JC in GB 250 Gallon Reverse flow offset smoker build

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JC in GB

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Well, I finally got some shop time to start my 250 gallon smoker build. This is just the start and I will be continuing on throughout the summer as I only have a limited amount of shop time available.

I started out by doing a good deal of research on what was needed to build one of these units. I used the design template that daveomak daveomak provided and drew up the smoker plans.

So far, everything is following the calculations very closely. I am happy for that. As Dr. Who once stated so eloquently, "Only through mathematics shall we find truth."

I was able to get the old fittings cut out from the top of the gas cylinder and cut the doors. I was only able to get one set of hinges done though.

I have never used a plasma cutter before so this was a very sharp learning curve experience. The first old fitting I cut out with the plasma cutter was damn ugly. I got the hang of it by the third fitting.

Next part of the project will be putting hinges on the second door and cutting out the opening for the firebox. If I have time, I am also going to install the reverse flow plate rails. I need to calculate the arch length to achieve a 13 inch height from the bottom of the cylinder for the firebox. I will be getting that done today.

I was quite impressed at what a nice clean cut the plasma cutter made. A very handy tool.



Fittings cut off the top of the tank. Metal bar tacked welded onto tank for straight plasma cut on the door.

20210515_120741_HDR.jpg


Doors cut and hinges added to left door.

20210515_145729_HDR.jpg



Door and hinges work as planned. Very nice for such cheap hinges.

20210515_145715.jpg
 

JC in GB

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After looking over my design, I realized that the firebox is going to be a PITA to fabricate.

I liked the way jeffthewelder jeffthewelder did his firebox and I am gong to take a page from his design.

In my first iteration, I was planning on doing a freeform build of the box with clamps and welds.

I realized that this was going to be very hard to fabricate with the tools available and also be difficult to repair if needed.

I changed the design to make all parts of the firebox modular. Once the modules are fabricated then they will be assembled and welded together.

Right now, all I have is the hand drawn rendering of the new design. I will evaluate the design for fitness of function and then draw out a formal plan.

----- End of update ------

JC :emoji_cat:
 

JC in GB

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Firebox update:

I did a redesign of the firebox and sent the drawing off for a quote on the metal pieces.

The firebox will weigh nearly 700 pounds and the cost of the metal plates for it comes in at $1200.

That was $400 over my expected budget. That is not welcome news for sure.

JC :emoji_cat:
 

Berettaclayshooter

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Jul 14, 2018
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What in the heck are you using for a fire box that is going to be 700LBS? Use 3/16" or 1/4' plate and if you want insulate with ceramic insulation jacketed with sheetmetal, not need for anything over 1/4".
 

LanceR

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Jun 1, 2012
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Good morning, JC

1/4" steel weighs a bit over 10 pounds per square foot so 700 pounds indicates around 70 SF of steel. Can you share your design? And what are you concerned with being able to repair?

What plasma cutter are you using? And what welder?

Thanks,
 

JC in GB

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Good morning, JC

1/4" steel weighs a bit over 10 pounds per square foot so 700 pounds indicates around 70 SF of steel. Can you share your design? And what are you concerned with being able to repair?

What plasma cutter are you using? And what welder?

Thanks,

I am using a Miller 211 MIG welder and a Miller Spectrum 875 cutter.

Here is my firebox design. I made the end plates 5/16.
 

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  • SMOKER 250_FIRE BOX PLATES REV C.pdf
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LanceR

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Thanks. By the way, I'm embarrassed for you that you have a nasty Spectrum 875 cluttering up the shop. Feel free to box it up and ship it to me if you need more space and want to avoid the stigma. :emoji_wink:

I've had a Hypertherm Powermax45 XP on back-order for 5 weeks and they're saying to expect several more weeks before I get to the head of the line..... :emoji_disappointed: I have five tanks sitting around and have sheets of 1/4" steel for fireboxes and RF plates on the rack and don't want to snip them up with my Evolution 9" saw or a cutoff wheel. I'll be lurking around watching your build.

What are your tank dimension? Mine run from 120 to 75 gallons. Three are standard 120 gallon tanks and two are longer and smaller in diameter as they came off vehicles.

Lance
 
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JC in GB

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I am making a 250 gallon cook chamber. Standard size 250 gal propane tank.

The cutter is not my, it belongs to the brother in law. He is great at metal work. I am just learning...

Follow this thread for updates....

JC :emoji_cat:
 

Colorado0321

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Feb 28, 2021
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Yeah, steel prices have at least doubled in the last year. One reason why my build (which was going to be all plate) is on hold.

Looking forward to more progress pics!
 

LanceR

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Yeah, steel prices have at least doubled in the last year. One reason why my build (which was going to be all plate) is on hold.

The week before last I was quoted over $600 for HRPO (hot rolled, pickled and oiled) 4x8' sheet of 1/4" steel that was roughly $230 a few years ago. And those prices were from a couple of suppliers so they would seem to be pretty standard for small orders. I used to think $6 to $6.50 a square foot was high but over $19 a square foot is just plain nuts.

Fortunately, I have 2-2/3 sheets on hand but I'll have to be pretty frugal in hopes that prices will come down before I need more.

Best regards to all,
 

JC in GB

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Build update:

I was able to get some shop time in this weekend to get my firebox started and maybe finish the doors.

I got the firebox as far as I could. I didn't have the rockwool sheets I needed so I will have to install those next time. The box is just tack welded right now. I want to get it fully assembled before I finish the welds.

I also found that my hinge design left a bit to be desired. Once I tacked the seal strips on the door, the hinge alignment made the door close badly. I am going to rehinge the door with a bullet style hinge. That should fix it.

This was my first time welding so I am sure my weld joints will look a bit shaky. It took me a few hours to really get the hang of using the MIG welder. If you are going to critique my welds, be kind, it was my first time doing it.

JC :emoji_cat:

tank door strips.jpg



plate 1 welds.jpg


box 4 sides.jpg


box 5 sides.jpg
 
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LanceR

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Looking good so far! I don't want to have to muscle that firebox around though....

You might want to build a jig to make welding all those outside seams easier. I plan to make something similar to the one in the thread linked below but long enough to span the longest side of the firebox as I don't have to worry about curved welds as the thread's author does in boat making.


I'm still learning what settings and technique make the prettiest rounded outside corner welds on 1/4" plate with my new welder so that I have a quarter-round bead on the corners. I just cut and cleaned up a stack of coupons last night to practice on..... Once I'm happy with the profile and consistency of the welds I'll be cutting steel for the next smoker. The five propane tanks in the edge of our tree line have been calling me and one is currently having a soak with water and Dawn dish detergent.

Best regards to all,
 
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JC in GB

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Sep 28, 2018
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Green Bay, WI
Looking good so far! I don't want to have to muscle that firebox around though....

You might want to build a jig to make welding all those outside seams easier. I plan to make something similar to the one in the thread linked below but long enough to span the longest side of the firebox as I don't have to worry about curved welds as the thread's author does in boat making.


I'm still learning what settings and technique make the prettiest rounded outside corner welds on 1/4" plate with my new welder so that I have a quarter-round bead on the corners. I just cut and cleaned up a stack of coupons last night to practice on..... Once I'm happy with the profile and consistency of the welds I'll be cutting steel for the next smoker. The five propane tanks in the edge of our tree line have been calling me and one is currently having a soak with water and Dawn dish detergent.

Best regards to all,

Very nice. I was thinking of tacking a strip along the length of the box seam to guide the MIG tip.

I used the 1/8" MIG setting for welding the 1" x 1/8" tube to the 1/4" plate. It worked out quite well. I had only one spot where I burned through the tubing. That was welding the first corner.

JC :emoji_cat:
 

Displaced Texan

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Looking good. I'm not sure I would ever endeavor to attempt something like this, so I would never criticize anyone else's welding as I have never done it myself.

Curious where you got the propane tank, and how did you ensure it was completely empty before applying welds to it?
 
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