I knew I read that somewhere!
200 gal reverse flow build - Page 3
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got some more done ton. got the racks welded up but not mounted yet. put the flange on the door and got it mounted and a handle made not sure if it like the handle though. i did a 2 x 1/4 inch strip on the top since thats where the hinges mount and the other 3 sides are 2 x 3/16, i used rib wizards method then did a few beads on the outside of the top. also monted a jack on the front of the trailer. i wanted to get more done but run out of welding wire so had to run and get some then they didnt have any .035 so got a 10lbs roll of .030 to use intil i can get another 50lbs roll of .035.
ok guys i need some help again i need to figure out how to get my lower intake vent large enough in the space i have i was gonna go it on the bottom but dont want to remove the fire brick thats already there so i am thinking a intake vent with a shroud to have it draw from the bottom so its not affected by wind. i have 20 inch wide to work with. maybe im over thinking this but im stumped
Started with a broken clamp similar to this
Came up with this not real pretty but I plan to put a shroud over it so it draws from the bottom and it not as effected by wind
Symonds, afternoon..... well, In my opinion, the FB air inlet was calculated to provide adequate air flow through the CC to keep it hot... and keep the temp up..... It's difficult to explain.. the volume of the CC and that surface area, require a certain amount of air flow for all the numbers to work.... Btu's, CFM... etc.... No one runs their smokers with the bottom vent fully open.... It's there to start the fire, move a great volume or air to get the smoker up to temp...... Opening the door during start up will help...... Having a second air inlet above the fire grate to move air without having to stoke the fire is important and can play a roll in initial heat up of the unit....
Soooo.... that being said.... go with what you have, make sure the air inlet above the fire grate is 5-6 sq. in..... and open the door, if needed, during warm up of the smoker....
The calculator numbers are there to insure you have a smoker that works... If stuff doesn't work out, and you can't fit your smoker to the numbers, then that's the way the wind blew today... No biggee... If the smoker needs more air, you will find a way to make it happen.... If the smoker runs fine with what you have, the that is really cool.....
This is how the chimney is now should I open the ole upwards more or leave it as is?
i fired it up today to see how it would work and i figured earier to fix and change stuff now then after it was painted. took about 45 min to get up to 250 with fb doors open. then i seemed to have good control from 225 to 300 with the vents. i do however have a couple problems one being a 20 degree difference from one side to the other was over 50 degrees difference while it the doors were open but settled to around 20 after i shut the air down and got it to 225. any ideas how to fix it im thinking its the heat from the fire because the fc side is the hot side. a baffle might help i suppose if i can figure out how to get one in there now that its welded up. the other problem is getting over 250 is difficult maybe i need a bigger fire or something but that problem isnt really a big deal because i dont normally exceed 225 to 250 while cooking any input is welcome thanks guys
The higher temp at the firebox end is likely due to the radiant heat from the fire heating that end of the RF plate. This is common on RF smokers that have the FB tucked under the end of the tank.
Ribwizzard has a pretty good drawing that I have seen on another post that illustrates the problem pretty well.
The fix is to mount a plate about one inch below the RF plate on the FB end that extends into the firebox if possible, or buts up against the end of the firebox if the top of of the RF plate is not even with the top of the FB. This plate will take the brunt of the radiant heat and result in a more even temp across the RF plate.
A far as the cooker not getting over 250 degrees, there could be several causes. First thing I would check is to make sure that the opening at the far end of the RF plate is at least as big as the FB to CC opening. If it gets hotter with the FB doors cracked open, you are likely starving the fire of air. How does the smoke look?
i cracked the door and the temp didnt really change maybe 5 degree increase, i am wondering if my fb opening might be to small it is the same size as the diagram but i could open it to the top of the rf plate as it is about 2 inches under that now i have seen pictures of other cookers where when they have a large fire the flames suck into the hole if i do that my flames are pretty much still straight up and down not sure just an idea
Symonds.... Since you have chose to change some of the dimension I provided, let us know what dimensions you used on the smoker so we can help you fix your smoker..... Dave
In the drawing below, the RF plate does not look to be 9" from the bottom of the smoker and the opening between the FB and CC does not appear to be 7" from the bottom of the smoker....... What are those dimensions..... Dave
Your chimney is way oversized.
For a square chimney, you calculate the Hydraulic Diameter = 4 * Area / wetted perimeter, to take into account the additional friction drag which in your case is equivalent to a 7.5" dia round pipe. You have an equivalent volume of 1502 cu-in.
However, the larger you go, the less important the grometry becomes. If you calculate it out without considering the added friction drag of the square pipe, you are at 2040 cu-in.
The recommended chimney volume for your cooker is 770 cu-in.
You may be losing too much heat up the chimney.
Draft (pressure) is directly proportional to the height of the chimney and the temp of the smoke. At a given draft pressure, the FLOW is directly proportional to the cross sectional area of the chimney. I believe you may be moving too much smoke too fast.
I also suspect that your FB-CC opening may be too small, but that is just a guess based on your pics. Let us know what the numbers are for that when you get them and we can work it out for you.
Edited by SmokeJumper - 7/29/13 at 9:31am
the fire box is 22 high 28 wide 25 long. my rf plate is 8.5 inches from the bottom of the cc in the middle and 9.5 inches on the outside edges. and dave you are right the hole i cut is only 6 inches tall in the middle an inch to smaller then the drawing somehow i messed up when i marked it out on the fb and never caught it when i cut it thank you for the help guys as for the chimney i can resize it by making it narrower or do what ever what would be best thanks for the help