Pit Building -- Getting started help needed.

[lcbateman3]

Hey All,

So, I kinda ran across a 500 gallon tank, a boat trailer, some steel, and other items. I have a FIL that is a pretty good welder. So we are going to build another pit. (He built my last one)

I am looking at a Lang clone really. The barrell is 36" in Dia, and 98" from end to end. Using a spreadsheet that someone up here linked to I need a square fire box with a vaolume of 33234. (Which is 32.25 by 32.25 by 32.25) Cool deal. Opening for the fire box to chamber needs to be roghly 16x16 or come up with a difffernet one.

Now according to the spreadsheet you want 1 firebox air inlet that needs to be 10 sq inches. Is this correct? Or should I go with two?

I know I am going have to addust the calculation for the exhaust cause i can run a 5.33" dia by 73.5" smoke stack...might be a little large!

So do these things look right to you? How about the air inlet? Just one?

Also underneath the racks (going to setup like the Lang is, two teir rack system, doors on each side) what do I need to do there. I am guessing some time of plate to help the smoke flow from the firebox down the chamber.. This is where I am lost at. Really have never seen the inside of one.

Any tips would be great!

Thanks!

 

[stiffy]

Here is a link to a Reverse Flow Build which Lang's are known for kinda...Smoker Rebuild by Fatdaddy

 

[Philly-QueMaster]

Your firebox estimates seem rather large. Your estimates are almost 3ftx3ft. That seems really big.

 

[BigBrad]

I just built a offset this spring and I will give you a very important suggestion you can't have too much exhaust pipe. You can always choke it down at the inlet but you can't increase your maximum exhaust. Just my thoughts. Oh yeah I built my cooker with a 4inch stack and had to change it to a six inch pipe to get enough draw.:doh: not a big deal but still a pain after everything is done and painted. Good luck.

 

[kcchiefdav]

I agree with Philly, you've got like 140 or so gallons of firebox to go with your 500 gallon tank smoker. Seems like overkill.

 

[lcbateman3]

I was thinking it was rather large as well. According to the calculations, the fire box should be 1/3 the size of the cooking section. So if the volumbe of the SMoker is 99701 CI the fire box would roughly be 33234 CI. Now I am all for changing it if need be!

Brad, yea I was just going to go with a larger diameter pipe then it called for.

 

[roksmith]

The firebox calculations are correct, don't downsize.

Firebox can't be too large(within reason).. but it certainly can be too small. Same with the exhaust stack. Always Err on the side of bigger. You can always restrict the airflow with a large exhasut and build a smaller fire in bigger firebox.. Can't go the other way. Also make sure you don't undersize the air inlet. If you go with multiple inlets rather than one, make sure you calculate correctly for the amount of air volume. Correct calculations make for an easy to control smoker. Undersize any of the components and you'll wish you hadn't.

 

[Stevesonfire!]

I built mine over the winter...thank God I hadn't found this forum yet! All this talk about calculations would have scared me off building it! I never gave any of that the first thought. I sketched a drawing of what I wanted it to look like. Bought an old air compressor tank, used an old "energy mate" wood stove for the fire box, thought dual stacks would look cool...then learned how to weld.
In the end...the thing works great. I've even started cooking for cash with it...
Guess I got lucky, I remember many times over the winter saying to myself "Ah, that looks good..weld it" Good luck with yours!:shocked:

 

[lcbateman3]

What would be suggested then? One air inlet or two? I would think control would be a little finer with two air inlets. But then again, I have been wrong before.

How about firebox thickness? 1/4" sound about right? Or do I need thicker or thiner? Thinking about insulating as well, got to find that thread up here about one somebody did. If I go reverse flow way the damper below the cooking grates, 1/4" as well??

 

[Stevesonfire!]

What would be suggested then? One air inlet or two? I would think control would be a little finer with two air inlets. But then again, I have been wrong before.

How about firebox thickness? 1/4" sound about right? Or do I need thicker or thiner? Thinking about insulating as well, got to find that thread up here about one somebody did. If I go reverse flow way the damper below the cooking grates, 1/4" as well??

I will be adding a second air intake for that very reason...better control. 1/4" is pretty standard for home builds. Any heavier and the thing becomes a monster to move. Mine weighs 620 lbs!

 

[countyliner]

Always Err on the side of bigger.....

....Undersize any of the components and you'll wish you hadn't.

Agree

 

[lcbateman3]

Well the weight doesn't bother me to much as long as it does exceed the trailer limit, not like I will be moving this thing around by hand much.

Okay, so now to mark up some drawings...I'll post them here in the next couple of days to get everyones opnion.

 

[jestridge]

Maybe you should think about a firebox on the backside or under the tank. here a small one I built it has a bottom firebox