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-   -   Thinking of modifying the firebox on my NBBD - Comments? (http://www.bbq-brethren.com/forum/showthread.php?t=171150)

CtTradArcher 09-16-2013 09:48 AM

Thinking of modifying the firebox on my NBBD - Comments?
 
I have a New Braunfels Black Diamond offset that I have recently resurrected. I am thinking of modifying the firebox by simply moving it down.

A little about the smoker and my reasoning:

Smoker:

Cooking chamber is 16" diameter by 34" long. Firebox is the same diameter, 17" long, so about half the size of the cooking chamber.

The firebox is bolted on and is located such that the top is half way down the cooking chamber. The opening into the cooking chamber is approximately 10" wide x 6.5" tall.

Reasoning:

Smoker runs very hot at the firebox end and according to Feldman's pit calculator, the opening is twice as big as it needs to be.

By moving the firebow down 3.25", I will decrease the opening by about half, which according to Feldman's still just a bit bigger than needed.

It will also move a lot of the radiant heat below the cooking chamber, which I hope lowers the temp at the firebox end of the cooking chamber.

Lastly, it will lower where the heat enters the cooking chamber to below grate level.


The mod should be pretty easy to do and not permanent if it doesn't work. My plan is to just make a plate to bolt to both sides using the existing holes.

Does anyone see any shortcomings with the idea? Or agree with the reasoning?

Thanks!

peeps 09-16-2013 10:03 AM

I would keep the firebox where it's at and just mount a plate to restrict the opening to see how it does, but if you had plate fab resources, then your idea sounds like it's easy enough.

ButtBurner 09-16-2013 10:05 AM

I would just try putting a cookie sheet or a piece of cut foil pan over the opening to close it off some and see how that works.

I bet it restricts air flow and you will have a hard time maintaining a flame

oldbill 09-16-2013 10:30 AM

Quote:

Originally Posted by CtTradArcher (Post 2626610)
I have a New Braunfels Black Diamond offset that I have recently resurrected. I am thinking of modifying the firebox by simply moving it down.

A little about the smoker and my reasoning:

Smoker:

Cooking chamber is 16" diameter by 34" long. Firebox is the same diameter, 17" long, so about half the size of the cooking chamber.

The firebox is bolted on and is located such that the top is half way down the cooking chamber. The opening into the cooking chamber is approximately 10" wide x 6.5" tall.

Reasoning:

Smoker runs very hot at the firebox end and according to Feldman's pit calculator, the opening is twice as big as it needs to be.

By moving the firebow down 3.25", I will decrease the opening by about half, which according to Feldman's still just a bit bigger than needed.

It will also move a lot of the radiant heat below the cooking chamber, which I hope lowers the temp at the firebox end of the cooking chamber.

Lastly, it will lower where the heat enters the cooking chamber to below grate level.


The mod should be pretty easy to do and not permanent if it doesn't work. My plan is to just make a plate to bolt to both sides using the existing holes.

Does anyone see any shortcomings with the idea? Or agree with the reasoning?

Thanks!

I cooked for 16 years with Black Diamond and the best thing that I ever did as far as mods was to add a heat deflector over the opening of the firebox in the main chamber. I used an aluminum roasting pan which I cut in half, put the two halves one on top of the other and then attached them to the wall of the main chamber directly over the firebox opening with screws. After the heat interred the main chamber it was directed down and into the center of the pit rather than being allowed to go strait up, move along the lid and exit as it wanted to. The result was better use of the heat from the fire and being able to build a (much smaller) fire to heat the pit. Your pit needs plenty of draft and restricting the opening to the main chamber in any way may lead to airflow problems. Try the heat deflector, I'll bet you'll notice a huge difference in efficiency and getting the pit to hold temps where you want them.:wink:

sliding_billy 09-16-2013 11:04 AM

^^^this!

CtTradArcher 09-16-2013 11:06 AM

I had already done the heat deflector mod. I have also tried tuning plates.

My temps are about 50 degrees different from one end the the other at grate level.

I that about the best I can hope for?

oldbill 09-16-2013 11:20 AM

Quote:

Originally Posted by CtTradArcher (Post 2626724)
I had already done the heat deflector mod. I have also tried tuning plates.

My temps are about 50 degrees different from one end the the other at grate level.

I that about the best I can hope for?

Hmm! The heat deflector should have done the trick to even out the temps across the chamber, most cookers of the Black Diamond's size really don't require tuning plates but I have in the past raised the nose a little to urge more heat to travel toward the end by putting some 2x4 under the wheels. Another mod to do however, if you haven't already is to extend the stack down to grate level. I used some aluminum dryer hose to do this and it works with the deflector to direct everything to the far end of the cooker. The key is in not allowing the heat to go up and exit too soon.

CtTradArcher 09-16-2013 11:57 AM

Hey Oldbill,

Thanks for the responses.

I did that one too. I found that a soup can fit perfectly inside the smoke stack. I have it about an inch from the grate.

One thing, I am measuring the temp at either end by having put themometers through in either corner of the chamber door. I may have them too far apart, meaning measuring at the extreme ends of the grill. Just a thought. Maybe I should do the whitebread test instead.

oldbill 09-16-2013 12:24 PM

Quote:

Originally Posted by CtTradArcher (Post 2626775)
Hey Oldbill,

Thanks for the responses.

I did that one too. I found that a soup can fit perfectly inside the smoke stack. I have it about an inch from the grate.

One thing, I am measuring the temp at either end by having put themometers through in either corner of the chamber door. I may have them too far apart, meaning measuring at the extreme ends of the grill. Just a thought. Maybe I should do the whitebread test instead.

Yeah, there are a lot of variables in this stuff as far as heat displacement. With the deflector, the stack extension AND the tuning plates you aught to be getting the heat where it should be in the cooker. The only other thing that I can think of is making sure the airflow is good and moving easily through to the exhaust stack.


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