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Need Help on New Cabinet / Trailer Smoker Build

post #1 of 7
Thread Starter 

I'm building a smoker to make Pulled Pork for our high school football games.  I believe this design will support 750-lbs (15 racks supporting 50-lbs of shoulder each.

 

The oven below will sit on a trailer.

 

I've started welding the chamber.  I need to enclose the oven.  Since I have a rigid frame to attach the steel to, I was thinking 14 or 10 ga. steel would be sufficient... I see all sorts of smokers built of 3/16 to 1/4-inch steel, but these are all pipes, and are part of the structure itself.  My Char-Broil that I've used for nearly 8 years is thin as can be, and works just fine.  I'm going bigger... how much thicker do I need?

 

Also:  I was hoping the use gas burners to keep it to temperature after the initial smoke (after 8-hours, but supporting the remaining 8 hours or so).  I've read the messages about gas inside the chamber and don't like it... so I've shown small burners under the "floor" of the cooking chamber... will these keep the inside at that wonderful 220 degrees?  

 

Any suggestions appreciated.

 

Attached is the "design"

post #2 of 7
Thread Starter 

Attached is a photo of the oven framework.  The tube steel is easy to weld for a rookie... Since the pic, I've made all of the rack supports double cleats, so you can pull the shelves out and still have them supported.

 

I was thinking 14 GA on the walls / roof, and 10 GA on the doors (1/8-inch).  I keep comparing to my char-broil with much thinner steel, and i it did fine.. so do I really need to go to a much heavier ga steel?

 

For a door this size, do you need to reinforce it... 10 GA seems pretty rigid at the steel store...?

 

post #3 of 7
Thread Starter 

From reading many of the articles / posts on the site, I can see the benefits of thicker steel for the firebox.  For that, I'm planning on 3/8 steel for the "exterior" wrapping of the frame. I'm also building a shield around the sides of my removable wood tray, providing a protection to some degree from the exterior walls for the firebox.

 

The questions above were for the cooking chamber.  Many have built smokers from 55-gal oil drums.  Those are only 18 ga.  If I'm not building this for competition purposes, but for personal use at family / church / school events, I was thinking the 14 ga would be sufficient for maintaining the heat for the oven area.  Our Phoenix area temps dont get so cold that the smoker should stay sufficiently warm.

 

I'm also considering the propane burner(s) to support keeping the entire cabinet at the desired temperature.  The firebox should generate plenty of smoke, and I'm hoping that the distribution of the smoke stacks will allow me the opportunity to distribute the smoke across all of the oven. I've read in forums that many add gas support in the firebox, but I'm concerned with the size of this cabinet, it would get distributed evenly enough.  I thought that if I put a burner under the floor of the cabinet, below the channel where the heat from the firebox is distributed, it would keep the interior at a constant temperature, and not have the risk of the burner getting choked with no oxygen and pumping the area full of gas.

 

With Labor Day approaching, I'm hoping to weld the framework for the foundation of the oven, including the frame for the firebox.  I'll start to cover the various frames with steel sheeting after the holiday. I'll continue to post pictures.

 

This build might be a little bigger than most home units, but I'm assuming that all of the principles I've read will work.

 

Another challenge I've not figured out yet.. how to attach the smoke stacks to the ceiling of the smoker.  I'm not that good of a welder... and attaching the pipes to my proposed 14 ga steel sounds like a challenge.  Should I build a flange for the stack out of thicker steel as a base, then weld that to the "roof" of the smoker?

 

Any suggestions are appreciated....

 

The costs are not that bad for such a big unit:

 

Steel for the framework:  $350.

Shelves / grates: Pending

Exterior steel sheeting:  Pending

1800-lb capacity trailer to haul / move smoker $220 (Harbor Freight... $500 on sale.. plus 25% coupon...= $220)

post #4 of 7

Hola,

 

I have built the insulated vertical smokers before. (see pic)

14 GA is fine, but use cold rolled for the outside so it is easy to sand and paint.  drill 5/16" holes and spot weld to the frame every 4 " .  I make each panel 6mm (1/4") short on all sides, so you can then weld it to the edge of the square tube and grind off the excess with a flapper disc so you end up with a nice radius.

 

Use mineral wool for insulation, but be sure to paint the inside of the frame and all panels with a high temp anti oxidant paint before welding them on as it may sweat and rust.

 

Make an X on all the doors as they can bow once they get heat on one side of them.

 

I use 5/16" plate for the floor and walls of the firebox ad the orange smoker in the pic has been used nearly everyday for the past 3 years without problem.

 

Go extra heavy duty on the door hinges.    I use these door latches http://www.amazon.com/gp/product/B00X9H5S62?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00  

 

The CAD drawing is one I am going to start building for a restaurant

 

post #5 of 7
Thread Starter 

Thank you!

 

I appreciate the information!  Can you elaborate on the X on all doors?  Did you build each door as a frame and cover both sides?  I was planning on using a 3/16" thick steel for the doors, and thinking of adding reinforcement behind them.

 

I found the same hinges at my steel supply company. Thanks for the link to the latches!

 

For your restaurant build, are you making three fireboxes on the bottom, one for each cooking chamber,or is it a combined, open area?  Are there walls in between the three cooking chambers, or does it all get mixed inside?

 

At the moment, while I used some of the SMF spreadsheets for sizing the firebox, i'm still concerned about how I'm going to keep the size of this beast hot with an offset firebox. I killed the idea of adding burners to the outside as shown above... not enough heat transfer. Once the unit is together (two weeks I hope), I suppose there will be some trial and error on using a burner in the firebox to provide supplemental heat once the smoking stage is done.

post #6 of 7

Why would you want to go so thick on the doors?  

Make the frames out of 3/16" material, but you don't need anything more than 2 mm (14ga) for sheeting the doors.

The X brace is an internal X on the frame of the door to stop it warping when hot.  (Try making an X out of some small wood and tape it to a shoebox, you will see how it won't warp when you try to bend it.)  (Think Triangles when you want to make something strong)

Yes build the frame with X and then sheet each side of it. (Make sure to spot weld to the X or it will buckle)  drill with a hole saw and mount your temp gauges (watch for them hitting the shelves when you close the door).  Make the door about 3/4" larger than the cooker frame for the gasket. I also weld on 1/2 x1/2" angle to the door for the rope gasket to stick to help it stay on even with HT silicone.

On the restaurant build it has 1 firebox and 2 warming drawers on the bottom. Each cabinet can be  temp controlled individually. 

 

Probably many may disagree, but your firebox size can probably be as low as 20% of the cooker volume if everything is well insulated on all sides for a vertical smoker like this.  Make sure you insulate the firebox before someone cremates themselves accidentally.  

I would be more concerned about how you are going to mount the bottom plate in the cooker and drain the grease at this stage.

My 2 cents

post #7 of 7
Thread Starter 

Your suggestions are well taken! It appears you have constructed a double-walled unit throughout. I was planning on building the frame, and wrapping only the outside with the rolled steel.  Since I cook in AZ, and all of my experience is on a smaller, thinner walled smoker, I never had issues with losing temperatures (granted... never cooked on this size scale either).

 

So... my proposed doors are not frames, but sheets of steel similar to other traditional offset smokers. Perhaps when I'm all done and the thing runs too cold, I can still go back and add insulation and another layer of insulating steel... but that was not my intent, nor within my budget for this project.

 

Another progress picture is below... the base for the cooking chamber is now welded, and attached to my trailer. I plan to wrap the base in 14-Ga steel.

 

The end of this picture (under the extended handle bars of this "cart") is where my firebox will attach.  Just inside the interior of the frame is a 1x1-inch tube to support my tuning steel inserts (the 1/2-inch bar in the middle is resting on the tuning skid rails).

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