Standard Reverse Flow Smoker Calculator... by DaveOmak and others... Ready to use.. rev5.. 6/19/15.

[gary s]

Hey Smokin Jo, here is what I come up with.

Feldon's has a few glitches when it comes to RF's  The increased FB to CC opening size will result in much better heat, smoke and air flow. These figures come from trial and error.

My son and I build 1 to 2 pits a year during his slow time. These calculations work better than Feldon's .

Also:  33% of the CC for the FB is really the minimum you can take it on up to 35 -40 %.

                                          Cook             Firebox           Stack      FB to CC          Firebox                  Firebox     

Recommended  Size    Chamber        33% of CC         Vol.        Opening      Opening (Low)      Opening (High)    

                                         25,334             8,436              506.7          101.3               25.33                       5.07    

Gary

                                    

                                    

 

[ribwizzard]

Yall been getting fancy since ive been away!

 

[ribwizzard]

But I will say that im going smaller with the firebox on my next build. This is a 250 and has 30" by 30" firebox. With double plated top of firebox they dont need to be so big. This runs all day at 250 with small fire and is up to temp in 30 minutes.

20150926_131341.jpg

• ribwizzard
• Sep 26, 2015

 

[ribwizzard]

20150926_131357.jpg

• ribwizzard
• Sep 26, 2015

 

[daveomak]

Holey smokes..... look who dropped in....... Howdy RW.... been awhile....

 

[gary s]

Hey RW  good to hear from you

Gary

 

[ribwizzard]

Ive been trying to get on here for a week now. Just now had time. Looking forward to see all the new builds over the last year. Ill be starting another as soon as it cools off a bit. Im going through way to much wood and building up way too much crust on the reverse plates. Time for something better.

 

[daveomak]

Try adding an upper air inlet to the FB to burn off those volatiles inside the FB before they get to the RF plate...

 

[ribwizzard]

Its crust from the dripping. I ended up adding sheet pans to make it easier to clean but that still is a full time job

20150926_135701.jpg

• ribwizzard
• Sep 26, 2015

 

[daveomak]

WOW... That's a lot of work... Slide out RF plate ??.... Design a different cooker ??...

 

[ribwizzard]

Not sure yet Dave, got a couple ideals Im thinking about...

But its definately something to consider when building a reverse flow. If you plan on doing alot of cooking, those dripping and morsels of food dont flow out the drain like you think they would. My smokers are going from 6:30 am till after 8pm during operating days, so no time to go in and power wash them out. And if not careful, the stuff can work its way under the reverse flow plate where it can and has cought on fire and toasted all the food. Also, as the crud builds up on the plate, the smoker looses efficency due to less heat coming up through the plate. Now your using more wood and slowing down production.

 

[ribwizzard]

Almost tempted to use a large piece of pipe instead of a plate, that way the drippings go down into the bottom of the tank and should not build up on the pipe too bad. They would not be exposed to direct flame and an access door could be installed on the bottom for when its time to wash it out. I need cleaning to be quick and easy becouse Im paying for the labor to clean them.

 

[daveomak]

Think about a "down draft / flow" smoker with no baffle or reverse flow plate....

Down Flow Smoker.jpg

• daveomak
• Sep 27, 2015

DownDraftSmoker.jpg

• daveomak
• Sep 27, 2015

 

[ribwizzard]

Ive been thinking about something like that as well. Except mounting the firebox on the 250 gallon tank , recessed into the end cap, with the top of the firebox at cooking grate level. But instead of cutting the opening from the firebox to cooking chamber on the side of the firebox, cut it in the top so the heat goes straight up into the cooking chamber.???

 

[daveomak]

Sounds good..... Will it be ready to fire up by Friday ?????

 

[ribwizzard]

Nah, got firebox built but dont want to cut into the tank until I get my head straight about how I want to build it. The jambo style above would work for drippings but would probably burn wood like crazy. Might have to run a 4" pipe from firebox below cooking grate to grab some more heat before it exits the cc

 

[daveomak]

You could put a choke plate on the exhaust to slow it down.....

 

[ribwizzard]

If I took 3 or 4 hyd. Cylinder rods, like 5ft long x 4" diameter, and ran them from inside the firebox where the flames hit them and then under the cooking grates, how much heat transfer do you think they would give?

 

[bill1]

Newbie comment...I'm just not appreciating the reverse flow concept in these layouts.  The smoke stays in the cook chamber longer but the lower half of the trip it's not doing anything other than some added heating to the RF plate.  Why not put the RF plate BETWEEN two grates of meat?   That's putting the lower half of the "smoke time" to work for you on the lower grate of meat.  After reversing, the smoke goes to work on the top grate.  Seems you want to keep the cross sectional areas roughly equal between top and lower halves so the smoke flow velocity is the same for both halves, which would lead you to put the RF plate in the middle.  

What am I not understanding?  

 

[smokejumper]

Hello bill1,

You are correct that the "lower half of the trip" is just heating the RF plate. That is what contributes to the even heat distribution in the CC.

The heat is not wasted, and the smoke is not depleted in any way so that the meat does not suffer form lack of smoke.

The RF plate also acts as a drip pan so that grease does not fall to the bottom of the CC where it could catch fire.