Char-Broil Reverse Flow Conversion

[Buck]

Hi Guys! So I bought a Cheap Char-Broil offset smoker for $100 and have had pretty good success and caught the smoking bug ... UH OH! So I was going to convert it to a reverse flow smoker and see if this could stop me from having to move the meat around so much and screwing with the fire constantly. I naturally had some questions about placement of my deflection plate and stack and the gaps/sizes that would be ideal. I ran across the Feldon Smoker Calculator and after entering in the dimensions of what I have, I can see that a lot of things are out of whack. So I was thinking about making mods to the undersized (~20%) firebox by cutting it and extending it 3" and also shrinking the firebox to cook chamber opening while I have the thing apart to make things more in line with what the calculator says I need. I'm planning on making a full sized, heavy gauge backyard smoker at some point and figured this would give me a chance to get my feet wet and maybe make some of my rookie mistakes for almost no money and have a smoker that works better and might have more value for the next sucker ... I mean "new smoking enthusiast" ... I pass it along to when I get my big one done.

So I have 2 questions. #1. Has anyone ever done this before? I tried searching the forums but didn't see anything. #2. Would I be better off just making a deflection plate and re-locating the stack (which will take WAY less work) and worry about the other things when I do my big build. Thanks in advance for any advice/input. Only been on these forums 3 days now but this place is GREAT!

Buck

[Frank_Cox]

You are on the Money....
It is a cheap way to experiment and wind up with a useable Backyarder. I would do both Mods you suggested. move the stack fix the FB and add the BP. use 1/4" for the BP.
and by the way,

[SoloQue]

Looking forward to seeing some before and after pics

[Smokeone]

I think Frank and Solo covered it all.

[The Czar]

and times two....and sorry I didn't get to warn you about S1.....

[Gizmo]

Welcome BUCK! I did this on a thread a few months ago - think maybe under "MODS" department on here ... fwiw

[Buck]

THX Rick ... I'd love to see how things went for you but can't find the thread. If you wouldn't post so much it would be WAY easier Checked the mods dept and didn't see anything. It would be fantastic if you had a link for me ... or even some unique search terms would probably be enough.

Picked up a more manageable torch and smaller wire for my welder yesterday and just ordered some steel so I'm about ready to rock and roll.Thinking I'll do one thing at a time and smoke in between to see what helps the most. First order of business will be making it reverse flow. Cutting the plate today. Might get it welded in and the stack relocated if I have time. I'm probably going to add sealing up the cook chamber to the list of mods. There is no door on this thing, the whole top just open up. Was thinking I could weld angle iron all around and add a gasket on top of that to get a good seal since the top overlaps the bottom all the way around ... and I could extend the iron out and make a shelf while I was at it. If anyone has any better ideas for a seal I am all ears.

I wasn't planning on Pics but I guess I I'll do it as long as you guys don't laugh at my welds LOL. Should I start a new thread under mods or builds or just keep it here since this really is more of a design project?

THX for all the input everyone. Good to know I have some experience behind me

[Gizmo]

Sorry Buck - I found it.

It's called: "Chargriller? Maybe? " and it's under "First Smoker" (so it's your turn to laugh at my pics).

You'll see I converted it to propane to compensate for the FB being too small - enlarging yours is on the right track I think.
The baffle plate is a little hard to see but it's there - I used some old 10 gauge tread plate and it worked fine. I think it was a 4 inch gap?
The old chimney is still on it in those pics but since the baffle plate just lays in place you can go back to an end fed if you want to.
I positioned the baffle to go just above the transfer opening from the FB. That gave me enough gap up to the grate to put in disposable aluminum pans as drip/water pans.
The juice can held wood for smoke.
It still works and makes some darn good "Q"

I like your idea to better seal the door cause mine leaked like crazy.

Enjoy

[The Czar]

viewtopic.php?f=45&t=298

this should be the link

[Buck]

Thanks for the links guys! Good to know your smoker found a new home and gets used Rick. I don't seem to have a problem getting the chamber up to 250 with 3 chimneys of lump charcoal but it sure don't stay there long. There is a HUGE leak between the firebox and cooking chamber and the firebox lid and my paint is already showing wear in that area. I'll fix that when I modify and re-attach it.

Well I decided to do some baselines "as is" this afternoon while I was cutting the baffle plate. Not surprisingly, the firebox side was, depending on firebox temps, 75-90 degrees hotter than the other side at grate level. Gauge mounted on top was, on average, reading 40 degrees cooler than the firebox side and 40 degrees warmer than the other side. Lit 1 chimney of lump and dumped it on 2 chimneys of unlit lump. Firebox side grate went from 373F to 200F in about 6 hours all vents open. Probably could have got a longer burn with lower temps if I had have closed the firebox intake but wanted a wide range of temps to see what was happening inside at different heat ranges. This is much different that what I was doing while cooking before but I also wanted to see what Joe blow would go through if he just screwed it together, lit her up, and threw some meat on. No wonder these are a dime a dozen on craigslist

I cut a 16 gauge deflector/baffle out of stuff laying around as a template/experiment. I'm going to relocate the stock stack and just set the baffle in and light her up to see the difference, if any, before I weld in the 1/4" plate. I'm just curious if reverse flow or a 30lb hunk of steel will make a bigger difference.

Rick, I had the BP gap calculated at just 1-3/8". My BP will be sitting higher as I'm going to seal it up, install a drain, and use it as a water pan as well (3-1/2" inches below the grate at firebox to 4-1/2" below grate at opening) so I guess that will make it a little bigger but still much smaller than yours. The firebox to cooking chamber was calculated to ideally be 17" so I tried to match this as close as possible but it may end up being about 2" since my cooking chamber is 26" and 1 less cut/weld is a good thing . I hope that calculator scales down correctly.

It Starts ...

[Gizmo]

Nothing magic about my BP gap - just guessed on mine and thought it got me by okay ...

One thing to remember - a good seal everywhere is sure important but you're dealing with just 14 gauge sheet-metal construction and it will "sweat" heat about as fast as you can throw heat at it so I think that's a big part of the reason why it isn't staying at temp long - when you build your own design someday and go with heavier steel and/or insulated walls that won't be nearly as big an issue. fwiw

[Buck]

OK guys ... I moved the stack, extended it with a thin aluminum insert and put in the temporary 16gauge baffle plate for my first test. Tried cooking some chickens and it took me about 6 hours!!! Couldn't get the thing up past 205F at grill level (it would get to about 300F max before I started screwing with it). The baffle plate wasn't really sealed that well at the firebox side and I think some of the heat may have just been going from the firebox straight up the stack. I know the firebox is undersized and the seal from firebox to cooking chamber isn't that good but I got it SUPER hot and still couldn't get the temp up. The firebox isn't sealed up all that well either so maybe that's the problem?

I got the 1/4" baffle plate cut, welded in and sealed up tonight so I'll know if that was the problem this weekend.

So I've been trying to figure out why I couldn't get any heat into the cooking chamber. Maybe someone can explain to me what makes the smoke and heat flow through the cooking chamber. Do you guys think that the leaks are the main problem here? When I re-size the firebox, I'll get it all sealed up and mounted to the cook chamber air tight and have a plan to seal the cooking chamber but I want to make sure something else isn't wrong. Thx to everyone for the comments and help

Here's pics so far ...

Kept the stock stack ... probably a bad idea. Will probably end up cutting it off.

Badly sealed Baffle plate after the chicken cook. Mounted it too low and had to weld an extension on... luckily this was temporary.

1/4" Baffle plate welded in. 2-1/2" from grate on firebox side, 3-1/2 inch at the end.

[SoloQue]

What size is the opening from the firebox to the cook chamber?

[Buck]

It's 7" x 4" ... according to the feldon calculator, it's about 40% bigger than what it needs to be. I'm going to adjust it to the size it's supposed to be according to the calc when I make the firebox bigger. I figured bigger wouldn't hurt anything but maybe it does? Here's a pic of it.

[SoloQue]

So now the next choke point would be the baffle plate. How far does that extend to the far wall? In other words you have ample opening to draw heat from the box do you have sufficient area for the heat to come up and over the end of the plate into the smoke chamber. If all that heat isn't flowing then somewhere is a choke or your chimney is not drafting suffiiciently to draw the air through and pull the heat. OK, that is my breakdown of how I see it. As always I'm sure others will fill in the gaps or offer other insights.

[Buck]

Well I made the baffle plate and smokestack the size the calculator asked for. The stack is small diameter (2.75") but I made it the length recommended by the calculator ... not sure if the small size is a problem. The new baffle plate gap is a little bigger than the temp one because of the size of plate I had on hand. Maybe opening that up will help things. Will find out tomorrow.

[Smokeone]

Are you saying that the diameter is smaller than what was recommended? If that is the case, that could be you problem. It is not drawing enough air all the way through.

[Buck]

I was just saying that the stack diameter seems kinda small to me. There is no recommended diameter on the calculator. Is asks for the diameter and then calculates the length you should use. I was using the stock stack and made it longer with an aluminum insert. I will change this later but wanted to change one thing at a time so just used what was there. I was assuming that the interior volume of the stack was what needed to be right so didn't think much about the diameter until my heat problems started.

[Buck]

Sorry guys. Been busy but I have some updates. I welded in the 1/4" baffle plate, welded 1" angle all around the edge of the bottom cook chamber so the lid is actually sitting on something all the way around (not sealed yet but way less smoke leakage), welded the fire box to the cook chamber so no more leaks there, and got a steel pipe of correct size and length extended down to grill level welded in. Cooked a full packer brisket and things went a lot better. Got the temp up nicely and actually got it too hot a few times ... encouraging. Biggest problem I have now is that the firebox isn't big enough to go more than about 3 hours without a re-fuel. I've decided to just fabricate a new firebox rather than extend the existing one. Between the steel being too thin to really work with and the way the existing firebox seals, I decided a new one is the way to go. The new firebox is probably 80% complete (ran out of gas this afternoon ). I made it from 14 gauge steel since I didn't want it to be too heavy for the light cook chamber. Probably a mistake. SOooo ... now I have this shinny new firebox and I'm looking at my old smoker and thinking "do I really want to put this thing on that hunk of crap?". I've been looking for a tank but just can't find one around here (or don't know were to look). I guess I can always cut it off. What do you guys think? Here's some pics.

1" angle welded all around. Had to shorten it up on the back. those hinges aren't long for this world.

Finishing up the brisket. Turned out awesome.

[SoloQue]

[Gizmo]

Could you just pop-rivet the firebox to the cook chamber for a test? Maybe a small bead of high-temp silicone at the joint to get you by?

[Buck]

That might be a good idea ... I could just do a couple of plug welds that I could drill out easily. I'm not even sure the firebox isn't going to tip the whole thing over long-ways when it gets installed. This thing is getting heavy.

[Gizmo]

So cut yerself a scrap of peice of steel and touch weld it under the firebox for a leg and git on with it ...
Nothin better than KNOWING something works before putting the time/expense into it to get it finished up ...

[Buck]

Got the door done, fire basket made, and hinges on! ... Just need a closure mech of some kind, fire rope attached, a way to get the ashes out, a stop for the fire basket, and to un-stick the vents and make the stops for them and it'll be done. I'll post detailed pics later but getting dark so just took a quick one ... here's what she looks like.

[Frank_Cox]

Nice Job!!!