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17mbpro
10-12-2015, 10:58 AM
Good morning....I'm getting geared up to build a new offset and was wondering what the rule of thumb is on firebox placement? I thought I read somewhere that the top of the firebox should be about grate level high, but most I see are a tad higher than that. I ran my dimensions through the Feldon calculator and it's telling me I need an 11.86" diameter for my opening. I just want to make sure I have it all correct. FYI...I'm using 20" diameter pipe for my chamber and firebox. Thanks for the help!

SmittyJonz
10-12-2015, 11:02 AM
I'd put it dead center underneath myself.


http://i1326.photobucket.com/albums/u645/bobjones79/2CEE1846-95C1-4E49-BC1F-979F70F64ED2_zpsyooalr1h.jpg (http://s1326.photobucket.com/user/bobjones79/media/2CEE1846-95C1-4E49-BC1F-979F70F64ED2_zpsyooalr1h.jpg.html)

Smokin J's PIts
10-12-2015, 01:05 PM
I just built one out of 20" pipe, and I have mine set up so the grate is at the mid point in the pipe so I can get the biggest grate possible. I ran mine about 4" below the center line. Basically what I try to do is use the lower 1/3 for the cross over. It hasn't let me down yet, and after this weekend I will let you know how this one ran.

Doog
10-12-2015, 05:28 PM
Just wondering what the length of your cooking/smoking chamber is going to be?

ClintHTX
10-12-2015, 05:45 PM
Google feldons calculator it will help a lot on building your smoker right.

dwfisk
10-12-2015, 06:18 PM
Several options here. A "Jambo" style has a deflector that shunts the opening an inch or two ABOVE the main cooking grate. Many builders (including Aaron Frankln if you look at his new book) advocate a deflector that shunts the opening a couple inches BELOW the main cooking grate. Then, of course, you could always go reverse flow. With a 20" diameter, I would either go RF if your main goal is uniform temps across the entire cooking grate or the "Jambo" or "Franklin" style if you can accept (or you want) a hotter zone near the firebox.

Edit: Oh yea, on either the "Jambo" or "Franklin" style pits, the exhaust really needs to be AT the main cooking grate level, not out the top of the cook chamber. I really suggest you take a look at the way Franklin does this in his book, pretty neat!

Doog
10-12-2015, 06:51 PM
http://www.feldoncentral.com/bbqcalculator.html

17mbpro
10-12-2015, 09:54 PM
My chamber will be 44" in length. I did buy Franklins book and reading it now, I like his style a lot, especially the door to control airflow method. I'm definitely going to add a plate below the grates, I don't mind the temperature difference and might come in handy when cooking different meats.

SmittyJonz
10-12-2015, 09:57 PM
:sad: