Franklin smoker design question

[Brisket Envy]

Concerning Direct Flow (standard offset) smoker designs, and airflow...
I have built a number of smokers, and have my preferred methods, but am still always reading others’ ideas and preferences, because it’s just hard to know EVERYTHING about pit design and smoking processes.
The question I have about Aaron Franklin’s design and method centers around his huge stack, open firebox door, massive airflow method.
The first that struck me, was how in his videos, he has the firebox door standing open, and then I couldn’t see any intake dampers on his backyard model.
If I were to leave my firebox door open, my cooking chamber temps would exceed smoking temperatures, and reach roasting temps soon, even with a bed of coals and only two or three smallish splits in the FB.
How does he keep his cooking chamber temps down, with all that oxygen feeding his fire??
Is the answer in his huge (eight inch) stack?
Is it because he has the door open, and the massive air flow pulls in In unheated ambient air, in addition to the air that passes through the fire, and more heated areas of the firebox?

If that is the case, I am thinking the rate at which the air/smoke passes through the CC is rapid enough that it does not have as much time to cool, and that might mean more even temps across the length of the smoker.
It might also mean he may be burning a lot more firewood, since more heat would also be exiting through the stack, due to the high rate of air exchange.

Personally, I control the heat by opening the intake only enough to supply an amount of air Required to support a fire big enough to maintain my desired temp (225deg). Depending on ambient temperatures, and presence or absence of wind, those intakes may be closed down to fractions of an inch.

Does anybody have experience with this open door method, and if so, can you share your thoughts?
Thanks!

[hogaboomer]

Are you cooking with 1,000 gallon smokers like he is?

The pics I saw of his new backyard model had his name cut out in the firebox door and also had vents. Not sure if that's the one he's selling, I don't see any way to manage that vent.
When I first started I used to leave the door open like he does, it used a lot of wood. But I was only cooking on a 100 gallon smoker.

[Brisket Envy]

Are you cooking with 1,000 gallon smokers like he is?

The pics I saw of his new backyard model had his name cut out in the firebox door and also had vents. Not sure if that's the one he's selling, I don't see any way to manage that vent.
When I first started I used to leave the door open like he does, it used a lot of wood. But I was only cooking on a 100 gallon smoker.

No sir. Like you, Most of my cooking has been done on a 125+- gallon smoker, and some on a 250.
Both are larger than the one pictured (which is also the backyard model I mentioned)
Seems like you would really need to draw a LOT of air through there to “dilute” the hot air the fire produces.
...but apparently it works.

[Big T]

I also don't have any experience with that method of fire management but both of your theories probably have something to do with the way it runs. I remember several years ago there was a member (Solo Que) who had pit built for him, I believe it was a 500 gallon offset. It had large intakes cut in both sides of the FB but they were up high on the sides instead of down bottom like everyone does them now days. It also had twin exhaust stacks that were oversized. He came to the forum because his pit would only run in the 200-210 range no matter how big his fire/coalbed was. After discussing his problems with some of the smarter guys on the forum at that time (Frank, Tom, Gizmo, CRS, RC and a few others) they realized that the pit was drafting so hard that the air coming from the higher intakes didn't have time to be heated in the fire box before being drawn into the cook chamber and that was causing the low temperatures that he was trying to overcome. He added dampers to the stacks and dropped the intakes down low on the FB, he may have done something similar to what Frank did with Lou Ann with the diverters and that corrected his issues. I'm sure that all of those 12-15 lb briskets that are jammed into the 1000 gal cook chamber absorb a lot of heat also.

[Brisket Envy]

I also don't have any experience with that method of fire management but both of your theories probably have something to do with the way it runs. I remember several years ago there was a member (Solo Que) who had pit built for him, I believe it was a 500 gallon offset. It had large intakes cut in both sides of the FB but they were up high on the sides instead of down bottom like everyone does them now days. It also had twin exhaust stacks that were oversized. He came to the forum because his pit would only run in the 200-210 range no matter how big his fire/coalbed was. After discussing his problems with some of the smarter guys on the forum at that time (Frank, Tom, Gizmo, CRS, RC and a few others) they realized that the pit was drafting so hard that the air coming from the higher intakes didn't have time to be heated in the fire box before being drawn into the cook chamber and that was causing the low temperatures that he was trying to overcome. He added dampers to the stacks and dropped the intakes down low on the FB, he may have done something similar to what Frank did with Lou Ann with the diverters and that corrected his issues. I'm sure that all of those 12-15 lb briskets that are jammed into the 1000 gal cook chamber absorb a lot of heat also.

Good information Big T, thanks!

[Dirtytires]

We get a lot of interest and references to Franklins pits. Kinda interesting to hear they have major issues right off the showroom floor. They apparently work for him (Franklin) so it also shows how much the actual daily use of a pit differs from pitmaster to pitmaster.

[dacolson]

I think it’s interesting the Johnson bros quit Franklin to start Mill Scale. They build some incredible pits. Gotta be a story there.