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Modified RF Build Opinions

post #1 of 3
Thread Starter 

So I'm getting prepping to do my first run at concessions with a small(100ish) cook. To handle that volume I borrowed my Grandpa's smoker, which he and his little brother built ages ago. She's a good old gal, nice and reliable, but like most side fireboxes she has temperature variation problems. Now if things go well with the concessions, I have intentions on building a 500 gallon RF. I'm pretty happy with the way most RF cookers are set up as far as the cooking chamber is concerned, but I got to wondering it it would be possible to build something like my Grandpa's smoker except reverse flow to alleviate those temperature issues. Below are the pictures of his smoker. Now basically what they did was halve an old tank, removed the end caps, and then attached what's basically a large box atop the tank. This allows for there to be not only shelving, but also rods to hang meat. Not sure if it is possible for that much open area, and I would have no clue where to begin doing the math because the large box on top of the tank completely throws the normal calculator. The crappy paint drawing is what my basic thoughts were. In the upper left side of the chamber there would be rods for hanging if the shelves are pulled out on that side. Nothing is to scale on that drawing, just so we're clear.










post #2 of 3

The math is not a big deal. Take half the tank volume, then add the volume of the box above it to get the total CC volume. Plug that into the calculator and you are off and running. Given that your drawing is not to scale, I must still add that the firebox is way too small.
Your concept is valid and should work just fine.

post #3 of 3
Thread Starter 

Lol, yea I wasn't going to have it on that drawing, but the firebox was one of the last things I added and my canvas was short on space at that point.


So I was using the RF how to, just using some rough dimensions. I wasn't having problems with the figures up until I got to the exhaust diameter/length calculation, and then onto the segment calculator. It seems when I plug in the radius of the tank which would be roughly 18.5" I can't actually get a number high enough to match my RB/CC opening.


Here's my math so far. These measurements for the box atop the tank aren't perfect because the propane tank is 37"x120" and I just used the length for the box on top at 96" which I figured was probably close to the tank length if I cut both end caps off. Not saying I want to do it this way, I just didn't know a quick way to calculate otherwise.



500g/2=250g propane tank = 57750 cubic inches
H:36" x D:37" x L:96" = 127872ci/231=553.56g


803.56g total or 185622ci


185622" x .004 = 742.488 square inches = FB/CC opening


185622" x .004 = 742.488 square inches = Area under RF plate


185622" x .004 = 742.488 square inches = Area at end of RF plate


185622" x .33 = 61255.26 cubic inches = FB volume


185622" x .001 = 185.622 square inches = FB air inlets
^upper and lower air inlets share value 
^20% upper = 37.1244 and 80% lower = 148.4976


185622" x .022 = 4083.684 cubic inches = Exhaust Stack volume

Edited by KRJ - 5/21/16 at 12:01am
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