# Need help with fire box



## pirk56 (Mar 18, 2017)

I'm having trouble keeping my pit at temp. With the firebox door closed and vent wide open, it's not getting enough oxygen to keep the fire burning, Smoking a brisket today, I had to constantly open the door to get the temp up. My thought is that the vent is positioned too high on the door where oxygen get under the rack. I've thought about cutting a new vent at the bottom. See pics for reference, thanks for your input in advance!


----------



## pirk56 (Mar 18, 2017)

IMG_0270.JPG



__ pirk56
__ Mar 18, 2017


----------



## flippers (Mar 18, 2017)

To me it looks like you can use more air intake. Maybe put it  lower on the sides.? Also it looks like you have a good ash buildup under the fire. That could maybe prevent it from getting up to temp. What kind of smoker is it? It looks pretty nice!


----------



## pirk56 (Mar 18, 2017)

Yea I've got through some wood today, I'm using an old fire place grate, using bricks to support it. Wonder if that's blocking air, I can turn them side ways. 

Reverse flow, thanks, my second cook and I love it, ready to get the heat figured out. 













IMG_0273.JPG



__ pirk56
__ Mar 18, 2017


----------



## pirk56 (Mar 18, 2017)

IMG_0271.JPG



__ pirk56
__ Mar 18, 2017






For some reason I can only tag one pic at a time


----------



## joe black (Mar 18, 2017)

Leave the FB door cracked a little to introduce more air.


----------



## 416bigbore (Mar 21, 2017)

pirk56 said:


> I'm having trouble keeping my pit at temp. With the firebox door closed and vent wide open, it's not getting enough oxygen to keep the fire burning, Smoking a brisket today, I had to constantly open the door to get the temp up. My thought is that the vent is positioned too high on the door where oxygen get under the rack. I've thought about cutting a new vent at the bottom. See pics for reference, thanks for your input in advance! [GALLERY="media, 520523"][/GALLERY][/quote]
> [img]https://statich.smokingmeatforums.com/smilies/others/welcome1.gif  to the SMF pirk56.
> 
> Judging from your pic, for me it looks like smoke is wanting to come out your door when you have it open, Correct?
> ...


----------



## pirk56 (Mar 22, 2017)

416bigbore said:


> :welcome1:  to the SMF pirk56.
> Judging from your pic, for me it looks like smoke is wanting to come out your door when you have it open, Correct?
> 
> If so, that is telling me you have an issue with your exhaust and or your Smoker has cooled down to much and you lost the Drawing flow of your heat and smoke up and out of your chimney. In return causing the smoke from your fire to take the easiest path out and up when you open the door. More air intake will not fix this type of issue, I am guessing you need to look more at your path of exhaust flow out the other end of your smoker.
> ...



Some will come out the door but it does flow on out the exhaust. 

It's not gas fired yet, the bottle is there to fuel me fryer, I want to install a gas fire eventually. 

Smoke flows real good while cooking, I don't think that's the issue, but I'm not sure. When the door is wide open like in that pic, some smoke does come out the fire box, but I cooked with a 2"-4" gap and all smoke was flowing. 

 A good friend of mine told me to make sure the pit was level, that that can affect the flow. I've left it connecedt to my truck so the tail end has been way low


----------



## 416bigbore (Mar 22, 2017)

Next Question I need answered first before I can go further with your issue. Is your smoker open between the two compartment for smoke to flow from one end to the other, or closed off in the Middle? I see two separate exhaust stacks, that's why I am asking this question. Thanks Mike


----------



## pirk56 (Mar 22, 2017)

Yes, 6"-8" (I think) circle going from the pipe cook chamber to the smoke box / holding box. I'll take a pic when I get home from work

I've left both open during my cooks and smoke comes from both, haven't noticed more smoke coming from the other.


----------



## 416bigbore (Mar 22, 2017)

Ok, now we can get down to business with your issues. You try and post up a few more pics later if you can? and I will help explain a little theory behind why I think you are having the issues you are experiencing. Then you will have a little better understanding and maybe you will be able to pinpoint the issue looking right at you, maybe because you just weren't aware of it at first? 
	

	
	
		
		



		
		
	


	





  

A little TWEAKING in the right places and that Bad Boy will operate just like you want it to! 
	

	
	
		
		



		
		
	


	





  

I also encourage others to jump in and help and ask more questions also.


----------



## pirk56 (Mar 22, 2017)

IMG_0305.JPG



__ pirk56
__ Mar 22, 2017





Inside the warmer box













IMG_0307.JPG



__ pirk56
__ Mar 22, 2017






Inside the main chamber

Let me know what other pictures you want













IMG_0309.JPG



__ pirk56
__ Mar 22, 2017






Stacks


----------



## gary s (Mar 22, 2017)

Several things are relevant.  Proper calculations for openings based on Cook Chamber Cu. In. is a must  Looking at the pics it seems like you FB damper is a little high.

You need air flow under the splits. I also added a top damper in my FB door to really fine tune heat adjustment.

If leaving your door cracked improves the fire burning you have an air intake problem Larger Damper

Gary


----------



## 416bigbore (Mar 22, 2017)

Great pics 56 that helps, Thanks. From a closer look at your pics you must have just bought this or had someone build it for you? The steel appears really new and your pit doesn't look like it has had very much use, correct? 

From your pic of the round hole going from your warmer box into your main chamber, your stack opening is right above, correct? 

First I am not understanding the reason and or possible theory behind someone mounting the two stack the way they did on your pit? If You had only ONE stack on the far end of your Pit you would have a more even flow of the heat and smoke, in return giving you a more consistent temp.

I will stop here so you can tell me a little more info behind the history and build of your pit. Thanks Mike


----------



## 416bigbore (Mar 22, 2017)

bbqcalculator_diagram.png



__ 416bigbore
__ Mar 22, 2017






Maybe this pic will help you understand a little better on what you have going with your pit?


----------



## 416bigbore (Mar 22, 2017)

900x900px-LL-2d5cbd03_ReverseFlowHorizontalSmoker-



__ 416bigbore
__ Mar 22, 2017






I found a little better pic to show you the correct  Reverse Flow. I am not seeing this being able to happen from the pics you posted.


----------



## pirk56 (Mar 22, 2017)

416bigbore said:


> Great pics 56 that helps, Thanks. From a closer look at your pics you must have just bought this or had someone build it for you? The steel appears really new and your pit doesn't look like it has had very much use, correct?
> 
> From your pic of the round hole going from your warmer box into your main chamber, your stack opening is right above, correct?
> 
> ...



I had the pit built by a local group, they have made several pits, but by know means pit builders. It's build damn well. They had never built one with a hot box like mine and when I got there to check it out during Fab they already had the 1 stack on the main chambe. I wanted to be able to smoke in the hot box too so I had them put the second. Not knowing any better. Smoke flows beautifully from both of them. 

I've seasoned it and have done 2 cooks. 

Yes the main cook chamber stack is right above the hole going into the hot box.


----------



## 416bigbore (Mar 22, 2017)

So if that is true, you do not have a reverse flow main cooking chamber and the heat and smoke flows right in and out the top, correct?  Your heat and smoke does not flow under your food first then back over the top and out, am then out your stack, correct? 

If this is true, are they still around to fix this problem for you?


----------



## pirk56 (Mar 22, 2017)

416bigbore said:


> So if that is true, you do not have a reverse flow main cooking chamber and the heat and smoke flows right in and out the top, correct?  Your heat and smoke does not flow under your food first then back over the top and out, am then out your stack, correct?
> 
> If this is true, are they still around to fix this problem for you?



Yea it does work as a reverse flow, under the meat over the meat & out


----------



## 416bigbore (Mar 22, 2017)

If that is true, I don't understand the round hole cut on top of the cooking grate. Is there a hole under the grate also then, so you would have two hole cut top and bottom?


----------



## pirk56 (Mar 22, 2017)

416bigbore said:


> If that is true, I don't understand the round hole cut on top of the cooking grate. Is there a hole under the grate also then, so you would have two hole cut top and bottom?



Yes that's correct, the lower hole comes from the fire box and top hole goes into the smoke box. Fire box & smoke box are connected but has a 1/4" thick plate in between.


----------



## 416bigbore (Mar 22, 2017)

Sounds to me like you need to plug that top hole off then, because your heat and smoke is taking the easiest path out and up your stack and not under like it was designed to do. Correct?  am I not seeing something you are  for it to not be closed off and work correctly for you still?


----------



## ahumadora (Mar 22, 2017)

Hi there,

Whats your stack length?  The pics don't show the top of the stacks.  

To me they look long and small diameter which will cause friction and for the smoke to cool too much.

I would open it up a lot more between the cook chamber and vertical cabinet. (try to open it lower down).

Also mount the cook chamber stack lower on the chamber if you really want to keep 2 stacks.

For me I would toss the stack on the chamber, open up between the 2 compartments and make a larger intake.

Post more pics so we can help isolate the problem.

(cut out between firebox/cc , gap at end of Reverse flow plate etc,  full pic of stack with diemensions. )

The more info you give the better folks here can give you a accurate answer.


----------



## pirk56 (Mar 22, 2017)

416bigbore said:


> Sounds to me like you need to plug that top hole off then, because your heat and smoke is taking the easiest path out and up your stack and not under like it was designed to do. Correct?  am I not seeing something you are  for it to not be closed off and work correctly for you still?



It works just like that 2nd pic you posted, it has baffles under the grate


----------



## gr0uch0 (Mar 22, 2017)

pirk56 said:


> It works just like that 2nd pic you posted, it has baffles under the grate



If you have "baffles" as you describe, the heat and smoke are bypassing the far end of the cook chamber and finding the paths of least resistance between your plates.  There needs to be a solid plate running nearly the full length of the chamber for RF to work--not segmented "baffles".


----------



## pirk56 (Mar 23, 2017)

I hope these are clear enough, but the question (unless I'm not thinking of something) is not the function of the reverse flow, that works flawlessly. Smoke comes out of the fire box, under a removeable plate, up on the left side, travels around the meat and then out the stacks.

 Main cook chamber stack is 4" x 3' the warming/smoke box is 4"x2'. Again we only added the stack on the smoke/warming box so that I could smoke meat inside there if I wanted. I can close either stack off or adjust as needed. 

The question is how can I get my fire box to burn better, I may should of stated my question like that not keeping temp. I do think I need a larger dampener like stated above, but with out having to have a new door done, my throughts were to put some vents on the sides of the box that I can adjust. 













IMG_0316.JPG



__ pirk56
__ Mar 23, 2017





Plate covering hole from fire box













IMG_0317.JPG



__ pirk56
__ Mar 23, 2017





Opening on left hand side of pit where smoke comes













IMG_0318.JPG



__ pirk56
__ Mar 23, 2017





Fire box













IMG_0321.PNG



__ pirk56
__ Mar 23, 2017





Smoke box, my thought is to put a sliding dampener on each side of the box. 

I hope this clears up any questions. If not let me know.


----------



## gr0uch0 (Mar 23, 2017)

pirk56 said:


> I hope these are clear enough, but the question (unless I'm not thinking of something) is not the function of the reverse flow, that works flawlessly. Smoke comes out of the fire box, under a removeable plate, up on the left side, travels around the meat and then out the stacks.
> 
> Main cook chamber stack is 4" x 3' the warming/smoke box is 4"x2'. Again we only added the stack on the smoke/warming box so that I could smoke meat inside there if I wanted. I can close either stack off or adjust as needed.
> 
> ...


I'm not seeing it, but that's ok.  I misunderstood you, as you'd stated "baffles", meaning more than one, but you clarified now saying there's only one (nearly) full length plate.  I do know there was a thread a couple of weeks ago where the poster was not getting good airflow on an RF, and also had large (50+ degrees) temp variances from one end to the other--which is exactly what RF is supposed to eliminate.  It was because the deflecting plate redirecting the air and smoke flow underneath the plate wasn't completely and absolutely shutting off any leaks that could flow into the CC.  He redid this plate (widened and sealed it the full width of the CC, if I remember correctly), and it solved his issue.  Last suggestion I'll make is to check that aspect:  make sure that there are no leaks at all around the plate between the FB and the CC--it must fully redirect everything under the RF plate.  Otherwise, the other gentlemen providing intel on this thread have better knowledge than I when it comes to opening sizes, damper placements, sizes of stacks, etc.  Good luck.


----------



## 416bigbore (Mar 23, 2017)

Starting to generate some participation on this Pit problem issue that's great, the more the merrier! 
	

	
	
		
		



		
			






The only thing better than pics to try and solve this issue, would be to stand right in front of it and be able to look it all over. So back to looking at the pics we go! LOL

My take on this issue would be this, IMO More intake air isn't the answer. Reason why is this, with the door wide open you should have all the air you need for the fire to burn and burn as hot as you would like it to burn. IMO, The problem is a thing called Draw. The pit doesn't draw the heat and smoke through the chambers even and consistently to have more of a regulated constant temperature for proper cooking and or smoking.

My Theory and or observation on how a wood stove operates correctly is this. First, an airtight burn chamber or as close to an airtight burn chamber as you can have the better. Next for the fire to Burn correctly you must have an air intake and an exhaust out.

Air intake whatever size you would like, needs to be adjustable. let's say a 4" round hole with a 5" round plate that will swing over your 4" hole to adjust it. 4" full open or 1/2, 1/4, or close, whatever. Just move the 5" plate over your 4" to where you basically want your fire to burn at. Full 4" open hole is your highest air adjustment for your fire to burn the hottest it can.

Next and most importantly, the exhaust out! Your exhaust needs to be larger than your air intake. 4"air hole in, 5" or better yet 6" exhaust chimney out. Taller the exhaust stack the better for the Draw factor of your burned exhaust gasses out from your burn chamber.

Next the damper in your exhaust stack. This is a flat plate that is inside your 6" stack and can be adjusted to wide open, closed or anywhere in the middle to control the flow of your exhaust gasses leaving your burn chamber. 

Now for the theory and understanding behind how everything works together. Oxygenated air molecules, colder air temps means these air molecules are closer together, when heated they expand and move away from each other and take up more room. This is the one reason it helps to have a large diameter 6"exhaust stack over the same size  4" diameter cold air intake hole.

With a sealed airtight burn chamber having just the 4" diameter intake hole as the ONLY source of air to feed your fire and a 6" exhaust stack out with damper wide open, you can get your fire to roar with a rocketing type sound. This is why a chimney flue pipe, exhaust temp gauge is an important tool to have on a wood/coal stove. This makes sure you don't let your exhaust chimney temp gasses become too hot and then you will run into a possible chimney fire situation from any Creosote build up you may have in your pipe?

Once again in theory you can have your 4" intake hole wide open to give your fire all the oxygen it needs for the fire to burn.Wide open air intake is not an issue with a airtight burn chamber.The damper is allowing you to control the DRAW of the heat and smoke from your burn chamber to flow through your RF smoker and out your exhaust stack, at the rate you want it to.

Having an airtight burn chamber is the key, whatever air that comes into the burn chamber and is heated rapidly and expands, has to go somewhere. Since heated air rises that is the direction it will flow the best. A chimney flue pipe will Draw and flow at a 45 degree angle, Straight up and out is the best for Max Draw of your exhaust out.   

So now back to 56's issue with his pit. I am thinking that middle warming box might be part of the issue because of the hole that goes into the main chamber at the top and straight up and out the stack. The heat and smoke is going to want to take the easiest path out, so the heat and smoke is not traveling on the bottom under your meat like you would like it to and then go out your stack. Correct on this 56?

I hope my brief explanation on Draw and flow helps you look at your pit to trace the path your heat and smoke travels out, so maybe you can spot your problem? I am thinking maybe that top hole needs to be blocked off into your main cooking chamber so your pit Draws the heat and smoke like a RF. keep asking questions we will GET-R-DONE  and figured out at some point! LOL


----------



## smokin peachey (Mar 23, 2017)

Looks like the opening between the firebox and cook chamber needs to be bigger. The hole between the CC and warmer could also be bigger. 
Is the warmer only heated from the hole coming out of the CC?
Looks to me like you have to many restrictions for heat and smoke to move through.


----------



## ahumadora (Mar 23, 2017)

Smokin Peachey said:


> Looks like the opening between the firebox and cook chamber needs to be bigger. The hole between the CC and warmer could also be bigger.
> Is the warmer only heated from the hole coming out of the CC?
> Looks to me like you have to many restrictions for heat and smoke to move through.


Exactly like I was thinking.  

Also tell us the total length of the stacks or stand back and take a pic that shows the total length .













IMG_0318.JPG



__ pirk56
__ Mar 23, 2017





   Here's one of your problems.  It is too small and there is no grease bridge on to stop the grease running into the fire.


----------



## pirk56 (May 15, 2017)

Just to update everyone, I took my pit to a good friend of mine that's a welder/pit builder. After his inspection he said that it's built like a tank, but the air intake on the smoke box was built wrong. They have the opening on top instead the bottom and instead of paying for a new door, he welded a stud on each side and drilled 3 holes. Pictures will explain better. 

Anyway that did the trick, fire burns better, hotter & longer. I also had him build me a rack two hold two fryer racks and did some other tweaking. I also took it to the paint shop. 
	

	
	
		
		



		
		
	


	





[/IMG]


----------



## pirk56 (May 15, 2017)

IMG_0103.JPG



__ pirk56
__ May 15, 2017


----------



## pirk56 (May 15, 2017)

IMG_0105.JPG



__ pirk56
__ May 15, 2017


----------



## pirk56 (May 15, 2017)

IMG_0109.JPG



__ pirk56
__ May 15, 2017


----------



## pirk56 (May 15, 2017)

IMG_0017.JPG



__ pirk56
__ May 15, 2017


----------



## pirk56 (May 15, 2017)

IMG_0018.JPG



__ pirk56
__ May 15, 2017


----------



## noxwaste (May 19, 2017)

You wouldn't happen to be around the Lubbock area, would you? I noticed the Tech logo, and if you say there's some folks in the area that can put together pits, I'd like to contact them. But only if I'm able to at least guide them in the direction of how I want it built, haha..


----------



## pirk56 (May 19, 2017)

Naw I graduated from Tech, the pit was built in Kilgore, TX. I can get you in touch with the guys that built it.


----------

