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Custom Smoker Problem

NCoonis said:
Thanks Andrew. Yeah I put the 4" pipe as high up as I could, it's just under that top corrugated bead/bump in the fire chamber barrel. I didn't want to mess with cutting a hole through that bead. There's only about 3" from the pipe to the lid of the fire barrel, so some heat is sitting up there. Maybe if I beef upy exhaust like landarc mention it will pull more of that heat through.
Click to expand...

yes, i agree, it will pull a draft! right on!
 
NCoonis said:
Thanks dwfisk! I appreciate your compliments. I couldn't really find any upright offset drum smokers anywhere so I thought I'd try one. Maybe there's a reason why I couldn't find another on like it! Haha!!

I think you're right about the airflow, definitely the exhaust. I think I'll start with new gauges, then more exhaust and see what happens from there. Two bad those 3/4" ball valves are like 14$ each!
Click to expand...

I clarified a little on my earlier response. If I read your original post correctly and you are keeping your existing 2" closed when cooking then you are getting zero air flow. Thats an easy fix, open the exhaust wide open and control airflow with your inlets. I'm certainly not a UDS expert, don't even have one (yet) but you might be OK with 4@3/4" inlets, ball valves on a couple and just let the other two run wide open with no valves.
 
No maybe I miss typed but I definately leave the 2" exhaust open at all times. I don't even have a damper on it.
 
Any ideas on materials for a chimney? I can cut the 2" existing hole bigger and make it 3 or 4", but what should I use for a chimney? Home Deeps only has black Iron pipe up to 1" or galvy sheet metal ducts and chimney caps. Is galvy ok to use just for the chimney outlet?
 
NCoonis said:
Any ideas on materials for a chimney? I can cut the 2" existing hole bigger and make it 3 or 4", but what should I use for a chimney? Home Deeps only has black Iron pipe up to 1" or galvy sheet metal ducts and chimney caps. Is galvy ok to use just for the chimney outlet?
Click to expand...

aluminum dryer vent
 
Look in the electrical conduit department at Home Depot or Lowes. They should have something that screws right into that bung hole, and even if it is galvanized its just being used for exhaust. You can even soak it in toilet bowl cleaner and that will eat the galvanizing right off of it.
 
Great lookin build! I'm jealous, I definitely want a vertical offset one of these days. Is the gauge you bought a Brinkmann by chance? If so I bought the same gauge and dont worry... its a POS! I had my rig up to about 325 with that worthless gauge reading 175 degrees.
 
OK I see you are leaving the 2" exhaust open, my bad. I would think you need at least a 3". Look for a custom muffler shop, they should be able to cut an sell you a 3 ft chunk of 3" pretty cheap. It will be galvanized or nickel plated but its OK for the exhaust.

One 3" will give you the same 3.7 square inch exhaust area you have with the four 3/4" inlets.
 
SmokinSlowPoke said:
Great lookin build! I'm jealous, I definitely want a vertical offset one of these days. Is the gauge you bought a Brinkmann by chance? If so I bought the same gauge and dont worry... its a POS! I had my rig up to about 325 with that worthless gauge reading 175 degrees.
Click to expand...

Thanks!! Yes it is a Brinkman I believe. It was the only one they had there. Anyway that makes me feel much better. I am definitely switching it out today. My wife wants my to smoke something for Easter on sunday so I guess I'll try round two with all these suggestions.
 
dwfisk said:
OK I see you are leaving the 2" exhaust open, my bad. I would think you need at least a 3". Look for a custom muffler shop, they should be able to cut an sell you a 3 ft chunk of 3" pretty cheap. It will be galvanized or nickel plated but its OK for the exhaust.

One 3" will give you the same 3.7 square inch exhaust area you have with the four 3/4" inlets.
Click to expand...

You're awesome Dave! I am most definitely making all these mods this weekend. I still have other small things like door handles and latches to put on. I'll post new pics after this weekend and let you know how it went.
 
NCoonis said:
You're awesome Dave! I am most definitely making all these mods this weekend. I still have other small things like door handles and latches to put on. I'll post new pics after this weekend and let you know how it went.
Click to expand...

I would think you would want a larger exhaust than the intake, since hot air expands.

but maybe I am full of hot air, I dont know

there are smoker building calculator sites out there you can check with
 
Well I'm cooking brisket on Sunday so we'll see what happens. I'll be modifying her all weekend starting with the temp gauge and bigger exhaust and adding a chimney. I'll let you know for sure how it goes with some new pics do my hopefully finished product.
 
do you have a small fan? use that for extra air flow, of course aimed at the fire box.

just another tuning option
 
dwfisk said:
OK I see you are leaving the 2" exhaust open, my bad. I would think you need at least a 3". Look for a custom muffler shop, they should be able to cut an sell you a 3 ft chunk of 3" pretty cheap. It will be galvanized or nickel plated but its OK for the exhaust.

One 3" will give you the same 3.7 square inch exhaust area you have with the four 3/4" inlets.
Click to expand...

My math doesn't match your math. We may need a third opinion.:wink:

I get:
.5625 Sq. In. for the 4 3/4" ball valves
3.14 Sq. In. for the current 2" exhaust
7.065 if the exhaust is changed to 3"

After running these numbers I'm of the opinion that the OP doesn't have enough intake air. By my numbers NCoonis would have about the right intake by adding 2 1-1/4" intakes to the existing 2. NCoonis, make sure you have and get full flow valves. Not all ball valves have full sized holes in the balls.

My best advice would be to find a pit calculator and run some numbers thru it.
 
Here is how my math works, I hope area still = pie-r-squared
INTAKE
diameter 3/4 = 0.75 in
radius = 0.375 in
0.375 x pie = 1.178 sq in
4 of them = 4.71 sq in
EXHAUST
diameter = 2 in
radius = 1 x pie = 3.14 blah blah blah
1 exhaust = 3.14 sq in
or
diameter = 3 in
radius = 1.5 in
1.5 x pie = 4.71 sq in
Have I screwed up somewhere?
I would get my exhaust AT LEAST in balance with intake. Actually, I'm a pretty strong beleiver in a wide open exhaust and control at the intake so I would be tempted to oversize the exhaust and go to 4 in. I dont know squat about UDS cookers, but I see a bunch on here with only 2 or 3 3/4 inch intakes so I'm assuming 4 might be enough.

Oh yeah, in my house, pie-r-round, cobblers-r-square (maybe rectangular).

PS: stopped by my local muffler shop and picked up a 3 ft chunk of 4 inch for $20 for another build we are starting.
 
I would think the 4" pipe is a bit small. Not enough air flow.
 
dwfisk said:
Here is how my math works, I hope area still = pie-r-squared
INTAKE
diameter 3/4 = 0.75 in
radius = 0.375 in
0.375 x pie = 1.178 sq in
4 of them = 4.71 sq in
EXHAUST
diameter = 2 in
radius = 1 x pie = 3.14 blah blah blah
1 exhaust = 3.14 sq in
or
diameter = 3 in
radius = 1.5 in
1.5 x pie = 4.71 sq in
Have I screwed up somewhere?
I would get my exhaust AT LEAST in balance with intake. Actually, I'm a pretty strong beleiver in a wide open exhaust and control at the intake so I would be tempted to oversize the exhaust and go to 4 in. I dont know squat about UDS cookers, but I see a bunch on here with only 2 or 3 3/4 inch intakes so I'm assuming 4 might be enough.

Oh yeah, in my house, pie-r-round, cobblers-r-square (maybe rectangular).

PS: stopped by my local muffler shop and picked up a 3 ft chunk of 4 inch for $20 for another build we are starting.
Click to expand...

Dave, I could be wrong but I thought the formula for area of a circle was radius squared x pie. So in my case I'd have:
.75/2= .375 radius
.375 x .375 = .1406 radius squared
.1406 x 3.14 = .4415 square inches of one 3/4" circle
.4414 x 4 = 1.766 is my total intake.
A 3" exhaust using the above formula would give me a 7.06 sq in exhaust.
I'm going to look for a airflow calculator now to see where I should be at.
 
NCoonis said:
Dave, I could be wrong but I thought the formula for area of a circle was radius squared x pie. So in my case I'd have:
.75/2= .375 radius
.375 x .375 = .1406 radius squared
.1406 x 3.14 = .4415 square inches of one 3/4" circle
.4414 x 4 = 1.766 is my total intake.
A 3" exhaust using the above formula would give me a 7.06 sq in exhaust.
I'm going to look for a airflow calculator now to see where I should be at.
Click to expand...

You are right, missed the squared step.
 
dwfisk said:
Here is how my math works, I hope area still = pie-r-squared
INTAKE
diameter 3/4 = 0.75 in
radius = 0.375 in
0.375 x pie = 1.178 sq in
4 of them = 4.71 sq in
EXHAUST
diameter = 2 in
radius = 1 x pie = 3.14 blah blah blah
1 exhaust = 3.14 sq in
or
diameter = 3 in
radius = 1.5 in
1.5 x pie = 4.71 sq in
Have I screwed up somewhere?
I would get my exhaust AT LEAST in balance with intake. Actually, I'm a pretty strong beleiver in a wide open exhaust and control at the intake so I would be tempted to oversize the exhaust and go to 4 in. I dont know squat about UDS cookers, but I see a bunch on here with only 2 or 3 3/4 inch intakes so I'm assuming 4 might be enough.

Oh yeah, in my house, pie-r-round, cobblers-r-square (maybe rectangular).

PS: stopped by my local muffler shop and picked up a 3 ft chunk of 4 inch for $20 for another build we are starting.
Click to expand...

Yeah your formula can't be right becuase a 3/4" circle has to be smaller than 1 sq. in. You show 1.178.
 
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