Trailer pit build questions + Illustration

Phrasty

Phrasty

Babbling Farker
Joined
Jan 19, 2008
Messages
3,244
Reaction score
3,213
Points
0
Location
Jamaica
Hey brethren. Been planning a 250 gal reverse flow build lately. Something similar to this: http://www.smokymtbarbecue.com/store/TS250_Barbeque_Smoker-pid-61-3.html What I'm curious of is what temperature ranges do the units of this size generally hit? What's the fuel usage like (lump)? And what design elements would I need to be able to hit the steady 300-325's? I want to have the options for fast cooks. My design... well not "MY" design, but my inherited... modified design is a Reverse flow, offset with tuning plates rather than solid sheet for the reverse flow plate. Here's an illustration I did to give a better idea... Do any of you see any flaws here or things I should be aware of? Thanks for the help. :becky:

Cheers
 

Attachments

  • screen-capture-208.jpg
    screen-capture-208.jpg
    31 KB · Views: 277
I've never seen a design like that. It kind of a hybred. A standard RF smoker has a solid plate running the length of the pit. Those look like adjustable tuning plates. Very interesting design. It seems to me just looking at the drawing that it should work just fine. I think you might be defeating the purpose of the RF part... I also think that the warmer is a watse of space, materials and effort. I find a warmer to be of no use cooking comp or backyard. Using lump in that would be a rude awakening to you as far as cost and volume of lump needed. I like that design as a potential standard offset more than an RF design.
 
it looks cool but since i know nothing of builds i will let them chime in. However, i would like to be educated. thus said, what does reverse flow mean? reverse as in how? Whats a non reverse flow like?

thanx
 
I like the idea, kind of a tuned lang RF. Very cool, I love a new idea. You'll get a lot more posts once you start building it for sure. Good luck with the build and post lots of pics.
 
LT72884, Reverse flow is when the heat leaves the firebox and travels below a steel plate or a set of steel plates to the end of the cooker. Once it arrives here it rises and reverses its flow across the food and exits the chimney. If you look at the design above, you will see that the firebox and chimney are on the same end and the fire travels below plates and reverses to cook the food and exit the smoker. Typically, the idea is that heat stabilizes the further it travels creating a more even temp for the cook.
 
Roll Tide said:
LT72884, Reverse flow is when the heat leaves the firebox and travels below a steel plate or a set of steel plates to the end of the cooker. Once it arrives here it rises and reverses its flow across the food and exits the chimney. If you look at the design above, you will see that the firebox and chimney are on the same end and the fire travels below plates and reverses to cook the food and exit the smoker. Typically, the idea is that heat stabilizes the further it travels creating a more even temp for the cook.
Click to expand...

that makes sense. How well does this idea work?
 
The only obstacle I see is with the 'tuning plates'. You would need to make them a few inches narrower on the sides in order for them to function, which would leave a gap along the walls. As you turn the one end down, you would come into contact with the closing radius of the cylinder (If you know what I mean?).

I guess you could radius the one end of every plate to match you cylinder and cut a corresponding crescent on the end of the meeting plate so the interlock.
 
The idea of reverse flow works great. I am with Zilla here though, once you add the tuning plates and open them, you are using less of a reverse flow and more of a normal offset pit design. In a way, if you can get the tuning plates tight enough, you actually have more versatility in that you can go RF or not with your cooking.

I suspect due to the size of the chamber, you should not be focused on fuel consumption, it is a large smoker for lots of food, you will burn a lot of fuel. Is there a reason you would not go stick burner instead of charcoal?
 
Ive used a Lang 84 many times and we start with charcoal then go to all stick. My main concern with your design is a grease fire. Normally on that design, the drippings hit the plate and flow away from the firebox to a drain.

I really like your idea. If you can devise a way to catch the drippings and use the tuning plates I think you have a winner!!
 
The problem I see with the idea is going to be with the draft. The tuning plate idea is to allow smoke and heat to flow up at regulated intervals. I would be concerned of bad flow and stale smoke.
 
I cobbeled together a smoker out of a 250 gallon tank two thirds of it ids cooking space one third is the fire box I can run a steady temp of 275 up over 300 if I want that's all fire management. I start mine with charcoal then go to straight hickory. Its grate temps are within a few degrees of each other and its no reverse flow I cook my comp ribs on it.for hot cooks like for burgers I wish I had made my side fire box door go higher up. It looks just like my two doors for the cooking grates. And I wish I had built a removable grate directly over where I burn my wood.
 
Make sure that you build your firebox the correct size, mine is a little small and it makes for hell when conditions arent correct. You will get some good advice here from other peoples mistakes.

I am with Fourthwind on draft being an issue. of you wanted to keep the ability to use it as a reverse flow or with tuning plates you could put a stack at both ends so it would work properly for either use.

For the grease trap I cut a hole about 6" from the firebox and took the drop that I cut out for the stack and rocked it over toward the firebox and welded it solid across the back. That way the grease runs down the lowest point in the cylinder to the hole and will not run past it. It also works as a damper for any air that blows under the smoker so that it does not run into the firebox. Changing wind directions make for a hellatious buzz kill in the middle of a big cook. A friend of mine has air intakes on all 3 sides oh his firebox to compensate for this. It looks like you have a good project on your hands, cant wait to see the finished results.
 
Great feedback guys... This is exactly what I needed. Some very valid points here that I did not take into consideration! I guess there IS a reason why you don't really see RF/ reg offset hybrids out there. I am noticing that I basically have to go either /or... the point about draft is a definite problem I think I'm going to have to re-think this all.

Mtmouse The only obstacle I see is with the 'tuning plates'. You would need to make them a few inches narrower on the sides in order for them to function, which would leave a gap along the walls. As you turn the one end down, you would come into contact with the closing radius of the cylinder (If you know what I mean?).

I guess you could radius the one end of every plate to match you cylinder and cut a corresponding crescent on the end of the meeting plate so the interlock.
Click to expand...

That is a obvious problem I was oblivious to...:doh: Thank you. I think the rotating plates will be done away for the new design. Either scrap the tuning plates and go for straight reverse flow or just do sliding tuning plates on angle iron guides.

ZILLA I've never seen a design like that. It kind of a hybred. A standard RF smoker has a solid plate running the length of the pit. Those look like adjustable tuning plates. Very interesting design. It seems to me just looking at the drawing that it should work just fine. I think you might be defeating the purpose of the RF part... I also think that the warmer is a watse of space, materials and effort. I find a warmer to be of no use cooking comp or backyard. Using lump in that would be a rude awakening to you as far as cost and volume of lump needed. I like that design as a potential standard offset more than an RF design.
Click to expand...

What kind of weight are we talking here for about a 8 hour smoke? The issue is my location... Briquette coal is an imported & expensive item and I can get a 75lb bag of lump coal for about $8-$10. Its not THAT much of a cost issue.. it's quite readily available. As for stick burners, I've never truly smoked via all wood, I mainly use it added to lump. The other "issue" I have with 100% stick burning is since I've never done it I don't know the amount of smoke given off, I don't know if it will be over-welming. The local palette is not used to heavy smoke on their food... therefor I don't want to heavily smoke my food. So yeh... that is my self-determined reason why I'd rather not have a stick burner... Oh as well as having to find my smoking wood myself and not having a steady supply of it.

To add to all of this I think I'm going to size down to the 120Gal tank I also got. That should help out with the fuel consumption. I know its less cooking space but if it ends up insufficient for some of the bigger jobs I have other smaller smokers I can back it up with as well as just diving into the 250 build and then have all the cooking surface I will probably need with the 2 rigs.. :thumb:

Ok I know this post is getting long now... few more things. As far as Reverse flow and offset (with tuning plates) do any of you know the heat ranges of each (I know diff models vary) I basically want to know if one can generally get hotter than the other as well as which one has a more even heat distribution. Which would you rather build?

Phew... Ok I think thats it. I will re-draw the plans for the 120gal tank and post it up here for another review. Thanks for your help guys... I'm sure you have already saved me plenty time and wasted effort.

Cheers
 
So does anyone have an approximation for the necessary size of a firebox, cubic foot wise, for a smoker of X cubic feet? I suppose I could measure a functioning rig.

Would a baffle around the air inlet on the firebox prevent the problem with the wind?

Is there a big difference in flavor with the RF vs. normal flow? I would think there would be more uniform heat with RF. The tuning plates may be more trouble than they are worth.... but as long as you are investing all that time and money, do it how you want.

I hope this thread keeps going, I am thinking of building something myself.
 
Pit-building ratio calculator.

I grabbed this from another forum... (I don't know the rules on naming other forums here) Its an excel spreadsheet with the firebox, intake, exhaust length & firebox to cooker chamber opening calculator based on cooking chamber size. I don't know what the calculations are based on but it "looks" about right to me. Check it out, here's the download link:

http://webpages.charter.net/tomchism/Dodis%20Calculator/

Cheers
 
Here's the tank for the job... It's in pretty good condition. Planning on marking and cutting this week.

Cheers
 

Attachments

  • screen-capture-220.jpg
    screen-capture-220.jpg
    66.5 KB · Views: 52
Thanks Phrasty!

The spreadsheet suggests a firebox 1/3 of the volume of the smoker. I would not have guessed it needed to be that large.
 
The Frog said:
Thanks Phrasty!

The spreadsheet suggests a firebox 1/3 of the volume of the smoker. I would not have guessed it needed to be that large.
Click to expand...

Thought it was a bit large as well, I think i'm gonna make mine a shade smaller that 1/3.

Cheers
 
You must log in or register to reply here.

Similar threads

S
Small trailer offset smokers today?
Replies
18
Views
3K
cowboyupbbq
C
bonz50
smoker size/builders
Replies
19
Views
1K
Connor_Macleod
C
B
Winter Project_250 build
3 4 5
Replies
98
Views
11K
Fooball
F
C
280 gallon build
Replies
11
Views
935
Cheshire Bbq
C
Headgear
New Stick Burner Help
Replies
16
Views
830
cayenne
cayenne
Back
Top