1st time trailer RF build-150 gallon tank

[good 2bthe dawg]

what's up! very excited to get my first build going. i've got most materials rounded up or at least available locally. done my research here SMF and i'm ready for some input. wanting (i know what that means) to build a 150 gallon RF trailer smoker.

where i am at:

i have a 150 gallon water tank off a concrete truck. i've cut off and ground down all odd and ends. i've measured 1/4 of the tank diameter, mark & cut out the door.

i have a 2' square firebox being welded this week. 2' runs me 119% per BBQ calculator.

Question #1: BBQ calculator tells me that i need a firebox to cook chamber opening of 16.78 inches. is that the width of the cut i make? if so, how high? maybe i'm over thinking it? and then i realize that size needs to be the reverse flow opening, right?

Question #2: once someone explains #1, how high (6" is my guess) do i weld in my baffle plate above the firebox to cook chamber opening? i'll need to measure and have the baffle cut for me, it is the next and maybe only piece i need to purchase.

Question #3: how high do i put cooking grate above baffle? i have 1/4" woven grate to do the job that i'll rest on some angle iron.

i'm running everything thru BBQ calculator which is a life saver.

no welding skills at all but have 3 great friends that do and are free! i'm trying to fab all pieces to make it easy on them.

door flanges, hinges, intakes and chimney have been answered on other threads, but won't be afraid to ask.

with these questions answered i'm hoping to get a big chunk knocked out this week and weekend.

i am gonna try and get pics off my phone to add along, thanks for any and all help

Erin

 

[good 2bthe dawg]

Question #1: i was over thinking it. my nephew explained it and were gonna cut it now.

 

[weedeater]

The most important think is that you end up with the proper # of square inches of opening between the firebox and the tank.  That can be square, round, half moon, etc.  I think in your case it will be about 110 square inches.  As for other questions I will defer to the more experienced on the site. 

 

[rasimmo]

#1 I guess you got that figured out, but you can use this http://www.1728.org/circsect.htm  to figure out the area of a section of your circle. Use the segment height and radius and play around with differnt heights until you get the right square inches.

#2 Most folks say 1.5 times the FB to CC opening for the area under RF plate. Again use the circle calculator to figure out the height. The opening at the end of the of the RF plate needs to be at least the same size, if not a little bigger. 

#3 4.5" seems to work good

I hope this helps.

 

[good 2bthe dawg]

thanks rassimo, that link did the job. i believe ive got the sq in needed. might have to cheet a tad on baffle heigth after running the numbers, but i hope not much.

thanks again

 

[good 2bthe dawg]

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• good 2bthe dawg
• Jan 30, 2013

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• good 2bthe dawg
• Jan 30, 2013

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• good 2bthe dawg
• Jan 30, 2013

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• good 2bthe dawg
• Jan 30, 2013

 

[rasimmo]

No problem. I just started a build myself, so I went through all the same stuff for mine.

 

[daveomak]

Erin, morning......  What is the inside diameter of the Cook Chamber (tank)..... I will run some numbers for you....  Dave

I just noticed something.... the tank looks like it is aluminum.....  Is that the case ????

If so, I recommend finding a steel tank....  Dave

 

[themule69]

looks like you off to a great smoker.

david

 

[good 2bthe dawg]

That would be great Dave!  My inside diameter is 26"

It is a steel tank.  Thanks so much.

 

[daveomak]

what's up! very excited to get my first build going. i've got most materials rounded up or at least available locally. done my research here SMF and i'm ready for some input. wanting (i know what that means) to build a 150 gallon RF trailer smoker.

where i am at:

i have a 150 gallon water tank off a concrete truck. i've cut off and ground down all odd and ends. i've measured 1/4 of the tank diameter, mark & cut out the door.

i have a 2' square firebox being welded this week. 2' runs me 119% per BBQ calculator. Good..

Question #1: BBQ calculator tells me that i need a firebox to cook chamber opening of 16.78 inches. 111 sq. in.

is that the width of the cut i make? if so, how high? maybe i'm over thinking it? and then i realize that size needs to be the reverse flow opening, right?

Question #2: once someone explains #1, how high (6" is my guess) do i weld in my baffle plate above the firebox to cook chamber opening? i'll need to measure and have the baffle cut for me, it is the next and maybe only piece i need to purchase.

Question #3: how high do i put cooking grate above baffle? i have 1/4" woven grate to do the job that i'll rest on some angle iron.

i'm running everything thru BBQ calculator which is a life saver.

no welding skills at all but have 3 great friends that do and are free! i'm trying to fab all pieces to make it easy on them.

door flanges, hinges, intakes and chimney have been answered on other threads, but won't be afraid to ask.

with these questions answered i'm hoping to get a big chunk knocked out this week and weekend.

i am gonna try and get pics off my phone to add along, thanks for any and all help

Erin

.........Click on the calculator below...............

http://feldoncentral.com/bbqcalcula...46&fi=11,4,0,41.47,0.94&fc=11.87,16.78,110.59

http://www.1728.org/circsect.htm

FB fire control inlet  41 sq in (below the grate)

FB heat control for CC  6 sq in..  (above the grate)

FB/CC opening    23W x 6.1" segment height  113 sq in.

RF plate  24.7"W x 9" segment height.... 163 sq in.

Exh stack   6" x 25" above the CC..

I think those numbers are correct.... Having computer issues...    

Dave

 

[good 2bthe dawg]

thanks dave. those numbers are very helpful. we cut the FB to CC opening, we didnt think it was big enough are we were right. easy to take more off!

have a couple of more fine tune questions:

FB fire control inlet 41 sq in (below the grate)                  understand

FB heat control for CC 6 sq in.. (above the grate)            understand

FB/CC opening 23W x 6.1" segment height 113 sq in.     now i do, will cut out more

RF plate 24.7"W x 9" segment height.... 163 sq in.           is this the baffle opening? or the width of the baffle and how high it's off the bottom?

Exh stack 6" x 25" above the CC..                                     understand

i'm worried about running out of room from bottom to grate level. i'll have 6" with FB to CC opening then baffle height (that i'm 50/50 sure on), then 4.5" above that for grate?

thanks again dave, i tend to over think sometimes.

hoping to go pick up my firebox today after work!

 

[daveomak]

RF plate 24.7"W x 9" segment height.... 

Baffle.... Reverse Flow plate....  I think we are talking about the same thing.....  9" above the bottom of the tank...

[color= rgb(24, 24, 24)]FB/CC opening 23W x 6.1" segment height .......The opening to the cook chamber is 6.1" high from the bottom of the tank...[/color]

So 9" from the bottom of the tank is the RF plate.... Cooking Grate can be set 2-3" above the RF plate...  That leaves 14-15" of head room for food on the cooking grate...   If that concerns you, lower the RF plate to 7-8" above the bottom of the CC.... and lower the cook grate the same...  Be sure the opening at the end of the RF plate is 163 sq in or larger to facilitate good air flow around the end where the smoke/heat take a 180 deg turn....    Dave    

End view FB-CC-RF plate.jpg

• daveomak
• Jan 31, 2013

 

[good 2bthe dawg]

thanks dave. that wrapped my head around it. going out to make cuts. will post a pic.

 

[bruno994]

I would try and get the lower grate somewhere in the 4" to 4 1/2" range above the RF plate.  Mine is about 4 1/4" and works great. 

 

[good 2bthe dawg]

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• good 2bthe dawg
• Jan 31, 2013

made the cut. 6 1/4" segment height.

bottom of lower tape is 9" for RF plate that leaves me 4" to the grate height, top of upper tape mark.

all the numbers work, well, really close.

waiting on my firebox, should be ready anytime. ordering my RF plate tomorrow.

will be doing some work on the tank in the meantime, removing paint on outside, rust on the inside.

i'll take any pointers there, all i know is grider/wire wheel for rust and grinder/blending wheel outside.

thanks again for the help and thanks dave for the drawing.

 

[daveomak]

When you get the FB, take a pic and post it....  don't do any more cutting at this time....   To be sure I understand the new cutout, is the top of the cutout, on the end of the tank, 6 1/4" above the bottom ??

 

[good 2bthe dawg]

yes sir, i would say 6 1/8" would be more acurate. FB wasn't ready, so i be doing cleaning and some fabicating today/saturday. 50% chance of rain tomorrow and i'm doing this outside.

i think i drawing will be in order for the FB, i'll do one this weekend and post it for review. thanks dave

 

[weedeater]

Looks like you have your head wrapped around it now.  Are your planning on having slide out grates.  I would highly recommend it for a smoker of this size.  It makes life a lot simplier when cooking a full grate of food.  If you are going to have slide out grates the actual grate level would need to be higher than currently taped out. I would recommend raising the bottom of the grate1/2 inch above your door opening to insure it doesn't drag.  Looking good. Joe

 

[good 2bthe dawg]

thanks Joe. my first plan was to have removable bottom grate and slide out top. mostly because a guy gave me a 1/4" rod woven grate and thought it would make a good bottom grate. nice and sturdy and i really didnt think i needed a pull out. now....i'm thinking pull out, plus the extra space helps my numbers some. thanks for the input. 50% chance of rain and smoking for super bowl this weekend equals more designing and SMF time!