Rocket Grill!

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Picture of Rocket Grill!
Want a D.I.Y. way to cook food WITHOUT using fossil fuel L.P. or having to buy charcoal? I know I did. That's why I built a "Rocket Grill"!
This is just one variation of a "rocket stove" - a simple appropriate technology for cleanly burning bio-fuels.

The rocket grill is fired by twigs, wood scraps, wood chips, or nearly anything else you can put in it. It naturally drafts air to maximize combustion. Once the the grill is really going, NO smoke comes out the top, only heat, and the grill really does sound like a rocket!

The grill is designed to not only grill, but also boil, bake, braise, and roast!

Because of the simple design and robust construction, it is nearly maintenance free. Unlike an LP grill, the burner will never burn and rust away to nothingness. (And cost good time and money to replace.) There is no piezo-electric starter or other "modern" technology in the grill, which would be prone to failure.

Despite how it looks, the grill is small and light enough for one grown man to lift into the back of a pickup truck. That way, it can travel with for camping or tailgating. (The lid and side tables are also removable for storage and easy packing.) Because it's covered and enclosed, it also qualifies for use as a "backyard fire-pit" in areas that do not allow open fires.

This project is mostly simple metal work. While it does require welding, it's pretty straight-forward. This was really my first-ever welding project.

So lets' gather together our tools and materials and get started!
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Step 1: Tools and Materials

Picture of Tools and Materials

  • Angle Grinder
  • Grinding disc
  • Cut-off disc
  • Welder
  • Safety glasses, work gloves, welding gloves, Welding helmet, hearing protection
  • Drill and drill bits
  • OPTIONAL: Laser Level, Bubble Level

This project is made mostly from scrap metal, but will need several other parts.

Parts for the Grill itself:
  • A Base. Something for the grill to stand on. Must be heat-proof. I used a scrap steel farm implement disc.
  • Steel Pipe - Diameter of your choice, but will effect cooking size and fuel rate. I used 6.5 inch diameter scrap steel pipe. About 3 feet in length.
  • Steel Water Tank. This becomes the "bowl" top of the grill and cooking surface area.
  • 4 x pieces of small diameter steel pipe, about 6" in length
  • 2 x 90 degree pipe elbows of same diameter
  • 2 x pipe flanges of same diameter
  • 2 x pieces of flat material that you like to make side countertop surfaces
  • Small scraps of steel plate

Parts for the lid of the grill:
  • A piece of wood, species of your choice, sized for a lid handle.
  • 2 x Carriage bolts (about 5" long) with matching nuts and washers. Stainless steel is ideal, as these will be exposed to both heat and the elements. Plain steel is fine, lower cost alternative.
  • 2 x pieces of copper or steel tube or pipe, slightly larger diameter and shorter length than the carriage bolts, to use as spacers.
  • The top end of the water tank.
  • Steel plate, about 6" side by 12" long. Perferations or slotted is ideal.
  • JB Weld
First, gather together your materials for the main section of the rocket grill.
  • Base
  • Large Diameter Pipe
  • Water Tank
The base needs to be large enough to keep the whole grill from tipping over. It also forms the very end bottom of the grill, which hot coals and asses will fall into. Any sort of steel plate would work fine. I found a piece of old farm machinery that fit the bill. It's a domed disc about 16" in diameter.

The large diameter pipe needs to be cut into two sections. Make one about 1 foot, and the other about 20" long. The 20" section will be the "vertical tube", and the 1 ft. section will be the "feeder tube"

That water tank that I chose was 16" in diameter. It was already cut apart from a solar water experiment I worked on. The bottom section of the tank is cut to about 1 foot tall. This becomes the cooking area "bowl" top to the grill. The water tank was also chosen because is is large enough diameter to fit my camping cast iron Dutch Oven, and a stock pot that I use for boiling corn.

Stacked up, the base, vertical tube, and water tank section should come to a comfortable standing height for you. The top of the water tank section is the height that grilling will take place.

To cut the steel, I found that an angle-grinder with a cut-off disc works best. I cuts quickly, without removing to much metal, and makes a nice, straight line. You could also use a reciprocating saw with metal cutting blade, or a plasma-cutter if you have access to one.

To mark a line on a cylindrical object like the pipe or water tank, wrap a straight section of sheet metal around it, and secure with masking or duct tape. Mark this line with a permanent marking pen, then remove the sheet metal.

Cut the pipes and water tank to length, using common-sense safety precautions. (Wear work gloves, eye and hearing protection, etc.)
Cut the top off the water tank, and save to make the lid.

Stack up the base, vertical pipe, and water tank section to get a feel for how your grill will look. If you ware working on a level surface, like a concrete garage floor, you can use a bubble level to make sure your vertical pipe is perfectly straight up and down. (Plumb!)

Step 2: The Special Cut

The most distinct feature of the Rocket Grill is how the feeder pipe and vertical pipe come together.

While the exact angle that they connect at isn't super-important, it should be somewhere between a 90-degree and 45 degree. Having this connection at some angle makes it easier to feed fuel, and not bend over too far. Too steep of an angle will not allow for proper air-flow and can prevent the grill from drafting properly.

Cutting the two pipes to fit together can be geometrically-challenging. An angle-grinder makes straight cuts, but both pipes are rounded. Still, they have to meet together tight enough to get a good weld between them.

What you need to do is imagine how two straight cuts would look projected onto two curved surfaces. One easy way to do this is to use a laser level that has the ability to project a straight line. Several inches up from the end,point the laser at the vertical pipe, at the angle you want the feeder pipe to meet it. Then mark the laser line with your permanent marker. Rotate the laser 90 degrees, and mark the line again.

On the feeder pipe, mark two lines at 90-degrees from each other the same way.

Another way to mark the same cuts is to use sheet metal, which you can wrap around the pipes. It is possible to make a projection of what the cuts should look like, and cut that out of the sheet metal. Then wrap the sheet metal around the pipe and mark it. A friend of mine already had made a sheet metal template, so that's the technique I used.

When you are done, you will have a notch in the vertical pipe, and a "bird's-beak" cut in the feeder pipe.
Fit the two pipes together, and see how close they match up. It's more that likely that you will need to use a grinder to get the parts to fit together well.

Step 3: Welding

Weld together the vertical and feeder pipes.
That's easiest to do with both pipes laying flat and sideways. Weld around one side, then flip it over, and weld the other side.

Next, stand the Y of pipes on top of the base. Make sure it is centered, and that it is plumb and level.
Weld the pipes to the base. (Make sure to always brush down the metal where you will be welding, and where the ground clamp connects.)

The bottom of the water tank needs a hole cut in it, the same diameter as the vertical pipe. Mark that diameter hole on the bottom. One way to do that is just set the other parts right on top of the tank, and trace it.

Then cut the hole in the bottom of the tank. I had a plasma-cutter at a friend's house, so I used that. Otherwise, a cut-off disc, Sawzall, or large diameter hole-saw could work.

Stack the whole grill together upside down and weld the vertical tube to the water tank section. Again, make sure the parts are plumb and level. If there is a "front" to the water tank, make sure it's where you want it to be. On mine, there were two pipe ports that I wanted to be left and right, with the feeder tube on an angle to my right as I faced it.

At this point, the basic grill is done, but we still need the lid and a few other details.

Step 4: Fuel/Air Plate

Picture of Fuel/Air Plate
Another distinct feature of the Rocket Grill is the Fuel/Air plate.

It holds the fuel up and in place, let allows plenty of air to naturally draft into the grill and up through the fuel for a very hot and clean burn.

The plate needs to be able to hold up to high temperatures.

Take some scrap steel plate and cut it to a width just slightly smaller than the diameter of the feeder pipe, and about the same length. This way, the plate sits INSIDE the feeder pipe, and divides it to an upper and lower area.

Fuel goes in ABOVE the plate, and air goes in BELOW the plate.

The plate has holes or slots in it in the far end so that it supports the fuel, but allows plenty of air through. The plate I used was already slotted, but I added a few more for good measure.

You could also use a heavy-duty grate, or weld together re-bar to serve the same purpose.

When you are ready, just slide the plate into the feeder tube. Gravity and friction will hold it in place for you.

Step 5: Building the Lid

Picture of Building the Lid
When I cut the water tank apart, I also cut off the top, and saved it for use as a lid.
It's already the same diameter as the top of the grill, so it should fit perfect.
It really just needs two modifications, a handle, and a way to let air through.

The Handle:
The length and width of the handle is based on the size of the user's hand, preferably with enough room for an oven mitt.

I found a scrap of Oak firewood, about the right diameter for a handle, and left it long to start with. I could always shorten it later.

Drill two holes in the wood, and push the carriage bolts through.

Use these to mark where they should go through on the lid.

Drill two holes in the lid.

Cut two sections of pipe a little shorter than the length of the carriage bolts. These will be spacers to hold the handle the right distance from the lid. I had some scrap copper pipe around, which is easy to cut and looks very nice.

Slide a washer and then the pipe over the carriage bolts, and then the carriage bolts into the holes in the lid. On the bottom side of the lid, attach washers and nuts, and tighten.

Air Spacers
The lid also needs some way for hot air to constantly exit the grill to continue the chimney effect.
You could make a vent, similar to one a Weber brand grill, or even make some sort of chimney right on the lid, but it seemed much easier just to add some small steel tabs. These tabs space the lid away from the grill to allow air flow.

I cut three steel tabs from scrap metal, and welded them evenly around the lid.

On the inside of the grill, I welded in three matching tabs that line up with the ones on the lid. Three tabs makes the lid not wobble.

By simply rotating the lid a little, it can still sit all the way down on the grill (such as when you are done with the grill and want to smother it, or for storage.)

Step 6: Side Tables

What's a grill without some workspace to hold your utensils, your plate of meat, and your favorite beer?

That's why the grill needs side-tables.

The water pressure tank used to make the top of the grill, included pipe connections in the sides. I purchased just a couple short sections of pipe  and elbows so that these could support the side tables.

I threaded in a horizontal pipe into each side, then a 90 degree elbow into that, A vertical pipe section then completes an "L" on either side of the grill.

Both side tables have a pipe flange going to a short piece of pipe SMALLER in diameter than the vertical side pipe. That way, the side table pipe sits INSIDE the vertical pipe. This makes it easy to remove the side tables for travel. Drilling a hole through both pipes allows me to slide a small bolt through, preventing the side table from accidentally rotating.

At first, I wasn't sure what I wanted to use for the top surface of the side tables. I dug through my pile of scrap/salvaged/recycled materials and found an assortment of stone, tile, steel, aluminum, and wood.

I simply set different pieces of materials on top of the side-arm pipes to see what looked good. In the end, I decided on a blue/green slate stone for the left side, and a steel deck place for the right side.

For the steel on the right, I just welded the pipe flange to the bottom of it, threaded in the short section of pipe, and slid that into the slightly larger diameter vertical pipe. A horizontally-drilled hole with a bolt slid through it completed that side.

The slate for the left was a little more work. The slate was rough and pointed, but it is a very soft stone. I experimented and found that RUBBING the edges of the stone with a cold chisel allowed me to shape the stone a bit and smooth the rough edges.

To attach the stone to the side pipe, I found some scrap metal about the right size for the bottom of the stone side table. I welded the pipe flange to the bottom of the metal and then glued that to stone with a tube of "JB WELD" adhesive.

Again, the pipe on the side table just slides into the vertical pipe on the side of the grill.

Step 7: Odds and Ends

Picture of Odds and Ends
Paint Removal:
The water tank section of the grill is painted, and the paint had to be removed before using the grill for cooking.

I thought about what the most "eco-friendly" way to remove all the paint was. I thought about all the nasty chemicals used as paint strippers. In the end, I decided make a very hot test fire to both try out the grill and remove the paint.
The painted easily peeled off.

Pot Bracket:
To hold either the stock pot or Dutch Oven, there still needs to be air space in the bottom of the grill. The easiest answer was just to span the fire tube with two short sections of slotted C-channel. They support the pot, and let plenty of heat and air through. They are not welded in place. I didn't see any reason to, and this way they are removable. 

Heat Diffuser:
One downside of this grill design is that it gets an extreme hot-spot in the middle of the grill, and is much cooler towards the outside edge. That's a bad thing for cooking burgers and sausages. So in put in a "heat-diffuser" when grilling. It's just a small steel plate that I practiced welding on before welding the grill together. It simply sits directly on the pot bracket and works well to spread out the heat. At some point, I may make a more aesthetically-pleasing heat-spreader, but this one works fine for now.

Ash Clean-Out:
You may have noticed that there is no ash clean-out on the grill. In truth, I really haven't seen a design for one that I like. I have seen similar steel rocket stoves that use a threaded pipe port, which seems like it would gunk up the threads easy. Also a large diameter pipe port gets expensive quickly, and I was trying to use as many free, inexpensive, and recycled parts as possible. For now, I just flip the whole grill upside down to empty the ash. It makes far less ash then you might think. In the future, I may use the angle grinder to cut an angle out the bottom back side of the grill, and then hinge it, so that there is a flip-up flap to access and empty the ash.

Grill Grate:
The grate is just a standard round grill grate. It's the medium size. It actually overlaps the top of the grill, which makes it easier to use the entire top. Downside? It's easier to slide a burger right off the top of the grill as well!

Step 8: Fueling and Firing

Picture of Fueling and Firing
One of the best things about the Rocket Grill is how it's fueled.

No longer do I have to purchase fossil-fuels to cook my backyard fare!

Because of the amount of air that flows through the grill, almost any bio-fuel burns great in it. This one is really designed for twigs and sticks.

After every wind-storm, all of my neighbor's trees shed their sticks downwind into my yard. Before, I would grumble at the yard-work of picking up all those sticks and moving them back to the brush pile. Now, I instead gather them up looking forward to burgers, corn-on-the-cob, or whatever I am going to cook up next.

To start the grill, I just put a little bit of tinder (usually a bit of newspaper) and a few twigs onto the far end of the Fuel/Air Plate. I light it with a match or cigarette lighter, and then just feed in a few more twigs. After that, a fair amount of sticks, firewood, or other fuel can be loaded on the top side of the fuel plate.

The fire is very simple to light and starts right up.

Even EXTRA LONG fuel can go right in. Just slide it a little farther in every once in a while. The chimney effect makes all the heat goes up the vertical tube. No smoke or fire comes out the feeder tube.

I am right-handed, so I designed the grill so that the feeder tube comes out on an angle to the right. That way, it is easy for me to fuel, but I don't hit my shin on it.

Since pots sit down INSIDE the grill when boiling, the heat transfer of the fire to the pot is very good. The heat hits not just the bottom of the pot, but travels up the sides as well. This means you get a boil going faster, while using less fuel.

I also used my grill in a rain storm a while back. My concern was rain running down the lid and then inside the grill. It wasn't an issue - any rain hitting the lid simply vaporized or sizzled right off!

Step 9: Grill It Up!

So far, I have used the grill for chicken, burgers, brats and sausages, corn on the cob, shish-ka-bobs, and more.
The design also allows me to boil in the stock pot, or bake in the Dutch Oven. (I'm working on baked desserts now too!)

A friend of mine has designed both a giant skillet and a very nice wok for his
Another possible future modification is to create a high-thermal mass pizza oven top for the grill.

Rocket stoves lend themselves well to infinite variation and re-use of existing materials. Combine that with versatility and efficient use of fuel and you have the cookstove of tomorrow, today.

Remember, this isn't rocket science, just good use of appropriate technology!

I hope you find my Rocket Grill to be inspirational. You too can cook net-carbon-zero deliciousness over open flames and take pride in your own design.

If you have built one, please post a photo in the comments section!
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Dairk Laird4 months ago

Amazing. I've seen done for heat sources and the like but never a grill. I was looking at the heat output and that cherry red glow. It got me to thinking how this could be applied to the furnace design for a smithy forge. No bellows nor powered air supply needed - a smoke free rocket forge!

alanbooth017 months ago

Very cool grill, I'm busy making a "Franken-webber" pizza oven and thought a rocket stove beneath would heat up the oven in no time. I made the rocket portion this morning and fired it up, got it sounding like a rocket in no time.

jshultz57 months ago
Nice job.. I've built small rocket stoves but never thought of doing one this size. I'm glad I saw this because I have lots of stainless pipe in all sizes and I'm gonna start on one this weekend. I'll post pics and I have a few ideas on making it easier to clean. Also I have a great idea on the diffuser..pics coming soon..great job man..thanks for the instructable

Damn, you're lucky, I wish I had some stainless steel lying around. I made mine out of scraps of steel I had lying around, looks a bit like Frankenstein's monster. Works like a beast though.

bennelson (author)  jshultz57 months ago
If you have the material and welding ability to work with stainless steel, your project should turn out GORGEOUS. Many of my projects are either "rat-rod" or "steam-punk", but it's great to see what people can do with different materials and skill levels!
jimbus_com8 months ago

Have you considered cutting and sleeving the vertical tube near the base to ease ash removal? You could leave it as a lift off or put some set screws to secure it, like a Christmas tree base.

Great project!

kelms18 months ago
I like your grill a lot i'm going to make one but I'm going to use high temperature grill
paint just make it look better
bennelson (author)  kelms18 months ago

Let me know how the grill paint works out for you. Please share a photo when you finish!

tpagels9 months ago

I built one a few years back. I've never been able to get it to work though. My buddy who did most of the welding said he had it working but that was before adding the tank to the top. My pipe is a bit smaller and I actually used an old charcoal grill on top. Recently messing with it has come to mind as it's time to make it work or take it to the scrap yard.........

diamondemb1 year ago

I love It! A steam-punk grill!!

Great job.

tnowling1 year ago

Just welded mine together. Still need to finish the lid

bennelson (author)  tnowling1 year ago

I like the base!

It is sweet, very heavy. it won't fall over but makes it a bit of a pain to move. gotta love trash reclaimed from work. This was all made from things that were either being thrown away, or recycled. didn't buy a thing, just cost me some labor and my grandpa made all the welds pretty for me.

thoover672 years ago
Neat. Not sure I understand the process of burning completely. Is wood fed from the top (is there a hole on the inside), or just through the feeder tube?

Does the grill draught through the hole in the bottom (implement disk) & out the feeder tube, or are other vents involved?
bennelson (author)  thoover671 year ago

Both wood AND air come in through the side tube. It is divided in half with a plate. The wood goes inside the side tube on TOP of the divider and air is drafted in through the same tube on the BOTTOM of the divider. The divider has air holes in the end of it for the air to get up through the wood (and the fire.)

Gunther451 year ago

Like the BBQ .Just a thought about Ash Clean up. Attached is something I made to clean out pipe going to my furnace. It is basically just PVC pipe reducers and then a valve with a quick connect to attach to an air line from your compressor. It is attached to the pipe with a coupler with 2 worm drive bands. I am not saying the person cleaning the ash is not going to get dirty but it still would be easier than trying to scoop out ash down that long pipe.

Great JOB !!!!
I will make one soon
yummyribs1 year ago
That's really cool! Excellent the idea of grilling over wood,

Could you just make some holes in the bottom and make the whole input pipe into a fuel holder ? So you could remove the ashes through the air holes, and more fuel would fit in.
bennelson (author)  yummyribs1 year ago
The only thing that I could think of for why NOT to do that is that air-holes through the bottom might be a good place for hot coals to escape through or that perhaps they could easily get clogged with coals or ash.

So far, the divider plate is simple and works well. If anyone makes a variation of this project with the suggestion made by yummyribs, please post a photo and let us all know how it turned out!
wilys wagon2 years ago
can you up load video of you grill in action some ware please
mkrepel2 years ago
Excellent work! I am inspired.

I was curious...what did you do with the rest of the water tank? I thought it would make a good insulated base (fill it with vermiculite) between the grill and the disk. Of course, that would make the thing quite a bit heavier.

Another idea for emptying the ashes would be to use a shop vac...if you have one. Of course, make sure the ashes are cold first!

I am going to start looking for a used water tank.
aroberts253 years ago
this is fantastic. thank you for the inspiration!
SIRJAMES093 years ago
This is just too awesome!!!!!!!
Before reading this, I had never heard of a rocket stove....
This is something that I would like to learn(welding/metal work) so that I could make a similar project.

TY for sharing Sir!! 8)
Sl0whand3 years ago
Thank you very much for your ideas and your taste in expressing yourself through your words and your creations.
Enjoy your cobs!
sethcim3 years ago
Fantastic! Love the simplicity and effectiveness.
Where might I source the thick-walled pipe you used? I've been looking all over but just can't seem to locate 4-5 inch pipe with a thick enough wall. I'd like to build a very-long-life stove for our conservatory.
bennelson (author)  millenniumtree3 years ago
This was salvaged metal that was at a friend's house. I believe it was well casing.
Try looking at a metal salvage yard sometime, they are fun places to visit.

Since this project doesn't require new materials, the costs to build can be kept low.
smpash3 years ago
Hmm i have always wanted to weld

for grilling certain woods are better than others for southern or mexican if possible use mesquite wood for grilling mm
although it might not work because there is little to no smoke to smoke da steak
iFirefly3 years ago
What causes the "rocket sound" you referred to? Is that from the air drawn in from the bottom? If so, that could probably be mitigated by the airflow design.

A note of caution: I have seen many older water tanks of this type that are galvanized, which will emit toxic gases when heated, so try and make sure your materials are not plated; the galvanizing can be removed safely using different methods, but the effort is hardly worth it, since grinding it away also produces toxic airborne particles and acid treatments are hazardous in their own right.

Alternates to water tanks are decommissioned welding gas tanks, which come in either short, wide tanks or the more common thin style (making a smaller grill for a really compact outfit).
So, I would feel more comfortable if someone confirmed this, but I'm pretty sure galvanized steal will have the galvanized part burn off after the first hot temperature. That's why I tend not to worry about the fact things do release toxic gases, because the first time I have a coffee can stove, grocery cart (galvanized steel), etc, I just burn it off in a very hot fire that I shortly step away from after starting up.
Even welding galvanized steel is problematic. It needs to be done in a well ventilated area, with a fan set up to carry welding fumes away from the operator. I'd certainly not use this grill for cooking food until all the the zinc has been burned away.
Yes. It burns off, or is reduced to oxide VERY quickly once heated. Stand well away, "zinc fume fever" is a work-related illness and is reportable !

The risks are mixed, but the simple answer is to not use galvanized material; if you wish to have a comprehensive view of the subject, I just found the following PDF available from a quick Google search for welding galvanized metal:

bennelson (author)  iFirefly3 years ago
There were not galvanized metals here. It was all bare steel, other than the water pressure tank, which was only painted.

The stove makes a pretty cool sound when it's really running full tilt. It's because of how much are naturally drafts through it. I wouldn't change that at all. I really like the way it sounds and how the air and fire travel through it.
heelercjwww3 years ago
Great instructable. This is a really great idea, kills two birds with one stone. I think I will have to make one of my own here soon. Thanks.
Bubbler3 years ago
A great grill. How easy is it too get the ash out of the bottom, and what do you do with the ash once you get it out?

It really is a major rocket stove. LOL
bennelson (author)  Bubbler3 years ago
Originally, the base-plate had a hole it in.

When I would lift up the grill, the ash would fall right out the bottom. It also left nice little burned holes in my lawn! So, I welded that spot shut.

As it is right now, I just turn the grill upside down. It is lighter than it looks (without the side tables and lid) and I just dump it out into a steel bucket.

It doesn't make that much ash. One advantage of using fuel more efficiently is that there's less waste in the end.

I put some of the ash in my compost pile and the rest spread out in my brush pile.

I've played around with the idea of cutting a "door into the bottom-back of the grill base, and hinging it as a place for ash-removal, but really, it's just so easy to tip the grill over to dump it out when I need to.

An ash clean-out would be a nice feature for a larger or more permanently mounted version of this project.
I don't know about the original one, but mine you just lift the stove off the little pile left after the burn. The ash makes a good fertiliser
Absolutely awesome! Love the rustic look, hate buying charcoal and like the various uses.. I've not welded before but have wanted to start...and I want a new grill this year...thanks for the inspiration..I hope to post my own here soon!
Sonoffar3 years ago
What a great build.
I heat my 2 story house with 2 wood stoves and a LOT of wood. For a few months I have been looking at various alternatives to the old wood stoves and your project has FINALLY made it clear to me that builds like your Rocket Grill are the basics of a Rocket Burner that can be simply adapted to a host of heat required applications.Thanks for providing one of those sorely needed, "palm slap to the forehead", moments that has started the ball rolling.
Thanks :0)
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