Portable 6" Rocket Heater Now available

[Sandy Mathieu]

Dragon Heaters is now shipping a 6" portable rocket heater. If you have wanted to try out a rocket heater without all the fuss of building a cob system, this may interest you. You can see more pictures here.

(broken link removed to http://www.dragonheaters.com/6-portable-rocket-heater/)

cheers
sandy

 

[Swedishchef]

Very nice!

$1450 for the unit eh? I am unfamiliar with those type of stove prices..but that seems like a lot!

 

[BrotherBart]

"the powder coasted steel box"

Really?

 

[Slow1]

"It does not include the barrel, vermiculte insulation, or chimney/stove pipe connections."

Hmm... gee, how will I ever get my barrel powder coated to match the box? For that price I'd think they could throw in the barrel.

 

[Sandy Mathieu]

The price is more than just the steel box, it includes the feed tube, combustion chamber and heat riser as well as gaskets. Maybe if we were doing production runs of thousands the price could be better, but we are not making that much on them. There is a fair amount of fabrication involved. The barrels can be sourced and prepared locally easily and it would only increase the product and shipping price. Basic black works with all the colors.

These stoves are extremely efficient. They burn at over 1800F and have virtually no ash, and when up to temp there is no smoke. These are NOT thrown together BARREL stoves! Attached is at testo 330 gas analysis run of the same combustion system in masonry heater box also shown below. As you can see this log was over an hour and half. You can see more of the analysis posted on the blog.

(broken link removed to http://blog.dragonheaters.com/category/flue-build-part-3/)

 

[webbie]

Very neat!

Just FY, Sandy, our forum rules don't allow for direct placing of advertisements for stoves........but since this is R&D, we'll allow it.

Generally, though, this is what we have a Press Release Section for.....
https://www.hearth.com/talk/forums/hearth-industry-press-releases.34/

I have to bless your account to be able to post there. Let me know if you desire that....

 

[dunsee]

That is ALOT of money.
I would rather learn to use cob because people have built their own rocket mass heaters for 20 dollars if u can find recycled materials , even if u used new materials the most expensive thing would probaly be the barrel and the duct anyway? And rocket mass heaters are supposed to be getting up to 3000 or higher degrees where steel melts so u would want your core to be fire brick , perlite and cob not steel of you want it to last

 

[Sandy Mathieu]

The cob approach certainly has a lot of advantages as well as disadvantages. Its advantages are it's price, if you manage to source all the required components from scrap or recycle and understand rocket heater principles well, you can build a good rocket heater that will last more than 6 months. However, many people don't really understand all the physics. They do lots of substitution of materials because finding the ideal bricks etc. is hard. For example there are tons of rocket heater you-tube built with metal burn chambers and heat risers. Of course none of these will be working 20 firings later.

A few points of clarification, rocket heaters don't burn at 3000F. They typically burn at 1500F to a max of 2000F. All the talk of 3000F is just that. I have never seen a single data log showing such a number. Now 1500F-1800F is great! Steel looses structural integrity at 1000F and spalls badly at higher temps in low oxygen environments (which is what you have in well designed combustion chamber). This why our combustion chambers are made from cast refractory rated for 2700F. Attached is a picture of the combustion chamber (feed tube, burn chamber, and heat riser) which goes inside the metal box. This combustion chamber is a big part of the price for the stove, it is not just the steel. The feed tube is metal (so that it can take the abuse of feeding wood) but the design uses a secondary air feed to cool the steel and prevent back burning.

I have also attached a picture of the inside of the combustion chamber (patent pending), as you can see it is cast in a way that facilitates documented improvements in rocket heater performance. This combustion chamber has two distinct advantages over what you can build with bricks. 1st the curved walls and wedges that line the chamber increase turbulence and efficiency over a square brick burn chamber. 2nd the cast material we use is significantly higher in its insulating properties. This means the burns from our combustion chambers will get hotter faster. and stay hotter, than the heat absorbing material like bricks that traditional rocket heaters are made from. The key to high efficiency and low emissions is high temperature burns, any element which robs the combustion zone of heat, too much air etc. will reduce the performance of any stove. We then fill the gap between the burn tunnel and the outside of the metal box with perlite. This insures a super insulated combustion zone.

If you don't find the recycled materials, the most expensive thing will be the large number of fire bricks required. I am not against cob built rocket heaters. I think they are great. But they do have disadvantages; they are

• not portable,
• not the optimum design materials for burn tunnels
• not the optimum design for capturing heat
• not the optimum design material (clay) for heat storage
• not suitable for everyone's decor
• are tricky to build correctly for long lasting heater, resulting in failures, sometimes dangerous ones

 

[begreen]

I think portable is somewhat of a misnomer here. It is more "movable" than portable. Or portable in the way that a wood stove is portable, but usually not described in those terms.

 

[Sandy Mathieu]

Well its lighter than a wood stove. It's only a bit over 100 lbs, and can be easily disassembled, but I take your point.

 

[begreen]

Can you tell us a bit more about what it's like feeding and firing this rocket stove? How large is the combustion feed tube? What is the recommended wood diameter? The reason I ask is I am trying to figure how many times one has to reload in order to achieve 12 hrs of home heating at say a home heating loss of 25K btus/hr.? In other words how large a space is reasonable to heat with this stove?

 

[mellow]

Hey Sandy, good to see this thread got more replies than the last one

In case you guys didn't know Sandy was one of the Wood Stove Decathlon finalists, but due to some misunderstandings she wasn't able to setup her stove at the competition.

Do you have some video of this prototype in action?

 

[Sandy Mathieu]

Here is a short clip of the Helix burning.

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[Sandy Mathieu]

Can you tell us a bit more about what it's like feeding and firing this rocket stove? How large is the combustion feed tube? What is the recommended wood diameter? The reason I ask is I am trying to figure how many times one has to reload in order to achieve 12 hrs of home heating at say a home heating loss of 25K btus/hr.? In other words how large a space is reasonable to heat with this stove?

The 6" castle build in the picture needs to be fed every 40 mins or so. Fuel is should be 1.5"-2.5" split. Length of 2 ft works fine, if you had a ring taller to make sure wood stays upright you could go longer. Only the tips of the wood burn and as it is burned, the wood self feeds. Of course unless you are using lumber scraps, wood is often split unevenly, so i find it best to put the thickest end in the fire first so that as it burns down, it does not "hang". If feeding just a few pieces at a time I put the fresh pieces towards the fire and push the lit pieces towards the back. This keeps the older burning piece upright and fuels the burning of the new cold pieces.

Generally you would run the stove for 3-4 hours and then it will give off heat for the next eight. The longer you fire it the more heat it stores. So a 12 hour cycle would be 3-4 hours of burning and 8 hours of release. The dip was from stirring coals. After 6 hours the inside of the 1st bell was still around 135 F, the outside 120 F. It take about an hour per 1.5" of material for the heat to show up. So if you have the 2 inside layers and then skin the stove, it may take a couple hours for the heat to really show up strongly. But like masonry heaters it will keep coming for hours.

Here is link to a blog that show a heat loss data log for 6 hours.

(broken link removed to http://blog.dragonheaters.com/category/flue-build-part-4/)

The 6" can only burn about 4-5 lbs of wood an hour. The 8" 12 lbs. The radiated BTUs will be 10-15K for the 6" and 20-25k for the 8". Basically for your heat load you would need either 2 6"s or an 8".

Hope this helps.

 

[Bigfoot]

Cool stuff. I wish I had one of these to play with. Would be nice in my shop...

 

[DevilsBrew]

Thanks for posting this, Sandy. Hope you will continue to post updates. Too bad you couldn't set up the castle in DC. The look of it would have got a lot of attention.

 

[begreen]

The 6" castle build in the picture needs to be fed every 40 mins or so. Fuel is should be 1.5"-2.5" split. Length of 2 ft works fine, if you had a ring taller to make sure wood stays upright you could go longer. Only the tips of the wood burn and as it is burned, the wood self feeds. Of course unless you are using lumber scraps, wood is often split unevenly, so i find it best to put the thickest end in the fire first so that as it burns down, it does not "hang". If feeding just a few pieces at a time I put the fresh pieces towards the fire and push the lit pieces towards the back. This keeps the older burning piece upright and fuels the burning of the new cold pieces.

Generally you would run the stove for 3-4 hours and then it will give off heat for the next eight. The longer you fire it the more heat it stores. So a 12 hour cycle would be 3-4 hours of burning and 8 hours of release. The dip was from stirring coals. After 6 hours the inside of the 1st bell was still around 135 F, the outside 120 F. It take about an hour per 1.5" of material for the heat to show up. So if you have the 2 inside layers and then skin the stove, it may take a couple hours for the heat to really show up strongly. But like masonry heaters it will keep coming for hours.

Here is link to a blog that show a heat loss data log for 6 hours. View attachment 120951

(broken link removed to http://blog.dragonheaters.com/category/flue-build-part-4/)

The 6" can only burn about 4-5 lbs of wood an hour. The 8" 12 lbs. The radiated BTUs will be 10-15K for the 6" and 20-25k for the 8". Basically for your heat load you would need either 2 6"s or an 8".

Hope this helps.

That is what it looked like. I think the average home would need the 8".The feed rate of the Castle requires someone be present to feed the stove for several hours in order to meet the btu requirements for the house. This is where a larger masonry heater has a significant advantage. Problem is that I get up at 6am, feed the stove and need it to be on its own by 7am.

 

[Slow1]

That is what it looked like. I think the average home would need the 8".The feed rate of the Castle requires someone be present to feed the stove for several hours in order to meet the btu requirements for the house. This is where a larger masonry heater has a significant advantage. Problem is that I get up at 6am, feed the stove and need it to be on its own by 7am.

I quite agree with this - as much as I like feeding the stove and all, with kids etc I need to be able to load and go most of the time. I know my wife would not be willing to feed the stove for a few hours.

Also - if adopting such a thing I'd have to get much more talented with my splitting as it seems I'd have to split everything down to a couple inches in diameter? I don't know how much more efficient this could be than what I'm using now - I go through 3-3.5 cords/year, if splitting down to a few inches that is another major time eater... Now, if I happened to be near a good source of scraps that could change the picture dramatically.

 

[DevilsBrew]

Begreen, rocket stoves are basically cores inside a mini Russian stove. I'm not even sure why they are called rocket stoves any more.