Fire box opening

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Original poster
Apr 21, 2014
Morning all,

I have a NBBD for 11 years and it has served me faithfully.

But now it needs some tender love. I am going to make a new frame for it and put on some decent wheels as a start.

I have been looking on line at the various different upgrades that have been done to this type of grill and I am probably do most if not all of these, seal the doors, baffle plates, fire bricks, extend the chimney down to the grill and perhaps reverse flow.

While I was looking at all these different sites I came across Feldon's BBQ pit builders calculator.

I punched in the sizes for my grill and the recommended opening is 25in sq. I went out and checked the opening in my smoker and it is coming in depending on my math between 51 and 60in sq.

For this reason I was planning on lowering the fire box by about 4-5in to reduce this opening.

I am going to use a piece of 3/8 x 12 x 14 plate to fill the resulting holes and give a bit of stability to the joint.

I was also going to raise the height of the opening from the fire box by about 1 1/2in to encourage the smoke/heat to travel straight into the smoke box under the baffle plates.

Does anyone see any major flaw with what I am proposing? Other than the pain and time involved in doing it.

Thanks in advance.

Hey Karl, nice to see that you want to keep that smoker going. We have a number of fabricators on here that have used the Feldon calulator to build their smokers, so I'll let them weigh in on your numbers. I know one thing that will be mentioned will be to add an air intake to the door of the fire box above the fire grate as this will help in carrying the heat into the cook chamber.

Enjoy the Smoke!
Karl, welcome and morning..... Also, Feldon's number for the FB (firebox) to CC (cook chamber) opening is lacking in area... I recommend enlarging that area by 50% to allow the FB to move more air to the CC and reduce over heating of the FB.....

Good morning Karl, welcome to the forum, Dave is the man, he is right on with his advice, Gave me some suggestion for mine, did what he said and improved my smoker a bunch.  Looking forward to post and pictures.

Gary S

Thanks for the information.

Dave, I am going to split the difference between you and Feldon.

I will leave myself with the ability to move it again if it doesn't work.

I am going to start work on this tomorrow for you guys today for me in Ireland.

I will take some before and after pictures and let you know how I get on.

Again thanks for the help.

Hey Karl

Welcome to the Smoking  forum.   You’ll find great , friendly people here, all more than willing to answer any question you may have.  Just ask and you’ll get about 10 different answers—all right.  LOL.   Don’t forget to post qviews.

Well all,

After two long and dirty days days(her in doors refused to talk to me before I had a shower last night) I am starting in to see light at the end of the tunnel.

When I split the FB from the CC and ground away the rust I found that the FB was a lot worse than I thought it was.

There was a couple of holes that were at least 1/2'' dia. and the thickness of the remaining metal was little or nothing.

We were modifying some CO2 ducting in work and the old sections were coming out they were going into scrap so I asked if I could take them instead.

The ducts are 20'' so I cut them up to replace the bottom of the fire box.

Getting 20'' 1/8 SS pipe to form and mold to a 16'' FB takes some BF&I (brute force and ignorance) it was about then that I drew first blood.

I was trying to bend a 6'' section of the duct using a slash clamp when the SS popped out of the clamp and hit me in the face luckily for me I was wearing my safety glasses. I had the glasses on my forehead and the SS hit there. However it put the nose piece of the glasses straight into my forehead. There were some choice words and a lot of foot stamping and kicking things. All things considered I got off lightly.

I had planned to completely enclose the inside of the CC with SS but this experience has forced me to question the worth of such an adventure.

I got the FB lined eventually and I am deliberating on the best way forward with the CC.

I have the new frame completed. I used 2'' box, I probably could have used 11/2 but as the saying goes ''If you you are going to be a bear, be a grizzly''.

Cut the plate to lower the FB and cut the hole. This worked out really well( I say this now but I haven't actually used it yet.)

On a side note being in Ireland it is tough to find good smoking material hickory, mesquite. There are a couple of apple trees in the home house so I have taken over the care of them since I came back and hording the trimmings. I was in my local hardware store (Woddies) and they have hard wood logs for sale for chimeras. Would this be alright to use in my smoker.  

I have tried to add some photo's to this without any success.

I will keep you posted how things are going and thanks for the warm welcome.


I am happy to say that seasoned the new and improved NBBD this morning and cooked a couple of chickens on it today. 

Lowering the FB made such a difference, just after I put a chimney of 15 coals into the FB with the doors of the FB and CC open I was drawing some smoke through the chimney.

I coated the inside of the CC with peanut oil and baked the unit up to about 450 for an hour or so.

I spatch cocked a couple of chickens and cooked them yesterday. I still need to play about with the baffle plates but the temp was only out by 10deg at the end of my initial cook.

NBBD looking very neglected and unloved.

Damage to the bottom of the fire box

The ducting in the background

The internal lining of the fore box. I did the same for the cook chamber.

First coat of paint.



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