Instructables

Fabricating a Heavy-Duty Rocket Stove

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Picture of Fabricating a Heavy-Duty Rocket Stove
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Rocket stoves are small efficient stoves that can produce a hot flame with only a few small pieces of wood. The reason it is called a rocket stove is because when wood is added to the fire the flames create an internal draft. As the draft is created, the fire begins to produce a jet of fire coming through the stove pipe. The stove flame eventually becomes so hot that it produces very little smoke. The stove should be able to produce a hot continuous flame that will lick the bottom surface of a pot or pan placed on top of the stove.

These stoves were created out of necessity in third world countries to cook small meals and have recently become more popular as a do-it-yourself camping stove. A rocket stove is usually made from readily available materials that can be recycled for reuse. To make a large stove, it is not unusual for the outside shell of the stove to be made from an old propane tank, Freon tank, or air compressor tank. To complete the following instructions for making a rocket stove, experience in welding and metalworking is needed as this project requires a great deal of it.
 
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Step 1: Materials

Picture of Materials
Changes may be made to the materials in the schematic according to personal preference or based on availability of materials. Materials for fabricating stove legs are not present because many different configurations may be acceptable. Any design may be accepted for personal preference, as long as it is able to support at least 100lbs and withstand high temperatures for this model.
arhodes1813 days ago

I'm sure he means tack welds. In the end though, it doesn't make much difference what he calls it since there is a more than adequate picture.

waterworks6 months ago

Need for ashes emptying in case os indoor setting... how you will go about with a permanent setting? Maybe a center cone with a bottom gate or something similar...???

Bbecause this one doesn't exhaust through a flue, I'll keep looking for a different design rather than build this one for indoors. If I could get the gases outside I'd still worry about sending too much of my heat through the flue with a rocket style stove.

For what this is, though, and for its intended purpose, kudos to the poster!

AJMansfield4 months ago

Those are not spot welds attaching the risers to the stove. A spot weld is when you use two metal electrodes on opposite sides to weld pieces of relatively thin sheet together. You used either FCAW or SMAW, not RSW. (As you have already welded the top on, there is no way to reach the interior to perform a spot weld anyway.)

Mobetta641 year ago
Excellent Plan. Can this be made so that it portable? Smaller cylinders possibly with the same base concept? I like your design but am looking from some thing that is "BOB-able"

What are your thoughts about making the components nest-able (contain within each other for transport and storage?

Also-- Do the interior walls get a full load of Pearllite? (up to and below the pressure relief drilled holes?

Awesome
Nice plans and design. Impressive. You may be interested in the rocket-style-with-a-twist space heater we have been making for our workshop. It is made from scrap materials and burns long sticks/branches. Its on our blog FloweringElbow.org
avatar_i1 year ago
Nice desigh and beautiful workmanship, but I don't understand where the initial wood smoke/gas is being recirculated into the flame. Please explain what I am missing...
Thanks.
fretted1 year ago
I think some folks are thinking of rocket mass heaters when they see this and confusing the 2 a rocket mass stove just burns hotter and faster than a regular stove for cooking a rocket mass heater burns and re burns wood gasses for a greater and longer heating time with less fuel and burn time !
FrankGregg2 years ago
Great looking stove!
I would caution all against using vermiculite as insulation for something like this. Vermiculite has a small amount of asbestos in it. Not a good thing to be releasing into the immediate environment where you might inhale in into your lungs.
Cheers!
I notice a lot of guys using pearlite
SIRJAMES092 years ago
regardless of weather it fits the bill to be considered a rocket grill or not, I love this idea & wish I had the knowledge & tools to build one.

I thank you for sharing Sir, I love this thing!!!
Dockbob2 years ago
I don't understand how this is a rocket stove. There doesn't seem to be anyway the secondary gases can join the flame. It appears to me to be a very nice insulated wood stove.
From my understanding, the length of the chimney, approx 3 times the hieght of the burning chamber, will be long and hot enough for complete combustion of all the gasses.
oking Dockbob2 years ago
I second your question.
Amen to that !
mpmitri2 years ago
It's great, keep up the good work.
I'm afraid while it may appear like a rocket stove, unfortunately if I am correct, the similarity is only skin-deep. It's a just very nice stove, well constructed. Rocket stoves have certain characteristics, which are essential to performance [efficiency and low emissions], a design that departs significantly from those characteristics means it isn't one and it will most probably be not as efficient. IIRC, there are stoves which are not of the rocket type which achieve similar or greater efficiencies, but are much harder to construct. Rocket stoves are intended to be very simple to make.



See the 'Ten Design Principles'

The Rocket stove was invented by Dr Winiarski at the Aprovecho Research Centre.



References

Design Principles for Wood Burning Cook Stoves

http://bioenergylists.org/stovesdoc/Pcia/Design%20Principles%20for%20Wood%20Burning%20Cookstoves.pdf

Designing Improved Wood Burning Heating Stoves

http://bioenergylists.org/stovesdoc/apro/Heat/Heating%20Stoves%20LO-RES.pdf

eaahnen (author)  totally_screwed2 years ago
I definitely agree with you that it is a bit of a deviation from the rocket stove design. I wanted to feature an inner chamber so that it may function like a rocket stove if you want, but it may also function as a forge.

The addition of a removable platform plate in the feed tube helped it to function like a rocket stove so that a draft could go underneath long sticks, and the material burned hotter and more efficiently with even less smoke. The inner chamber was added to the stove so that after getting some hot coals in the chamber from burning sticks, charcoal could be added to the chamber if forging applications were desired.

Also, thank you for the references they were great to look at.
i look forward to hearing a response from the author on this, because the understanding of several folks who've commented here mirrors mine: This doesn't appear to actually function like a rocket stove.
stoobers2 years ago
Hi,
I made something similar, to melt aluminum which used a hair dryer to create the air blast, instead of convection.

The problem I had - sparks coming out the top. No smoke, but LOTS of sparks. I deemed my project a failure due to the fire risk. I never got to melt aluminum with it. :( I toasted a few marshmallows with it, though.

Based on your experiences with this type of stove, which is a sort of "self-blasted" furnace, please comment on these questions:

1. How did you address the spark issue? Does it make many sparks?
2. Have you checked for sparks AT NIGHT when you can see them up in the sky?

Thanks!
eaahnen (author)  stoobers2 years ago
At first it may seem that the stove produces lots of sparks, but once some hot coals form in the inner chamber the smoke dwindles to barely any and the sparks also die down.

I agree with what rallen71366 said, using uncompressed charcoal briquettes make great heat.
I've managed to melt aluminum in a coffee can w/hair drier, and you're right, there are a LOT of sparks at first. I found that using a hardwood charcoal (Kingsford (tm) was a good brand) got hotter, quicker, and had fewer sparks. The cheap charcoal was held together with a lot of binder and filler, and produced a lot of ash, sparks, and sometimes wouldn't get hot enough to melt.

If you have access to knot-free hardwood, and a method to cut it into fist sized chunks, you might investigate making your own charcoal.

The old steam locomotives used "spark catchers" to keep from setting everything ablaze. I believe it was just a heavy gauge screen, across the exhaust stack, and far enough from the burner to keep from melting.
cliqboom2 years ago
While this is a nice cook stove and good quality work, I don't think it would qualify as a rocket stove since a true rocket stove takes advantage of the gassification process of the wood. This is the process that enables them to be truly efficient and produce the low smoke output.

The gasses are recirculated into the fire in a manner that there is enough heat and oxygen present to ignite the remaining flammable gasses left in the inital burn smoke. When those gasses and particulates ignite it burns away the majority of the normally wasted material and produces an extremely efficient and hot fire with less material.
eaahnen (author)  cliqboom2 years ago
It does work similar to what you described above. It produces little smoke to no smoke when the fire burns hot and plenty of hot flame.
oking2 years ago
So why only sand?

Why not vermiculite or perlite? If it was to insulate then perlite or vermiculite would work better.

Ash seems to work well too. Sand would just seem to add extra unneeded weight. Perlite, vermiculite, or ash would all reduce the weight of the finished project.

eaahnen (author)  oking2 years ago
Next time when I make a more portable version, I will be sure to put something lighter inside.
Jislizard2 years ago
Nice to see one completed and not looking like it has been thrown together out of scrap metal.

A quick question, most of the designs I have seen have a platform for holding the fuel off the bottom of the feeder which allows the air to pass unobstructed under the fuel to feed the flame, not necessary?

Also have you seen the gravity fed fuel hoppers where you can drop sticks down and the tips slowly burn, apparently good for controlling the speed of the burn. Is that something you considered for this build and dismised, or is it very difficult to get set up correctly?

I have seen some filled with concrete + vermiculite/perlite mix. Seems like a lot more work than just filling with perlite but might hold the bits in places better.

I like this and I have access to a scrap metal dealer and a welding set.

If anyone needs me this weekend I will be in the Emergency Department.
eaahnen (author)  Jislizard2 years ago
Jislizard,
I recently made a removable feeder-platform plate and it made it easier to burn longer sticks and scrap woood.

Also I had considered the angled fuel hopper but decided against it due to the fact that sometimes I may want the stove to function more like a melting forge than a stove, and the angle may make it harder to pump air into the inner chamber.
A great little stove!

Might I suggest that you use only three legs as the fourth leg makes anything (stool, table etc) wobble.

Obviously make them equi-distant (120 degrees) apart.

Same for the pot supports, just use three instead of four.
eaahnen (author)  Kelticpaddler2 years ago
I know what you mean, if I ever make another I will consider 3 legs.
zer0vector2 years ago
My only concern is that is looks a bit "tippy" being so top heavy. How does it handle getting bumped?
eaahnen (author)  zer0vector2 years ago
It seems ok when it gets bumped, the legs were made very sturdy. Before lighting the stove I always make sure it's on level ground too.
tfraser22 years ago
Another wonderful device that moves me forward to getting off the grid. I love the idea!! Now to build one and see it in practical use. Thanks eaahnen!! Keep it up...!!

...Todd
bennelson2 years ago
Nice job! Looks great! I did mine in the style of a backyard grill.

http://www.instructables.com/id/Rocket-Grill/



 
 A friend of mine builds a lot of rocket stoves and wood gasifiers and LOVES using old propane tanks. They are nice metal, well-suited for projects like these.
Very nicely done.  It ought to last a lifetime (or two!)

I wonder, though, at the use of sand to fill the void between the shell & the combustion chamber.  If perlite, vermiculite or some other type of lightweight & non-combustible insulation were used instead, the resulting structure would not be as top-heavy, have greater insulating effects and less heat transfer to the outer shell, which would lessen the risk of burns to the user.
...or wth a filler at the top, and a tap at the bottom, you could boil water with it!!

See Kelly Kettles for details

http://kellykettle.com/
bricobart2 years ago
I like it, sooner or later I'll make one too!
rimar20002 years ago
Very good work!

Reading your intro I understant why my stove "roars".
buirv2 years ago
Great Work!!! I like it.