Building a Traditional Offset

Try the Feldon's BBQ Pit Builder Calculator.

Have you seen Franklins pit build video? That should help you with a lot of it. Also keep in mind Feldons calculator is just a guide not an exact science. According to the calculator the fire box should be 1/3 the size of the cook chamber. So according to the calaculator, Aaron Franklin is doing it all wrong.

We had a Franklin inspired smoker build this past spring. Tank is 1000 gallon and firebox is half a 250 gallon. This think works unbelievably well. I took a chance and emailed Aaron and Stacy. The were kind enough to reply with answers to my questions.

I'm no pro at building these....we had someone do it for us. He's a killer welder so if you have specific questions please feel free to PM me....

razorbrewer said:

Do you have thoughts on the pipe I posted as the potential stack? Looking at yours, it appears to be at least a 10" pipe on your 1000 gal....is that correct?

Click to expand...

I'm not an expert but I would say you should be good with that free pipe.
We have a 10" stack yes. It's heavy beyond belief. Aaron suggested 12' tall but I went with 8' since driving the 12' around might catch on any number of things. I thought I'll just add 4' of stovepipe if needed. We don't need it.

razorbrewer said:

Scrap piece of pipe, 6.25" ID, 1/8" thick and plenty long for the stack. I had in mind an 8" diameter pipe for this but this might work...and is free. Any thoughts?

Click to expand...

Here's a member's Moberg. That stack looks like at least 8". If you're going to go through all the trouble of building, I would at least do it right. If you short cut, it might not draw properly or as well as it could. 6" just seems way to small for a 500. Just my free opinion...

When I stood on the trailer rails of Dylan Taylor's Austin Smoke Works 500, I would just barely touch over the top of the stack. That would put the height of that stack of around 8 feet somewhere. I don't know the diameter of it. I'd say 8"-10" though.

SMOKERBUILDER.COM is were I got my plans. Very detailed and helpful.

Rockinar said:

Here's a member's Moberg. That stack looks like at least 8". If you're going to go through all the trouble of building, I would at least do it right. If you short cut, it might not draw properly or as well as it could. 6" just seems way to small for a 500. Just my free opinion...

When I stood on the trailer rails of Dylan Taylor's Austin Smoke Works 500, I would just barely touch over the top of the stack. That would put the height of that stack of around 8 feet somewhere. I don't know the diameter of it. I'd say 8"-10" though.

Click to expand...

That's my Moberg, the stack is nearly 9"s diameter and almost 8 ft tall.

Feldon’s calculator is a bunch of complete bunk BS. The inputs are the wrong variables and the formulas are absurd. The output will result in a smoker that works within a reasonable size range, but it is in no way optimized or in anyway superior to other designs.

The good news is these things don’t require any precision in design. Make your firebox big enough to work in. For me that means about a 2’x2’x2’ cube as a minimum. Another 6” or more in one of more dimensions may be nice to have, but BTU wise, a firebox with half the volume will still hold a fire that will put out more than enough heat for even a very large smoker. For exhaust, you want somewhere around 5-6’ of vertical difference between your air intake and the top of the stack to have enough draft for most normal conditions. An extra foot or three won’t hurt you, but too tall will make it harder to store and trailer. For a cooker up to about 300 gallons, a 6” diameter will more than get the job done, for a 500 gallon size I would go with an 8” pipe.

The cool air coming in is more dense than the hot air leaving so the intake area can be a bit smaller than the exhaust area (about 50 sq in for an 8” circle) but for easy math I would shoot for 75-100% (38-50 sq in) give or take. The hottest least dense air is leaving the firebox going into the smoke chamber, so make that opening 50” or a little bit bigger.

That’s about it. Follow those guidelines and your smoker will have plenty of airflow to cook hot and fast and way more than enough for low and slow or mid temp smoking.

Rockinar said:

Click to expand...

How is that smoker passing the 40/60 weight test for a trailer? I am assuming the firebox is insulated...

The nose appears to be on the ground in the photo, so it must have some tongue weight. The angle may be deceiving.

Czarbecue said:

How is that smoker passing the 40/60 weight test for a trailer? I am assuming the firebox is insulated...

Click to expand...

The firebox is insulated, pulls behind the truck with ease.
Sunny Moberg (the builder) owned a trailer fabrication company for many years.

sickhick said:

The firebox is insulated, pulls behind the truck with ease.

Sunny Moberg (the builder) owned a trailer fabrication company for many years.

Click to expand...

Any pics of the trailer from the side?

The piece of pipe that you have is 6" sch. 10 resulting in that thin wall. That should work out OK. Just try to keep it from rusting. As far as flow is concerned, a lot of thin wall pipe is MIC coated and will be slicker than sch. 40 and will give it a better flow characteristic. You should be OK.

czarbecue said:

any pics of the trailer from the side?

Click to expand...

View attachment 164221