Center feed build, of plate. 188 US. Gal

[etotore]

I have been around for some time looking for any tank, propan, air-compressor not possible to find in my area of the world..
Only offer was an hydraulic oil tank, I polity declined that one.

So my plan is to cut steel plates... I don't have a fancy tool room so it will be interesting.
Side drawing of the planned build.

Length of smoker is planned to be 63", I'm a metric guy so please bear with me. So 188 US Gallon did I calculated it to be.
length of FBox is 23" should give 62 Gallon. Since its center feed it can be 30 % less in size?
Opening's should be 173 Cuin2 ?

First question is baffel plate distance from bottom any advice. Will probably make this one in SS, since some said it was working very well.

Will order 1/4 inch plates, should be okay?
Any thought before I jump into some covid hobby project.

Tormod

 

[daveomak]

Please stop into .... https://www.smokingmeatforums.com/forums/roll-call.133/

and introduce yourself.. Tell us something about yourself.....

 

[flatbroke]

Welcome to SMF. Look forward to your progress

 

[kmmamm]

Might want to take a peek at what 1/4” Stainless cost in your area. Last time I checked it was about 4x more $ than regular 1/4” A36.

 

[etotore]

Might want to take a peek at what 1/4” Stainless cost in your area. Last time I checked it was about 4x more $ than regular 1/4” A36.

Yeah, agree with you there.
SS was for the baffle plate inside only.
Maybe for the racks too, not sure if it is any benefit in using SS there.
Any feedback?

 

[etotore]

Done the layout for plate cutting.
My poor 5" grinder will be abused a lot :)
Bottom of Firebox, will join two of the leftover bits

 

[kmmamm]

My advice is simply.....Don’t waste your money on stainless steel. Mild steel is not that hard to clean and will last every bit as long. You might want to consider expanding your cutting tool inventory by picking up an inexpensive plasma cutter (used or maybe something from a discount tool supplier like Harbor Freight) to get through the plate. It will save you a ton of time and with a little practice, much cleaner cuts to work with.

 

[etotore]

My advice is simply.....Don’t waste your money on stainless steel. Mild steel is not that hard to clean and will last every bit as long. You might want to consider expanding your cutting tool inventory by picking up an inexpensive plasma cutter (used or maybe something from a discount tool supplier like Harbor Freight) to get through the plate. It will save you a ton of time and with a little practice, much cleaner cuts to work with.

Taken your advice and ordered a plasma cutter, living far away from any proper Hardware store, so it will take some time.

Reason for baffle in SS material is not corrosion, it's its K value. Temperature properties.

So with a baffle in SS more of the heat is transferred in the smoke, less through the baffle, so hot spot issues will hopefully be less problematic. Will probably test both materials to see if it makes a difference. Have access to thermal camera, could be fun.

 

[kmmamm]

Yes, stainless will transfer heat faster.....keep in mind the primary purpose that plate serves is to direct air flow, manage renderings. Using thicker material will also allow it to serve as a heat sink to help even cc temps and facilitate recovery after the lid is opened. At the end of the day, using stainless will work...it is just going to cost more $$$.

 

[etotore]

Got the steel plates, already started the cutting can't wait.
With my luck I will get the plasma cutter when I'm finished.

The end piece, would you recommend to weld it on the outside?
Or make it fit on the inside, use it to build around, any thoughts?

SS is having less conductivity of heat, with 125C is approx three times less.
See table attached above in post 8, so 3mm SS is same as 9 mm mild steel.
So smoke will transfer more heat, as i aim for.

Will add some pictures in a few days..

 

[etotore]

Plasma Cutter is stuck in covid-19 lockdown in Manila, still between rain showers, short circuit of the cable to the grinder. things are slowly progressing. Used 50 cutting discs so far.
FB looks very big, so read a bit more, I can reduce it's size with 30 % since it's center feed?
Think I will reduce internal volume by insulating and making the shape more like a dome internally.

The white line where the arrow pointing too will put a plate there and insulate above, think it will give better chimney effect too.

Here is a picture of the internal, the baffle in the middle, is an idea to block direct radiation from the fire to hit bottom plate of cocking chamber. Will mount a tube/ thin plate box on top of this baffle with a lot of small holes in it, Upper air vent will air into that box, from the side. So its air gets heated and spread out into the whole top chamber. Is a common way in clean burning ovens in Noway. Not sure it will work for me worth a try anyway.

Still trying to get the welder right, but its getting there.

RF Baffle placement still struggling to get grasp on that one.
If I use 173in square divide it in 2 since it's flow in both directions.
I get that the RF plate is going to be an inch above the bottom, sounds close..

Opening to FB should be the same so a square of 13in?

 

[etotore]

RF Baffle placement still struggling to get grasp on that one.
If I use 173in square divide it in 2 since it's flow in both directions.
I get that the RF plate is going to be an inch above the bottom, sounds so close.
If I double that, or triple, 2"or 3" and restrict area required at the end of the RF plate to correct square inches, would that make any issues?

Opening to FB should be the same so a square of 13in or a little bit more will give 173" square.?

 

[daveomak]

Reason for baffle in SS material is not corrosion, it's its K value. Temperature properties.
View attachment 455369
So with a baffle in SS more of the heat is transferred in the smoke, less through the baffle, so hot spot issues will hopefully be less problematic. Will probably test both materials to see if it makes a difference. Have access to thermal camera, could be fun.

Nice chart showing how heat is conducted in metals...

SS does not conduct heat as well as other metals...

However, if you have heat impinging on the RF plate, it will stay where it impinges and a hotter spot will be created than if you used a more conductive material... SS will also warp more readily than a more conductive material... It has it's pro's and con's...

 

[etotore]

However, if you have heat impinging on the RF plate, it will stay where it impinges and a hotter spot will be created than if you used a more conductive material... SS will also warp more readily than a more conductive material... It has it's pro's and con's...

Thank you so much

Hot spot is, on my list of things to look into with center feed, with any material, is a problem issue in this design.
Would like to try both mild steel and SS, to compare on RF baffle.
Warp is a very valid point, will see if I can mitigate some of the issues, then again reverse flow is mostly low and slow.

The steel baffle I made inside the FB that blocks radiation waves from the fire to go through the air opening, and hit the RF baffle is a good first step. Forces more heat to be convection, and conduction through the materials.

On a second note, thanks to you, I will make a big opening between FB and CC, and make a sliding valve to find the sweet spot for air opening, between chambers. Since the mathematics for center feed is not invented yet, still volume vs fire should have some correlation in all designs.
Will have little less than 6" in distance from RF to the bottom plate, way to big distance I know, but easy to implement. Then adjust airflow in area required at the end of the RF plate, use the calculated value as a proven starting point. So I create an "over-pressure zone" below RF plate.

Is there any flaws based on your experience to this idea?

 

[daveomak]

Be careful when 'trying' to control convection air flow... The driving forces for convection air flow are 'subtle' and lacks force... What usually happens is... the air flow is severely diminished....
The mathematics for a center feed is simple... Create the 2 sides equal... Conflicting factors in getting equal results, meats on the food grates being unequal in mass, meat temperature, radiant heat affecting the CC, wind direction affecting cooling, meat moisture evaporative cooling effect, etc...
I was readying to cold smoke bacon one AM about 4AM... Had the smoker at 100F and it was cooling down... Ambient temp about 65F....
I put a 10# belly in the smoker to preheat and dry and it was about 35F...
The airflow in my smoker completely stopped and reversed direction in the smoker... exiting out the Mail Box mod....
Seems stupid... BUT.... the thermal mass of a 10# belly, and a 30 deg. difference had more force than a smoker at 65F ...
Been there, seen it....
I think that adequately displays the sensitivity of a 'gravity', 'convection' NON driven air flow...

 

[daveomak]

Your center feed will be driven by BTU's from a fire... Unequal heat from the fire will affect the temperature and air flow distribution in the smoker...
It will drive you crazy trying to control equal distribution in the smoker... I think that's why a Reverse Flow smoker was invented... Center Feeds are a PITA.....

 

[etotore]

Made a sliding Throat adjuster:

I can see on the welding drops I have made, how many inches wide the opening is.
So I have sort of good control over throat opening, 6 inches wide and max length is 10,5"
Think I will need to reduce the size of opening when I find out my operating area.

Sliding doors, first Tig splatting around in 30 years. I seriously need to sit down and practice

Temporary handle, but it show the opening size.
After I had done it, I found out how I will make it later.

How it looks when open

Sliding dampers are 1.5 mm SS, so they not so easy get stuck by rusting into plate below.

Then I managed to do the front.
Insulated with 1" rockwool the front plate.

Think I will order some fire tiles to play with size of Firebox volume too
And current status is as follows
.

Borrowed a nice tool for checking operation sadly not to soon
My test subjects, my two dogs.

Lol not for the BBQ