Fabricating a Heavy-Duty Rocket Stove

316,394

402

42

Posted in WorkshopMetalworking

Introduction: Fabricating a Heavy-Duty Rocket Stove

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.

Metal Challenge

Finalist in the
Metal Challenge

Step 1: 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.

Step 2: Methods of Fabrication and Tools Needed

There are many different methods and materials that could be used to make a rocket stove. The methods detailed in this instruction set have been selected to make a heavy-duty model. This model may also be used as a small forge to melt soft materials such as lead and bronze. In order to make a simpler model, materials like tin containers and tin cans can be cut with simple tin snips and fitted together. Brazing or soldering is a good alternative to welding when working with light tin materials to make a smaller stove.

Common tools used for fabrication of this project are:
    • Grinding/Cutoff Wheel
    • Horizontal Bandsaw
    • Pneumatic Cutoff Tool
    • MIG Welder

Step 3: Cutting the Stove Tank to Size

When selecting an old steel tank, precautions must be made to be sure that the tank is no longer under pressure and that the contents have been completely removed. A multitude of different tanks may be used for this project depending on the desired size of the stove. This rocket stove was made from an old propane tank purchased from a scrap metal yard. Before cutting into the tank, have it completely emptied of all contents and remove the valve from the top to expose the tank to atmospheric pressure. Fill the tank with water and empty it several times to remove any leftover propane fumes and gas. This will ensure that the denser-than-air propane is flushed from the tank. Next, the top of the tank must be cut off just below the top curve in the tank, and a hole must be cut in the lower bottom side of the tank for the feed tube to come through.

Step 4: The Burning Chamber Weldment

The burning chamber of the rocket stove is where hot coals, heat, and flames are contained when the stove is in use. Before welding the plates into place, the hole for the feed tube must be cut because warping may occur after welding. Next, the bottom plate is centered and welded into place at the seam of the burning chamber tube. The top plate is also centered and welded, and has a hole where the stove pipe will be welded later. These plates are cut 0.5in larger than the tube to apply welds. The feed tube must be inserted into the hole in the burning chamber 0.5in and welded into place, but be careful to not cut the feeding tube too long, because later it will have to be fitted through the hole on the side of the stove tank.

Step 5: Making Legs and Carrying Handles

The legs of the stove are usually meant to be short, as to be able to easily look into a pot or pan on top of the stove from a standing position. 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 stove, small lengths of C-channel were used to make a sturdy base. Weld the legs to the tank before going any further; when the tank is full it is very heavy. Another feature that may be added and/or altered on the stove are the carrying handles.

Step 6: Positioning the Burning Chamber

The burning chamber weldment must be positioned a few inches off of the bottom of the tank. In order to seat the burning chamber in the proper place, use some of the sand to pack a level surface 2-3in high to place the burning chamber on. After fitting the feed tube through the side of the tank and centering the burning chamber in the tank, the feed tube can be welded into place.

Step 7: Positioning the Stove Pipe

Use a square to position the stove pipe at a 90 degree angle, and tack weld it on one side. To check the positioning of the stove pipe, place the baseplate on top of the tank and see if the stove pipe clears the baseplate hole. The stove pipe will be easier to weld to the top of the baseplate if it sticks 0.125-0.25in above the baseplate. If it is not close enough to finish welding into place, use the square and a hammer to tap the stove pipe into proper alignment. After matching the stove pipe alignment with the baseplate, finish welding the base of the stove pipe. Next the burning chamber and the stove pipe must be covered and packed with sand all the way to the top of the tank to insulate the burning chamber and stove pipe. The sand should be packed tightly to eliminate air pockets.

Step 8: Fitting and Welding the Baseplate

After filling the entire inside of the tank with sand, put the baseplate into position and weld all the way around the top of the stovepipe. The baseplate must be cut 0.5in larger than the diameter of the tank to get a good weld all the way around the bottom edge of where the baseplate meets the tank wall.  Next, weld the area between the hole in the baseplate and the stovepipe.

Step 9: Installing the Baseplate Burner-Risers

In order for the stove to be able to push hot air and smoke from the stove pipe, risers must be welded to the baseplate to elevate the cooking surface from the stove pipe. A few simple spot welds on each end will firmly hold them in place.

Step 10: Drilling Depressurizing Holes

During the first fire that will be burned in the new rocket stove, moisture trapped in the sand may become pressurized and possibly hazardous. Drill a few small holes a half inch below the weld seam of the baseplate so that the pressure inside of the tank can always adjust to the outside atmosphere.

Step 11: Grinding, Deburring, and Applying Stove Paint

To complete the fabrication on the rocket stove, remove all sharp exposed edges, deburr all surfaces, and surface grind all weld beads. To protect the exposed steel surfaces and weld beads, apply two evenly spread coats of black stove paint. Do not use regular spray paint for this step, or it will bubble and burn during use. High temperature stove paint is required to adequately protect all outer surfaces. Allow 2-3 days of drying time before firing up the stove for the first time.

Share

    Recommendations

    • Spotless Contest

      Spotless Contest
    • Microcontroller Contest

      Microcontroller Contest
    • Space Challenge

      Space Challenge
    user

    We have a be nice policy.
    Please be positive and constructive.

    Tips

    Questions

    42 Comments

    nice innovation

    good luck

    AJMansfield -- who cares what they are called. Pickey, pickey, pickey.. Looks like he used a "Stick" welder in the first place for the risers on top, so that make the wells there, (I hate to say it) TACK WELLS.......... Old Stick Welder

    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.

    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...???

    1 reply

    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!

    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.)

    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

    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.

    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 !

    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!

    1 reply

    I notice a lot of guys using pearlite

    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!!!

    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.

    3 replies

    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.

    I second your question.

    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