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My self feeding, wood chip burning Rocket Stove

Michael Newby


Joined: Apr 06, 2011
Posts: 165
Location: Mount Shasta, CA Zone 8a Mediterranean climate
    
    9
So I finally built a rocket stove that I don't mind showing off (version 4, not too bad) and I thought that I would post the videos I took of it here first, see what you guys think.

It's mostly scrap materials from around the property, fire bricks, 8" stove-pipe, a 12" diameter old oil barrel, some local rock and one bag of fireclay that I bought for about $6.

I've managed to get aluminum to melt in the riser tube, about 4" from the top.  I've also dropped a copper coil into the riser tube and made some decent steam.

You'll have to forgive the videos, they were taken with my cell phone and I was more concerned with documenting than with cinematography.

Stove cold so you can see inside the burn tube and how I install the louvers:
http://www.youtube.com/watch?v=HYjfofnWVvw

Stove Burning:
http://www.youtube.com/watch?v=Hop25uBJp90

Making Steam:
http://www.youtube.com/watch?v=buaeS-okWPc

Let me know what you all think!

Do you Hugel?

I like trees because they seem more resigned to the way they have to live than other things do.  ~Willa Cather, 1913

God has cared for these trees, saved them from drought, disease, avalanches, and a thousand tempests and floods.  But he cannot save them from fools.  ~John Muir

My Project Page: http://www.permies.com/t/15915/projects/Mnewby-Projects
Michael Newby


Joined: Apr 06, 2011
Posts: 165
Location: Mount Shasta, CA Zone 8a Mediterranean climate
    
    9
The chip feed tube (the one in the front) is a 6" stove pipe.  The chips gravity feed into the burn tube with no external input.  I get around 30 minutes of burn from one full pipe (~.75 cu in).

I have ideas about routing the exhaust into the house and back through a large heat sink.  If the return came back to right above the heat riser, you could re-heat the exhaust after it exits the house to help with the draft.  I'm currently collecting the materials (junk) to try this out in my house, which has no heat in the lower floor.

The footprint of the stove is roughly 18" x 36" and the heat riser would be very easy to make as a single unit that would drop into the burn chamber.  The chip feed tube is removable, also.  The base/burn tube is the heaviest part and it is still something that 2 men could move together.  I have a few more tweaks to make to the system, but I think that it would be a good, portable unit, not counting the heat sink inside the house, which isn't an insurmountable challenge.
Abe Connally


Joined: Feb 20, 2010
Posts: 1404
Location: Chihuahua Desert
this is very nice, I like it!


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Kathleen Sanderson


Joined: Feb 28, 2009
Posts: 977
Location: Near Klamath Falls, Oregon
    
    1
Is there any way to measure how hot the bottom of the unit gets?  I've been trying to figure out something that could be installed inside an existing structure without tearing a hole in the floor for a foundation.  Not sure that's what I'll end up needing, but it would be nice to know something is available if it is needed.

Kathleen
Michael Newby


Joined: Apr 06, 2011
Posts: 165
Location: Mount Shasta, CA Zone 8a Mediterranean climate
    
    9
I don't have any means of measuring the temp in the burn chamber, but when I stuck my wife's candy thermometer in the exhaust tube (about 3" in) the thermometer wrapped around more than 3 times in less than a minute before I pulled it out.  Needless to say the thermometer's ruined.  The lower barrel and burn tube bricks are getting too hot to touch, that I can tell you.  I think that you could place the entire system on a sheet of fireboard and be just fine, though.

The base of this stove is a  small concrete slab, approx. 18"x28"x4".  I built the burn tube up from this using the 2.25" thick fire brick on the inside and 4.5" fire brick around that.  I mortared everything using straight fireclay ($6 per bag, used half a bag) and put about a .25" thick layer around the inside of the entire burn tube. 

I'm now working on a larger chip storage - with the burn rates I'm getting I would need around 3 cu ft of chips to get a good 2 hour burn which I think would be plenty of burn to heat a large mass or for hot water production.

I'm also brainstorming on how I'm going to redirect the exhaust through a large mass to harvest all that heat out of it.  I'm thinking that I can push it through a large brick or rock wall then have the cool exhaust coming out of the mass go directly over the burn tube to re-heat the exhaust and help increase my draft. 
Rob Sigg


Joined: Feb 04, 2010
Posts: 710
Location: PA-Zone 6
Very cool. Im curiuos to know where the steam is coming from. just ambient moisture inside the coils that have condensed or is it attached to water somewhere?


permaculture wiki: www.permies.com/permaculture
Michael Newby


Joined: Apr 06, 2011
Posts: 165
Location: Mount Shasta, CA Zone 8a Mediterranean climate
    
    9
I'm feeding the coil with water from my water hose.  I'm making decent dry steam with the hose pushing around 5 gallons per hour.  I know that I could do much better - there's lot's of room for improvement in my coil system, but the 12' of copper tubing was as much of a purchase I could justify to the wife for this little experiment. 

The tap water flowing in is around 43F, great for drinking, making steam not so much.  I'm certain that just preheating the incoming water will drastically improve the performance and there's plenty of heat in that exhaust.  I'm thinking about using an old radiator placed in the exhaust to run the water through for preheating, but my old toyota radiator is a little big.  A good heater core would probably work great.

on another note, anyone know a good place to source a pressure gauge that would be easy to hook up to this set up?  I'd really like to know what kind of pressure I can make at what flow rates! 
R Hasting


Joined: May 10, 2011
Posts: 163
Location: Middle America
    
  11
mnewby wrote:
I have ideas about routing the exhaust into the house and back through a large heat sink. If the return came back to right above the heat riser, you could re-heat the exhaust after it exits the house to help with the draft. I'm currently collecting the materials (junk) to try this out in my house, which has no heat in the lower floor.

Great Rocket Stove
I love the way that functions, and I love the self feed. mechanism. I'd like to see what 1-3" logs would do in this hopper.
But I'm a little confused here. Aren't you looking for a rocket mass heater
http://www.youtube.com/watch?v=LfKHVoCY2so
Michael Newby


Joined: Apr 06, 2011
Posts: 165
Location: Mount Shasta, CA Zone 8a Mediterranean climate
    
    9
Richard Hasting wrote:
Great Rocket Stove
I love the way that functions, and I love the self feed. mechanism. I'd like to see what 1-3" logs would do in this hopper.
But I'm a little confused here. Aren't you looking for a rocket mass heater
http://www.youtube.com/watch?v=LfKHVoCY2so



I've used 16" firewood split into roughly 1"-3" pieces, but I was having real problems with burning up into the feed tube.  This was partially solved by plugging the feed tube so that there's no draft up or down the tube.  Performance is much better with chips, though, as that's what I've been designing my system around - you see, I'm an arborist in NorCal and therefore I have an abundance of chips.

As far as what I'm calling the unit, I figure that right now it's a rocket stove since there's no large thermal mass in the system.  From what I understand, once I start pushing the exhaust through that thermal mass I might run into drafting issues that I'll have to overcome.  Once I overcome those potential issues, then I'll feel comfortable calling it a RMH - call it splitting hairs if you will.

I've been fascinated with Rocket Stoves and RMH's ever since I first stumbled across them about a year ago while researching the GEK (Gasifiers Experimenters Kit) and I am just now at a point where I can afford the time to try out some of the many ideas that I have.  Right now I don't have the supplies to do the thermal mass so I have been playing more with making steam, with my latest run making steam with the water flowing at about 15 GPH.  I'd love to make enough steam to turn a gen set that could charge up a battery bank for an off grid house.

                            


Joined: Mar 28, 2011
Posts: 23
nice work M...

has the tube ever clogged? I wonder how much smaller diameter feed tube (so you could get a slower / longer burn) you could get and still have smooth fuel flow with that sized chips. 
Brice Moss


Joined: Jul 28, 2010
Posts: 700
Location: rainier OR
    
    2
Be very very careful working with steam it gets dangerous at lower pressures than it gets useful, I worked on steam plants for over ten years, and saw some things that give me nightmares on occasion.
Dale Hodgins
pollinator

Joined: Jul 28, 2011
Posts: 4076
Location: Victoria British Columbia-Canada
    
  57
      In just about every city there are tree companies who need to get rid of vast amounts of wood chips. Anyone who creates a proper system to burn chips will never have to gather firewood again. I've had free loads of wood chips delivered to put  under my kids playset and to build pathways at a muddy jobsite. There seems to be no end to this free resource. I've even received calls asking if I'd like more


QUOTES FROM MEMBERS --- In my veterinary opinion, pets should be fed the diet they are biologically designed to eat. Su Ba...The "redistribution" aspect is an "Urban Myth" as far as I know. I have only heard it uttered by those who do not have a food forest, and are unlikely to create one. John Polk ...Even as we sit here, wondering what to do, soil fungi are degrading the chemicals that were applied. John Elliott ... O.K., I originally came to Permies to talk about Rocket Mass Heaters RMHs, and now I have less and less time in my life, and more and more Good People to Help ! Al Lumley...I think with the right use of permie principles, most of Wyoming could be turned into a paradise. Miles Flansburg... Then you must do the pig's work. Sepp Holzer
Michael Newby


Joined: Apr 06, 2011
Posts: 165
Location: Mount Shasta, CA Zone 8a Mediterranean climate
    
    9
Scott911 wrote:
nice work M...

has the tube ever clogged? I wonder how much smaller diameter feed tube (so you could get a slower / longer burn) you could get and still have smooth fuel flow with that sized chips. 


No, I haven't had any clogging problems with the 6" tube.  I'm keeping my eyes out for some cheap (read:free) sheet metal to see what kind of problems will arise with a square shaped feed tube having sloped sides - I'm trying to increase the amount of fuel I can hold without increasing the feed tube size.  If you want a slower burn rate, I think that changing the amount of air allowed in, always ensuring that the air comes into a focused area to prevent smoldering will achieve that.

dale hodgins wrote:
      In just about every city there are tree companies who need to get rid of vast amounts of wood chips. Anyone who creates a proper system to burn chips will never have to gather firewood again. I've had free loads of wood chips delivered to put  under my kids playset and to build pathways at a muddy jobsite. There seems to be no end to this free resource. I've even received calls asking if I'd like more


This is very true.  I'm an Arborist and although my business is in a rural area, I have plenty of chips.  This is one of the main reasons I've started this project - much easier to chip small trees and branches than to cut them into a bunch of short, woodstove sized sticks. 

 
I agree. Here's the link: http://stoves2.com
 
subject: My self feeding, wood chip burning Rocket Stove
 
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