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Mailbox mod not working

post #1 of 23
Thread Starter 

Yesterday I decided to attempt the mailbox mod for my smoker. I use a pellet tube and when it is placed inside the smoker, it tends to be a pain for the reason that I believe the burner consumes the oxygen and thus keeps the pellets from really smoking. So I did the research and decided on the mailbox mod.

 

This morning I was going to smoke two butts and time for the mailbox mod to shine. Well after a few hours of more smoke coming out the front air holes on the mailbox, I have abandoned the mail box and stuck the pellet tube inside again. I have no clue why I wasn't getting any smoke to come thru the smoker. Chimney was even wide open for air flow. Yes I nuke the pellets to get rid of extra moisture.

 

I didn't cut a new hole in the side of the smoker. I just opened the one vent and connected the mailbox and piping to the one side of the open hole. Used HVAC tape to connect and seemed to hold real well. I did notice that when I opened the bottom door of the smoker, all of a sudden I could see smoke coming in but nothing thru the chimney when the door was closed. So what the heck is going on? Disappointed.

 


Edited by ps0303 - 5/17/17 at 8:48am
post #2 of 23

You should have a 3" hole entering the smoker body...    The MB needs more air...  may I suggest holes like I have in mine...  3 each ~7/8" to 1" for good air flow..   the hole in the top on the MB door stops the air from recirculating inside the MB...  Recirculating air is very low on oxygen....

 

 

post #3 of 23
Thread Starter 

Yep I have three holes in the MB similar to yours. Three 3/4" holes. So you think I need to cut that 3" hole into the smoker itself to feed the smoke into and forget trying to feed it thru one portion of the vent? 

 

Holes in MB to close to each other?  Also, I didn't note that I had the pellet tube sitting up on a block of wood so it was sitting in the middle of the box.  I just now thought about that and didn't try sitting it on the bottom of the MB.  Maybe that would have created an issue as well? 

 

Thanks!

 

post #4 of 23
The tube works great with one hole big enough for it to fit through.

http://www.smokingmeatforums.com/t/159801/the-mailbox-mini-mod
post #5 of 23

How open was your top vent? You want a good airflow in and out.  It should flow naturally via the stack effect with heat.

post #6 of 23
Thread Starter 

Chimney vent was all the way open as I usually keep it 90% of the time.

post #7 of 23

What size hole goes into the smoker, where the 3" flex duct is ???

post #8 of 23
Thread Starter 
Quote:
Originally Posted by DaveOmak View Post
 

What size hole goes into the smoker, where the 3" flex duct is ???

 

Right now I am just using part of the existing side vent that the manufacturer of the smoker installed. I just taped the duct line to the smoker and then blocked off the other half of the vent on the smoker. I have not yet cut a hole in the smoker to actually install the duct into.  I'm guessing you're thinking is I am obstructing the duct some and that is why I had little to no flow of smoke into the smoker.

post #9 of 23

There should be basically a free path for air to flow starting at the inlet to the mailbox, up the tube, into the smoker body, and out the top.  Only "obstructions" should be the adjustable top vent and inlet holes on the front of the mailbox which will allow you control over the air flow if needed.  You want as little obstruction at the point the ducting enters the smoker body as possible.  If you are partially blocking off the point where the duct enters the smoker body, that is likely your air flow issue.

 

Once you start applying heat inside the body of the smoker, convection or the "stack effect" should get air moving upwards towards the top vent naturally.  As the hot air naturally rises it "draws" colder air in from the ducting which draws air in from the mailbox.  That's basically how it works.

post #10 of 23
Quote:
Originally Posted by ps0303 View Post

Right now I am just using part of the existing side vent that the manufacturer of the smoker installed. I just taped the duct line to the smoker and then blocked off the other half of the vent on the smoker. I have not yet cut a hole in the smoker to actually install the duct into.  I'm guessing you're thinking is I am obstructing the duct some and that is why I had little to no flow of smoke into the smoker.

That's exactly what I do on my propane smoker. Once again no issues with the smoke not flowing into the smoke chamber.

In the thread that I posted above the exit into the Mini-WSM is only 3/4". Again no problems with Smoke getting into the smoke chamber.

One large hole in the door that the tube sits in. Leaks a bit of smoke there but not much.
post #11 of 23
Thread Starter 

OK so I did some testing this morning.  The chimney top vent is wide open. Put the smoking tube in the MB, closed MB door, left all three holes open. Opened the lower door of smoker and saw plenty of smoke coming into the smoker. Closed the lower door, smoke came out the top chimney nicely.  Opened the lower door, lit the burner. Closed the door. Smoke stopped entering the smoker and instead came out from of the mailbox thru the three 3/4" holes I had put in the door.  Turned gas off, smoke started coming out the smokers chimney.  Opened the other side vent on the opposite side of smoker, opened lower door, lit burner, closed door. Smoke came out mailbox vent holes. Turned gas off, left side vent open, smoke filled the smoker and came out side vent and chimney top.

 

It is seems the heat from the burner is still causing issues. 

post #12 of 23
Thread Starter 
Quote:
Originally Posted by dward51 View Post
 

There should be basically a free path for air to flow starting at the inlet to the mailbox, up the tube, into the smoker body, and out the top.  Only "obstructions" should be the adjustable top vent and inlet holes on the front of the mailbox which will allow you control over the air flow if needed.  You want as little obstruction at the point the ducting enters the smoker body as possible.  If you are partially blocking off the point where the duct enters the smoker body, that is likely your air flow issue.

 

Once you start applying heat inside the body of the smoker, convection or the "stack effect" should get air moving upwards towards the top vent naturally.  As the hot air naturally rises it "draws" colder air in from the ducting which draws air in from the mailbox.  That's basically how it works.

"Once you start applying heat inside the body of the smoker, convection or the "stack effect" should get air moving upwards towards the top vent naturally.  As the hot air naturally rises it "draws" colder air in from the ducting which draws air in from the mailbox.  That's basically how it works."

 

Well I guess I have the only one smoker that defies the laws of how it's supposed to work. LOL

post #13 of 23

Is there a diffuser plate above the flame and smoke inlet to the smoker body..  The rapid expansion of air, from higher temps, could be reversing the air flow...  also, the air currents from the burner are exceeding the exhaust... 

post #14 of 23

For hot smokes with the pit temp up to 285°, I just place the tube right in the smoker. Even for cold smoking, when the outside temp is below 40° I place the tube right in the smoker. Propane requires a bunch of Oxygen to burn, so it can cause issues if you don't have ALL the vents open.

 

 

 

 

 

 

 

 

post #15 of 23
Thread Starter 

No diffuser plate.

 

dirtsailor2003, I've had issues with the tube inside as well. There I clearly know that the burner is eating all of the oxygen.  This is why I am attempting the MB mod. 

post #16 of 23

In my photos above as you can see it is working in the smoker, All of those photos, with the exception of the fatty were below 180°. The fatty smoke was at 250°-265°. You need to have some sort of diffuser between the flame and tube. All vents wide open. This is another scenario where having a needle valve to control the flow of propane will help. Everyone tries to control temps with the vents on a propane smoker. The reality is a needle valve is what you need. It allows you to get enough oxygen into the pit and still be able to control temps.

post #17 of 23
Thread Starter 

I have had a needle valve on my smoker for many years.  I also have gasket material on both doors.

 

As I said before, I have used the tube in the smoker but I usually fight it to keep it going due to the oxygen issue.  Yours might work ok but you have a different smoker than I do.

 

Also if you read my entire write up test from today, even with ALL vents open, once I lit the burner, smoke stopped entering the smoker from the mailbox.

post #18 of 23
Quote:
Originally Posted by ps0303 View Post
 

I have had a needle valve on my smoker for many years.  I also have gasket material on both doors.

 

As I said before, I have used the tube in the smoker but I usually fight it to keep it going due to the oxygen issue.  Yours might work ok but you have a different smoker than I do.

 

Also if you read my entire write up test from today, even with ALL vents open, once I lit the burner, smoke stopped entering the smoker from the mailbox.

Where are you placing the tube when it is in the smoker? The further away you place it from the burner (and above the burner) the better it will work.

 

I have used the tubes in the master forge smoker. My cousin uses the 12" and 6" tube in his. I assume that is what you have from the small piece that we can see in the picture.

 

The problem with the mailbox is that the intake vent is too close to the burner. If you had it enter above the top of the lower door you'd have better luck.

post #19 of 23
Thread Starter 

"If you had it enter above the top of the lower door you'd have better luck."

 

OK that is what I was suspecting. I just didn't want to start cutting holes all over the place of it was something else.


Edited by ps0303 - 5/19/17 at 12:04pm
post #20 of 23
I had issues with my tube burning in my propane 40XL, so I now position the tube front to rear along one side (left) about 1 and 1/2 inches off the bottom and 1 inch from the outer wall then drilled 1/4 inch holes the length of the tube (6 holes in all) level with the bottom of the tube. I then drilled a 3/4 inch hole on the opposite side top of the cook chamber. This increased airflow beautifully and the tube smokes like it should and the additional 3/4 inch vent hole at the top seems to provided nice cross ventilation.
I know it's not a solution for the mailbox mod but it did help me getting the tube to burn in the smoker...
Good luck.

Walt
Edited by jokensmoken - 5/19/17 at 2:55pm
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