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Question: 100 mm square steel rocket stove -- dent in heat riser (images attached)  RSS feed

 
Stewart Hung
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Hi everyone,

I was wondering if there would be a problem in operating a rocket stove of this type with a dent in the heat riser.

It was scrap metal and just cut the 100 mm (4 in) square tube into the three parts in the images. I am going to weld them sometime later this week, but wanted to see if I should add a secondary air intake (on the side wall at the base of the heat riser) and possibly an afterburn.

Any other thoughts or insight would be greatly appreciated!
J-tube-rocket-stove-parts.jpg
[Thumbnail for J-tube-rocket-stove-parts.jpg]
dent-in-heat-riser.jpg
[Thumbnail for dent-in-heat-riser.jpg]
 
Satamax Antone
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Metal is doomed!
 
Byron Campbell
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Successful long term use rockets do not use metal in the flame path. Refractory materials are the only way to go, especially for constructing the J-tube and heat riser, if you want the stove to last any significant about of time.
 
Peter van den Berg
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Not even that, a rocket isn't working properly when the steel is holding. Only possible to some extent without high-temp insulation around the whole thing. Without that, it is running very sub-standard, by the way.

The dent won't have any repercussions as far as I know.
 
Dale Hodgins
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I placed a metal rod in my masonry stove, about a 18 inches from the intake, at the end of the horizontal burn chamber. It got reddish-white hot, which was suitable for my blacksmithing experiment. Presumably, the riser gets hotter. It's a little 6 inch system.
 
Stewart Hung
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Thanks for the feedback! I was thinking of moving towards this kind of system. What is the lifetime of a metal rocket stove?

The primary features of the rocket stove should have: (a) portability, (b) performance, and (c) easy to clean out. Longevity would be nice, but it sounds like that there is concensus that it would not be possible with a steel based fire path?



Also, I was smitten by this afterburner effect on this metal form rocket stove:



Peter, so the metal will conduct away too much of the heat and an insulating jacket should be placed around the burn tunnel and heat riser?



 
Peter van den Berg
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Stewart Hung wrote:Peter, so the metal will conduct away too much of the heat and an insulating jacket should be placed around the burn tunnel and heat riser?

Yes.
Not around the top of the feed but the rest should be insulated. Actually the metal won't melt but will corrode like mad because in there will be a high-temp, oxygen-rich and carbon-frugal environment. Absolutely killing for steel but ideal for complete combustion.

Try it, done that, been there. Steel is good for prototyping but you also could use aerated concrete. Wouldn't last either but it will show you how it should work.
 
Stewart Hung
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Peter, I guess that is the compromise: more air for complete burn, but the steel will deteriorate quicker. Cleaner combustion products would be ideal.

For a first build, I may be biting off than I can chew. Would Ianto's and Leslie's build described in "rocket mass heaters III" be a good place to start? What I mean is, should my first build be that rocket core? I can easily find regular bricks, but they don't have the same dimensions as fire brick.

Thanks in advance.
 
Satamax Antone
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Stewart, notice in the second video, how the flame is yellowey orange? = bad combustion.

https://en.wikipedia.org/wiki/Flame#Flame_color



But if you want to make a light cooking rocket. Well, steel can be used. Since thoses are considered disposable. But whenever you want something to last, refractories are in order.
 
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