New Build -Trailer mounted reverse flow smoker

Discussion in 'Reverse Flow' started by bbq engineer, May 16, 2009.

  1. bbq engineer

    bbq engineer Master of the Pit OTBS Member SMF Premier Member

    Hi Everyone,

    I am planning a trailer mounted reverse flow smoker with a side rib rack, and I am to the point that I might actually get to the workshop and start cutting some metal today. I thought I would put up a primitive graphic of what I am am shooting for and get your comments and suggestions as I go along. I have plans in my head of what I want to accomplish and will make subtle changes as I need to, but the finished product will look something like this.

    The horizontal chamber will be 4' in length, and ~26 inches square. I am actually going to cut one corner off, so the side that the doors are on is not sitting vertical, but slanted a bit...sort of like a side view of the old time Ice Machines that sat outside of gas stations and grocery stores...). In my graphic, the red is the fire, and it will traverse the horizontal unit and enter the blue smoking chamber. It will then flow across the meat, and then enter the side rib rack at the bottom (represented by the yellow). It will exit the top through a 4" square chimney.

    Did I mention that the whole thing will be double walled and insulated!

    I am excited to get going on this and would welcome your suggestions as I go along.
  2. pineywoods

    pineywoods Smoking Guru Staff Member Administrator Group Lead SMF Premier Member

    Not sure about this but by having the intake into the vertical low won't that trap stale smoke in the main chamber? My other thought would be dampers from the firebox into both chambers so you could actually close the main chamber off and use the vertical chamber only for small smokes and save fuel.
  3. bbq engineer

    bbq engineer Master of the Pit OTBS Member SMF Premier Member

    Hey Pineywoods,

    I couldn't draw it, but I plan to have a damper that would seal off the area under the baffle plate and also one to separate the two smoking chambers so I could just use the vertical chamber for the smaller smokes. I'm open to suggestion as to the placement of the entrance from horizontal to vertical chamber. This would be no different than a question of how deep do you place your chimney entrance on a horizontal grate level, or above it??? Thoughts?

    The vertical chamber will follow along with some of my previous builds of verticals like these.

    Thanks for any input.
  4. pineywoods

    pineywoods Smoking Guru Staff Member Administrator Group Lead SMF Premier Member

    That is a great looking vertical. What about inlets high and low? I'm really not sure where the best placement would be
  5. gotoleep

    gotoleep Fire Starter


    Really looking forward to following this build. Double walled and insulated, nice. You may only need to buy all of your wood in matchstick bundles from now on. [​IMG][​IMG] BTW, what program did you use to do the drawing?
  6. bbq engineer

    bbq engineer Master of the Pit OTBS Member SMF Premier Member

    I wanted to get to the shop and get some metal cut, but first I had to get the sheet up on some saw horses. I am using 10 Gauge CR steel (.134" thick) and some of the sheets I have are 4' X 10' and weigh 225 lbs. I Had Mrs. Engineer who weighs in at a whopping 130 lbs drippin' wet help me! It was touch and go for a minute when I about tipped the sawhorses over, but we got through it.[​IMG]

    I have already altered the original plan, as I got the sheet on the sawhorse, and a 48" horizontal chamber just isn't going to do it for me, so I decided to go with a 60" horizontal chamber.

    Gotoleep - In response to your question, You would think that as an engineer I would have an awesome 3D Modeling and CAD program, but I don't. I used Excel and adjusted the pixel count for rows and columns the same. Therefore, it was actually drawn to scale before I changed the horizontal chamber to 60".

    Here are some of the photos so far.

    I'll start with the tools I am using...Here is my new plasma cutter...It is really nice!

    Here is my welder...I will be using FCAW (flux core) as I weld outside my shop.

    Here is a sheet of steel on the sawhorses ready for layout. I actually got the steel for scrap price...don't look like scrap to me!![​IMG]

    Here I am working with my new torch...

    Mrs. Engineer was helping me with some photos.

    Plasma cutters are really sweet for slicing this stuff up. I am a rookie with my new unit, but I will be a pro in no time.
  7. pineywoods

    pineywoods Smoking Guru Staff Member Administrator Group Lead SMF Premier Member

    Awesome equipment and looks like a great start!!
  8. pops6927

    pops6927 Smoking Guru Staff Member Moderator Group Lead OTBS Member SMF Premier Member

    Any chance of edeecating us who know nothing about metalworking? I'm a woodworker, never did anything other than a little flashing with metal.

    The plasma torch just cuts the metal, correct? Or can it do more? What makes that better than any other type of cutter? Like a torch?

    Also, that's an electric welder, is there any other kind?

    And, what kind of power and amperage do you have to dedicate to run those machines, and what kind of electric bill spike does it cause, or is it unnoticeable?

    Please humor an old man who just likes fire! lol!
  9. mossymo

    mossymo Master of the Pit OTBS Member SMF Premier Member

    BBQ Engineer
    That is a very professional looking build in your pictures, you do nice work. Are those latches stainless steel? If so, where do you purchase them at?
  10. meat hunter

    meat hunter Master of the Pit SMF Premier Member

    Hey there BBQ, I see your playing with your new toys LOL. Looks good so far. Hows the plasma working for ya? Getting the hang of it? How did you ever get along without it[​IMG]

    Can't wait to see the end result of this one, I bet its gonna be awesome. I have yet to start on my fridge conversion. So many things going on here. Take care and look forward to seeing the finished product.
  11. fire it up

    fire it up Smoking Guru OTBS Member

    Lookin good Engineer, loved the plasma torch.
    Really nice work!
    I'll have to make sure to keep an eye on this thread.
  12. bbq engineer

    bbq engineer Master of the Pit OTBS Member SMF Premier Member


    I’ll try to answer your questions, but in no way am I a metal working expert…I just play one on the internet (LOL!!). The Plasma cutter is strictly for cutting metal. Without getting to much into what Mrs. Engineer calls “Nerd Speak”, Plasma is the fourth state of matter (from science class), and occurs when you boost a gas to extremely high temperatures. Plasma cutters utilize this principle by sending a pressurized gas (in this case, regular old compressed air) through a small channel across a negatively charged electrode. When you touch the torch to your workpiece and pull the trigger, a circuit is completed which generates a powerful spark. This heats the air moving through the nozzle until it reaches approximately 30,000° farenheit, moving at 20,000 feet per second. This will make precision cuts in metal, that have the cut quality of using a bandsaw. This is preferred over Oxy Acetylene torches as it is much safer, and the quality of cut cannot be beat. Using the plasma cutter, the surrounding metal gets hot, but the cut happens so quickly that it doesn’t get anywhere near as hot as a regular acetelyne torch. The Oxy Acetylene torch will melt the metal and then blow it away, where the Plasma cutter really just slices through it. I can’t explain it any better than that.

    My welder is a mig welder, and has a spool of wire inside the unit. When I press the trigger on the gun, this wire acts as the electrode and is fed at a constant rate to the workpiece, melting the workpiece (and wire). The wire is then deposited as well and acts as a filler to fill gaps and voids. I am using flux core wire, which is self shielding because it has a center that, when burned creates a shielding for the welding process. If I didn’t use this, I would have to have some sort of backing gas. Since I weld outside and there is frequently wind here in Kansas, creating the shield at the actual weld is probably better than if I were to use gas to do the same thing.

    My welder and plasma cutter run off of 220 volt AC…I believe I ran a 40 Amp service. I don’t know what they do to the electric bill, because it is so darn high anyway, it would be like a teaspoon of water in the ocean!


    I got the latches for the cabinet smoker from J.W. Winco at this website.

    They have a great selection of stuff like this, and I believe the ones I am using are model 431 or a subset of that.

    Meat Hunter,
    Plasma is working great…This has sped the process along like your wouldn’t believe! I used to cut this stuff with a metal cutting carbide blade and my circular saw...the shrapnel was out of control! Thanks for all of your tips and suggestions. I reserve the right to bother you with more PM’s if I get in too deep! Have your taken your “Survivor Man” trip yet?

    On Tap for today...I am going to melt some wire, and start tacking some of the pieces together. I also have to get the insulation ordered and on it's way. Maybe an update later today.
  13. meat hunter

    meat hunter Master of the Pit SMF Premier Member

    Hey again. Yeah no problem, contact me anytime. Well you say you are not a metal working expert, but you sure did explain the principals of the plasma and welder like an ole seasoned pro LOL. Good job. No the trip is not for another 3 weeks. Have been in the process of dehydrating our meals, buying new sleeping bags, some dry bags in case the canoe tips(god forbid because the water temp is like 40). Just finished drying about 5 pounds of Morel mushrooms and wild leaks (ramps) for the trip. Figure they would go great with some fresh Walleye. Going to try to do a smoke this week. Was going to do a stuffed beef heart from one of our cows but did not want to fire it up just for that. Maybe get another brisket and add to it. Later.
  14. bbq engineer

    bbq engineer Master of the Pit OTBS Member SMF Premier Member

    I got some pieces welded together and am starting to form the horizontal chamber. I started by building a jig out of 2X4’s to form a right angle that I could use to set the pieces on. I have fought and fought with magnets in the past, and I am just not going there. I have also decided that I quickly need to get the bottom side of this thing finished, because it is going to get too heavy to easily move around for me.

    Here is the jig I built, and the bottom of the horizontal chamber in place.

    Next, I put the back of the horizontal chamber so it sat on the bottom at a right angle. I put some angle iron in the corner and tacked it all together. Then I came back and filled in the rest of the weld so the entire thing was welded. I welded this in sections, as if you just throw heat at it nonstop, the workpiece can warp and twist…therefore I choose to do it in pieces.

    Then I cut the front of the inside chamber. Here is a picture of the dross or slag that the plasma cutter leaves on the bottom of a cut. It is nothing compared to an Oxy Acetelyne torch, and pops off if you whack it.

    If you touch it with a grinder it leaves a good edge to weld to.

    I welded the front inside shell for the horizontal chamber in place.

    Here is the inside shell of the horizontal chamber…front, back, and bottom.

    I will get some more completed some time mid week, as I have to travel for work...ever notice how work gets in the way of BBQ [​IMG]!
  15. cajunsmoke13

    cajunsmoke13 Master of the Pit OTBS Member

    Looking good BBQE
  16. waysideranch

    waysideranch Master of the Pit OTBS Member SMF Premier Member

    Nice fab work. Look forward to seeing this smoker finished.
  17. bigsteve

    bigsteve Master of the Pit

    Well I'm impressed so far.

    What are you going to use for insulation?
  18. bbq engineer

    bbq engineer Master of the Pit OTBS Member SMF Premier Member

    Big Steve,

    I am going to use a product called "Superwool 607". It is a ceramic fiber blanket that is used in kilns and ovens. It is rated at over 2000° and is way over-kill for what I am doing, but it is easy to work with, has great insulatory properties, and is conveniently packaged. You can check it out here:

    I got the side of the horizontal chamber cut out, and it will show what I mean by looking like an old time Ice Chest that sat outside of a gas station or a grocery store.

    I don't know if I have shown a decent photo of what a clean cut that a plasma cutter will make. I have never used one before I got mine, so I am in no way a professional with just makes me look like one. Here is a top view of the cut. You can see that it really does slice through, and doesn't heat the metal up hardly at all...the heat affected zone barely extends past the cut! The angle iron is used as a guide so I can keep a straight cut.

    Here is the same cut except looking at the cut is really clean. Man, good tools make all the difference!

    More late this week!
  19. bbq engineer

    bbq engineer Master of the Pit OTBS Member SMF Premier Member

    I made a little progress yesterday, and expect to get more over the weekend. I am working to get the inside of the horizontal chamber finished, so I can move on to the vertical side. Messing around with the baffle plate has consumed a lot of time, but I think I am done. I have seen some plates where they use a piece of angle iron in the center and then slope sheets to the center channel. I decided to shamelessly steal Meat Hunter's Idea from his build and just slope them to the center in the first place. I will add a drain once I get it welded in place.

    I have mounted it 6 inches from the bottom shell, and 6 inches from the side wall. There will be a flat that extends into the firebox. Here is how it will look. I will clean up all the welds before welding it in, because once it is in, I can't get tools in to shine it up. I also have the side of the horizontal chamber welded in place.

    I also have started to weld on the frame that will separate the inner and outer wall. It is 1" square tubing, 11 Gauge and .120" wall thickness (far right of pic).
  20. pineywoods

    pineywoods Smoking Guru Staff Member Administrator Group Lead SMF Premier Member

    Looking very good I can't wait to see more [​IMG]

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