Offset Smoker Build

frieed

Jeepless in Draper
Supporting Member
Location
Draper, UT
I've wanted to build an offset smoker for years but never got around to it.
With the recent addition of pellet smoker I was assuming that I'd never want an offset smoker again. I was wrong.
There is one single thing about a pellet grill that I despise and that is the noise they make.
Cooking is probably my favorite hobby and I really enjoy hanging around outside while the food is on. It's kind of my happy place.

The noise from the pellet grill just ruins that.

So I guess it's time to finally build a smoker...

I started with an 80 gal propane tank I scored on KSL for a mere $20 and a 26 gal air tank courtesy of @Kevin B.
The propane tank had been stored for years with the vent open and I was able to unscrew a fill port to fill it with water and about a quart of cleaning ammonia in hopes that it would tone down any odorant left in the tank. It worked surprisingly well.

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With the contents flushed, I cut out the bungs and cut the tank in half with the plasma cutter with plans to have enough material to make two smokers.

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After some pondering about the size and the looks of the tank with one domed end and one flat end I decided go with a larger smoker. To do that I spliced the dome end of the half with the holes (to the top edge of the hole second from the top above), to the other side and patched the one hole in the side.

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Now came the nasty part. I decided to strip the paint off. Mistake, big mistake. I should have just hit it with a wire wheel and called it done or maybe slap some paint on it, but no, I had to slather it up with paint stripper. I started with citrastrip and thought I was being clever by wrapping it with plastic wrap to keep the stripper wet longer. Mistake, big mistake. All the plastic became one with the tank. grrrr. Wire wheeled it again, slathered on a more betterer kind of stripper (nasty smelling stuff) and after 2 coats you get the nastyness below. ( why can't I just have some good old MEK )

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I finally got it done by stripper, grinder, wire wheel, and cursing. Time for the fun part.
Full size layout for the legs is the easiest way. Used a left over piece of the tank to draw the circle.
Legs will be 1-1/4" square tube.

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Here's my setup to do 45* miters in the cold saw. I leave the saw set for 90* and clamp my 45* square to it.
I then clamp the work to the square and don't use the saw's clamp.


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When welding up the legs I just clamp the pieces onto the cardboard, make sure it all lines up, then tack it together.
Here is todays result, a mobile smoke bomb...

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coming soon will be the firebox, door, cooking grate, and chimney

Oh, and todays fun PSA, don't weld above the trash can full of rags that you used with acetone to wipe the grease off the tubing. :rofl:
I got a large "Whooomp" and a warm rush of air, but nothing left burning.
 
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UNSTUCK

But stuck more often.
I never thought of my pellet smoker as loud. Either the camp chef or the Traeger. Just a small hum of the auger motor now and then.
 

frieed

Jeepless in Draper
Supporting Member
Location
Draper, UT
Pretty sure the level of noise from the pellet grill is due to the fact that it is contained by 5 walls...
Awesome for cooking in the middle of a snow storm, but the fan from the grill echos off every wall.

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Got the firebox stripped and extended today and then set up next to the cook chamber to get the mating area marked out

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Got the firebox in position and marked it out with soapstone..

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and the new hole..

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Now to work on the end cap for the firebox. the top vents into the smoke chamber. I didn't cut all the way to the bottom of the smoke chamber to keep the grease from running back into the firebox..

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frieed

Jeepless in Draper
Supporting Member
Location
Draper, UT
Very cool project. I can't wait to help you test it out!;)😚

What are the plans for a finish?
finish will be high-temp flat black paint.
I should have started this a month sooner.. I have a 15lb brisket and 3 racks of pork ribs on the pellet smoker today. (ok, so the ribs aren't on yet, but soon)
I spent 3 hours yesterday cleaning up the garage. So much grinding dust on the floor it was getting unsafe to walk :(
 

frieed

Jeepless in Draper
Supporting Member
Location
Draper, UT
was out of town for the weekend so not much progress. I realized my plasma skills cutting circles really suck so I made a circle guide.
(Hypertherm sells one for $208 :eek:)
I was fortunate that I had some tube with an inside diameter that fits the barrel of my plasma cutter (1"). I cut off a chunk and welded a threaded stud to it.
Add a couple of flat washers and a really thick flat washer as a wheel. Add some 3/8" all thread and some couplers.


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The pivot is a 3/8 coupler with through holes drilled and tapped for 10-32 screws. With the 3/8 x 16 threaded rod and a single pivot pin, a full turn of the coupler moves the pivot 1/16". Since it's a radius, the diameter changes by 1/8 but that's not close enough, so I drilled and tapped 6 positions on the pivot nut so I can get 1/48" resolution which is more than good enough.

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frieed

Jeepless in Draper
Supporting Member
Location
Draper, UT
I wanted to correct the out of round freehand cutting I did on the end plate for the firebox but needed to find the center for the circle jig guide pin.
To do this, grab a framing square and lay it on the circle with the corner touching the edge. Mark where the sides cross the edge of the circle.

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a line drawn through those two points will also go through the center point

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move the corner and repeat
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where the lines cross is the center point

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In practice I use a fine scribe to get the lines more accurate, but they didn't show on camera so I used a fat silver marker...
 
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frieed

Jeepless in Draper
Supporting Member
Location
Draper, UT
worked on the firebox today. I resized the plate above to fit better then separated the rounded end from the firebox barrel.
I'm making the entire rounded end the firebox door. Once you cut the end off barrel becomes easily deformed so a cut 1" rings to weld into the barrel and the door/end to help them hold their shape

Circle cutting jig works nicely.

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Ring where it will be installed in the barrel which makes a large mating surface for the door.

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Barrel and door showing the rings

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And with door and barrel mated together

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And this is why you should always drain the water out of your compressor tank. The metal is getting thinner due to rust.
I don't know why they can't spray some form of plastic coating in these things.

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tomorrow I'd like to install a damper in place of the hole in the door, fab some hinges and attach the door, then mount the firebox to the main body.
 

frieed

Jeepless in Draper
Supporting Member
Location
Draper, UT
It took longer to sort out the hinges than I thought it would, but I did get them done and the door is mounted.
I also got the firebox damper done as well.

I wanted the hinges separated by a pretty good distance to resist being torqued when the door is open so I went with about 8" separation.
I wanted to use a 3/8 bolt since it would fit inside the piece of 1/2" tube I had but I couldn't find one 8" long so I opted for a piece of mild steel
round bar and I would thread the ends.

Today I discovered that cold rolled round bar can be work hardened. I trashed two portaband blades before this dawned on me.
In the end cut it with a zip disk and then fired up the oxy-acetylene torch, heated the bar to bright red, and then shoved it in a pile of ashes to cool slowly and anneal.

Hinges on and door attached.

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The hole in the door gets enlarged to accept the damper assembly.

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Ready to weld in the fixed plate of the damper

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and the final assembly

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all that's left is to add some form of latch, add the other end plate, and attach to the body of the smoker.
It should become an assembled unit next weekend.

Thanks for looking.
 
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frieed

Jeepless in Draper
Supporting Member
Location
Draper, UT
The acetylene torch got put to use today making hinges and bending bar for handles.
Cut the main opening and added flat bar to cover the joint.

90* bend in 9/16 round bar to make a hinge.

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First cut the top of the door and part way down the sides. Added the top door edge banding and then welded tubes to the body to house the hinge. To keep the hinge moving smoothly, I used a single long piece of 9/16 round bar to align them while I welded them on. Then with the hinge in the tube, bend the hinge to provide clearance for the door edge treatment.

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Door stops added to limit how far back it goes.

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1/2" round bar bent to hold another coil and make the handle

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frieed

Jeepless in Draper
Supporting Member
Location
Draper, UT
This is awesome
Thanks. It has turned out to be far more work grinding than I anticipated

I got the grease drain and the cooking rack supports in this morning then spent about 2 hours cleaning up...

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This afternoon I got the cooking grates framed up and fabbed.

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If I slide them to opposite ends of the smoker there is a 6" gap between them so I may pick up some more 3/4" tube and make a skinny grate at some time in the future. These were sized to use the expanded metal that I had on hand (and I can fit them into my gas grill for cleaning)

I'm going out of town next weekend but the following weekend I should be able to get the collector and smokestack done.
 

frieed

Jeepless in Draper
Supporting Member
Location
Draper, UT
Since this is an experiment I decided to put a chimney at each end and make tuning plates that would allow me to use with normal or reverse flow.
First off is a baffle to direct the firebox gasses lower in the main chamber.

The firebox outlet

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I made a cardboard template using lots of cut, fit, repeat.

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A bit of time with the plasma a a bit of grinding and here it is installed.

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Then I cut baffle/tuning plates to cover the bottom of the smoker.
With all of them in place the smoke travels to the left end before it gets to the food and doubles back to the right end.
This is known as a reverse flow smoker and is supposed to greatly help getting the temps even across the width of the smoker.
I'm thinking the ledge on the right might be a good place for a water pan

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Next I cut the 7'x4.5" chimney pipe in half and set up the chop saw for 11.25* to cut the pie cuts for the chimney elbows.
Mark a center line on the pipe with the help of a piece of C-channel

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Use a piece of paper to determine the circumference of the pipe, find the half way point, and make a mark down the other side of the pipe. This will help line up the pie cuts when I weld them back together

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Smokestack with completed elbow.

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Smoker with the two stacks

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Left for tomorrow: install thermometer, damper caps for the smokestacks, paint, spray interior with PAM spray, then fire it up....
I also want to line the firebox with about an inch of vermiculite concrete to help prevent burn through.

Crazy thing looks like it should roll coal :rofl:
 
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