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250L build - now a 35? gallon build - Page 8

post #141 of 153
Thread Starter 
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)
post #142 of 153

Munx, afternoon......  Is there some reason the 4" stack idea wasn't used.....  (4" exh stack 27" above the CC.....)

                                   Just curious....   I'm here to help..... others are also.....   We just want your smoker to cook very well and make

                                    very good Q.....   Your success reflects on us...  Soooooooo.....   we want you and your smoker to be

                                     the best.....           Dave




post #143 of 153
Thread Starter 
Those are the old calculations from when I thought I was getting a bigger tank. With the smaller compressor tank 4" wound up too short iirc.

And if need be, I could cut a bigger hole easier than closing it up for a smaller one... Heh
post #144 of 153

Oh....   so you didn't use the 18 x 80 tank......  I see......

post #145 of 153
Thread Starter 
Nope that fell through. Was going off the drawing that came later. Give me a bit to find it on my phone.

post #146 of 153

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.......



post #147 of 153
Thread Starter 
I can appreciate that, a 2.5" pipe can still flow a lot. I'll see how this mod affects things before cutting it out for a bigger pipe.
post #148 of 153
Thread Starter 

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. 

post #149 of 153

Good news..........    Dave

post #150 of 153
Thread Starter 
Everything turned out pretty good. My wife says better than the last test, ribs were juicier.

post #151 of 153

looks good to me.......  Dave

post #152 of 153
Thread Starter 

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...

post #153 of 153
Thread Starter 

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. 

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