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RF temp help?

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davefan360

Take a breath!
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Me and my buddy built a 120gallon RF smoker. we followed the bbq calculator and are right on with all that. everything is 1/4 in thick, other then the fire box. that is only 3/8. we fired it up today for the 2ed time today. we could only get it to about 200 after the first hour I tried for 4 hours. it was even temps on the top, bottom, front and back of the smoker. we has some air loss from the door, but can fix that. maybe someone need to talk me thorw how to get this thing to cooking temp?
 
And your running the intakes and exhaust wide open and can't get up to temp with a good bed of coals and some splits every hr? Got a picture of this thing? Hard to speculate without pics but its definitely lacking airflow somewhere.
 
Check your airflow, exhaust and intake.

A friend of mine had exhaust exiting his intake, preventing a good positive flow out the chimney. Not sure if this will help, but it might be a start. He opened the exhaust fully and then adjusted the intake to increase his temperatures
 
Pictures would really help!!
I can easily pull 500' in mine, one way to increase air-flow would be by extending the exhaust higher, try slipping a larger and longer piece of pipe over yours and see what happens. I used the calculator when I built mine, but when it came to the exhaust I figured to go longer than recommended figuring I could always cut some off later.(never did)
 
RF pits require more draft as mentioned it is a Chimney issue. Most pits have womens names and as any honest woman will tell you PIPE SIZE MATTERS. You want your Gal to warm up for you give her a longer pipe.
 
Just went back and checked the numbers I used when building the pit(72"x24"), the calculator called for a 28" by 5" chimney, I ended up using a 40" piece of 5" pipe.(firebox is 22"/cubed). Very happy I went longer.
 
smoke.bmp




Just thought of another possible reason, if you placed the bottom of your chimney pipe too deep into the inside of the pit that could also cause problems, I mounted mine flush with the top where no part of the pipe extends down into the cooking area. My train of though always was that by extending the chimney down inside the cooking area you would trap the hottest air at the top of the cook chamber which would reduce flow.
 
Any chance you can measure or post pics of your intakes & exhaust (sizes, height, etc)?
 
ok I think we messed up with the chimney, height. it does extend down into the cook chamber. our thought was to extend it lower into the cook chamber so it does not have to go as tall outside. thought over all length was what mattered not how far on the outside.
Chimney size is 3.5in and 35 in tall but we added the extra volume we needed with a 6by3 in tube inside of the cook chamber. the 2 air inlets on the fir box are 2by6.

our pit looks like the top photo that Columbia1 drew. here are some photos
 

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I was a pipefitter for many years the 90s in my opinion are restricting flow. I currently work in a refinery and have for a long time any engineer will tell you 2 many 90s closer together = flow restriction
 
TuscaloosaQ said:
I was a pipefitter for many years the 90s in my opinion are restricting flow. I currently work in a refinery and have for a long time any engineer will tell you 2 many 90s closer together = flow restriction
Click to expand...

This ^^^. With the 90* bends, you aren't drafting. Also, will you post pictures of your air intakes on the firebox?
 
pipes, if you can, OVER the fire box, and as high in the tank as possible. Remember, heat RISES. Let it rise to exit, creating a draw.
 
Without knowing the size of the firebox you have just looking I would say a 6" pipe 20" long would get you there. Personally I feel like your location is not the Killer it is flow restriction associated with the 90s
 
Can't see all the 90* bends, but TQ is right. I would wack off the exhaust so it does not extend any lower than the top cooking grate. The 3.5 inch exhaust is too small but keep the altitude (35 inches is pretty good for draft). Also, the intakes (2@2x6=24 sq in) are right at the minimum limit, given your cook chamber size you need intake and exhaust to be more like 30 sq in.

Bottom line (IMHO) for a 120 gallon tank, a 6 inch exhaust = 28 sq in is enough but you need a little more intake (2@ 2x6 = 24 sq in) try to add another 2x6. Either cut the stack flush with the top of the tank or not more than the top of the upper cooking grate and keep that stack at 36 inches+.

Best of luck!
 
TuscaloosaQ said:
I was a pipefitter for many years the 90s in my opinion are restricting flow. I currently work in a refinery and have for a long time any engineer will tell you 2 many 90s closer together = flow restriction
Click to expand...

Amen. You have to go straight for every 90 and it's measured in pipe diameters. Same in HVAC.
 
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