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I have a welded rm j tube 10" schedule 40 feed tube with 8" steel pipe burn chamber and 10" chimney .

Do I have an 8" rmh or a 10"?
What is the Ideal exhaust length for my Jtube?, utilizing what size stove pipe? How many 90 degree turns to maximize efficiency ?
 
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gardener
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Location: Southern alps, on the French side of the french /italian border 5000ft high Southern alpine climate.
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Thanks David!
 
Phillip Baldwin
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Hey thanks for the info , although I'm a guy who don't like failure. My j tube already works even without insulation. (Although it has to get hot first.) and is built very well, couldn't I line the inside with chimney mortar to eliminate oxidation? and how do those super thin barrels survive the burn?
Thanks!
 
gardener
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Location: Upstate NY, zone 5
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You could line your J-tube with castable refractory cement, but it would need to be at least 1" thick to have enough strength to stay in place on the sides and especially roof. I do't know if chimney cement has enough high-temperature capacity to last in the hottest parts. Lining the 10" feed and riser with 1" and a bit of castable would actually make a properly sized 8" system (sizes are typically referred to in diameters, and 7 x 7 1/4 or so is equivalent to 8" diameter). The 8" burn tunnel would have to be replaced, though. Steel, even heavy structural steel, will be destroyed faster than you would think in the temperatures and atmosphere of the combustion zone. The barrel will survive for decades because it sees only heat, after the combustion is complete, and there are no reactive gases there.
 
pollinator
Posts: 4154
Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
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books fungi hugelkultur solar wofati woodworking
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Philip Baldwin : I am not sure exactly what you mean when you wrote about ''Chimney mortar'' but most of these Dry Rockhard! Their expansion rates will be different
than the metal ! I expect that they will soon crack, and fall apart. Refractory Cement is kinda $pendy and I am very sure of failure of this material too! The best use of
a Refractory Cement in a Rocket Mass Heater RMH Build is for glueing broken Bricks back together !

These materials Are not insulating !

Actually counter-intuitively, Rusting is not even close to the reason that Iron / Steel Metals fail ! !!! A quick google search for '' High Temperature Hydrogen Attack '',
or Hydrogen and Steam Embrittlement Will help understand the Fate of Iron / Steel metal in those locations.

A large part of the difference between the metal core of your Rocket and the barrel, is the barrel will only occasionally see 1,000ºf -not the 1,600ºF and above that you
can expect from its core !

The Barrels Heat Exchanger acts exactly like the Heat Exchanger within the " Blower cabinet '' of any of the Fossil Fuel Fired Forced-air Furnace. Both are made of very
similar Ductile Steel, All F.F.F.F-a.Furnaces Heat exchangers use a Thinner gage ductile steel than even the lightest Barrels/Drum ! The furnaces Heat exchanger usually
Gets a 20 year warrantee !

Hope this is timely, and you find it useful. For the Good of the Craft ! Big AL
 
Phillip Baldwin
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This sucks. Thanks for info.
 
Phillip Baldwin
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So is firebrick the only suitable rocket mass heater material ? The sorry part is it works beautifully. It weighs about 300lbs stick welded by union pipefitters, a work of art!.......My heart is as broken as my Rocket mass dreams.

 
allen lumley
pollinator
Posts: 4154
Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
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Phillip Baldwin : Yes, but- We have a single working Unit that started out to be a Rocket Cookstove that graduated to being a simple forge that allowed simple shaping and

bending of common steels on hardwood without the use of bellows, as the rocket family creates its own forced air !

This unit was prototyped in late 2012 by the moderators of this Forum thread Ernie and Erica Wisner.

As this unit was supposed to be a Commercial Cook stove as originally envisioned, and directly there is not much call for simple forging in their lives it awaits the Arrival

of a new champion ! E & E have decided not to let ANY plans out until they have debugged them so things are in a holding pattern right now !

We Are living in interesting times, keep coming back we have lots to share ! For the Good of the Crafts! Big AL
 
Phillip Baldwin
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Thanks. Curse you YouTube! On to fire brick.
 
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