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View Full Version : Building 500 Gallon Reverse Flow Smoker Advice


Harm
03-05-2014, 09:55 PM
I'm not sure if this is the right place or not, if not please change it or let me know what to do.

I'm now looking at building a 500 gallon reverse flow smoker. I have read various builds and found the size calculators but one piece of information I haven't found yet is how high from the bottom do you place the baffle and how high from the baffle do you place the first rack to hold the meat?

From pictures I'm guessing 4 inches from center/bottom for the baffle and 6 inches up from baffle for bottom rack?

Chime in with all your ideas and experiences.

Thanks

Harm
03-05-2014, 10:00 PM
I know its important to have proper area for flow of smoke and heat so I know this is an important measurement.

Also I rarely see the inside of the firebox so Im looking for different ideas on how to do the fire box on the inside as well. Im thinking of having a removable tray on bottom so you can empty the ashes. I also have been thinking of a top door to load more wood on the coals instead of a side or end door where you have to bend over and hope it fits through the door.

buttburnersbbq
03-05-2014, 10:04 PM
First you need to use the pit calculator and find out how many sq inches your opening needs to be from fire box to main chamber. I built a 250 gallon RF smoker. My plate is 6" from bottom of tank and I have from plate to first rack 9". You need to make sure you use the pit calculator so you get your draft correct. If you are too small then your draft is too small and you can not get your pit up to temp . Due to the air flow and starving the fire. I was nervous at first. But followed everything and it works like a champ. Best pit I own is the one I built.

buttburnersbbq
03-05-2014, 10:09 PM
Here is a link to my video of my smoker build. May help you with some ideas

My First Smoker Build - YouTube

Harm
03-06-2014, 08:00 AM
I did the calculations with the pit calculator and it game me a half moon size of 28.14 so my question is do I need to measure that along the top of my fire box (centered) and cut the half moon out of the side of the fire box? Also how do you know how far to recess the fire box into the end of the cooking camber?

First you need to use the pit calculator and find out how many sq inches your opening needs to be from fire box to main chamber. I built a 250 gallon RF smoker. My plate is 6" from bottom of tank and I have from plate to first rack 9". You need to make sure you use the pit calculator so you get your draft correct. If you are too small then your draft is too small and you can not get your pit up to temp . Due to the air flow and starving the fire. I was nervous at first. But followed everything and it works like a champ. Best pit I own is the one I built.

Harm
03-06-2014, 08:29 AM
Very nice video. Very nice detailed pics. Yes this did help answer many questions. I do know the importance of getting that opening correct and the hight of the baffle for correct air flow. So if my thinking is correct the number from the calculator is telling me how wide to make my half moon cut. If I match that cut to the end of the tank it should give me the correct position as to how high to cut the hole in the tank.

Here is a link to my video of my smoker build. May help you with some ideas

My First Smoker Build - YouTube (https://www.youtube.com/watch?v=42S30S2lMr8)

popeye
03-06-2014, 08:47 AM
One word ... beutiful

buttburnersbbq
03-06-2014, 07:03 PM
I did the calculations with the pit calculator and it game me a half moon size of 28.14 so my question is do I need to measure that along the top of my fire box (centered) and cut the half moon out of the side of the fire box? Also how do you know how far to recess the fire box into the end of the cooking camber?

Even though your opening to your main chamber is rounded . This is How I calculated the sq inches into the main chamber from fire box. I measured the width of the RF plate and divide in 1/2 . Then times that number by how high the plate sits in the middle. So my RF plate measures 24" was the width of the RF plate . The plate sits measures 5 1/2" from plate to bottom of opening in the middle. So 12x5.5 = 66 sq inches . My pit calculator said I needed 57.6 sq inches . So I over sized a little. I also made my air intake at the fire box oversized but as you can see I used slide dampers to control the air intake . I also used a 6" pipe for the exhaust and also made it a little longer than calculator said . So that being said I get plenty of draft through the pit . Make sure you have the same or even more at the end of the RF plate . If you go to far with the RF plate to the end of the chamber you will not get the correct flow. I can get it up to temp with no problem and use the air intakes to control the temperature. I have my exhaust stack always wide open even though I made a damper at top. It is very easy to control and maintain temp.

buttburnersbbq
03-06-2014, 07:09 PM
Very nice video. Very nice detailed pics. Yes this did help answer many questions. I do know the importance of getting that opening correct and the hight of the baffle for correct air flow. So if my thinking is correct the number from the calculator is telling me how wide to make my half moon cut. If I match that cut to the end of the tank it should give me the correct position as to how high to cut the hole in the tank.

I recessed my firebox into the chamber 9". I have seen one that are not even recessed into chamber. The only reason I did it was to make the RF plate easier and square cuts. Also easier to put together .

Harm
03-07-2014, 09:15 PM
Am I correct to assume that when I use the calculator and it says I need an opening from the fire box to the cooking chamber of 28.14 that this is a straight line measurement in inches across the top edge of the side of the fire box, then find that same width inside the tank (cooking chamber) and cut a straight line at that height around the end of the tank providing me with the height of where I will recess the fire box? Then I will decide how far into the tank I will recess the fire box and cut the part of the bottom of the tank out. This gives me my fire box opening to weld the fire box into, mounting it to the tank. Then I assume that I use the bottom shape of the tank to provide me with the arc that I will cut out of the side of the fire box matching up to the ends of my 28.4 inch cut along the top. This will provide me with the correct opening....right?

I have read that the opening at the end of the baffle plate is to have the same amount of opening as the opening from the fire box to the cooking chamber. Do you know how to measure this? Do I run the baffle plate our to the point where it reaches a width of 28.14 inches within the cone part of the tank? It seems to me this would then give me the same exact opening as from the fire box to cooking chamber... correct?

Sorry I am looking at this so complicated but I know this is a vital part of getting this right.

buttburnersbbq
03-07-2014, 10:14 PM
You are on the right track. once you find how many sq inches your opening needs to be from fire box to main chamber . Which for a 500 gallon tank you are probably looking at 110 sq inches or more .which you will find when you put everything in the pit calculator . So what I did was I placed my first rack at center of my tank 15" since the tank is 30" in diameter ( center of tank). Which you want to make sure you have at least 6" from RF plate to first rack . I needed 58 sq Inches . my plate is 24" wide and sits 5 1/2" from bottom of tank ( my rf plate is 9" to first rack). Which gives me 66 sq inches and works great . You always want a little more than not enough. for cutting out the opening at tank for fire box to fit. I found centers on out side of tank to measure down to get my line and cut that section out once I found what my RF plate width was going to be. You can see in the video. The opening at the end of the RF plate ( opposite end of fire box. I went 6 inched from end of RF plate to center of tank. It is the same concept as the opening from fire box to main chamber. Since the end of the tank is rounded also.

I was quick to start but when I got to the point of getting ready to weld in the RF plate I got nervous. I did a lot of research on the internet ( probably 4 months) . I was reading that a lot of guys having issues getting up to temp or keeping temp. In all the problems which lead to not enough draft or intake . So I wanted to have the most efficient fire but get up to temp and maintain. So in the fire box I built the shelf to hold the fire up off bottom of firebox and my intakes below the shelf. So air comes from bottom through the fire to make fire efficient. I put one split a hour. Which if you read in all forums is good for a stick burner. I want to make sure I had enough draft so I over sized my intake with a slide damper at firebox on both side. To make sure I had enough air coming in to burn clean fire.The air intake dampers are key on mine since they control my temp of the pit . Second I made sure I was at or above the sq inches from firebox to main camber. Third made sure my opening at end of RF plate was at or bigger than fire box opening to main chamber. Fourth was to make sure diameter of exhaust pipe and length of exhaust was correct. I used a 5 3/4" diameter pipe and it is 6" longer than pit calculator told me it needed to be . Longer the pipe the better draft you get . If you follow the pit calculator you should not have any issues . It sounds scarier than what it really ended up to be. I was over thinking at time and that is why I read a lot before i welded in my plate. Plus I never welded before and this was my first time. So I watched a lot of you tube videos on welding.

Good Luck on your build. If you need anymore advice just let me know

Harm
03-08-2014, 09:44 PM
Has anyone had success adding a gas burner to their LARGE smoker?

I would like to add a gas burner to the fire box so that after smoking the meat to desired amount I want to continue cooking but would rather not have to keep adding fuel to the fire and kick on a gas burner to maintain heat levels for the remaining cooking time.

What BTU would be most efficient for a 500 gallon smoker?

I would like to divide my fire box into 2 sections with a slim section nearest the cooking chamber for a pipe burner and have the wood burner section out from that ith a plate that separates the 2. The plate would not go all the way up to allow heat and smoke to cross over and into the cooking chamber.