John F

I do believe that the basics of the "rocket" burner can be made to work here, and work well.
I may have wandered a bit earlier: to some important points:
* Use the vertical insulated burn tube to consume the fuel. With enough air inlet (and some way to control it perhaps) and a tall burn tube, you probably don't need to concern yourself with secondary burn or mixing of fuel/air (it's done in the tall tube).
* go from the top of this, directly to your "black radiator" horizontal run across the ceiling.
This takes the maximum released energy and puts it right into the skin of the HX pipe. Suggest to minimize the distance between the burn tube top and the radiator pipe, if you wish to direct the released heat using your parabolic reflector, otherwise it will furiously warm up the air right there, and whatever is nearest the pipe.

* The "primer" (small heat release at the beginnning of the final run up & out) is a good idea. With your electric fan, it might not be needed. WIth a tall "Rocket" burn tube, the fan might only be needed to keep the draft at start-up, until it heats up the guts.

I maintain that the barrel is not needed. It is the heat exchanger of choice for that design: a flat space at the top of the burn for some cooking utility, and it re-directs the flow back down to the lower exhaust into the cob mass horizontal run. This is the heat exhanger for the "mass heater".
You aren't using this. You're using immediate heat, from the exhaust, right into the room air.

I do not know what success you will have with your controlled stack burn, and self-feeding of the fuel from the stack into the burn area at the base of the insulated vertical burn tube.
You may very well be the one to innovate this with a "rocket stove".

All we've seen in the literature is the "L" and the "J" with their respective methods  (either the continuous manual feed into the lower part of the "L", the other the self feeding, bottom burning sticks of the "J".

If this clears it up a bit:
All that makes it a "rocket" is the insulated vertical burn chamber. This creates a fast moving energetic colllumn of air, by maximizing the time the 3 sides of the fire trangle are present in the most favorable conditions.


I ignored fuel input and everything upstream.. This might very well sit above the floor: you won't need much more than 40" of vertical insulated burn tube for a complete combustion and very energetic flame.
At the top, it'll be furiously hot. over-build as necessary.

Suggestion: concentrate instead on a vertical burn tube. Insulate around it, and several diameters up the length of the rise. (some of the household systems use as much as 50" for a 7" tube. I'm certain there's a roaring flame at the top, eating away at the barrel lid...
There are impressive videos of things as small as a 4" tube "rocket", insulated about 12", with an uninsulated pipe about 3' tall above it, and it's putting out a roaring jet of flame about a foot tall above that.
Use the vertical tube to help generate a rapidly moving energetic collumn, and then push it through your horizontal heat exchange pipe.


Your decisions come down to mechanics: How to feed it and contain the fire (which produces the heat and smoke to then run into the vertical tube). The standard "rocket stove" model is the horizontal tunnel to the bottom of the burn zone, and you push in as much fuel as you need. When you stop pushing it in, it goes out.
The usual "rocket mass heater" uses the feed pipe for some convenience of letting it gravity feed itself. The "throttle" is in how much fuel you stick into the upright feed.

Other stoves will have what seems more like a normal fire-box, insulated, and a pre-heated secondary inlet leading upward to the base of the insulated vertical burn tube. This seems more like a normal fireplace: build a normal fire, and let the guts heat up to encourage complete combustion.
Either you place a mass of fuel and control the air inlet to control the rate of burn, or you meter the fuel, which either means you feed in the desired amount, or you use something like an automatic pellet feed.
The famous Ashley stove uses a stack of normal firewood, that falls down into the combustion chamber, with secondary pre-heated air inlet and a volume of baffles to burn it all before the flue. The thermocouple that controls it varies the amount of primary & secondary air, so the magazine holds a big lot of wood, and you start the fire in the morning, and that's it. I've heard reports that you build one fire per season, and load fuel & empty out the ash sump as needed.


I suspect that your electrical blower system won't be needed beyond starting it up, and getting the inner tube hot. After that, it should draft on its own.

I like that at every turn, you have it going up higher. You might be able to get away with some down-draft somewhere, but why tempt murphy?

[quote author=Joel Hollingsworth]
The barrel serves partly to mix the combustion gasses and cause a secondary burn, so I think you might want to include it, or something with the same function, in your design.The barrel is a heat exchanger and it also serves to bring the flow from the vertical burn tube down to the lower level of the pipe that people run through a cob bench.
The burn takes place in the vertical tube. Everything after that is ducting to point of use.

The "rocket" burner uses the insulated vertical space to thoroughly mix air & fuel at the point of highest energy release. The length of the vertical insulted run gives it time to mix & burn thoroughly. That's all the encouragement the burn needs to completely combust, in its simplest form.

In the simplest form, no forced draft is needed, nor secondary air. If you over-build things to take the heat, you can use these to strong advantage: After the fan, divert part of the flow to the bottom for primary, and bring the rest of it up around/past the combustion tube and inlet it a few diameters up.

Other considerations... Instead of the piled fire-brick burn tube, think of a steel tube, insulated with a larger outer tube around it. Less mass to pre-heat and get things going (if it can take the heat of forced secondary combustion air).
Somewhere I saw a more-or-less standard "rocket mass heater" that uses a pyrex baking pan built into the cob mass at the bottom, in front of the feed inlet...
I've seen various heat exchangers. Your pipe with the reflector will be interesting, but others have been as simple as the 55 & 33 gallon barrels, or a simple "donut" of chimney pipe, forcing the draft through more surface area.
Your vortex baffles should work, but simply turning and running it through various geometries should do to prevent laminar flow from keeping the hottest part in the center of the tube.
Maximizing surface area, with the same draft area for unobstructed flow is all that's usually built in. Think also of flat rectangle volumes, instead of round pipe.

paul wheaton wrote:
Saywhat?

That stuff is flammable?

I heard about a lawsuit: after using the stuff, a guy set his hands on fire lighting a cig.
I tried it, and even with a thick coat still fresh, nothing. (Urban myth?)
I've set my hands on fire with isopropyl, and the occasional booze. Not to mention naptha, and even playing with gasoline while cleaning bicycle parts. Alcohol doesn't burn hot, so as long as you don't sit and stare while your hands heat up...
For that matter, next time you see non-dairy creamer powder, see if the ingredients mention anything that sounds like aluminum. It's a pretty energetic fire powder. Not in a little pile like black powder, but sprinkled down over a tiny wadded paper fire, it has enough air mixed through it to surprise you.

I was startled to learn recently about the fire piston too. No real evidence that it was prehistoric, but no reason it couldn't have been neolithic.
I've decided it's about the best thing out there. I'll play with fire bows and such if its a highly evolved variant, but nothing more messy than that for real use, when the piston is so ... neat.

Tinder of choice is always an issue. Cotton soaked in vaseline, lint, tiny shredded moss/bark/pine needles.

BTW, burning junk mail is actually discouraged by some stove/fireplace makers, because the weird colored papers throw off some nasty products, and can build up strange creosote deposits.
Don't know if that still goes for re-burner (secondary combustion) stoves.

Somebody writing about a project like this (metal & cans):

Rocket Stoves.. Experimenters corner.. Answers questioned! :: Rocket Stoves :: Experiments, results :: Scaled Down Rocket Heater.

http://donkey32.proboards.com/

I don't think you need to register to view... but it's worth it for the entire site.

(edited)
Sort of what I'm trying for

ronie wrote:
Perhaps you didn't understand. It is a rocket cooker and i used it for two years to cook with and smoke foods. It would not be applicable to this thread as it is an outdoor stove.

Correction understood. Perhaps I should have used more words, or left it to others to read your own work. Yours is more the size, and probably very like the output of the smallest of those marine stoves (I'll bet with less smoke and fuel use? I doubt these little commercial stoves are "re-burners" which cycle the smoke through for complete combustion. In fact, I'll bet the camping ones are pretty dirty.)

What I meant by "unpolished" was that the implementation wasn't worked through enough for this kind of vehicle application, as you said (Nor was my tiny experimental job). Like those great little marine stoves, it needs to be fastened down, made from better materials (I'm toying with second-hand sheet metal, and won't ever even try using aluminum or galvanized, and won't consider anything even close to operational status if it isn't of good solid steel)

So, what we're looking for (myself, anyway) is something no bigger than your outdoor burner, or the small marine stoves, that's secure and heavy duty enough to serve. I suspect a rocket burner would need more attention paid to ash or fuel spill-out of the intake horizontal of the "L" than any of the "can-based" ones we see out there.
Note my observations about the entire small thing getting hot enough that any fuel stored in a chute will ignite; so it's not continuous self-feed, but rather continuous tending.

I also still think some sort of heat exchanger on the uptake pipe can be used to get more of the heat out of it. Experimentation will show if there's enough draft to drive it through some sort of concentric can or maybe a donut of stove pipe.
The rocket stove will produce the energy, and it'll get hot itself, but I believe lots of heat will go out the pipe, if some extra air surface area isn't offered to transfer heat to the room air.
Hmmm... Another idea to that: if it's cold you'll want such additional heat, but if it's a hot day you might want to remove the heat exchanger and run straight pipe outside immediately after the hot plate? Experimentation...

I hadn't thought about adding mass. Some household woodstoves have had removable tile/bricks for bedwarmers, and many have fire brick liners which will act as heat sink. If cartage weight isn't an issue (truck or stationary as opposed to going along with a tent), something could be arranged.
If nothing else, firebricks to set on the hotplate after cooking is done.

It'd be lovely to cast it out of refractory... Insulate the burn tunnel a bit to help it start drafting, but for a vehicle or stationary use, make it a massive heat sink.

I won't repost here, but in the thread

Permaculture Forums  |  permaculture  |  alternative energy  |  Topic: mini rocket
https://permies.com/permaculture-forums/2553_0/alternative-energy/mini-rocket-

I've mentioned something I'm toying with, along exactly this line. Thinking of small room/shop or RV/tent heater. (not at all what the OP writer in that thread was asking about)
Mine was 1.5" square, and needed to be taller than the 4" I made. Seemed to work great, for an initial experiment. Lots of heat.
Another writer left pics of a larger coffee-can scale experimental thing he built, that's not very finished or complete.

I was partly inspired by the rocket lantern we have so little info about.
My ultimate idea right now is something with an air heat-exchanger on the uptake to make use of as much energy as possible, but at the top of the burn chimney, a hot plate for small cooking jobs.

similar to, though smaller than this

ROCKET STOVE built from 5 gallon bucket

http://www.youtube.com/watch?v=9M-4aUqa7RU

http://www.youtube.com/watch?v=9M-4aUqa7RU

this has interest too
Arkansas Rocket Stove




For a tent/RV or room, I definitely want a flue to vent it out of the habitable space.

I'm not sure how small is the smallest commercial stove with an uptake flue:
looking at these

Eldfell stoves
http://www.tentipi.com/index.php?id=153

and elsewhere
Wyoming Lost and Found


http://ellisstove.com/features.php

OK, but nobody makes a "rocket" stove "up-draft" burner in such a thing.
We want the clean complete burn, the smokeless nature, quick starting of a small fire, that does a lot of work for its size.
At times it'd be nice to have the feature some might call a drawback, that it needs constant feeding, and will go out & go cold quickly if you're not constantly pushing the fuel into the intake shelf. This means it will go out. A safety feature, if you look at it so.

ronie wrote:
You're talking about an L shaped rocket stove with a side load right? I don't know why you want one that small>>? did a toothpick factory go out of business and give you a huge amount of toothpicks?

Really small fuel, yes. The kind of stuff you get out of the way before you set up your tent, and don't need any tools to break it up to make it small enough to fit in.

For a tiny scale "rocket stove", we're not talking about a mass heater, just a burner. As I said above, it seems pointless to try to insulate the burn tube on something this small. I'm going to try just making enough of a "body" to hold it together, and support a 1.5L pot & skirt.

As for the laminar flow problem, and fuel/air not mixing enough, I fail to see it as a show-stopper (from experience with a 1.5" square X 4" riser I made. Make it rough, put in a grate to keep ash/coals from blocking the air inlet under the shelf, and it seems to break up the air flow well enough).

From my experience, seeking to make a small camp-size single stove, the 2.75" coffee-can job is actually too big for this kind of application. Way too much energy output for a single-burner campstove you set up in the vestibule.

I've camped with and gone on week-long trips with my zipstove, among other camp stoves. The zip stove is handy and cooks really fast. But it's tippy for setting a cook pot on, and you need to remove the pot & skirt and everything to re-fuel it. It also almost continually smokes, if there's actually any flame, as opposed to just coals. I'd like to see if a small-scale rocket with enough of a vertical burn tube could eliminate much of that. My litttle experiment seemed promising.

As for electricity, tegpower.com has a little generator that's air-cooled, and should put out enough to charge small appliances and run some LEDs, if you have the circuits and outputs right. From experience with my zip stove, it'd be a challenge to not burn the thermoelectrics out from too much heat. Probably enough to set it on the ground nearby.

found this:

Specs: Dual Power Output 4.5 VDC / 1.2 amps or 10 VDC / 125+ ma /. Can be ganged and wired together in multiples to achieve higher voltages and amperage. Life expectancy - 200,000 hrs. All aluminum construction, dimensions - 5" X 3" X 3".

Applications: Experiment with and demonstrate the practical applications of thermoelectric generators such as; charging batteries, cellphones and other electronic devices. All that is required to generate electricity is a source of heat (180-F to 300-F) Attach to side off wood stove, clamp to stove pipe, oil or alcohol lamp, candle flame, campfire, solar, etc.

(Oh, approx $99, if you want to experiment...)

I have thought about this too. If you don't want/can't build in the massive thermal battery (mobile home?), then how about a simple rocket stove burner, and heat exchanger?

Co-axial barrels, or zig-zags of pipe seem to be the answer. Maybe remember to always err on the side of ease of flow up & out? Make it as simple an up & out run as possible, while still getting some instant heat from it. First, as always, is the burn chamber. Make it clean and simple and safe. Once you've got the burn, then tinker and see how much heat you can take out of it.
Code is a big problem, and making sure that you don't kill yourself with creosote. Erica's extensive cautions are well-taken.


Check the aprovecho site archives. We're looking for something as simple as the Picasso stove, with a rocket burner instead.

Designing Improved Wood Burning Heating Stoves
http://www.bioenergylists.org/stovesdoc/apro/Heat/Heating%20Stoves%20LO-RES.pdf

[quote author=carbonout]
cool story got a pic

Not of that one. Tinkering about, getting ready for another one.
One reason I used the sheet metal & square shape construction, is that I pre-built everything of paper first.
It didn't take long to make & test it, so I'll quit procrastinating one day (and have access to a camera).

I'm thinking of a replacement for my Sierra Zip stove & its batteries, and a proper room air heat exchanger as well as cooking surface, and flue pipe for a tent/RV application.

There's been some mention of alternative air inlets, also of piping outside air in through the cob mass to pre-heat it and inlet it next to/around the wood. As always the key is to experiment thoroughly before you set it in stone. Any of the "professional "rocket stove sources will say that almost none of this is exact science, and it's a wide-open field for experimentation & innovation.

This includes the problem you stated with air flow area not being right. Test & experiment.

It seems that eliminating the vertical pile of bricks, and using the insulated pipe is a much better choice.
(Note especially the mention of the results on the outdoor test rig, of simply placing the pre-warmed updraft chimney over it.)
rocket stove mass heater workshop summary
http://www.youtube.com/watch?v=hmYaIrHRMLM

I also wonder about building as much as possible of this whole apparatus out of local materials. The problem is the liner of the vertical combustion chimney needs to be as rugged as concrete, without the thermal mass. The ideal would be something custom, like the Shengzhou stove cores. (anybody got a 1000 degree kiln?)


Aprovecho Research Center Publications
ARC has published eight manuals on cooking and heating technology which are designed for a non-technical audience in simple, un-intimidating language, with easy to follow diagrams.
http://www.aprovecho.org/lab/pubs/arcpubs

Good discussions of local mud techniques
Woodstoves for Uganda: Testing stoves and finding better designs
http://www.bioenergylists.org/stovesdoc/George/WoodstovesforUganda.pdf

HOW TO BUILD THE IMPROVED HOUSEHOLD STOVES
http://www.bioenergylists.org/stovesdoc/apro/guide/HOUSEHOLD%20Stoves%20Construction%20Manual%20Nov%202004.pdf