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RF air tank build

Johnscrub

Newbie
4
1
Joined Jun 4, 2021
This is my first time trying a reverse flow build. I have acquired an 80 gallon and a 25 gallon air tank. There dimensions are 20 x80 and 14x34.i am looking to use the smaller tank as a firebox. I know it will be slightly undersized. I'm looking for help on dimensions for cutting doors and other holes. I've used the calculator.. This is link to what I've got from it.. If anybody has time to look over it and give me some pointers it would be greatly appreciated.Link to BBQ Pit Calculator
Pics of what I'm working with..
Thanks
 

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LanceR

Smoking Fanatic
OTBS Member
877
161
Joined Jun 1, 2012
Good morning, John

There's a much better calculator than Feldon's right at the top of this forum. As a general rule the firebox wants to be at least 1/3 the volume of the cook chamber and long skinny tanks like yours do better with a bit more than that as the calculator here shows.

I'm not an expert at smoker design so take this with a grain of salt until Dave O or someone else with more experience comes along.

Given a nominal volume of 18,480 cubic inches I suspect your smoker really wants a firebox around 7,000 cubic inches and your smaller tank, at 5,800 cubic inches ,is small enough that I don't think it is going to be satisfactory, especially in rainy, cold or windy conditions when you need more heat than usual.

If you have access to 1/4" steel and the budget for it a 20" cube shaped firebox would give you 8,000 cubic inches and have enough reserve volume to be sure to handle anything you want to cook. As a bonus it will be a lot easier to fit too.

What are you welding it with?

Best regards,
 

Johnscrub

Newbie
4
1
Joined Jun 4, 2021
Good morning, John

There's a much better calculator than Feldon's right at the top of this forum. As a general rule the firebox wants to be at least 1/3 the volume of the cook chamber and long skinny tanks like yours do better with a bit more than that as the calculator here shows.

I'm not an expert at smoker design so take this with a grain of salt until Dave O or someone else with more experience comes along.

Given a nominal volume of 18,480 cubic inches I suspect your smoker really wants a firebox around 7,000 cubic inches and your smaller tank, at 5,800 cubic inches ,is small enough that I don't think it is going to be satisfactory, especially in rainy, cold or windy conditions when you need more heat than usual.

If you have access to 1/4" steel and the budget for it a 20" cube shaped firebox would give you 8,000 cubic inches and have enough reserve volume to be sure to handle anything you want to cook. As a bonus it will be a lot easier to fit too.

What are you welding it with?

Best regards,
Good morning, John

There's a much better calculator than Feldon's right at the top of this forum. As a general rule the firebox wants to be at least 1/3 the volume of the cook chamber and long skinny tanks like yours do better with a bit more than that as the calculator here shows.

I'm not an expert at smoker design so take this with a grain of salt until Dave O or someone else with more experience comes along.

Given a nominal volume of 18,480 cubic inches I suspect your smoker really wants a firebox around 7,000 cubic inches and your smaller tank, at 5,800 cubic inches ,is small enough that I don't think it is going to be satisfactory, especially in rainy, cold or windy conditions when you need more heat than usual.

If you have access to 1/4" steel and the budget for it a 20" cube shaped firebox would give you 8,000 cubic inches and have enough reserve volume to be sure to handle anything you want to cook. As a bonus it will be a lot easier to fit too.

What are you welding it with?

Best regards,
Yes I saw that but was all Greek to me. I used Feldons as it was automatic.. It was lazy way I did it. I work in hydraulic so so have access to any type welder.. More than likely mig or Tig. I'm cheap so am going with free parts. Budget is tight ..I have a UDS that works great that I built and to be honest don't really know how much this will get used.. It is either make this or stand it up and make a smoker that way.
 

radioguy

Smoking Fanatic
859
209
Joined Jan 12, 2013
John,
Welcome to SMF search is your friend. I built one similar to yours...52 gallon air tank. The tank is almost 100 years old.

I moved to to a trailer set up and just plobbed it down on the trailer...had a competion cook that year. I still would like to lower the tank by 6-8 inches and finish out the grate work. It cooks really well.

RG


 

Johnscrub

Newbie
4
1
Joined Jun 4, 2021
John,
Welcome to SMF search is your friend. I built one similar to yours...52 gallon air tank. The tank is almost 100 years old.

I moved to to a trailer set up and just plobbed it down on the trailer...had a competion cook that year. I still would like to lower the tank by 6-8 inches and finish out the grate work. It cooks really well.

RG


Thank you yes search is your friend. Nice build.. How did you determine your door cuts? Height mainly..I did search but nothing with a round firebox or cylinder one. Yes the main tank was made in 1976.. Little one no idea..
 

radioguy

Smoking Fanatic
859
209
Joined Jan 12, 2013
Thank you yes search is your friend. Nice build.. How did you determine your door cuts? Height mainly..I did search but nothing with a round firebox or cylinder one. Yes the main tank was made in 1976.. Little one no idea..
I did my door cuts at 9 and 11 o'clock. It's up to you. It depends on your tank size. I put my shelf slide in a 1/4 " above the opening. I didn't need anything more on the top. My tank has a welded seam, I put that on top.

About using round FB you will end up with a football shaped opening. It takes a little extra math to figure the size. Just treat it like 2 times a normal circular chord.

RG
 

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