Offset Smoker Build

Look WAY Too Big Around to me. Whats the diameter.?

I read a post somewhere that someone used an old pump surge tank and had quite a hard time cleaning up the rust and a surge tank sees less water in it's life than a water tank.

May be worth a road trip to the South to get a propane tank or 2.

to me their is no such thing as too big.. as long as the tanks are at least 1/4 inch thick and not galvanized or lined with any harmful chemicals.. I would use them. I have a 600 gallon offset cooks great can fit over 150 racks of ribs on it or 100+ butts.. I use the space I have to cook.. It purrs like a kitten once it gets to temp

My 600 gallon tank is 1/2 inch thick propane transport tank.

There is no such thing as too big, it just means you may want doors on both sides and or sliding grates for easier access.

As long as it is thick enough and plain steel it will work. You can also make a smoker with sheet steel, it does not need to be round or a former propane tank. The reason for the use of propane tanks is they can sometimes be had cheap.

Beware of online calculators and certain individuals on other forums who promote certain formulas for design. Every one I have seen is "wrong" in the sense that they use inputs that are at best a poor proxy for what a truly engineered design would require. They generally work within a certain size range, but if you are using an unusual shape and size tank, an eyeball test and common sense will be just as accurate or possibly much better. In particular, the Feldon calculator that works off volumes can give some pretty absurd results. The important driving factor is going to be BTU loss which is based on surface area, material and R value which are not even inputs to the model. A larger, wider cook chamber can have a surface area to volume ratio that is less than half of a smaller unit, and the calculator will ignore this and suggest a firebox and opening sizes that are double or more than necessary. in some cases much more.

m-fine said:

There is no such thing as too big, it just means you may want doors on both sides and or sliding grates for easier access.

As long as it is thick enough and plain steel it will work. You can also make a smoker with sheet steel, it does not need to be round or a former propane tank. The reason for the use of propane tanks is they can sometimes be had cheap.

Beware of online calculators and certain individuals on other forums who promote certain formulas for design. Every one I have seen is "wrong" in the sense that they use inputs that are at best a poor proxy for what a truly engineered design would require. They generally work within a certain size range, but if you are using an unusual shape and size tank, an eyeball test and common sense will be just as accurate or possibly much better. In particular, the Feldon calculator that works off volumes can give some pretty absurd results. The important driving factor is going to be BTU loss which is based on surface area, material and R value which are not even inputs to the model. A larger, wider cook chamber can have a surface area to volume ratio that is less than half of a smaller unit, and the calculator will ignore this and suggest a firebox and opening sizes that are double or more than necessary. in some cases much more.

Click to expand...

So, what formula would YOU use? Eyeball and common sense is a little vague. Not being a smart ass but you speak of heat loss/BTU/surface area etc. This sounds good and all but then you say to "eyeball" it?
That is just inconsistent data to me.

Simple answer: The math to do a "properly" engineered design is too complicated to quickly type up, and I really have no interest in doing it at this time. I also don't think precision in any sense of the word is necessary. Make the flow restriction big enough and add dampers to adjust flow downward as desired.

If you look at comercial smokers and tried and true designs, a 6" chimney works on a medium sized unit like my Lang 84. An 8" chimney will handle one much bigger. Figure that with an 8" chimney, your flow restriction with hot exhaust going through an area of roughly 50 sqin. The cold air coming in is more dense so total intake area of 50 sqin will be more than enough. The air leaving the fire box will be a bit hotter than in the chimney, so make the exit a bit bigger, say 75 sqin or more and carry that under the reverse flow or tuning plates. Making the openings any bigger without a bigger chimney diameter is not going to flow more air because the chimney is the choke point. Bigger won't hurt, either as long as you have input dampers you can dial back.

That leaves firebox size which is more a factor of space you want to work with as most are much bigger than necessary to meet the BTU needs. I would shoot for 2'x2'x2' as a minimum, but bigger is OK, especially if it is insulated.

Simple enough?

That sounds MUCH better than "eyeball it".
The OP may find this information more useful.

Move to Vermont....250 and 500 sitting here...

There are several pit calculators on the web to utilize. If a propane tank is not readily available, get a piece of 30" pipe or find a shop that can roll a sheet of 1/4" plate.

What you need to do is call your local propane supplier. Ask them where they send their junk tanks......there will be a salvage yard somewhere that evacuates the tanks and cuts the valves off for them to scrap. That's where I bought mine for my build, and I had a buddy who did the same. My 120 gallon tank was $30, his $500 was $150.

Best part was that I got a tank that I didn't have to mess with filling with water or the pucker factor and could get started on the build right away........

Good Luck.

^^^^^ What Cat said.

All American Propane (509) 488-2138

My company has a facility down the road from Moses Lake. These guys supply our propane.

I've found feldon to be an invaluable tool to help with builds.. I used it on both of my builds and it has given me great results I can get both of my pits up to 400+ if I want to no problem. I think Feldon BBQ Calculator is a great Free Tool home pit builders can use to build their pits. Lang doesn't go by this we know but to me there fireboxes on their bigger pits are undersized. To me they are doing this to conserve materials and reduce cost on mass producing pits.

I have heard of smokers made from "pipe" before........:loco: