Critique My Design

[Kcd2016]

I'm looking to build my first smoker and I was hoping I could get feed back from the community on my design so far. It's a straightforward RF smoker, here are the specs:

• 20" Dia x 36" long cook chamber (rolled plate)
• Firebox is 15.4" x 16" x 16" = 3,958.4 cuin (105%)
• Throat area is ~31.63 in^2
• 4" ID stack placed at grate level
• The baffle plate gap is ~1.9" from the back wall
• The baffle plate is a slight v shape, angles are 5 degrees
• Not including the 'elbow' the stack is 15 3/4" tall
• EVERYTHING is drawn as 1/4" plate at this time

Here are my questions:

• Is my cooker just generally too small for even heating... or a just a well functioning smoker? I know it'll have the capacity for the qty of meat I'd be cooking
• Are there any glaring problems with my design, anything from a fabrication standpoint to functional issues?
• This is a small backyard smoker, but should I consider different thicknesses of steel? If so what and where?
• The baffle plate is drawn level lengthwise, should it be slightly lower on the drain end?
• Is it necessary to have the BP bent?
• Where should the top and bottom of the cc door be cut out in terms of 12 o'clock to 3 o'clock, or 11 to 2:30, etc.? (I hope that makes sense)
• The firebox is nearly a perfect cube (16"x16"x16"), is this optimal or do I need to make adjustments for baskets, ash trays, etc.?
• Do I need to make the BP gap adjustable?
• Do I need to consider the travel in the elbow when figuring stack length?
• What is a good vert. spacing between grates?
• Anything you would change, anything at all? Please lay it on me!
• Finally; I don't see a lot of hexagonal or octagonal shaped CC. It would be cheaper for me to do that than get plate rolled, is there a reason we don't see more 'geometric' CCs (besides a lot more welding)?

I haven't drawn up much of the details yet like intakes, stack damper, grates, fire basket, etc.







[EDIT] So I was just doing some googling and found this production smoker that's just about the same as what I've come up with: http://www.katbbqsmokers.com/36x20_reverse_flow/

[Pete Mazz]

Here are my questions:

Is my cooker just generally too small for even heating... or a just a well functioning smoker? I know it'll have the capacity for the qty of meat I'd be cooking It's fine if it's large enough for what you want to cook.

Are there any glaring problems with my design, anything from a fabrication standpoint to functional issues? No

This is a small backyard smoker, but should I consider different thicknesses of steel? If so what and where? CC could be 3/16" but why bother

The baffle plate is drawn level lengthwise, should it be slightly lower on the drain end? no

Is it necessary to have the BP bent? No

Where should the top and bottom of the cc door be cut out in terms of 12 o'clock to 3 o'clock, or 11 to 2:30, etc.? (I hope that makes sense) 11 to 4

The firebox is nearly a perfect cube (16"x16"x16"), is this optimal or do I need to make adjustments for baskets, ash trays, etc.? No it's fine

Do I need to make the BP gap adjustable? No, only for tweaking but most are not

Do I need to consider the travel in the elbow when figuring stack length? No

What is a good vert. spacing between grates? ~5"

Anything you would change, anything at all? Please lay it on me! I'd like to be younger.

Finally; I don't see a lot of hexagonal or octagonal shaped CC. It would be cheaper for me to do that than get plate rolled, is there a reason we don't see more 'geometric' CCs (besides a lot more welding)? Make it rectangular and have more room for the upper rack. Tanks reduce a lot of welding.

[Squiggle]

Have to agree with Pete, & I'd like to be younger too!

[Dirtytires]

Pete is spot on. Id just add that tho many choose to bend the baffle plate, I made mine flat plate and couldn't be happier. It's easier to build with less cutting and welding, easier to clean (it's flat, so scrape it with a 6 inch putty knife) and Unless you are running your smoker nonstop for a week, there is no reason to drain off fat during a cook.

Unless you are religious about cleaning your ash right after a cook, I may suggest an ash pan.

Lastly, if you think you may ever consider adding a warming box, the location of the smokestack will be in the way. However, that can be fairly easy to move at any time.

Otherwise, looks good. I feel 0.25 is good to work with also.

And, oh yea, get a new pair of safety toe boots, good safety glasses and some ear plugs before you start. Nothing worse than a trip to the ER to put a halt to a good smoker!

[Kcd2016]

How would you guys feel about using this pipe to build a smoker?
I have no idea what it was ever used for in its previous life.
How much of a p.i.t.a is it going to be to get rid of this rust?

[Dirtytires]

Rust is no problem....a media blast or a few hours with a wire wheel will remedy that.

I'm guessing diameter is about 16-18 inch? That makes for a fairly narrow shelf and a crowded second shelf, if that was in the plans. It will work great, just depends on your anticipated use.

[Kcd2016]

Rust is no problem....a media blast or a few hours with a wire wheel will remedy that.

I'm guessing diameter is about 16-18 inch? That makes for a fairly narrow shelf and a crowded second shelf, if that was in the plans. It will work great, just depends on your anticipated use.

I'm told it's 20" dia, one is 36" long (exactly what I need) and the other is 24". $125 for both, kind of have to take the shorty or no deal. Sound like a good price?

And should I be worried about what these may have been used for before or just burn it out and no big deal?

[Big T]

I'm not sure about the price but if it's a lot cheaper than new rolled plate I would get it. If it's close in price I would probably get the new metal so you don't have to deal with the rust. I use old pipe for most of my builds, I lay it on its side and build a fire inside of it before I do anything with it. I let it burn for a while to get rid of what ever may have been in there.

[Rodcrafter]

I've used pipe on many cookers, but having added a square vertical to my trailer rig I think I will always go with square of one kind or another. The pans we use are square shapes and they fit into that much better.
jm2cw


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[Dirtytires]

I bought a 48 x 24 x 0.25 inch pipe a obout a year ago. It was new pipe, squared ends, cut to my exact length and absolutely no rust to deal with or waste time on. I gave $240 for mine at a major pipe yard here in town.

Your price is not out of line but only a good deal if you can actually use the pieces and they are the size you actually want. Also depends on how much your time is worth to prep it....it needs to be burned out and the rust cleaned before you can weld it.

[Kcd2016]

I bought a 48 x 24 x 0.25 inch pipe a obout a year ago. It was new pipe, squared ends, cut to my exact length and absolutely no rust to deal with or waste time on. I gave $240 for mine at a major pipe yard here in town.

Your price is not out of line but only a good deal if you can actually use the pieces and they are the size you actually want. Also depends on how much your time is worth to prep it....it needs to be burned out and the rust cleaned before you can weld it.

Thanks Dirtytires. I happened to just read through your build thread yesterday. It looks great.

The local steel supply here in town quoted me just shy of $900 for a 20' length of pipe, so unless I decide to build 6 smokers at once and sell the rest I don't think I'll be going that route (though it's not out of the realm of possibility for me to do something dumb and go all in like that). I'll call around to some other steel supply yards that I found on google and see what they have to say.

[Kcd2016]

I'm considering just using that second piece of pipe as the firebox.
Does the cross sectional area underneath the baffle plate matter? I'm talking about the full area outlined in red not just the throat:

Also, I've read conflicting information about the baffle plate gap, I *think* I've read where @Frank_Cox said he makes the gap 50-75% of the throat area, is that right? I know I've read elsewhere that the gap needs to be at least as big or larger than the throat area. What are the thoughts on this?

[Squiggle]

I believe they were talking about the gap at the other end of the BP, the gap up to the CC. I think you'll be right with that setup in the pic. You could always cut a section out of the FB pipe & put a flat piece on there. Then you could have the BP level with the top of the FB & have a place to cook a pot of beans or stew.

[Kcd2016]

Hmm, why not make the top of the fb and the BP one continuos piece?

[Squiggle]

Yep, that's the idea!

[Kcd2016]

Okay, how does this revision look? Anyone see functional or fabrication issues? (I forgot to draw the stack)

[Pete Mazz]

There should be a door on the FB!

[ajfoxy]

There should be a door on the FB!

Hahahahaha

[Kcd2016]

Lol, okay, I admit that my drawing lacks a few minor details

Have any other build actually made the baffle plate and firebox one piece? I know people try line the two pieces up.

[Squiggle]

Most people do that, usually the FB is square so it makes it a lot easier.

[Kcd2016]

Most people do that, usually the FB is square so it makes it a lot easier.

Okay, got ya.

I'm set to pick up the rusty pipe tomorrow, looks like I'm about to be pot committed.

When I've looked at production cookers that are my size of 20 dia x 36 I've noticed that they usually have a much bigger fire box than what I'm calculating, their fireboxes usually work out to 150-170% of our calculators recommendations. Do they know something that I don't?

[Pete Mazz]

Maybe they're insulated?

[Rodcrafter]

I would recommend that you be careful laying out the throat opening doing it with a flat top on a round FB. It will be easy to make it too small loosing the top portion of the radius


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[Kcd2016]

I would recommend that you be careful laying out the throat opening doing it with a flat top on a round FB. It will be easy to make it too small loosing the top portion of the radius


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What would be the best fab method? Im thinking either 1) just slide the bp into the fb, weld it from inside bottom, then use my torch to cut away the upper radius from the inside or 2) cut the top radius out, hope it doesn't spring out too much, and fillet weld from the outside.

I picked up my pipe today and got home and realized its 3/8" pipe, not 1/4". Can I still make the rest out of 1/4" plate? I've seen some recommend staying the same thickness for expansion reasons.

When I burn these out will that be hot enough to alleviate some of the stress that might cause the pipe to spring out?

[mp4]

Yes - 3/8ths will be just fine. That's the way mine is and I haven't noticed any issues with BP expanding differently.