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Reverse flow mods

post #1 of 17
Thread Starter 

I just got done making a convection plate and charcoal box for my COS and I had a terrible time getting it to heat up, when it did on the firebox end it got to 300 and the other end was only 200. I made the plate out of 3/16" deck plate with a slant on the firebox end and left a 4" gap on the heat & smoke end. The firebox got so hot it burned the paint off the top and I still did not have enough heat?


Any idea's?



post #2 of 17

Yes..... first post pictures.....   next add an air inlet above the fire grate....  that air inlet moves heat out of the firebox and into the cook chamber without having to stoke the fire.....   Maybe the RF plate end opening is too small......  maybe the stack is too small....  We need pictures and more information to help really well......   Start a new thread about your smoker......     


Please take a moment and stop into " /Roll Call/  " and introduce yourself and get a proper welcome from our members.... Also, if you would note your location in your profile, it will help in the future when answering questions about smokin'...   elevation, humidity etc....    

We're glad you stopped in and joined our group...    Enjoy the long smokey ride....     Dave

post #3 of 17
thinking some measurements would be a big help as well... what is a COS ?
post #4 of 17
Thread Starter 



I will get some pictures in the next couple of days, does the inlet need to be adjustable like the rotating damper? Just put a 3" stack on the firebox end about 1" above the cooking grate. What forum should I start the new thread in?


Thanks  Mike

post #5 of 17
Thread Starter 



A COS is a cheap offset smoker.....heard it on another site. It is 20" round x 36 " cooking area, firebox is about 1/2 that big with rotating damper in the bottom. Made a charcoal box 11 1/2" square by 9" tall out of grain screening material left over at the shop.


Thanks  Mike

post #6 of 17
Originally Posted by Ne Rookie View Post



I will get some pictures in the next couple of days, does the inlet need to be adjustable like the rotating damper? Just put a 3" stack on the firebox end about 1" above the cooking grate. What forum should I start the new thread in?


Thanks  Mike

Stop..... Don't start a new thread.....  I must have been thinking of another post somewhere.....  You are doing fine....   a lot better than me...   I guess 5 hours in the garlic shed at 98 degrees puts me on tilt....



post #7 of 17
Thread Starter 

Its hot here in Nebraska also



post #8 of 17
Thread Starter 
Smoker 001.jpg 1,254k .jpg file


Smoker 002.jpg 1,630k .jpg file


Smoker 003.jpg 1,128k .jpg file


Smoker 004.jpg 1,130k .jpg file


Smoker 005.jpg 650k .jpg file


Smoker 007.jpg 1,106k .jpg file


Smoker 008.jpg 1,184k .jpg file




Here are the pictures, any help would be appreciated. Don't look at the welds to close..........it has been a while since I welded on beer cans :)





post #9 of 17

Mike, afternoon....  


The deflector/RF  plate should be sealed pretty much air tight to the cook chamber body....

The exhaust stack looks like it could be cut off at an angle, above the food grate... maybe at an angle following the lid...  it can extend down from the lid but have it above the food grate....






The opening on the end of the RF plate looks good.....


The sloping metal piece looks as if it is not sealed to the smoker body.... 


Looks good....



The 2 piece firebox.... is it sealed air tight where the bolts are ??  should be...  


A second air inlet might be needed about where the bolts are for the handle...  

maybe several 1/2" holes.. use a step drill if you do.....


The lid to the cook chamber looks as if it is not sealed air tight.....    

Is that  something on top of the exhaust stack that could impede the exhaust flow ???

The picture is not too clear...... 



A reverse flow smoker needs to have everything sealed pretty much air tight so the heat and smoke and air flow

can be regulated and controlled to go where you want it....  Sealing up the unit will force the air flow through the smoker and out

the exhaust stack....  The holes where the rotisserie rod goes will mess up the air flow....   

To seal the lid that hangs over the bottom, I have seen folks attach an angle iron piece that has gasket material attached to it.... 

It doesn't have to be heavy angle iron... sheet metal is fine....  all you are doing is stopping air and not supporting the lid....  


For sealing up the RF plate, some thin sheet metal, scribed to conform to the smoker body, then screwed in place, should be adequate... 

Painted steel flashing in the roofing dep't will work ....  maybe 26 ga or so... even galvanized will work if you burn off the zinc....   get something heavy enough that it won't burn up in six months..... 

You have done a lot of work.....  You are so close to having it work..... don't give up now.....   


About the burning paint.....  the air flow to the fire keeps heating the firebox without doing much to move air through the smoker... 

An air inlet about where the handle is will move air without adding air to the fire...   It will move the heat only....  


I'm around to clarify anything you need help with.....     



post #10 of 17

Dave has you covered............................first.gif........  did you move the stack...........



post #11 of 17
Thread Starter 



Yep it was on the other end, also made it taller if that makes any difference.


Thanks for the help!



post #12 of 17
Thread Starter 



I will get the plate sealed up, probably was loosing a lot right up the stack.


I sealed the top of the firebox on the outside where it attaches to the cc, the metal is so thin it was warping from just being bolted together.


The lid is not sealed the greatest need to find some light angle and build a sealing surface on the bottom and top both, have not got the rotisserie holes plugged yet but will do that too.


The top on the stack is a cap from a stock tank heater, this is kind of a Frankensmoker with pieces from several things around the place :) it is more to keep the birds out, I don't think it is impeding the flow.


Would a "adjustable" air inlet work better than drilled holes or is it just something else to mess around with?


Thanks for all the help!




PS- We are about 20 degrees cooler here today than yesterday and got a little rain this morning too!

post #13 of 17

Would a "adjustable" air inlet work better than drilled holes or is it just something else to mess around with?


Yes, definitely and adjustable inlet will be better....   A pie vent works good... holes with a slide damper....  that way, you can measure the temps and adjust the air flow accordingly....   



post #14 of 17
Thread Starter 



Put a 1 7/8 hole where the handle was with a swinging door. Cooked some pork loins a couple of weekends ago and it worked good, held temp, still have some holes to plug up but much better than before.


Last weekend tried smoking some chicken breasts and could not get temp above 150 without opening the firebox lid with the damper open all the way and the top air vent all the way. Temp inside firebox was 650 at that time also. Do I need to add more damper opening or more air vent ?


Pork turned out very good chicken ended up dry :(


Thanks for all your help.



post #15 of 17

With that temp difference, I would bet there are air leaks that need sealing....   Take the thing on top of the exh. stack off, and use aluminum foil to seal up everything that could be an air leak.... do a test run and see what happens....    Air leaks will kill the air flow through an RF smoker...




post #16 of 17
Thread Starter 



Have removed the cover on the stack and did put some angle on sides to seal them up, still need to do the front and back.


Will let you know how it turns out.


Thanks for the help...........your up early!



post #17 of 17

Mike, us old folks don't want to miss any daylight.......   biggrin.gif

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