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Just a thought from a newbie, first post  RSS feed

 
Posts: 20
Location: British Columbia, Canada
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I've done a lot of reading up on the rocket stove and heater variations and I had a couple of ideas that I thought I'd post. First, just a suggestion regarding terminology. I've seen different phrases used to describe parts of the rocket stove which can make things confusing.

I think of the stove as having 3 basic parts, the burn box, (where the fuel actually ignites and starts burning and which may or may not have a feed tube), the primary burn chamber, (which may or may not be separately enclosed from the stove interior, as in the case of the J-Tube), and the normally insulated chimney section that I've seen referred to as the secondary burn chamber.

That said, my first idea for any rocket stove heater that has a vertical feed, would be to enclose it, add an adjustable air inlet near the bottom on the side farthest from the burn chamber and change the shape of the burn box. For example, by going from a typical bottom size of about 5"X5" to a 5"X10"X(whatever height) you obviously double fuel capacity. Even though half of that area is farther from the burn chamber, it should still burn. So long as there's enough draft and fresh air supply below and around the sides of the bottom area of the wood where you need it to burn, it shouldn't be a problem.

Just a though.

Keith.
 
Keith Coldrain
Posts: 20
Location: British Columbia, Canada
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Second post:

I hope I can upload some rough sketches to go along with what I'm going to describe here, but I don't have any fancy android app installed and will have to rely on freehand doodles, (when time permits).

The following is my idea for a non mass (massless) rocket heater. Measurements given are guesstimates only.

The basic exterior shape resembles a conventional squarish 30"X30"X30" wood heater (not including supporting legs or other components). Assume that a rectangular box is used as the feed box with an operable lid measuring 20" wide that is parallel to the side of the stove top, by 6" and a height of 30".

This burn box would have space inside for wood to stand vertically or to be laid horizontally with metal guides to keep the wood away from the sides and allow air around and below the bottom of the wood in the burn box area at the bottom of the feed box. It would also have a slot on the lower portion of the side against the stove measuring 18" horizontally by 1.5" vertically for flame travel from the burning wood, into the primary burn chamber.

I think it would be advisable to have the upper portion of the feed box spaced an inch or more from the side of the stove/heater, with a thin piece of stainless steel in that space to reflect heat away from the feed box. Having the feed box closed and so close to the heat source, might elevate internal temperatures in the feed box to near the flash point of the wood. (Opening the feed box to add more wood in such circumstances, could cause the as yet unburned wood to spontaneously combust, sending flames up towards the person opening the burn box.)

On the opposite side of the top of stove/heater, would be the protruding chimney that could be typically round, square or rectangular with its insulated section within the stove below it. The chimney section could be at least partly round to retain that "rockety" effect.

I also thought that a narrow air inlet passage could be located in the bottom of the stove and routed into the secondary burn chamber, (venturi style), to supply preheated air for this purpose.

In overview, all I'm saying is that all the focus I've seen to date, has been on circular and near square shapes, when there's nothing wrong with rectangles. I'm not a fanatic about rectangles, just so long as the area of the openings between the sections of the stove are approximately equal, and turbulence is kept to a tolerable level, things should work out fine. (If you really wanted too, you could use other shapes, like maybe that of a kitty cat, or a horsey, but I'll stick with more common shapes.)

As for the fire, it just needs fuel and air to burn. And enough draft to draw it wherever you want it to go.

DISCLAIMER:
I should add, that since I haven't yet constructed a rocket stove, (due to reasons that aren't important here), I can't guarantee that my variation of the massless rocket stove/heater will work exactly as described, or at all.

Have a nice day!

Keith.
 
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I'm glad you're excited about the rocket heater concept, though I believe you need some more focused study.
The basic terminology is pretty clear: for the standard J-tube core, the vertical feed tube receives the wood, which burns at its base, the fire goes horizontally through the burn tunnel, then vertically through the heat riser. Anyone using different terminology is outside the standard discussion methods. The batch box, the other common style of rocket heater, has a firebox with door in the front and a constricted port at the back connecting to the heat riser. There may be additional features like a secondary air supply in various positions, though the bottom back of the feed tube has been shown not to be advantageous.

The enlarged feed tube will not work, as it will give slower downward draft through the wood and allow flames to easily climb up and out of the feed tube top. Air supply at the base of the feed tube will do the same thing. It is critical for best function that the cross section of the system remain close to the same through the various parts, with a few exceptions like the barrel and the manifold that transitions to the ducting in the mass.
 
Glenn Herbert
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People have already not just suggested but actually built almost any variation you can imagine on the original RMH concept. Very few of them who have published their "look what I made!" videos have returned with a "this is how it failed" followup.

The best path by far is for you to build a test rocket heater outdoors or in a place that doesn't matter, and do it by the book. Then you can try experiments with something to compare success or failure to.
 
Keith Coldrain
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Location: British Columbia, Canada
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The mobile version of this site doesn't appear to allow for replies to individual posts or I just don't see that option, so I'll do this in the order I see fit.

I'm not sure that burn back is an issue in an enclosed feed box or tube. And the area of all openings and passageways for both airand flame travel would be consistent throughout my design, despite the increased area for wood fuel in the feed box.

Owing to the fact that its cold here at the moment, (just below freezing), and I don't have a warm place to work on such a project at this time, I'll have to wait a couple if months.

As for some of the phrases used, like "secondary burn chamber", this was used in one of several PDF files I downloaded from the Aprovacho website. Likewise, the idea of having a preheated air supply for this same chamber. Perhaps I could do up a signature for my posts with a terminology cross reference?

Keith.
 
Glenn Herbert
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If you actually have a fully enclosed firebox, top fed or side fed, there will be no burn-back; but you can't open the top while the wood is burning or you will have a big problem. This becomes no longer a vertical feed tube but a top-loading batch box, which has different optimal operating characteristics.

The Aprovecho Institute focuses on cooking stoves, not heaters, and its publications on the website are very old, showing some of the foundational thoughts on the subject. Essentially Aprovecho and Ianto Evans split around the early 2000s, with Aprovecho developing cooking stoves and Ianto developing heaters. His work has been carried forth by numerous currently active researchers who have settled on the common terminology for RMHs. The current publications will give you highly developed technical solutions to many situations, rather than the base for experimentation that the Aprovecho pdfs give. You can reinvent the wheel if it pleases you, but if you most want to get a functional heater, look at newer resources like the third edition of Ianto Evans and Leslie Jackson's rocket mass heaters book.
 
Keith Coldrain
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Location: British Columbia, Canada
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"If you actually have a fully enclosed firebox, top fed or side fed, there will be no burn-back; but you can't open the top while the wood is burning or you will have a big problem. This becomes no longer a vertical feed tube but a top-loading batch box, which has different optimal operating characteristics."

Thanks for the clarification. I'll try to use batch box in future references. I have had some luck in finding additional information, but I thought I should start a new post more specifically aimed at what I am trying to find.

Keith.
 
Maybe he went home and went to bed. And took this tiny ad with him:
What makes you excited about rocket ovens?
https://permies.com/t/90100/excited-rocket-ovens
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