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It's 2.5" ID pipe and I think 32" above the cc. Checked out with the calculator. I'm going to run it tomorrow for some fatties or ribs (or both... Heh)
I check most of the numbers on your plan.... they looked good.... The only thing that comes into play when making a small smoker and using a calculator designed for a large smoker is............
The surface area of the steel versus the volume of the parts....... the surface area represents a larger percentage compared to the volume.... therefore, friction loss becomes greater when using the calculator and accommodations need to be made to reduce that friction loss..... anyway, that's the way I figure it.... I could be wrong..... but I'm too old to argue if I am.... that's the way us backyard folks do stuff.....
As an example.....
circumference ratio ..... surface/area
4" pipe has 12.56 sq in area 12.56 in. also 12.56/12.56= 1
1" pipe has 0.79 sq in area 3.15 in. 3.15/0.79 = 3.99
Soooooooo ........ there is 4 times the surface area compared to the volume of a 1" pipe ..... that equals more friction loss....... those interpretations can be figured into the area under the RF plate also.... FB/CC opening.... air inlets.... etc....
To conclude..... the calculator is a great tool ..... Alien and friends did a great job putting it together.... when altering the original concept, there are some interpretations that definitely need to be included in the new design.......
Halfway through another test cook and cutting the chimney off has had a positive effect. It is running more efficiently, I'm able to shut the bottom vents about halfway and it's using half as much fuel as last time. Next thing I try will certainly be sealing up the CC door and any air leaks. I'll provide some Q-view when it's done, couple racks of ribs and some sausage for supper.
The next tweaks I may make at the same time. (I typically like to change one variable at a time but am getting antsy). Sealing the CC door and adding a heat shield/baffle to the firebox.
Sealing the leaks will improve draw and I think the heat shield will help direct heat into the cc. Might have to shorten the legs on my fire basket too...
I still have a few tweaks to make but have been busy with other things the past few weeks... hoping to get my CC door gasket, tack in a heat shield in the firebox and make a chimney cap for when it's not in use. Might trim my chimney a bit more inside the CC too but will wait and see how the other tweaks affect things. I'd like to do that this weekend but we'll see how things go.