newbie 125 gallon reverse flow build the start

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smokeytodd

Fire Starter
Original poster
Mar 15, 2017
41
10
Bay city michigan
just wanted to say wow, alot of knowlage here ! im in the design process and checking out alot of the builds here on this site.absolutley awesome! im hoping for input due to lack of math skills and never ever building one , basicllylong time smoker first time caller so to speak. i have a 125 gallon air compressor tank that im starting out with. its going to be a patio style roll around.. ive went on one of the sites for figuring the math and after reading a ton of the builds , cmae to the conclusion that its probably not 100% correct. so with that i want to ask for help with the calculations. any and all helpwould be great. i havent cut anything or welded anything yet and im thinking i need to cut the CC Door out so i can get actuall numbers. unfortuntley i blew out my right knee 3 days ago so getting to the tank and working on it is on hold. so lots of reading and surfing this site is all i can do for now .
 
Welcome aboard Todd, I am new around here too. I don't want to assume that you have read through the reverse flow calculator thread, if not start there:

http://www.smokingmeatforums.com/a/reverse-flow-smoker-how-to-calculate-build-tutorial

I am just getting started on my build as well.  Its on this forum under 200 Gallon Oval Oil Tank Reverse Flow Smoker, I posted a screenshot of my calculations on there (I did make it more difficult than it needed to be).  Do you have a picture of your tank you can post?  You can start to get an idea on your calcs by going to the Tank Volume Calculator and putting in your external tank dimensions to get an idea of your actual volume and at least to get a start on ballparking your firebox and other cuts:

http://www.calculatorsoup.com/calculators/construction/tank.php

The tutorial is a must though, it is a great place to start.
 
thanks fatbastard09 i did read thru some of the calculations,it wasnt even close to the numbers i first came up with, they are alot bigger, so thats what im going with for now. cant wait to get rolling, but for stuck with just reading and checking out other posts..
 
Welcome Todd I am also building a smoker for the first time. Write your calculation down on paper then take a picture and post it on here so people can check your numbers . That is what I did. The folks on here are every friendly and helpful. P.S. we like picture's they help with suggestions. My build is 250 gal propane tank.
 
so i have a question for all of ya's i unloaded my tank today and took measurements. the guy i got it from said it was a 125 gallon tank (air compressor) sits horizontal. the measurements o.d. are 24" x 70 " long . does that sound right for a125 gallon ait tank?
i havent cut into it yet but think its .250 thick. it was rated for 250psi and made in the mid 70's . the tag tore when we loaded it up and didnt think to grab it. but reading a bunch of other builds on propane tanks of simular gallon capacity seems my tank is a little bit bigger any thoughts? had the fire box diemensions figured out for 24x24x24 would that still be right or do i need to refigure all my diaamensions out? any and all help would be great thanks guys
 
here is some more info for ya's, feldons calculator called for 9625 cu.in , at 24x24x24 it equals 13824 cu.in . is this going to be ok and fb to cc opening to be 110.59 sq in . which i think is to small what size do i need? on both and then how far up for the baffle plate from the bottom of the cc confused here lol sorry guys . but dont want to cut anything till i know for sure whats what
 
My biggist concern is I don't think the tank is 125 gallon ,all the 120 gallon propane builds have been shorter in length,mine was a air compressor tank. So I'm thinking I need to cut the door out and get accurate I.D . MEASUREMENTS to confirm tank size
 
Using daves calculator the tank volume in gallons comes out to 137 gallons. I'm building a RF right now with a 24x60 tank which is 117 I believe I'm going with a 24" square box which is 150 percent of what's needed so same size FB should work well on your tank also.
 
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would there be any benifit to mounting the rf plate one inch abouve the fb/cc opening and tappering it down one inch at the other end , for grease flow? was also wondering if one big grate or two smaller grates has any disadvatages over the other? either one will be able to slide out out any thoughts or recomendations? thanks again guys
 
I think an inch is more than you need on a tank that size. I'd overlap the plate onto the firebox. Assuming you lever the smoker when in use that 1/4 inch drop should be sufficient to run to the drain. In my 60 gallon RF I made the plate level and use drip pans for easy cleanup. Anything that does make it past the pans I just put a little water in there heat up the smoker brush it a little and drain it out.
 
I was wondering if anyone looked at the numbers I came up with? I'm wanting to get started cutting and fabing but don't want to start until I know it's right
 
Smokey Todd,

Looking at the pic of of your tank, it is rounded on each end. Have you taken into consideration that the depth of the domes is approximately 12 of te tank at regular diameter Measure the depth of your domes and divide them by 1/2 then add to the tank volume at regular diameter.. My smoker is similar to yours, but a little shorter because I cut off one dome flat to add a warming box later. 

As to your reverse flow plate height you need 4 to 6 inches between the RF plate and the lower cooking grate. If you raise the RF plate too much. you may not have room.

Remember that in your tank volume calc to use the inside diameter of the tank not the outside. After you relook at your volume calcs we can see if your numbers are correct
 
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I went by the out side length and width, assuming it's was .25 thick. My uncle had a similar tank and it was that thick so if it a touch thinner shouldn't hurt, figured at 137 gallons
 
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