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Let the games begin! - 150gal Offset Build

MeatPopsicle

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Joined May 27, 2020
Started my first offset smoker project this week. It'll have a 150gal cook chamber (85in long - 24in diameter = 35,371cu in), a 26in X 24in X 26in semi insulated firebox (16,224cu in), and planning on having a 6in diameter/40in tall smoke stack (1,131cu in). Learning how to weld/fabricate on this project, so there's a boat-load of trial and (mostly) error. Weld distortion....

So far this week:
- Frame cut and welded (1/8in thick - 2in square tubing)
- Casters mounted to 1/4" plate
- Tank marked up for cuts

Thoughts and advice welcomed!
 

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SmokinAl

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Looks like a great project, especially in this lockdown!
I wish I had the space & tools for a build like that!
Al
 

MeatPopsicle

Newbie
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Joined May 27, 2020
Update #1:
Finished last week getting the frame fully welded up and casters mounted/welded. The plan this week is to start building the firebox and hopefully start cutting the tank.

- I'm still going back and forth on the semi-insulated firebox. The idea would be to insulate the front face, back face, and bottom. I'd leave the top un-insulated so I could preheat wood, or even use it as a flat-top grill. Just not sure the extra cost is going to be worth it (It'd be a $100 difference and probably an extra day of welding). That being said, the added efficiency and heat stability might be nice.

- I'm slightly nervous about cutting into the tank, although I've taken nearly every step to ensure there is no LP or fumes left in the tank. I completely purged the tank, filled it with Dawn soap and water and left it soaking for 2 weeks, cycled the water in the tank 3 times, emptied the tank, have had it sitting upside down for the last month, and have hooked up a leaf blower to one of the ports and cycled air through it. When I do cut the tank, my plan is to dump a bunch of dry ice in the tank to displace any oxygen with CO2.
 

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MeatPopsicle

Newbie
6
4
Joined May 27, 2020
Update #2:
Spent the week researching and trying not to blow myself up while cutting into the tank. I ended up going to a local welding shop and getting a 20# bottle of CO2. My tank is around 35,371cu in, which is about 20.5cu ft. A 20# bottle of CO2 has around 175cu ft (8.75cu ft per #), so there was no question of displacing all the air in the tank. I dawned my finest angle grinder and went to work. 3 hours and a fair amount of tendonitis later, voila! Going to looking into using a plasma cutter for the doors and smoke catch/chimney.

Steel plate, DOM tubing, and round bar coming Monday, so hopefully this week will bring progress on the firebox.
 

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MeatPopsicle

Newbie
6
4
Joined May 27, 2020
Update #3. I've been procrastinating posting, hence the photo dump.

- I decided to build an internal frame to support the firebox. The internal skin is 1/4" plate with 1" ceramic fire-blanket in between and 1/8" plate on the outside. The internal frame is 1"x1" square tubing. When all was said and done, I think the firebox weighed in the neighborhood of 400+lbs!

- I made the hinges with a small forge, which was a learning experience to say the least.. Sacrificed the hair on my right arm and damn near lost an eyebrow lighting it the first time!

- Got the firebox mounted and welded to the frame next, then moved on getting the tank mocked up. There was about 3/4" gap between the tank and the firebox cutout, which was a learning experience. Finally got the tank mounted on the legs and got the initial cuts done on the doors.

- Next up is finishing the doors, and building the smokestack/catch. The adventure continues!
 

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