free to cheap with the added clay.


Next a test of the partially assembled rocket stove - to start drying the insulation and for the fun of it- note that the barrel heat exchanger is not on and the heat riser is put temporarily into the stove pipe.

(https://i35.photobucket.com/albums/d184/glennkangiser/P1010358_edited.jpg)

I'm sure you are wondering what the square hole is on the stove's bottom.  That's it's ash hole. :)
Title: Re: Glenn's Underground Cabin Update
Post by: jraabe on December 27, 2006, 08:15:23 PM
Neat!

For those who like me needed to learn more about the basics of a rocket stove:

http://www.efn.org/~apro/AT/atrocketpage.html

(http://www.efn.org/~apro/AT/atpix/%7emax0007.JPG)
Title: Re: Glenn's Underground Cabin Update
Post by: glenn-k on December 27, 2006, 09:39:50 PM
That is very similar to the model I used on my rocket stove hot tub heater.  You will see the same thing above but with an added feed tube for the wood to stand vertically in so they are a bit self feeding.  Fire is lit on the bottom.  Air going through the fire tunnel is preheated to be hot enough to burn even the higher temperature gasses that normally go up the chimney in a chunk stove.  Burning from the bottom prevents over-fueling.  Flames do not pass over the unburned chunk of wood forcing unburned gasses to escape. In place of the pot of beans is an inverted barrel when it is finished encouraging the stove to give up some of its heat to the barrel providing radiant heat.  Since you are forcing the heat down it requires a primer to start the draft up the chimney.  I'll get to that part soon after this part is well tested.

Note that when this thing is hot, the flue gases are nearly breathable similar to the heat coming off a drier although not as wet.  I added quite a bit of water to my insulation mix to get the clay to cover well so it will take a bit to burn efficiently - after things dry- but is burning remarkably clean right now even in it's unfinished state.
Title: Re: Glenn's Underground Cabin Update
Post by: glenn-k on December 27, 2006, 11:36:04 PM
Insulation continues - mixed up about 6 wheel barrow loads - probably about 1/2 yard of sawdust or more.

Fire is progressing nicely and insulation is to the top of the riser now.  I made the outside of the insulation retainer from scrap flashing and welded spacers to the outside of the pipe riser.

The insulation is steaming and water in it is boiling now. Fire tunnel is mostly insulated now.

(https://i35.photobucket.com/albums/d184/glennkangiser/P1010360_edited.jpg)

Sassy still doesn't think it is beautiful yet. :-/
Title: Re: Glenn's Underground Cabin Update
Post by: Sassy on December 27, 2006, 11:47:32 PM
It does seem to work - even without it having near the capability for heating it will have when it's finished.  It will look nice in the living room once we get the cob bench built - sorta like on the cover of Ianto Evans' Rocket Mass Heaters and the stairway behind it.  I'm happy we're getting to the "great room"  :)

(http://us.st11.yimg.com/us.st.yimg.com/I/dirtcheapbuilderbooks_1927_4420333)

Image from http://www.dirtcheapbuilder.com/rostforcobbu.html
Title: Re: Glenn's Underground Cabin Update
Post by: glenn-k on December 29, 2006, 01:44:39 AM
Work continues on the rocket stove.  

I made a tin collector for the heat from the barrel heat exchanger.  Hot gasses flow through the heat riser in the center of the insulation then down the outside of the insulation between it and the barrel.  From there they are pushed and pulled through the collector and go into the decking channels under the cob bench.  They then go past the primer and up the chimney to the outside.  

(https://i35.photobucket.com/albums/d184/glennkangiser/P1010362_edited.jpg)

Today we cooked a garbage can lid oven pizza.  I burned it of course but we did it.  Temperature in the center got to over 450 degrees.  Note that you can see the deep decking I used for a heat channel, going to the stovepipe.  I used 2 inches of crushed rock covered with a piece of corrugated metal under the decking to give a thermal break from the ground.

(https://i35.photobucket.com/albums/d184/glennkangiser/P1010366_edited.jpg)

We got a start on the cob bench tonight -got it to about 10 inches high -- I smoothed it out in case I don't get back to it for a bit.  Note the water distilling from the insulation dripping on the bank behind the stove pipe.  Even with all the moisture and cold mud there was nearly no smoke.

(https://i35.photobucket.com/albums/d184/glennkangiser/P1010368_edited.jpg)

Title: Re: Glenn's Underground Cabin Update
Post by: glenn-k on December 30, 2006, 10:51:50 AM
With everything cold and wet it took a bit of coaxing to get the rocket going yesterday.  I have also noticed that high pressure build up on the side of the house causes wind to want to go down the chimney sometimes.  I guess I'll have to get it extended and get a directional weather cap that changes with the wind to help that out.  

Since heat is absorbed by the bench, exit temps are a bit low to get it started easily but that should improve as it heats up the mass.

I'll give it a try today and see if conditions have improved. :)
Title: Re: Glenn's Underground Cabin Update
Post by: glenn-k on December 30, 2006, 11:44:30 AM
Talk about a difference! :o

This morning the heat exchanger barrel and part of the cob was still warm.  A lit piece of paper indicated a slight draft at the feed tube, so I lit some more paper and kindling and it started up without even priming.  

This also tells me that a bit of the stored heat was going up the chimney, but the cap I saved for the feed tube can should stop that problem.  It will be put on after a burn and heat is stored in the bench. :)
Title: Re: Glenn's Underground Cabin Update
Post by: jraabe on December 30, 2006, 12:19:04 PM
Most interesting Glenn. A neat invention.

Would you like me to draw up a diagram showing how it was built? We could post it here or as a PDF download.

If you could send me some sketches we could work this up into a usable plan what with your photos.

Then, after a year or so, we can update it with what you would do different if you were to build it again. ;D
Title: Re: Glenn's Underground Cabin Update
Post by: glenn-k on December 30, 2006, 05:55:55 PM
I'll try to sketch something up in Paint and send it to you soon.  

Working great all day today- cob is drying and shrinking - I may make it higher for seating height then let it dry again and crack then grout the cracks.  

I went to the store today and bought 2 pizza's - frozen - room for one in the freezer so had to cook the other.  Raised the garbage can lid about 4 Inches with a sheet metal strip on edge curved to fit the radius.  Put a stone pizza pan on the top to spread the heat - temp was around 325 to 350 at the edge.  About 22 minutes and the pizza was done - a bit on the crisp side but I'm just learning.  I'd say it could be considered a success this time.  3 pieces of pizza and I am getting quite bloated. :-/  

The sheet metal ducting is my own variation of a cob duct - easy and fast then can be cobbed over without worry of blocking pathways.
Title: Re: Glenn's Underground Cabin Update
Post by: Freeholdfarm on January 01, 2007, 11:29:58 AM
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
Title: Re: Glenn's Underground Cabin Update
Post by: Amanda_931 on January 01, 2007, 01:02:11 PM
The model in the cover picture on the book is sitting on the earthen (flue) portion of the heater.  In front of her there is the rocket stove part.  Looks like the lower right is the feed tube and burn tunnel, and the heat riser is the 55 gallon drum.  That part should get very hot indeed when it fires.  

Links are most likely to be under "heated cob bench" or "rocket stove".   "Rocket Mass Heater" is the most current description, as well as the name of the expanded version of the book.

This violates a lot of principles of making/installing/using a wood stove.  The hot air goes down around the heat riser and flows up to 25 feet horizontally.  Then it goes up.  Because you burn your wood both hot and fast, the wood (and the wood-gas) is much more likely to burn completely (to nearly all CO2 and water) than most stove/fireplaces.  So, I'm told you only feel slightly warm, damp but clean-smelling air coming out of the chimney if you stand above it while it is firing.

Ocean, the reviewer quoted at dirtcheapbuilder.com, who has worked on a handful of these, believes that this really is a "study the book" before you try it.  But since everyone who hears about them loves them, I would think there are at least a hundred of them now.  Probably some have failed to work properly.  One of Ianto's didn't have enough cob on top so it singed the cushions there.

(I put a link on the small house heater thread--been there for a long time  ;) )

Here's a link I just found--a handful of pictures, including a rather squished looking one of Ianto Evans lounging on his, elbow on the big drum.

http://transitionculture.org/2006/03/10/top-five-things-to-do-with-oil-barrels-when-theres-no-more-oil-to-fill-them-4-build-a-rocket-stove/
Title: Re: Glenn's Underground Cabin Update
Post by: glenn-k on January 01, 2007, 05:09:59 PM
The top center of the barrel is where the heat riser hits, as Amanda mentioned.  We measured over 500 degrees with the oven thermometer laying flat.  Cook on top the drum just like you would a wood stove burner - top center is hottest.  I put a round stone pizza plate on top - made a 4" high shield and put a cover -(garbage can lid) over it to make a little oven.  This cooked a pizza in less than the recommended time so it was not quite browned enough on top.  I think a stone cover on top heated properly before cooking would do a little better-- maybe slate on the lid?

I made toast on it this morning -- faster than a toaster.
Title: Re: Glenn's Underground Cabin Update
Post by: jraabe on January 01, 2007, 05:21:03 PM
Thanks for the links and comments. Thanks for the sketch Glenn. I will send it back with some comments and questions.
Title: Re: Glenn's Underground Cabin Update
Post by: glenn-k on January 01, 2007, 05:36:47 PM
Another thing I find about this -- it does need attention every 1/2 to 3 hours depending on what you are burning.  Great for a pyromaniac who likes to fiddle with the fire - for less fiddling, smooth hardwood a couple feet long is good.  A hang up with softwood may put a bit of smoke into the room as fire starts to creep up the vertical wood- especially under low fire conditions, but not often.  A brick in the wood container that can be moved can limit the opening to make plenty of draft to suck the fire down the opening but still be adjustable.
Title: Re: Rocket Stove project
Post by: jraabe on January 01, 2007, 06:18:04 PM
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
Title: Re: Rocket Stove project
Post by: glenn-k on January 01, 2007, 06:51:35 PM
I think you have a pretty good handle on it, Amanda. :)
Title: Re: Rocket Stove project
Post by: glenn-k on January 01, 2007, 06:55:23 PM
QuoteI 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. :)
Title: Re: Glenn's Underground Cabin Update
Post by: glenn-k on January 01, 2007, 08:19:21 PM
QuoteI'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.
Title: Re: Rocket Stove project
Post by: jraabe on January 02, 2007, 01:25:02 PM
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.  ;)
Title: Re: Rocket Stove project
Post by: jraabe on January 02, 2007, 02:03:36 PM
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.
Title: Re: Rocket Stove project
Post by: Freeholdfarm on January 03, 2007, 08:31:36 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
Title: Re: Rocket Stove project
Post by: glenn-k on January 03, 2007, 09:19:34 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.
Title: Re: Rocket Stove project
Post by: jraabe on January 04, 2007, 06:04:47 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.

(http://www.countryplans.com/images/Rocket_stove/Notes-1.jpg)

(http://www.countryplans.com/images/Rocket_stove/Notes-2.jpg)

(http://www.countryplans.com/images/Rocket_stove/Notes-3.jpg)
Title: Re: Rocket Stove project
Post by: glenn-k on January 04, 2007, 06:23:44 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.
Title: Re: Rocket Stove project
Post by: jraabe on January 04, 2007, 06:43:29 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.
Title: Re: Rocket Stove project
Post by: glenn-k on January 04, 2007, 07:36:19 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.
Title: Re: Rocket Stove project
Post by: Freeholdfarm on January 04, 2007, 08:53:03 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
Title: Re: Rocket Stove project
Post by: glenn-k on January 04, 2007, 09:11:48 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.

(https://i35.photobucket.com/albums/d184/glennkangiser/P1010366_edited.jpg)

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.
Title: Re: Rocket Stove project
Post by: jraabe on January 05, 2007, 12:45:51 PM
I'm still working out the best way to show this. Here's one that might help.

(http://www.countryplans.com/images/Rocket_stove/Pizza_cooker.jpg)
Title: Re: Rocket Stove project
Post by: glenn-k on January 05, 2007, 12:59:37 PM
Outstanding, John - that should help. :)
Title: Re: Rocket Stove project
Post by: glenn-k on January 05, 2007, 05:50:40 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.

(https://i35.photobucket.com/albums/d184/glennkangiser/P1010397_edited.jpg)

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.

(https://i35.photobucket.com/albums/d184/glennkangiser/P1010399_edited.jpg)

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.

(https://i35.photobucket.com/albums/d184/glennkangiser/P1010398_edited.jpg)

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.

(https://i35.photobucket.com/albums/d184/glennkangiser/P1010400_edited.jpg)

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.

(https://i35.photobucket.com/albums/d184/glennkangiser/P1010402.jpg)


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.
Title: Re: Rocket Stove project
Post by: Freeholdfarm on January 05, 2007, 08:32:31 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
Title: Re: Rocket Stove project
Post by: glenn-k on January 05, 2007, 09:23:42 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.
Title: Re: Rocket Stove project
Post by: Amanda_931 on January 06, 2007, 11:15:29 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!
Title: Re: Rocket Stove project
Post by: jraabe on January 06, 2007, 11:45:08 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.
Title: Re: Rocket Stove project
Post by: jraabe on January 06, 2007, 11:55:25 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.
Title: Re: Rocket Stove project
Post by: glenn-k on January 07, 2007, 01:12:06 AM
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.
Title: Re: Rocket Stove project
Post by: glenn-k on January 07, 2007, 01:18:27 AM
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.
Title: Re: Rocket Stove project
Post by: desdawg on January 07, 2007, 10:07:36 AM
Outstanding Glenn. Keep up the good work. Who was that that said "It ain't rocket science"? Little did they know.
Title: Re: Rocket Stove project
Post by: Amanda_931 on January 07, 2007, 04:23:31 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.
Title: Re: Rocket Stove project
Post by: glenn-k on January 07, 2007, 10:02:12 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.
Title: Re: Rocket Stove project
Post by: Amanda_931 on January 08, 2007, 07:48:36 PM
What I was wondering was--is there an optimum length--or range--for the part under the cob, before the "chimney" starts up?
Title: Re: Rocket Stove project
Post by: glenn-k on January 08, 2007, 10:15:13 PM
The book says 20 feet for 6" - 30 feet for 8" and about 5 tons of mass.  Mine hasn't been getting that hot yet so that seems like too much for me but I don't keep after the fire well enough yet.  As I get more wood that is fit for it things should get hotter.

I may need to add more insulation around the fire box too and taking less radiant heat by insulating part of the barrel will send more to the storage also.   I have the air plenum exposed so we'll see in the future what other changes I make will do.

Title: Re: Rocket Stove project
Post by: Christopher on January 10, 2007, 11:39:47 AM
These sites may be of interest to some on the list:

http://home-n-stead.com/about/blog.html

This family built a rocket stove/cob bench like Glen's. Go to heading rocket stove

http://www.repp.org/discussiongroups/resources/stoves/apro/Heat/Heating%20Stoves%20LO-RES.pdf

This is a PDF describing the principles of better burning stoves. On pg. 27 they describe the first rocket stove/cob bench built with Ianto. The author says that the underground pipe should only go for 8 ft. maximum. However, Ianto must have tweaked the design, because he can get 20 ft. I found this PDF very helpful in understanding the principles behind the stove.

I was also wondering if you could install a small fan to push air into the chimney after it leaves the floor/bench and goes vertical to create a better draft to ensure that you do not get back drafts. Also if you install a fan, you could probably have more heat risers in series, in order to absorb more heat and make the stove more efficient. I would be interested in knowing what the temperature  is of the gases leaving Glen's chimney. The author seemed disappointed in the amount of heat absorbed by the mass of cob. He suggested using rectangular pipe that would yield more surface area in contact with the hot gases.

I would also like to thank Glen for all the knowledge he shares on this forum. Great work!

Title: Re: Rocket Stove project
Post by: jraabe on January 10, 2007, 01:21:20 PM
Christopher:

The Aprovecho information on Rocket Stoves (http://www.aprovecho.org/web-content/publications/publications.html) is very well done and quite extensive. The  PDF booklet (http://www.repp.org/discussiongroups/resources/stoves/apro/Heat/Heating%20Stoves%20LO-RES.pdf) you linked to is great and provides lots of information on building wood heating stoves of any type. They also have other information, videos and sometimes workshops in Oregon.
Title: Re: Rocket Stove project
Post by: glenn-k on January 10, 2007, 07:17:07 PM
Thanks Christopher.  

I also am not yet seeing as much heat into the cob as I would like.  The radiant heat from the barrel heat exchanger is good and I was assuming that maybe I didn't insulate the air plenum enough and was losing a lot of heat there rather than getting it to the bench.  

I am pretty sure you could assist the draft with a fan at the far end.  It is used for starting the wood gas generator for running a internal combustion engine, which really operates on the same principal.  It's just that here we are burning the gasses created for heat.  One caution is that the fan should be out on the suction end.  Blowing through it would work but could blow carbon monoxide ito the house.  Suction on the far end will onlu pull air into the system without hurting anything.

From my days soaking in the hot tub in Saline Valley, I would say the exit temperature is about 102 to 105. Feels about the same.  I'll try to get you better information later.  I only have 6 feet of underbench area too in the 3 3x6 inch sections of the decking.  Start of the bench gets pretty warm - rest is only a little warm. :)
Title: Re: Rocket Stove project
Post by: smwon on January 11, 2007, 04:48:33 PM
Even though I joined this board in Feb of 2005 I have never posted that I can recall... hadn't been here for awhile either. However, while doing a web search for the rocket heater I can upon this board once more. I am so glad I found it too! I intend to use a rocket heater in a small strawbale house I will be building in the very near future and was having a hard time finding anything on the heating aspect of it... Now here I find not only something about it but a step by step look into how it is done! Thank you!
Title: Re: Rocket Stove project
Post by: glenn-k on January 11, 2007, 04:52:21 PM
Glad to see you here and posting.  Be sure to check out Andrews project also.  We are both experimenting to see what these things will do.  

Please keep us updated.
Title: Re: Rocket Stove project
Post by: glenn-k on January 11, 2007, 04:56:32 PM
Here's his link - Cordwood House and Rocket Stove (http://www.countryplans.com/cgi-bin/yabb2/YaBB.pl?num=1168453897)
Title: Re: Rocket Stove project
Post by: Amanda_931 on January 16, 2007, 09:26:30 PM
My copy of the book arrived--along with the silliest calendar I've ever seen--but I can't find it right now.

:(

But I think I read that there really is an optimum (at least minimum) length for the pipe buried in cob.  I thought I would have to run either an s-curve or split the thing in two or three to get the maximum heat out of the mass heater part--in one of the two buildings I'm contemplating.

For the other, the only thing that would work would be the little coffee-maker rocket stove somewhere in the back--and that only if I gave it one of those inverted funnel type chimneys above the burner.  that one is a rocket stove but not a mass heater.

Or maybe experiment with some kind of water heater coil.
Title: Re: Rocket Stove project
Post by: glenn-k on January 16, 2007, 11:43:39 PM
Possibly extending the length could help although the exit temp doesn't seem to be that hot.  I made it easy to add to or change so I'll have to get back on it one of these days. :)
Title: Re: Rocket Stove project
Post by: Ernest_T._Bass on January 17, 2007, 03:16:12 PM
Did anyone else get confused when putting the insulation container around the heat riser, trying to follow Ianto's book? He never mentions cutting the insulation container to fit around the burn tunnel. He never talks about cutting the feed barrel, either... Maybe it's just me, but I puzzled over those things for quite awhile before going foreword. Don't get me wrong, the book was real good, but there were a few places like that that seemed to just kinda leave me hanging on my own..
Title: Re: Rocket Stove project
Post by: glenn-k on January 18, 2007, 03:07:47 AM
Some of that was a bit - do it and figure it out.  I got my clearances worked out then filled with insulating clay/sawdust mix or cob.

In reading it a dozen times I figured that the critical points were fairly clear then the rest were just fit to make the separation of gas flow and sealing as necessary.
Title: rocket stove for sauna?
Post by: jefv on April 10, 2007, 09:28:42 AM
Hi all,

I'm trying to figure out if a rocket stove can be used to heat a sauna. I have planned on building a corwood sauna. Instead of using a ordinary woodburning stove, I want to build a rockets stove. reading the pdf file mentioned earlier, i would probably need a good air to air heat exchanger. I was thinking of putting two barrels in a row. Each of the barrels would be dressed with bricks on the outside to give the whole thing a bigger mass. The bricks do not touch the barrel, but would be seperated from the barrel by a one inch space, with air freely circulating from bottom to top. That way I can directly heat the air, while also storing heat in the bricks, which also act as a heat shield when you are sitting close to the stove.

the things is..... I cannot figure out how big the diameter of the burning chamber would have to be to generate enough heat for a sauna..

Any ideas would really be appericated...

Jef
Title: Re: Rocket Stove project
Post by: glenn-k on April 10, 2007, 09:44:11 AM
Welcome to the forum, Jef.  How big is your sauna going to be?  How hot does the air in there need to get?   Does the sauna use dry heat or do you make steam in there too?  I am thinking you won't want to go any less than 8" from my experimentation.

Title: Re: Rocket Stove project
Post by: jefv on April 10, 2007, 11:34:00 AM
QuoteWelcome to the forum, Jef.  How big is your sauna going to be?  How hot does the air in there need to get?   Does the sauna use dry heat or do you make steam in there too?  I am thinking you won't want to go any less than 8" from my experimentation.


Dear Glenn,

thank you very much for your message. I'm planning a sauna of 400 cubic feet. I am looking for an air temperature with a maximum of 190 degrees farenheit. And yes, I would like to make steam. I am planning to reinforce or put a steel plate on top of the barrel(s) and load them up with sauna rocks, on which I would be able to pour water to make steam.
Oh, and are you talking about an 8" flue or combustion chamber?

thanks,

Jef
Title: Re: Rocket Stove project
Post by: glenn-k on April 10, 2007, 08:50:03 PM
The rocket stove information states that the flue, combustion chamber and entire piping system should have the same area throughout.  It doesn't have to be the same shape throughout but needs the same cross sectional area open so the flow is not restricted.

Remember that part of the successful operation of the rocket stove depends on the chimney temperature and combustion chamber being very high to burn the creosote.  Take your heat off after the insulated stack.

Do you have a design in mind for how you are going to do it.  You may want to go even larger - say 10 Inches if you want to heat faster.  I was a bit disappointed in the heat going into the cob bench  - it only got warm after quite a while running.  Feel free to post drawings, ideas and pictures here.  Temp at the top of the barrel would get to about 350F on a hot burn.  I wasn't too happy with my draft either and that may have held it back from going full blast.  Get to refractory materials - insulated brick or fire brick of some sort for the combustion chamber.  The steel I used was deteriorating pretty quickly in the fire tunnel.  The stack seemed to be holding up pretty well.

Are the rocks going to be up where I cooked the pizza?  Are you planning a similar design?  In a small room I think the rocket would do well and for a sauna room you wouldn't need to heat the earth mass so room temperature could go up pretty quickly.

The room I have it in is very large and drafty and I did it in the colder part of the winter.  The room was 61 feet long - about 16 to 20 feet wide and average 12' ceiling - not well sealed at all, so your performance should be better.
Title: Re: Rocket Stove project
Post by: jefv on April 11, 2007, 05:56:06 AM
I think I will go for an 8 inch flue. I think I also need two barrels as heat exchangers to generate the necessary 40000 BTU the sauna is going to need. The pdf file higher up on the board in quite instructive as to heat exchangers etc. Of course, if you cool down the gasses too much, you don't have enough draft.
I'm now thinking about a top loading rocket combustion chamber in combination with heating the primary air with a 1 inch tube that is wrapped around the combustion chamber. The air in the tube will be assisted by a small fan, to blow hot air into the feed tube of the stove. This way I get maximum heat out of the wood I burn. The electricity used by the small fan (maybe 12 Volt), will be minor compared to the gain in performance.

yes, the rocks will go where your pizza goes.... mmmmm .... maybe I could have one barrel with rocks and the other with pizza... yummy!

take care,
Jef

Once I get the to drawing, I'll post it on the board.
Title: Re: Rocket Stove project
Post by: glenn-k on April 11, 2007, 09:40:37 AM
Great Jef.  How many places - rough percentage in your country have saunas and what is the normal way to heat them?

I have another idea you may want t play with - it comes from the old heaters used in orchards - how about a re-generator - where a small pipe takes a portion of the flue gas and returns it to the intake to raise temperatures of the combustion chamber - the top has an elbow so the gases flowing up the stack pressurize it sending it down the pipe to the air intake and the small vacuum of the gases drawn into the combustion chamber also pull the hot gases through the re-generator.

The bottom elbow points into the burn tunnel.  I haven't tried this - it may not work.  Depends on how easy it is for you to experiment.
Title: Re: Rocket Stove project
Post by: jefv on April 11, 2007, 11:03:10 AM
Only a small percentage has a sauna in Belgium. usually those who can afford it. Other people go to public saunas. I wanted something for myself, in my garden and inexpensive. Also with I wanted it to be as environmentally friendly as possible. Most people heat with electricity, but then you need about 3kilowatts. That is roughly 15 amps at 220 volts. Very expensive if you want to run that for 2 hours

The regenerator idea sounds quite good. i may give that a try.

I was looking at an old oil drum today, but it seems to me that the sheetmetal they make it out of is rather thin. Are you sure it can stand up to the heat? Alos, I was wondering what temperature you get on the outside of your barrel. I want to make sure it get hot enough.
Title: Re: Rocket Stove project
Post by: glenn-k on April 11, 2007, 12:32:05 PM
According to the book the barrel will not deteriorate with the heat as the oxygen is used up during the burn in burn tunnel.  I find that to be correct.  My burn tunnel of steel had large flakes of steel oxidizing and delaminating, however the stack which is 1/8" thick steel - 8" dia. showed no signs of oxidation.  I measured the heat on top the center of the barrel with an oven thermometer at 350 degrees when burning hot  -about 250 when not -sides were less and you could touch them quite quickly without getting burned.  The barrel shows heat but no sign of oxidation.  In the book, Ianto mentioned that he expected the barrel to last a very long time.

Thinking about mine - it is in the bottom of the great room - about 6 feet or so below ground  so I am thinking it may have quite an effect on not drafting properly as while the heated air is trying to go up the stack -- outside, it cools enough that it will not want to rise rapidly, plus the cool air inside the stack is trying to fall down as the heated goes up.  My cabin is excavated into the ground so I think the problem is more particular to it.  I have about 12 feet of thin stovepipe stack outside and about 10 feet inside, plus the bench, so I think your arrangement will do a lot better.
Title: Re: Rocket Stove project
Post by: jefv on April 12, 2007, 07:31:20 AM
I guess if you use an insulated stack outside, your dreaft problem would be solved...

The temperatures of your barrel, 350 and 250... is that Fahrenheit or celcius? If it is Fahrenheit, i don't think this system will generate enough heat for a sauna. I'll experiment a bit and will let you know.

according to the formula in the pdf file, using two barrels as heat exchangers, I need at temperature of 600 Fahrenheit in both barrels  to be able to get 40000 BTU an hour
Title: Re: Rocket Stove project
Post by: glenn-k on April 12, 2007, 08:30:11 AM
That is Fahrenheit.  To keep the temperature up you need to feed it fairly small dry wood and keep after it - In the case of a sauna I would assume every 15 minutes to 1/2 hour.  4 foot long dry boards such as 2x2 inch  or 4x4 inch feed pretty well - the 4x4s would be best after heated up to maintain heat.

I picked up a non-contact thermometer yesterday that goes to 500+ Fahrenheit and will fire mine up to see what temps I can achieve and give you readings from different parts of the heater.
Title: Re: Rocket Stove project
Post by: glenn-k on April 12, 2007, 08:53:51 AM
I used to build wood stoves also from a kit a friend developed around 1976.  They were some of the best available.  I think maybe running your barrels horizontal or stacked  horizontal one above the other with good air flow to the fuel may give you the heat you want easier than the rockets stove.  The rocket stove is made for very efficient burning of small quantities of fuel with a pretty good output.  I think you may want a bit more capability to have pretty efficient burning of a lot of fuel for a rip-roaring fire.

You could still use ideas from the rocket stove design and the design of the old stoves I built to make a very hot burning stove using barrels and fire brick or clay to protect the firing chamber area.  The stoves we built had a removable ash pan on the bottom that doubled as under fire air when starting.  There were channels with fire bricks separated for air to go under the fire and an air damper on the back that was regulated by a bi-metal choke spring for semi-automatic heat regulation after the fire was going.  It had an over fire air damper in the door also.  This stove was fire brick lined on and around the bottom and had fins welded to the sides and a second wall outside welded to the fins to create a double wall that moved around 350 cu.ft. of air per minute without a fan.
Title: Re: Rocket Stove project
Post by: glenn-k on April 12, 2007, 11:10:00 AM
Another thing mentioned in the book was that for more BTU's you needed to make the system bigger throughout, so that may mean going to 10" or so to get the heat you want with the rocket stove.  Whatever the system size is according to the book, it needs to be the same cross sectional area as I mentioned above.