# Heat shield/deflector in offset



## Paulie Walnuts 440 (Sep 9, 2020)

Hey I wanted to know what is a sort of standard size and thickness for a heat deflector or shield in a standard flow offset smoker that is actually effective ?


----------



## Fueling Around (Sep 9, 2020)

Horizon Smokers make their deflector plates from 3/16" steel


----------



## daveomak (Sep 10, 2020)

What is a "heat shield deflector" ??  Where does it go ??  Do you have a picture of one ??


----------



## Chasdev (Sep 10, 2020)

They work for a while but during a long cook like a packer brisket, the metal itself heats up and the problem happens again to a degree.
The distance from the cook grate to the lowest part of the smoker body should be at least 8 inches and when you add plate or device/s to move the heat more evenly across the cooker, you move the  heat closer to the cook grate once the plate or device/s heat up which creates another set of issues that contribute to the problem.
I and no doubt others, chased this problem for a few years and there's no amount of tinkering or gear you can add that really works well.
Outside of buying a more expensive cooker that is engineered to evenly heat across the cook grate, that is.
Best low dollar/low effort plan is a water pan right over or nearest to firebox opening which you refresh as needed along with placing the meat all the way across the cook grate from the firebox end and then rotating the meat during the cook to expose both ends to the heat as the firebox end will always be hotter than the exhaust stack end.


----------



## Paulie Walnuts 440 (Sep 10, 2020)

Interesting chasdev and thanks for the info on that. ..and dave my understanding is the purpose of it is suppose to block the direct heat from the side closest to the firebox into the cook chamber


----------



## daveomak (Sep 10, 2020)

If one builds a smoker based on the tutorial on this forum, hot spots aren't a problem..
Upper air inlets and great air flow, the CC and FB can run at about the same temperature...   There is no "overheating" of the FB and first portion of the RF plate and cooking grate.... 
The lower air inlet adjusts the temperature of the fire while the upper air inlet moves the heat through the CC.....
When this all started, folks had a FB that was 6-700 deg. F....   Poor air flow was a huge contributor...   Opening up the air flow route and adding the upper air inlet to move the heat, solved the problems...

2 of many responses on how their new smoker works...






						500 gallon reverse flow build
					

Hello all building my first smoker trying to build almost the whole thing out of a 500 gallon propane tank I’m kind of looking for some firebox vent ideas and ash pan thank you




					www.smokingmeatforums.com
				









						Short/Fat 120 Gallon Build
					

Had a great day today! After doing a couple small little jobs on the smoker I decided to fire it up.   I started with a chimney of charcoal. Once that was going I added 3 small splits of wood. It came up to 200 and just stayed there. They were small so I added 2 more and closed my intake about...




					www.smokingmeatforums.com


----------



## Paulie Walnuts 440 (Sep 10, 2020)

Ya I'm going to have a my friends metal fabricator add an upper inlet like you mentioned. The rectangular configuration seems more practical since my FB is square and only about 4 inches of space available to do anything


----------



## Paulie Walnuts 440 (Sep 10, 2020)

And when my damper is open as u see in the picture should I adjust my stack damper according to how open my FB door is or should i just leave the stack wide open all the time and just adjust FB damper ?


----------



## daveomak (Sep 10, 2020)

Leave the stack damper open all the time....  Start with the upper air inlet about 50% open..  Adjust the lower inlet to get the smoker at desired temp...  
Use the calculator to figure out the size of the holes...
You might think about changing the air inlet you have now...  Too much air may be bypassing the fire, screwing up the temperature regulating job of the lower air inlet..  Difficult to tell from here...

Theory of how stuff works....





	

		
			
		

		
	
...

The air inlets can be simple or ?????....
I like this one...  Removable, easy to build....  
simple...  add more holes if needed...
Adjustable tension on the sliding plate...  all
you need is a hammer or a rock...






	

		
			
		

		
	
...


----------



## JayDoug (Sep 10, 2020)

Hey Guys, new here

Question Dave, does your theory only work for reverse flow pits?  I have a 250Gal offset and I can really only use the far size when I'm smoking.  Unless I'm cooking a chicken then I can put it on the side closest to the fire box because the temp is so much higher.


----------



## daveomak (Sep 10, 2020)

JayDoug said:


> Hey Guys, new here
> 
> Question Dave, does your theory only work for reverse flow pits?  I have a 250Gal offset and I can really only use the far size when I'm smoking.  Unless I'm cooking a chicken then I can put it on the side closest to the fire box because the temp is so much higher.



Welcome to the best forum on the web.....

Sounds like, in order to get the Cook Chamber up to temp, you have to have the lower air inlet, on the FB, open so much, you Fire Box is screaming hot, causing the hot spot...
Have you taken the temperature of the FB or the air temp as the heat comes out of the FB ???   I think I know what you will find....
You know, when I started this project years ago, folks told me I was crazy and it wouldn't work... They still do...   Some folks have to run their smokers with the FB door open...  A few air inlets and that problem is solved....  Some well known pitmasters on the circuit still do...   They learned how to control temps by opening the door..  Hey, if it ain't broke, don't fix it....
Well, first it's not a theory any longer... It was way back when....  Members built smokers, as we were trying to solve the 'hot spot' 'overheated FB' problem...  over time, they proved the upper and lower FB intakes worked... 
It will work on an offset...   Same deal.... 
The only criteria is.....   The smoker must be air tight so you are drawing air only through the FB...  Tramp air kills the air flow and control....


----------



## JayDoug (Sep 10, 2020)

You hit the nail on the head, coming out of the fire box is screaming hot.  
So air flow is key, my FB is 2'x2'x2' and the opening into the CC is 14" x 3 (42sq/in) 
Would it help if I made that opening a little larger and added air inlet toward the top on the side of the FB?


----------



## Paulie Walnuts 440 (Sep 10, 2020)

Thanks Dave and I didn't really have a problem holding temp just as long as I had decent coal bed and the dampers about 1/4 to half open depending on what temp I wanted but when my coal bed was crap spreading all flat in the bottom then needing to rake back in the middle. I'm having faith on buying that fire management basket and trying that until i can get this metal guy to add upper inlet. And dave is right this is the best bbq forum on the net ..im fairly new Doug and I've learned so much within the last couple weeks from several members here..


----------



## JayDoug (Sep 10, 2020)

Thanks Paulie, I'm not trying high jack your thread but I was thinking about doing the deflector thing too.  I thought that was the only way to get even temps across the CC.


----------



## Paulie Walnuts 440 (Sep 10, 2020)

No worries man I learn with every question so it's all good..i would look into lone star grillz fire management basket because it can really make a difference in how much wood your burning temps etc.


----------



## daveomak (Sep 11, 2020)

JayDoug said:


> You hit the nail on the head, coming out of the fire box is screaming hot.
> So air flow is key, my FB is 2'x2'x2' and the opening into the CC is 14" x 3 (42sq/in)
> Would it help if I made that opening a little larger and added air inlet toward the top on the side of the FB?


Yep...  but let's calculate the size needed....
Length and width of the CC....
I can calculate for you if you want....
Pictures of the smoker would help...  Pictures of the FB/CC opening...  exhaust stack... and interior of the smoker RF plate at the non FB end......





						Standard Reverse Flow Smoker Calculator... by DaveOmak and others... Ready to use..  rev5.. 6/19/15.
					

Here's to "Alien BBQ" and the folks that first put the calculator together and "1728 Software Systems" for this great "Circle Calculator" and all the folks at "SmokingMeatForums", with a special shout out to Ribwizzard, that contributed their ideas and feedback while this thing was coming...




					www.smokingmeatforums.com


----------



## daveomak (Sep 11, 2020)

Paulie Walnuts 440 said:


> Ya I'm going to have a my friends metal fabricator add an upper inlet like you mentioned. The rectangular configuration seems more practical since my FB is square and only about 4 inches of space available to do anything


Paulie, I just noticed your exhaust stack...  The height looks good but it looks too small a diameter...  or it's mounted weird to the CC...  Got a picture of how it's connected to the CC ??


----------



## JayDoug (Sep 11, 2020)

daveomak said:


> Yep...  but let's calculate the size needed....
> Length and width of the CC....
> I can calculate for you if you want....
> Pictures of the smoker would help...  Pictures of the FB/CC opening...  exhaust stack... and interior of the smoker RF plate at the non FB end......
> ...



Sure Man, That'b be awesome.  
CC is 80" x 24"
exhaust stack is 4.5" x 42"
FB is 24" x 24" x 24" and the opening into the CC is 14" x 3" (42sq/in)


----------



## Paulie Walnuts 440 (Sep 11, 2020)

Here is a picture of how the stack is mounted which I see some like this but not many. The extruded stack style I see is usually not as extended in some other smokers I've seen.


----------



## JayDoug (Sep 11, 2020)

Paulie Walnuts 440 said:


> No worries man I learn with every question so it's all good..i would look into lone star grillz fire management basket because it can really make a difference in how much wood your burning temps etc.



I'm actually not far from the Lone Star guys and I did look into the basket but decided to build one myself.  It has made a huge difference in fire management.  
(excuse the ashes, I cooked yesterday and haven't clean her out yet)


----------



## Paulie Walnuts 440 (Sep 11, 2020)

Ya I like that and I think for us with flat bottom fire boxes its vital to have something to concentrate the coal bed rather than constantly raking coals back into the middle etc..they are sold out of those baskets online and he said hopefully end of the week but still nothing. I may have someone make one for me. I have a lot of faith in the design that it should work way better than nothing at all


----------



## Paulie Walnuts 440 (Sep 11, 2020)

I know you mentioned having a real hot zone on the side closest to the fire box..why not turn that basket and maybe shorten it so its not as long near the opening from fire box to cook chamber? Just a thought while looking at your set up...im a newbie so what do I know Hahahaha just a thoufht..


----------



## daveomak (Sep 11, 2020)

24x24x.7854x80=36,192
x 0.004 = 145 sq. in. area for the FB/CC opening, under the RF  plate, and the end of the RF plate.....
x 0.001 = 36 sq. in. air inlets to the FB...
7 sq. in upper inlet and ~29 sq. in lower air inlet...
Upper air inlets.... I would go with 4 each, 2" holes.. torch cut...  slide to match and installed like this smoker....












36,196 x .022 = 796 cubic inch volume for the stack...
36,192/.7854 x 36 = D squared of the stack = 28.2 = 5.3" diameter of the stack...


Change the exhaust stack to 6".......
Stack should be ~36" above the top of the CC...

Cut out the opening between the FB and CC per the picture....






When you build your fire, run the upper inlets wide open...  adjust the lower inlet to achieve cooker temperature....

Slowly adjust theupper inlet to about 3 /4 open watch the temp and air flow.... You want lots of air flow.... the FB should be running close to the temperature of the CC... And use very little fuel...


----------



## JayDoug (Sep 13, 2020)

daveomak said:


> 24x24x.7854x80=36,192
> x 0.004 = 145 sq. in. area for the FB/CC opening, under the RF  plate, and the end of the RF plate.....
> x 0.001 = 36 sq. in. air inlets to the FB...
> 7 sq. in upper inlet and ~29 sq. in lower air inlet...
> ...



Man that is awesome, thanks.  I'll get started on it as soon as I can.  

I'll report back once I have her done.


----------

