Resources to learn about smoker design

[DogFaced PonySoldier]

Ok, Ahumadora thanks for the tips! Talking to you on the phone last night (actually this morning for you, I think!) was awesome! All the way in New Zealand via WhatsApp, free on the interwebz! What a world, eh? lol

Anyways, coupla questions:

2800mm total length, about 338 gallons.

Cut off 660mm on one end to make the firebox

New total length 2100mm or ~82.6" - new volume a hair over 250 gallons. Perfect.


A 660mm (~26") deep firebox (30" dia) is just under 80 gallons. You mentioned further cutting that in half and using the cut down portion to make a new interior wall to double the wall thickness of the firebox. That would leave let's say 330mm (13") in length for the firebox, which definitely doesn't seem deep enough to me. A firebox 13" long x 30" dia is going to look like an Oreo cookie stuck on the end of a roll of sausage.



Am I missing something or not understanding? I think the drawings you put up here don't account for cutting that firebox length down to double the wall thickness, which is what we talked about earlier. But then. I really don't want to cut this beast down below 250gallons, either.

Maybe we look around for another piece of large pipe to use as the firebox, see what we can find. Not sure how hard it would be to find a piece of heavy 30" pipe in someone's scrap yard - likely 24-30" long. But if I have to pay a coupla hundred bucks for one, I'm not overly concerned, that's a small cost, really, in the grand scheme of what something this size WOULD cost if I were having it made.

<edit> If I did find something like that to use as a firebox, it would allow me to keep the entire length I have now for the cook chamber - about 330 gallons. There's not a particular problem with this length or size, right? I mean mostly we see smokers here in the US made in 80, 120, 250, 500, 750 and 1000 gallon sizes - but I think that's mostly due to availability of propane tanks to use as starting points, not because those sizes or lengths are anything special in terms of the physics of things, I don't think. I mean, having a 9-foot long, 330 gallon smoker isn't inherently going to perform worse than a 250-gallon in the 7 foot range, is it?

Plus... my buddy who gave me this tank has a 250-gallon. He and I both would really like to see this one made up into one even larger. Just a man thing, right? If I have to buy something to build a firebox, that's not a big deal.

[DogFaced PonySoldier]

Yeah I get it now. Although... I still think I am going to look around and see if there is an easy and affordable option for an add-on firebox, rather than cutting the tanks and reducing my capacity.

[jfmorris]

DogFaced PonySoldier if you want to fabricate a firebox from scratch, one option would be to just get some square/rectangular 1/4" steel stock, and weld up a cube shaped box yourself, since you will most certainly be learning to weld as part of this project!

And of course, you could look for a 2-3 foot long piece of 20-24 inch diameter pipe as well and use that as the basis for the firebox. Salvage yard maybe?

[Ahumadora]

Yes. You understand using the top section offcut inside the firebox. Also you can find at a scrap yard offcuts either flat or curved to act as heat sheild inside tge firebox.

[Ahumadora]

Ok. If you want a bigger pit leave it whole and visit some scrap yards. I prefer round fire boxes to square as I feel they flow better. You will need pipe 24 -30" diameter for that size pit. About 4 -5 foot length.Either buy double the length to cut and double up or a large size to telescope over the top. Minimum thickness 5/16" or double walled can be 1/4". For your door seals we will double them up, having seals both inside and out using 1 × 1/8" flatbar.

[DogFaced PonySoldier]

Ok. If you want a bigger pit leave it whole and visit some scrap yards. I prefer round fire boxes to square as I feel they flow better. You will need pipe 24 -30" diameter for that size pit. About 4 -5 foot length.Either buy double the length to cut and double up or a large size to telescope over the top. Minimum thickness 5/16" or double walled can be 1/4". For your door seals we will double them up, having seals both inside and out using 1 × 1/8" flatbar.

Ok, so then for a firebox for a 9 foot cook chamber I need 24-30" diameter and 4-5 feet long? Or is that 4-5 feet the double length that needs to be cut down to be double-layered?

DIA x DEEP
24" x 48" = 94 gal
24" x 24" = 47 gal
24" x 60" = 117 gal
24" x 30" = ~59 gal

or

DIA x DEEP
30" x 48" = 148 gal
30" x 24" = ~73 gal
30" x 60" = 183 gal
30" x 30" = ~92 gal

Measured the firebox today on the 250 I'm using, it's about 19" in diameter internally and 24" deep. This makes it about 32 gallons or so. While I feel it could be larger, it doesn't seem particularly undersized -I've managed to get grate temps up to around 400ºF in the middle without too much trouble.

So I think 30" dia x 24" deep (73 gal) or 24" dia x 28-30" deep (55-59 gal) is quite a bit bigger firebox than the one I'm working with now - 2-2.5x the size.

Is there some formula to help determine ideal firebox volume in relation to cook chamber volume?

My admittedly naïve approach to this would suggest a larger diameter firebox would lead to a wider opening into the cook chamber, ostensibly leading to a slightly more even distribution of heat across the diameter of the cook chamber, at least at the end near the firebox.

[Ahumadora]

Stop over thinking at this stage and get yourself another whiskey. Go take pics of whats available at the scrap yard. Also start working on a steel list for grates, chimney, counter weights etc.

[DogFaced PonySoldier]

That's half the length of the cooking chamber? Really?

[Ahumadora]

Depnds what diameter tube you use. A long ger narrower tube seems to flow well and act like a blow torch. The 1000 gallon fireboxes I made are about 36" long and 30" diameter. See whats lurking at the scrap yard.

[DogFaced PonySoldier]

Just posting this here:

http://www.feldoncentral.com/bbqcalculator.html

I got this from Henrik's build log.

For my firebox, for a 108" long 30" diameter cook chamber (330 gal), it's recommending me a firebox of 30" dia x 36" deep (110 gal). So it is recommending 1/3 of the size of the cook chamber, which to me seems a bit excessive as you get into larger smokers. I could be wrong, of course.

[Ahumadora]

Yeah it's wrong. Have another drink to to relax your neurons.

[Henrik]

Agree, don’t trust that link/calculator, it’s just wrong all the way. Nothing I’ve ever endorsed.

[Stuey1515]

Did you read my post mate?

[DogFaced PonySoldier]

Yes, I read it Stuey1515, but we have limitations - first is getting the thing opened up and make sure it's safe inside with no oil or other petroleum distillate residue. We made some progress today, see below.

[Henrik]

I think you’re overthinking things way too much. I would follow Ahumadora ‘s plans and get started. You have a perfect firebox if you just cut 660 mm off the main tube. Why complicate things and try and get an even bigger/longer one?

Just have a drink, chill for a bit and the get that grinder started and get to building.

[DogFaced PonySoldier]

Because I want a BIGGER SMOKER???? What's wrong with that??? lol

The one I am borrowing now is 78" long cooking chamber, about 238 gallons. Because this is from my close friend and business partner, I am almost obligated to use as much of the length as I possibly can to make mine bigger than his in every way! lol It's just a bragging rights/pecking order kind of thing! lol

[DogFaced PonySoldier]

So today in the middle of a full day of offset cooking, we managed to make some progress.


We got the tank pulled off the trailer and positioned well away from structures and then with a whole lot of hammering, heating and Kroil penetrating oil, we achieved this:



I know it may not seem like much - but this was about 45 mins of hammering, mostly by my partner in crime (my shoulders aren't very conducive to hammering), a process which involved him standing on top of a rocking cylinder - OSHA would be horrified.

We're stoked. Tomorrow we're going to pour in a couple of bags of lump charcoal on top of a couple of chimneys of fired lump, then throw in a bunch of sticks and wood to burn out any potential hydrocarbons inside that may be clinging to the metal. The idea is just to get it to a couple of hundred degrees, not to superheat it. We have access to the ends as well, as the valves and hoses have been removed. We'll probably hook up an air hose to one of these to feed in a good supply of fresh oxygen and give it a couple of hours to heat up and burn out. My friend works in the oil & gas industry and between him and several others in the field, this was the recommendation multiple times over. Safety first, make sure it is cleaned out/heated up to remove any potential hydrocarbon contaminants before operating a cutting torch or plasma cutter of any kind cutting into that cylinder.

So I think that is on the menu for tomorrow


Then it will be looking for a trailer to mount this thing on so we can easily move it around and work on it. Right now it's just unbelievably cumbersome to do anything with.

[DogFaced PonySoldier]

Progress.... progress...

[lumbrjk]

Perfect!!

[Ahumadora]

Score. Will work great. Your plan is taking shape. If you are at the junk yard you will need a stack of about 6 1/2" diameter that will extend about 40" above the top of the pit.