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-   -   RF temp help? (http://www.bbq-brethren.com/forum/showthread.php?t=160761)

davefan360 05-12-2013 08:46 PM

RF temp help?
 
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?

jmoney7269 05-12-2013 08:58 PM

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.

IamMadMan 05-12-2013 09:00 PM

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

columbia1 05-13-2013 10:21 AM

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)

Bludawg 05-13-2013 11:20 AM

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.

boiler93 05-13-2013 11:50 AM

Similar issue, exchanged a 3" exhaust to a 6" and no longer a problem.

columbia1 05-13-2013 12:34 PM

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.

columbia1 05-13-2013 12:43 PM

http://elliottwavetrendsandcharts.co...3/05/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.

dwfisk 05-13-2013 01:05 PM

Any chance you can measure or post pics of your intakes & exhaust (sizes, height, etc)?

DownHomeQue 05-13-2013 04:12 PM

we need pics! :doh:

davefan360 05-13-2013 06:05 PM

2 Attachment(s)
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

davefan360 05-13-2013 06:08 PM

in the bottom photo you can kind of see how we extened the chiminy into the cook chamber. the chimney does a 90 into it then it 90s again down to 4 in over the firebox.

TuscaloosaQ 05-13-2013 06:13 PM

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

morgaj1 05-13-2013 06:53 PM

Quote:

Originally Posted by TuscaloosaQ (Post 2479756)
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

This ^^^. With the 90* bends, you aren't drafting. Also, will you post pictures of your air intakes on the firebox?

davefan360 05-13-2013 06:53 PM

ok so ditch the small pipe, get a bigger one and move farther back on the tank? if so what size do I need?


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