First build, Franklin'ish = many q's to follow

[Beagle Bones]

I bought a piece of pipe 20" od, 1/4" wall or a tick thicker, 63" long, torch cut ends. $75 Once i can square the ends, I'm hoping for 62" overall.

My initial plan was to build a 20x60 smoker per the plans on this site. Now, I'm looking in a smaller direction. if I build a ~48" CC I can use the excess pipe for a ~ 18" fire box. I bought a 20" od tank end cap w/a 2" flange. It gives me about 3" before the curve. If I go w/the round firebox, I save $400 in steel building a square fire box.

Here are the finished dimensions I'm spit balling. 20" od x 0.25 x 62". Cut 16-18" off for a firebox. Weld 20" od tank cap onto the cook chamber. Adding ~3" to the overall chamber, plus the dome.

My questions:
Am i right to enter the inside diameter of the pipe in the smoker calculators? In my case 19.5" ish
Is a firebox ratio greater than 100% suitable?

Link to BBQ Pit Calculator

[Barrion2018]

I think you'll be fine using the ID.

I built my first offset this past spring (20"x46"x3/8" CC & 20"x24"x3/8 FB. I went with an oversized FB) using pipe. when I put it into the calculator, I used OD measurements. I'm very happy with how it came out, and how it cooks.

Currently, me and my daughter are building a RF for her. And with her smoker, I'm using the ID measurements to see if it makes a differance. The only thing that I noticed, according to the calculator, is that the throat is a little larger using the ID measurements.

I'm also very new at this, so I would wait to hear from one of the more experienced guys or gals that can help you better.

Good luck, and post pics of your build as you go.

[Dirtytires]

You are correct. Use the inside dimensions in the calculator....you are looking for volume of the pipe and the thickness of the material is not revenant to the calculation.

[Beagle Bones]

I'm trying to determine the throat. I'm not certain what the above calculations are referring to. Using those calculations, a 10.46" diameter half moon and 43.0 sq inch throat is recommended.

Do I pull a tape across and move upwards until I read 10.5" inside to inside? I'm using pipe for the CC and the FB, so I'll be overlaying two circles.

[Pete Mazz]

Use ours: https://planetcalc.com/5155/

[Beagle Bones]

Thank you Pete. That's exactly the information that I needed!