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rocket mass heaters

fireboxes.... size and type ?'s

Posts: 67

posted 12 years ago

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im trying to decide on a type of fire box... i have already decided against a j type setup.

i am building a version of this...

im trying to decide on doing the fire box just liek in the video except a 5in tube or to do a horizontial fire box in 5 or 6 in like in this video...

thoughts? which would be better

i know the dragon heater uses a horizontal fire box..

im also going to do a vortex in the heat riser...

http://www.permies.com/t/29694/rocket-stoves/Refractory-options-buying-sources-links#231586

http://www.permies.com/t/29498/rocket-stoves/tear-failed-steel-heat-riser#230027

Satamax Antone

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Location: Southern alps, on the French side of the french /italian border 5000ft elevation

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posted 12 years ago

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Brian,

first of all, metal is doomed.

Secondly, stop watching thoses crapy videos of "one of and soon to die" metal stoves on youtube.

There's three types of rockets i'm aware of lately.

J tube like the first one you've showed. Even tho it's a slanted J tube, which everybody seem to say slanted ones are crap, not enough turbulence.

L tube, mainly for cooking. Looks prety much like your second one.

Horizontal batch Rocket.

Designed by Donkey Canyon and Peter van den Berg. http://donkey32.proboards.com/thread/511/adventures-horizontal-feed

Three types of heat extraction, metal barrel as a radiator. Metal containers, or anything else, like bricks, half barrels (half barrel system) stones or whatnot into bells. And mass with flues.

Then, do a good reading, and remember, metal is doomed.

God of procrastination https://www.youtube.com/watch?v=q1EoT9sedqY

Cindy Mathieu

Posts: 246

Location: near Houston, TX; zone 8b

posted 12 years ago

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I agree with Satamax. You are trying to get and keep your fire above 1200°F. Steel loses its structural integrity @ 1000°. Steel is tempting because its so easy to get a nice shape and we are all comfortable with the tools. But, it won't last. You will have wasted your time.

I am a partner in Dragon Heaters. We make a cast refractory burn tunnel in the traditional "wood is fed vertically" design. We are also taking a batch box (designed by Peter van den Berg) to the Wood Stove Design Competition. The batch box is much trickier and I don't think it will ever be as efficient as the traditional design. See our website and blog: www.dragonheaters.com

If you have no smoke, that doesn't necessarily mean you have a clean, efficient fire. Only the test equipment can tell you that for sure.

www.dragonheaters.com
http://blog.dragonheaters.com/

brian hall

Posts: 67

posted 12 years ago

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When you say soon to die... how long are you expecting life span of a metal burn chamber? im nott looking for a stove to last 5,10,20 years

if i get 2 years before i rebuild the thing im happy.

now im planning my heat riser of SS 1/4 tube 6in dia tubing wrapped in a 2in ceramic blanket with a 8" SS outer tube 1/4 thick

burn chamber in bottom of stove will be covered in refractory cement. im going to use a mixture of portland cement, natural clay, pearlite, and alum powder and pour in in from the top to cover and seal fire chamber in the bottom of my 100LB propane tank iv got.

my only place for any kind of rmh is to sit on my fireplace mantle so im limited on using certain methods.

http://www.permies.com/t/29694/rocket-stoves/Refractory-options-buying-sources-links#231586

http://www.permies.com/t/29498/rocket-stoves/tear-failed-steel-heat-riser#230027

brian hall

Posts: 67

posted 12 years ago

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Cindy.... as to structural integrity the firebox wouldn't be supporting any part of the stove its self and teh hottest part encased inside my system. i don't think ill ever meet to melting point of steel 2500F

what do you think of a dual walled steel firebox with a 1in ceramic layer in between...overkill, unnecessary?

http://www.permies.com/t/29694/rocket-stoves/Refractory-options-buying-sources-links#231586

http://www.permies.com/t/29498/rocket-stoves/tear-failed-steel-heat-riser#230027

Satamax Antone

gardener

Posts: 3472

Location: Southern alps, on the French side of the french /italian border 5000ft elevation

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posted 12 years ago

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Brian, metal is doomed. I have melted a gas bottle in about 14 burns.

The dip, where the screw is wend down just from gravity and melting.

http://scontent-b-mad.xx.fbcdn.net/hphotos-frc3/550186_2129483854084_1054008007_n.jpg

God of procrastination https://www.youtube.com/watch?v=q1EoT9sedqY

brian hall

Posts: 67

posted 12 years ago

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eeek... thats disparaging... what was that? and why dont i see photos of the 55 gallon thin walled drums melting when used as heat radiators?

http://www.permies.com/t/29694/rocket-stoves/Refractory-options-buying-sources-links#231586

http://www.permies.com/t/29498/rocket-stoves/tear-failed-steel-heat-riser#230027

Cindy Mathieu

Posts: 246

Location: near Houston, TX; zone 8b

posted 12 years ago

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why dont i see photos of the 55 gallon thin walled drums melting when used as heat radiators?

I'm not sure exactly to what you are referring here. However, if the drums are using water to store the heat...the water is probably only 180°F instead of 2,000° which would explain why it doesn't melt.

www.dragonheaters.com
http://blog.dragonheaters.com/

Karl De Pauw

Posts: 24

Location: Aarschot belgium

posted 12 years ago

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here's a nice video of how the metal get's eaten by a RMh

http://www.youtube.com/watch?v=54lOrITaXpc&feature=share&list=PLtIuZ9K-UzcNnCmoKicRLzYQndplSkUuR

it eate the hole iner heatriser

yolo, live for today but make sure that the one's you poducede can have a live too

Satamax Antone

gardener

Posts: 3472

Location: Southern alps, on the French side of the french /italian border 5000ft elevation

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posted 12 years ago

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brian hall wrote:eeek... thats disparaging... what was that? and why dont i see photos of the 55 gallon thin walled drums melting when used as heat radiators?

Simply because they are not in the hotest part of the stove. The top of a barrel, in an eight incher can glow cherry red, tho, it radiates heat soo fast that it doesn't melt. Inside the burn tunel and heat riser, there's insulation outside the metal, if you do it with metal, and it keeps heating up. The only one i've seen holding in a heat riser, is some weird aluminized steel. Which surface being turns to alumina after a while, and can whistand 2300C° iirc. Which protects the actual steel from being eaten by the exess oxygen. Tho, don't use this stuff in a burn tunel. That would be too hot imho.

God of procrastination https://www.youtube.com/watch?v=q1EoT9sedqY

brian hall

Posts: 67

posted 12 years ago

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ive seen that video and agreed using stove pipe for a heat riser is something id never do...lol that was dumb...

my eeek is from your photo of a melted top of the 100lb propane tank as thats what im using instead of a 55 gallon drum for my outer shell..
what caused the top of that tank to melt ?

i have cut open the top of my tank just like yours but i plan to drop in and weld shut a 10" 1/2" thick peice of plate steel to close it shut after assembly. and give me a surface for boiling a pot of water.

my stainless heat riser made from 440 stainless 6 in in dia and 1/4 in think walls it has a melting point of 2500F it should stand up just fine against temps in the 1000-1500 range i think. wont know till after winter when i disassemble to see how she held up..

http://www.permies.com/t/29694/rocket-stoves/Refractory-options-buying-sources-links#231586

http://www.permies.com/t/29498/rocket-stoves/tear-failed-steel-heat-riser#230027

Cindy Mathieu

Posts: 246

Location: near Houston, TX; zone 8b

posted 12 years ago

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Stainless steel is not the appropriate material for a heat riser even if it will endure the temperatures.

Combustion is still taking place in the heat riser. Consequently, if you make the heat riser out of steel which conducts heat away from the fire, your efficiency and emissions will be worse than they would be if you made the heat riser out of an insulating material.

Ernie & Erica make a wet mixture of clay and perlite inside a form of galvanized HVAC ducting. The clay dries up. It is known in advance that the inside layer of HVAC ducting will disintegrate leaving the clay and perlite hardened in place. Forgive me if I have made a technical error about how this is done; this is my understanding.

www.dragonheaters.com
http://blog.dragonheaters.com/

brian hall

Posts: 67

posted 12 years ago

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Info on stainless heat resistance if any one wants it...
http://www.azom.com/article.aspx?ArticleID=1175

@Cindy.

my reconing on this and im no expert or claim to be

my heat riser design consists of a 6 in inner SS tube 1/4 in thick wrapped in a 1 in ceramic blanket this assembly is then slipped inside a 8in SS tube

while the inside SS tube would heat tremendously the ceramic blanket would trap that heat preventing it from escaping now this inner tube would radiate heat all along the heat riser contributing to an evenly distributed heat field in the heat riser.
in my eyes helping to steady temps in the riser as a fire burns down in the box which should lead in theory to no lag in performance when you reload the fire box.

another thing that motivating me towards this plan is its different i have not seen it done like im talking about and all my materials are FREE except the ceramic blanket.. $35 amazon!!!

http://www.permies.com/t/29694/rocket-stoves/Refractory-options-buying-sources-links#231586

http://www.permies.com/t/29498/rocket-stoves/tear-failed-steel-heat-riser#230027

brian hall

Posts: 67

posted 12 years ago

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but all this talk is Great really getting my mind going..

http://www.permies.com/t/29694/rocket-stoves/Refractory-options-buying-sources-links#231586

http://www.permies.com/t/29498/rocket-stoves/tear-failed-steel-heat-riser#230027

Bill McGee

Posts: 187

Location: Southeastern Connecticut, USA

posted 12 years ago

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Brian,

I'm no expert in steel, but over the years I have warped steel stoves to the failure point. I have a steel wood pellet basket in my current wood stove that expanded/exploded in one year. Steel begins to fail at a much lower temp than the melting point

1). 425 C (~ 900 F)steel begins to soften. I think this is the actual failure temp.

2). 650 C steel has lost 50% of its strength

3) A 150 C temp difference in different areas of the steel causes buckling and failure

4). Sustained high temp of steel causes crystaliztion of steel and brittleness.

I think I remember 700 F and above weakens a standard wood stove. Correct me if I am wrong.

Bill

PS for what it's it worth, at 27 f outside I just loaded 5 lb of pellets and 2 Biobricks to a stove at 450F. It jumped right up to 600 F so I hard clamped the flue damper and the stove air. In 30 minutes or so if trending down I will crack the damper and open full air. The stove top therm has 100 deg gradients except after 600 f the next printed temp is 900 f which I consider the "melting/damage point"

Bill McGee

Posts: 187

Location: Southeastern Connecticut, USA

posted 12 years ago

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Stove is still sitting a 600 F. If I fall asleep it will smolder out and last thru the night. I prefer to open up the air and crack the damper to burn better and charge my water thermal batteries. So no sleep for another 30 minutes. (I am afraid of a burn above 600 F or a runaway stove - don't want to doom the metal, prematurely)

Satamax Antone

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Location: Southern alps, on the French side of the french /italian border 5000ft elevation

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posted 12 years ago

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Brian, the gas bottle is a 13kg we have in France. 5mm thick (a bit less than 1/4) Prety much the same size you see often in front of trailers in the us i'd say. May be a smidge smaller.

It was the core of a cyclonic rocket experiment. 14 burns later and it had melted like you can see, started spalling badly, and the pipe forming the first part of the J tube had spalled that much in the elbow, that it was unuseable.

God of procrastination https://www.youtube.com/watch?v=q1EoT9sedqY

brian hall

Posts: 67

posted 12 years ago

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@satamax that makes me feel better mine is a 45KG tank ill be using as an outter shell im now thinking about building a bigger firebox and lining the steel shell of the fire box with 1in fire brick. thoughts?

http://www.permies.com/t/29694/rocket-stoves/Refractory-options-buying-sources-links#231586

http://www.permies.com/t/29498/rocket-stoves/tear-failed-steel-heat-riser#230027

Satamax Antone

gardener

Posts: 3472

Location: Southern alps, on the French side of the french /italian border 5000ft elevation

196

posted 12 years ago

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brian hall wrote:@satamax that makes me feel better mine is a 45KG tank ill be using as an outter shell im now thinking about building a bigger firebox and lining the steel shell of the fire box with 1in fire brick. thoughts?

God of procrastination https://www.youtube.com/watch?v=q1EoT9sedqY

brian hall

Posts: 67

posted 12 years ago

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http://www.youtube.com/watch?v=qsB_52F8liE

another nail in the coffin for the metal heat riser...

how would a 2" cermic blanket on the inside of a 10 in stove pipe work for the heat riser ?

http://www.permies.com/t/29694/rocket-stoves/Refractory-options-buying-sources-links#231586

http://www.permies.com/t/29498/rocket-stoves/tear-failed-steel-heat-riser#230027

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