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Small RF smoker - 30 gallon

post #1 of 15
Thread Starter 

Hi all - Just wanted to throw my numbers out there and see if I am on the right track. I am building my smoker out of a 30 gallon compressor tank. So far I have the wheels and top plate removed so I wanted to check with ya'll before I started cutting any thing else. Any assistance would be appreciated,  Thanx Bob

 

 

 

Smoker Numbers

Wednesday, May 04, 2016

11:20 AM

Calculations for a standard design, reverse flow smoker..

 

Volume of the Cook Chamber.... Use the Inside Diameter of the tank...

                                                                                                                                                    

Diameter X Diameter X 0.7854 X Length = Volume in cubic inches / 231 = Volume in gallons

16 x 16 x 0.7854 x 36 = 7,238.2464 / 231 = 31.3344

 

Volume in cubic inches X 0.004 = FB/CC opening in square inches

7,238 x  0.004 = 28.952

 

Volume in cubic inches X 0.004 = Area under the RF plate in square inches

7,238 x  0.004 = 28.952

 

Volume in cubic inches X 0.004 = Area required at the end of the RF plate in square inches

7,238 x  0.004 = 28.952

 

Volume in cubic inches X 0.33 = minimum volume of the Fire Box

7,238 x  0.33 = 2,388.54

 

The above areas are necessary for great air/heat/smoke flow.... using less may cause an overheated FB.... Narrow / Long CC may require an increase in those numbers due to increased surface area friction to volume... Wide/Fat Short CC may use smaller numbers due to reduced surface area friction to volume...

 

Volume in cubic inches X 0.001 = FB air inlets in square inches…

7,238 x  0.001 = 7.238 

 

 

Recommended upper and lower air inlets... Upper air inlet directly across from the FB/CC opening to facilitate moving heat from the FB to the CC, and insuring good air flow through the CC.. The lower air inlet should be situated at or below the fuel grate.... The two air inlets can share the designated square inches of opening.... approx. 20% upper and 80% lower...

 

Volume in cubic inches X 0.022  = Exhaust Stack Volume in cubic inches, above the CC.... (ESV) .. (The increase in volume ~30% shows a dramatic improvement in equalized temperatures across the cooking surface... edit 6/19/15 )

7,238 x  0.022 = 159.236

 

Exhaust Calculation..

 

ESV in cubic inches / 0.7854 X Stack Diameter X Stack Diameter  = Stack Length in inches (36" +/-)

 

0.7854 X 4 X 4 = 12.5664

159.236 / 12.5 = 12.7389

 

0.7854 X 3 X 3 = 7.0686 

159.236 / 7 = 22.748 

 

0.7854 X 2.75 X 2.75 = 5.9396

159.236 / 5.9 = 26.9892    

 

0.7854 X 2.5 X 2.5 = 4.9088

159.236 / 4.9 = 32.4971  

 

0.7854 X 2 X 2 = 3.1416

159.236 / 3.1 = 51.3665 

 

 

 

 

 

The [Segment Area] box is what you area going to compare with the FB/CC opening in square inches...

 

 

Volume in cubic inches X 0.004 = FB/CC opening in square inches

7,238 x  0.004 = 28.952

 

If the FB/CC opening number is smaller, change the number in the Segment Height ED box to 5.... continue changing that number until the [Segment Area] matches the FB/CC number.....

 

Now look at the colored circles above.... Segment height ED is how tall the green area is and corresponds to the area to be cut out.....

 

Segment height ED = 3.250

 

Also, [Chord AB] corresponds to the width of the RF plate... NOTE... for ease in fitment, the FB should be at least as wide as the RF plate..

 

Chord AB (RF Plate) = 12.87

 

post #2 of 15

Numbers look good !! Will be a nice little patio smoker!!

Mike

post #3 of 15

Hi Bator,

 

Your numbers seem very close to mine  http://www.smokingmeatforums.com/t/245332/new-patio-build-from-australia

 

Mine is 34 gallons (longer but a bit skinnier) and the advice I have received is that for these smaller builds you need to exaggerate the numbers a bit. For example my segment height ED was 3.5" but I have pushed this up to 4.

 

I have gone for a 3" ID pipe for my exhaust sitting around 35".

 

Seems like you have a handle on the numbers though which to be honest is probably the trickiest part  :icon_biggrin:

 

Look forward to seeing your build.

 

Bazza 

post #4 of 15
Thread Starter 
Thanx for looking at the numbers Mike and Bazza, that helps great advice. Here are a few pics. Basically just cut off the running gear and mounting plate. I also cut out and patched the air inlets.









post #5 of 15
Thread Starter 

Hi all  - 

 

So the CC wall thickness is 1/8, should I make the firebox out of 1/4 or can I get by on 3/16? I have not bought materials but just wanted to check with you all.

 

Thanx, Bob

post #6 of 15
Quote:
Originally Posted by Bator View Post

Hi all  - 

So the CC wall thickness is 1/8, should I make the firebox out of 1/4 or can I get by on 3/16? I have not bought materials but just wanted to check with you all.

Thanx, Bob

I would go 1/4 on your fb as a minimum thickness
post #7 of 15
Thread Starter 

Ya that is pretty much what I figured but thought I would ask anyway, thanx!

post #8 of 15
Thread Starter 
Well got some work done this weekend. I got the tank cut for the firebox. I also cou the CC door an welded on the hingers. Of course after I cut the door I figured out it was a little out of square. I figure I can fudge a little on the CC border. Anywhy here are some pics.
post #9 of 15
Thread Starter 
Ok not sure what is up with the pics, will try in the am from my pc.
post #10 of 15
Thread Starter 

Ok so for whatever reason I can't seem to post pics from my phone. These were from this past week end.

 

 

 

post #11 of 15

Coming along nicely!

 

Bazza

post #12 of 15

How are you coming along on this project? I built a 250 gallon last year and now I've got a small compressor I want to use for a backyard smoker. My compressor appears to be a bit smaller than yours. I'd guess it to be around 20 gallon but this'll be a good thread for me to follow. 

post #13 of 15

Bator, morning....  If it's not too late, try increasing the FB/CC opening and raise the height of the RF plate and increase the width of the RF plate...  

 

From the tutorial....

 

The above areas are necessary for great air/heat/smoke flow.... using less may cause an overheated FB.... Narrow / Long CC may require an increase in those numbers due to increased surface area friction to volume...edit 8-16-16... small volume patio type smokers will need some increases in measurements also.. FB/CC, under RF plate, end of RF plate... ~20-30%..
 

 

I should have included that when it was written... 

post #14 of 15
Looking good! Keep posting!
post #15 of 15

Lookin good !! Getting closer to a spot on the Patio !!

Mikesuperjob.gif

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