120 Gallon Propane Tank Build

[Gunman9]

Hey yall,

I decided to build my own smoker and save the $$$$. I am going to a propane supplier tomorrow to get a 120 gallon tank. They have tanks up to 330 but that may be a little to big lol. I have seen some other build 120 tanks on here and was wondering what size firebox you went with? I'm undecided if I should use a smaller tank as the firebox or build one. I'm just doing a plane Jane offset. I also seen prefab vents on eBay for sale and hinges. What size vents on the firebox do I need and how many if anyone knows by chance. Will post picks tomorrow when I get the tank.

 

[dwfisk]

I build my own rectangular fireboxes but after reading Franklin's book, the round firebox sounds pretty interesting. Either way, run your tank dimensions through the Feldon Calculator and upsize a little.

http://www.feldoncentral.com/bbqcalculator.html

For a start, my personal cooker is a little less than 150 gallons and m firebox is about a 24 inch cube.

 

[Gunman9]

This will be my 2nd build.... My first one was done with barrels and I couldn't get the temp past 250 on it.... So I scrapped it and am starting over. I think my air intake and chimney weren't the right size to produce the air flow I needed. I did the calculations and it says my firebox needs to be 11550 cubic inches. Not sure what that computes to if I wanted to use a small tank as my firebox. Any idea? Also can't figure out the air intake size. They sell 8" and 6" dampers on eBay and I was just planning on using them but not sure what size and how many ill need. I'm guessing my chimney needs to be 4-6 inch in diameter.

 

[Gunman9]

Nvm it's a 50 gallon tank

 

[JohnnyB]

I made mine with a 120 gal tank. The formula calls for a 21" cube for the firebox. My vent is 7"x4" and it is plenty. Actually the issue is with keeping the fire SMALL enough without going out. It's crazy efficient, doesn't take very much wood to keep it going. Search my posts for my "Time To Brag" thread. I can take more pics if you like, to give you some ideas. Let me know.

 

[Gunman9]

I made mine with a 120 gal tank. The formula calls for a 21" cube for the firebox. My vent is 7"x4" and it is plenty. Actually the issue is with keeping the fire SMALL enough without going out. It's crazy efficient, doesn't take very much wood to keep it going. Search my posts for my "Time To Brag" thread. I can take more pics if you like, to give you some ideas. Let me know.

Thanks for the info man. I'll just go with the 6" damper then. How large is your firebox opening into your chamber and your chimney diameter?

 

[JohnnyB]

My firebox to chamber opening is a 14" half moon, plus a little extra because I used a 7" grinder to do the curve, haha. The chimney diameter is 4" I.D. It called for a little over 39" in length (elbow is included in that length), but mine is 42" and draws great. That may be why it gets so hot, the draw may be a little much.

 

[Gunman9]

Ok cool. I'm gonna pick a tank out tomorrow. I may step up to a 150 or 250 tank. Depends what I see when I get there. How much did it run to build the firebox?

 

[JohnnyB]

Here is a pic of mine. You can see what I did for the air inlet to the firebox. Easy to do, made it outta scrap I had leftover.

 

[Gunman9]

Here is a pic of mine. You can see what I did for the air inlet to the firebox. Easy to do, made it outta scrap I had leftover.

Nice. Yall I think I'll do the same with mine. I know the tanks the have are the long ones which I hope don't make a difference in the build

 

[JohnnyB]

I just ordered the steel to do the next one, and for 5 pieces of 21" square, and the 25"x38" baffle/top of the firebox, it was under $150. But that's all cut to size. You can get a 4'x8'x1/4" sheet for $200 give or take a few. The longer tanks are the horizontal, mine is a vertical. No difference in the build, same size internally, 120 gal is 120 gal whether it's fat and short or long and skinny.

 

[Gunman9]

I just ordered the steel to do the next one, and for 5 pieces of 21" square, and the baffle/top of the firebox, it was under $150. But that's all cut to size. You can get a 4'x8'x1/4" sheet for $200 give or take a few.

Where do you order that from? Online?

 

[JohnnyB]

Local place by me. Free delivery on orders over $300. It's easy to hit that when you order whole lengths and save for the next project.

 

[JohnnyB]

I edited a comment of mine a couple comments up, talking about the firebox pieces. Not sure if you saw it. When it comes to longer tanks vs. fatter tanks, they're the same when it comes to the build.

 

[Gunman9]

Ya I seen that. Guess I need to call around. I did find 3/4 #9 flat in a 4x8 sheet for $85... Is that to pricey? Did you paint yours with rustoleum?

 

[JohnnyB]

I paid $79 for my expanded, seems about right. I did mine with 1200* Rustoleum. Never had any issues with it before.