The idea was to build as cheaply as possible a BBQ smoker. I wanted something that I could do a whole hog on or just cook some weekend goodies. I also wanted something unique, different, conversation piece, but functional. My material hunt started with finding a tank to make the cooker out of. It didn't take long and I found one. The next step was to build a firebox to heat this tank. I soon discovered steel prices were approaching gold prices :-) Plan B was now in effect. I had to find another tank to make a firebox out of. After several weeks I found one for sale and bought it for about 1/10 the cost of steel to build one. Once I got it home and started looking at what I had I came up with an idea. I would mount one horizontal and one vertical. Part of the vertical would be the firebox and part would be a vertical cooker. So, now I had both the cook chamber and a firebox for far less than buying new steel and I recycled. The only thing left to do was to start building it.
Here I am about to start sampling some goodies off the smoker.
First a safety warning. I used old propane tanks for my cook chamber and firebox. Propane is VERY dangerous. You should seek a professional to render the tank safe for construction. Do not attempt this yourself.
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Step 1: Door Cut Outs
After you get your tank back from the professional who rendered it safe, you should mark and cut out your doors. Measure around the tank and divide by 4 to get the dimension for 1/4 of the tank. You will want to mark and cut your doors to be approximately 1/4 th of the tank. This will give you a good opening for your cook racks. Mark the door/doors with a colored Sharpie using a level as required to get a nice straight and level line at top and bottom. I use a fabric tape for drawing the vertical lines for the door as it will wrap around the curvature of the tank.
The door/doors design is a personal choice. Mark and cut whatever you feel will work best for you. I elected to make two larger doors with the little door in the middle (shown cut out in this pic) so that my cook racks could be one piece, slide out, and I would have room to place a whole hog in it without fighting to wiggle it in and around a center piece.
A word of warning here. Don't be surprised if when you cut the tank things warp a bit. This is normal and not your fault. There are ways of correcting this that I won't go into now.
Once you have your doors marked you can cut them out with and acetylene torch, plasma cutter, hand grinder with cut-off wheels, or a sawzall with metal cutting blades. I have also known people to cut them out with a circular saw with a metal cutting blade. I prefer to cut with a some sort of saw as the gap is less in the cut and I don't cut a very straight line with a torch and can't afford a plasma cutter.
Another tip is to not completely cut out your door. Leave some materiel in the corners and middle of the top and bottom of the doors to keep the tank in alignment for as long as possible. You will go back and make the final cut outs later.
Step 2: Stand or Mount
Now that you have your basic outline of the doors and have made a majority of the cuts it is time to think about a heavy duty stand for the smoker or a trailer. I selected a trailer as I knew this would be a very heavy unit to try to wheel around by hand. If you elect to cut these tanks down and make a smaller back porch smoker, you may very well get away with a stand with some small wheels to move it.
I purchased a used trailer to mount it on as it was cheaper to buy a used unit rather than buy the material to build one.
Step 3: Mount on Trailer
This step is very critical. Make sure you build a very heavy duty stand to hold this thing. Every step from here on will add more and more weight to the smoker. Also think about the load carrying capability of the selected trailer before buying or building one.
Here my stand is made from 1/4 inch 3 1/2 inch angle iron. Not shown in this picture is the additional frame supports I welded under the decking of this trailer to bolt the smoker to. Make sure you have it bolted down well when moving it.
The trailer mount serves two purposes. It makes the smoker portable and it allows me to use the jack in the front to level out the smoker depending on the terrain I have it set up on.
Plan out your mount. Here I knew I would have a firebox on the back and the additional weight would cause the front of the trailer to be light so I moved the tank further forward. If you don't get this right, you can always put screw down jacks on the back of the trailer to prevent tilting when you step up on it.
I have offset the tank to the side of the trailer to allow me room to work from the side of the smoker. If you mount it in the center of the trailer you likely won't be able to stand on the trailer with it.
Step 4: Door Hinges
Now it is time to put hinges on the door/doors. Remember you have not cut out the doors completely at this point right? I used weld on heavy duty hinges but you can fabricate a nice heavy hinge from round pipe and solid rod of the correct size to slide inside the pipe.
Obtain and weld on your hinges before making the final cutouts on your doors. Once the hinges are in place you can make the final cuts on the doors. This will keep the doors in alignment.
Step 5: Install Door Seals
I removed the tank from the trailer to make it easier for me to get close to my welder but this could be done on the trailer.
What you want to do here is get some flat steel to weld inside the door openings. The flat stock doesn't have to be very thick but wide enough to weld on and have about half the flat overlap the opening. I used 1 1/2 inch flat stock.
Cut and bend the pieces to conform to the inside of the door openings in the tank. I use several clamps or vice grips on each piece to hold it in place while I spot-weld it. Place half of the flat stock width in the tank allowing the other half of the width to overlap the opening. This will not only help seal the opening to prevent too much heat/smoke from escaping but it will act as a door stop also. Line all sides of the door openings with this.
Some builders elect to place the flat stock on the outside of their doors. This is a builders choice. I prefer inside as I think it makes a better seal. You can put flat on the outside for looks if required.
Step 6: Marry Tanks
Connecting the two tanks together starts here. Since I was about to connect a round tank to a round end and I didn't know how to make a pattern, I decided to trial and error it starting with a much smaller opening than I knew I would need.
Here I have the horizontal tank back on the trailer and I am cutting the end out in preparation of connecting the vertical round tank to it.
You can make a pattern from the side of the vertical tank but if it were me and it was, I would make it small on the conservative side. You can always make it bigger and you need the extra to adjust the fit anyway.
Step 7: Vertical to Horizontal Connection
In the previous step I had made a rough cut opening in the horizontal tank in which to inlay the vertical tank. Here you need to strap the two tanks together and start cutting out material until you get vertical tank inset 6 or so inches in the end of the horizontal tank.
Work slowly taking a little material out (1/4 inch) from both sides to keep the vertical tank centered in the horizontal tank. Once you have worked the two tanks together make a final check to make sure the vertical tank is sitting plumb by checking with a level. Some minor material removal may be required to obtain a good plumb.
Once you have the two tanks married and strapped together, now would be a good time mark the opening required from the vertical to the horizontal tank. This opening will end up being adjustable and is used to allow the heat/smoke to come in the horizontal tank. There is a picture a couple steps later showing this opening but lean in the horizontal tank and mark the vertical now so you make sure you don't cut too much out of the vertical. Mark your limits.
REMEMBER, there will be a plenum in the bottom of the horizontal tank so don't cut or even mark the vertical tank opening any higher than where this plenum will rest. In this case my plenum is about 6 inches above the bottom of the horizontal tank. I recommend at least six inches for the plenum.
Step 8: Final Fit
Here you can see the vertical tank fitted to the horizontal tank. It has not been welded together yet as there is still some work to be done that is much easier done prior to connecting the two tanks.
Step 9: Cook Shelf Supports
This is a view of the end of the horizontal tank with the angle iron in-place to support the cooking shelves.
I placed the lower shelf supports just below the opening of the front door to give me just a bit more space between the cooking shelves.
Place a level at or just below the opening of the front door and mark the level point on the backside of the tank. Run a horizontal line across the front of the tank (inside)for the front support for the bottom shelf. Level to the back and draw a line across the back. These lines can now be used to tack angle iron rack supports.
Place the angle up so that the shelves will not be able to slide around once installed.
Now measure from this lower rack frame to the top center of the tank and build a second rack support system half way between the top of the tank and lower rack supports.
If you do drop the first shelf below the opening in the door, you should make this shelf (3/4 inch angle iron and expanded metal) in two pieces for easy removal. Measure the length of the support rails and make the total length of the two shelves 1 inch shorter.
Your rack supports should be complete now. One final step here, you need to put in two support rails now to support the plenum plate that will route the heat/smoke to the opposite end of the horizontal tank. This plenum is what makes this smoker a "reverse flow". Reverse flow smokers route the heat/smoke under the cook area and down to the far end before allowing the heat/smoke to be drafted back across the cooking surfaces and out the stack. This design is supposed to make for more even cooking temperatures in the cook chamber.
Step 10: Vertical Tank Opening
If you followed the steps previously you should have marked and cut an opening in the vertical tank to allow heat/smoke into the horizontal. This picture represents that cut and opening.
Note, how close I have the bottom of the opening cut to the bottom of the horizontal tank. It is almost even. Well, DON'T do that. Make the open at least 1/4 inch above the bottom of the horizontal tank or the damper (door) will drag.
Step 11: Damper
Now is the time to build your damper between the horizontal and vertical tank. In this picture you can see I used the cutout piece to make an adjustable damper. This damper should be cut into the side of the vertical tank from your marks outlined in the previous steps.
Cut and weld some 1 1/2 flat stock perpendicular to the tank as pictured here. These pieces will need to be tacked on about mid way down the opening on each side. DON'T weld them on just a little tack weld as you will have to fiddle (southern term) with them a bit to make sure you get the whole tings to swing freely. You will need to cut or drill holes in these to be able to run a piece of round pipe or rod through i them from side to side. These holes will need to allow this pipe/rod to just touch the front center of the damper plate/door. Just tack the damper in the center to the rod at this point.
Now that you have this mocked up you will need to test to make sure things swing/open/close properly. Once the vertical tank is connected permanently to the horizontal this rod will need to be placed through the outside of the horizontal tank and back into the prefabbed flat plates and then welded to the damper plate. This is why to this point we have only tacked stuff together.
Step 12: Vertical Tank Prep
Now is a good time to do most of the work on the vertical tank before it is permanently connected to the horizontal tank.
Since the vertical tank will also be used as the firebox you will need to fabricate a plate (in this case round) that will partition off part of the vertical tank for the firebox. For a cooker this size you will need at least a firebox 2ft x 2ft x 2ft. I elected to make this one 2 x 2 x 30 inches. This divider plate will be welded inside the vertical tank just about one half inch above the opening previously cut for the damper opening. I would recommend a cardboard mock up of this round plate to make cutting and fitting easier.
With the divider plate cut out and cooling go ahead and mark the doors in the vertical tank like we did in the horizontal tank. Mark them, cut them all but a bit in the corners and centers, weld on hinges and complete the cuts. Now is also a good time to install the seals (flat plate) in the vertical door openings. This seal is not required for the door on the firebox.
You can see the flat partition plate welded in here that separates the firebox (bottom) from the cook chamber (top). This can be kind of hard to fit the round plate in the round tank if not perfectly round. I spent a bit of time with a marker marking the high spots and pulling the plate to grind it down. Be patient.
Step 13: Vertical Cook Racks
While the vertical tank is still easily accessed, lets build the cook a fire racks.
You will need at least a quarter inch round stock to make the outside bands. I prefer cold rolled round stock as it holds its shape better while bending. Attach one end of the round stock to something stable (work table) and bend into a circle. This circle needs to sized to fit inside the round tanks. Since my tanks were 24 inches in diameter I made my frames 23 inches in diameter. Make as many of these as you have planned for plus one for the firebox.
You should now have your circle frames made for the vertical cook racks and one for the firebox. Layout a piece of expanded metal on the ground and then lay the rings on top. Mark around the rings with a silver Sharpie. Now cut out these patterns with a hand held grinder with a cut-off wheel installed. Once cut out tack weld the expanded metal to the rings and grind off any protrusions to prevent injury. Your rings are done or you can cut some more round stock and install on the underside of the rings for more support.
At this point you need to decide where in the vertical unit you want your cook racks and firebox rack. Mark these levels inside the chamber in at least four places of about equal distance around the inside of the tank (quarters). Use a level to make sure your marks are level around the inside. Now, you will need to weld some rod stock on to these marks. These will need to be long enough to hold the racks but not too long as to prevent you from turning the cook racks up at an angle for removal. I found the rods on the above rack interfered with turning the rack below for removal and had to shorten them.
For the firebox rack you will need to mount it approximately 8 inches above the bottom of the vertical tank. This will allow a place for the ashes to be caught and allow for a side air let to be cut in the side of the tank below the fire grate.
Step 14: Firebox Air Inlet
For a fire to burn properly it needs oxygen. Here we make a simple adjustable air inlet in the side of the tank. You should try to keep the top of this inlet below the firebox grate.
Mark and cut out a rectangular piece using the hand grinder with cut off wheel. Then weld a couple small pieces of angle iron vertically on each end of the opening as in the picture. I welded a couple pieces of half inch flat on the cut out piece so that it would fill the entire area and it gave a good mechanism to use as slides inside the angle iron.
Next drill a hole through the cutout piece near the top and weld a nut over this hole. You can then use a piece of threaded rod or just a bolt to screw through the cutout piece and against the tank to hold it in position.
As you can see in the picture I also welded a piece of quarter inch round on the bottom of the opening for the cutout to rest on when closed.
Step 15: Stacks
Now we need to add the stacks (chimneys). The stacks will basically be the exhaust system. In order to get and keep a nice fire burning we need to create a means of letting the old burnt air so to speak out and the fresh in.
There are various rules of thumb for how long and what diameter stacks are needed. My rule of thumb is, bigger is better. My logic is, I can always choke it down but can't always open it up. When I built this one I did a lot of research and got input from guys that have been building these things for years and know what they need.
Given these are 120 gallon tanks, I calculated I needed a five inch diameter pipe and it needed to be 44 inches in length. So, given these numbers you could adjust up or down based on the size of your tanks.
Cut out a hole in each tank to fit the 5 inch diameter pipe into. As we discussed before this is a reverse flow on the horizontal tank so we want the outlet stack to be on the same end as the firebox. For the vertical chamber the stack can basically be placed any where in it. I elected to make it on the opposite side of the heat/smoke inlet.
The bottom of the stack should extend in to the tank approximately centered between the cooking shelves. See picture. This picture can be referred to for other assistance also if I leave anything out or I was not clear on something.
Step 16: Burnout and Seasoning
Now we need to burnout and season the tank. To burn out this setup I placed wood in the horizontal cook chamber and the firebox and lit her off and let her roar. This was done after a good wire brushing and the tanks were washed out with high-pressure water. A good hot fire at this point should take care of any contaminants remaining.
Let this burn down and out and then wash out with high-pressure water again. Once dry we want to wipe down the inside of everything with vegetable oil and a rag. This is what I use. Many builders use any kind of spray on oils such as Pam.
So get in there and wipe or spray everything down. Put it on heavy. Light a large fire in the firebox and bring the temperatures up to 350 or so. Temperature gauges can be installed in the cook chamber door or a digital temperature probe can be used. It mounting temperature gauges in the doors, try to get them centered vertically in the cooking area so you will monitor actual temps at the cooking level where the meats are at. For this purpose, hotter is better.
Let it burn out and cool. Once cooled enough to touch get in there and wipe it down again. Light a fire in the firebox again and repeat. Once this second burn is done the smoker should be seasoned and only require an occasional touch up on any dry spots inside.
Step 17: Lets Cook
Now it is time to cook. There is a plethora of information on the web pertaining to smoking meats. There are some really nice forums and I haven't met anyone on these forums not willing to help anyone from the beginner to the competitive cooker.
There is information on building smokers and cooking on them. For me to try to lay this out step by step would require a book. Oh, there are many books available on the subject also.
The basic design here can be applied to many sizes and shaped tanks. Your imagination is the only limiting factor.
One more thing I want to mention. The more you cook on your smoker the better you will get as a cook and the better you will get at operating it. You will learn a little about it each time you cook.
Does it cook? See below.
Step 18: Done
Now you can dress her up with some nice heat resistant paint, some handles and whatever you can think of. You can see the round gauges I mounted in both the horizontal and the vertical cookers. These are regular BBQ thermometers and have half inch iron pipe threads. Just cut or drill a hole big enough for the probe to go in, get a half inch black iron coupling, cut it in half and weld it to the hole you drilled. then you can just screw in the gauges. Cutting the coupling in half will make two adapters for the gauges. This makes it much easier to monitor your internal temperatures.
Remember, low and slow. Low temps (200-250) slow cook (4-10)hours) = Good eats!
I have affectionately named my smoker The Wild Pig.
Runner Up in the
Low & Slow BBQ Contest