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Author Topic: Reverse flow offset build.  (Read 595 times)

Offline 220

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Reverse flow offset build.
« on: November 13, 2017, 02:00:29 am »
Made a start on another project yesterday a reverse flow offset smoker.
Started looking at it back in May but hadn't made a start, finally cut the tank I had so size is now set and I can start on the firebox. I was planning on a square firebox but after cutting the tank I realised the offcut from either end welded back together would be more than big enough. Seeing as I am doing this on the cheap using what ever I can scrounge from around the farm a round firebox it will be.

Offline Acebird

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Re: Reverse flow offset build.
« Reply #1 on: November 13, 2017, 09:50:28 am »
This is a smoker?  And what would make it reverse flow?
Brian Cardinal
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Offline 220

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Re: Reverse flow offset build.
« Reply #2 on: November 13, 2017, 03:35:42 pm »
Where a conventional offset smoker has the firebox one end and the chimney the opposite end a reverse flow has them both at the same end. They are separated by a full length baffle plate, smoke and air comes out of the firebox and are forced to flow under the baffle plate around the end and back through the cook chamber. The idea is to even out the temp in the cook chamber and eliminate hot spots.
Obviously the baffle plate ends up hotter closer to the firebox and radiates more heat into the cook chamber but this is at the point air temp is at its lowest so in theory temps balance out very nicely.

Offline 220

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Re: Reverse flow offset build.
« Reply #3 on: November 17, 2017, 04:09:26 am »
Day 1  cut the cook chamber to length & tacked the cook chamber offcuts together for the firebox
« Last Edit: November 17, 2017, 04:21:24 am by 220 »

Offline 220

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Re: Reverse flow offset build.
« Reply #4 on: November 17, 2017, 04:14:50 am »
Day 2 cut out the ends for the cook chamber
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Offline 220

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Re: Reverse flow offset build.
« Reply #5 on: November 17, 2017, 04:18:19 am »
Day 3 fully welded the two halves of the cook chamber together, tacked the door end in place and marked out. Tacked the legs to the cook chamber. Only took around 2 hours but when I sat it all together it started to look like an offset

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Offline 220

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Re: Reverse flow offset build.
« Reply #6 on: November 17, 2017, 04:19:31 am »
Day 4 Cut out air inlets, welded both ends of the firebox in place, fabricated and installed hinges and cut out firebox door. Spent about 8 hours on it and compared to the previous day I had worked on it the progress is much less obvious

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Offline Acebird

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Re: Reverse flow offset build.
« Reply #7 on: November 17, 2017, 10:35:55 am »
Holy cow or should I say pig.  Are you going to shove the whole animal in there at once?
Brian Cardinal
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Offline 220

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Re: Reverse flow offset build.
« Reply #8 on: November 17, 2017, 03:06:42 pm »
Not quite big enough for that, 48" x 22" I have a charcoal spit that I do whole lambs up to around 20kg.
20kg of lamb has been enough to feed the masses at any party we have and this should do a similar weight.

Offline sawdstmakr

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Re: Reverse flow offset build.
« Reply #9 on: November 17, 2017, 03:32:35 pm »
Wow, nice work.
What gauge steel are the barrels? Looks like it is a lot thicker than a 55 barrel drum.
It looks like you left the 2 circles together. How big is the pass through between the barrels.
Jim
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Offline 220

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Re: Reverse flow offset build.
« Reply #10 on: November 17, 2017, 03:46:43 pm »
It is actually the tank from a electric hot water system, only 3/16 but a lot thicker than the drums we have now days.
Cut the 1st full circle and then overlapped the second with the cut out for the pass through sitting over where the first circle had been cut. Saved a bit of material and cutting, 7" height on the FB/CC, have run all the numbers trough a few different pit calculators and it should be good.

Offline sawdstmakr

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Re: Reverse flow offset build.
« Reply #11 on: November 17, 2017, 03:53:59 pm »
Sounds/looks like it will work well and last a long time.
Jim
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Offline 220

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Re: Reverse flow offset build.
« Reply #12 on: December 03, 2017, 05:51:07 am »
Build day 5

Decided to have a play with the firebox and modify it to include a grill. Thinking the ability to use it as a small fire bucket would be handy in winter also. With that in mind I took to my newly welded firebox and cut roughly a third of diameter out, fabricated a set of hinges attached them and some 50x3 as a cover strip around the door.
Got a bit of bowing welding on the cover strips so will have to work on straightening it to get a good seal. Hope welding the reverse side might pull things back into alignment.

Couldn't help my self, with the extra door done and it still raining I built a fire in it improvised a grill and cooked a few snags.
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Offline 220

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Re: Reverse flow offset build.
« Reply #13 on: December 03, 2017, 05:55:11 am »
Build days 6/7

Biblical rain predicted for the weekend so dragged everything under cover to get a bit more work done.
The biblical rain didn't eventuate although we did get 4" in 36hrs.
Finished welding the hinges and cover strips on the extra door I added to the firebox.
Plugged and welded the couple of holes where I cut some fittings off.
Welded some brackets inside to hold a grill, fabricated the damper slides and fitted them, fabricated a latch and handle for the firebox door and a handle for the grill door.
Might have blown my budget as I spent $16 on some 1" Tassie oak dowel to use on all the handles. Found some latches I knew I had stashed away, fitted 2 of them to the grill door leaving 3 for the cook chamber if I need them.
Tacked the firebox to the cook chamber.
Cooked a steak and some burgers on the grill.
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Offline sawdstmakr

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Re: Reverse flow offset build.
« Reply #14 on: December 03, 2017, 06:56:06 am »
Looking good, almost there. You're going to have to bust the budget again because you are going to need a good high temperature black paint to finish it and make it a true work of art.
Jim
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Offline 220

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Re: Reverse flow offset build.
« Reply #15 on: December 24, 2017, 12:04:12 pm »
Still haven't finished the build but have progressed far enough to have my first cook.
Had 11 to feed last night for Christmas eve so lamb shoulder and ribs it was.
Came out great, a little heavy on the chilli with my rub so I will back it off next cook but nothing left.
Pulled the shoulder and tossed in BBQ sauce, sliders or tacos with slaw, corn on the cob and ribs to go with them.

Shoulder developed a nice bark and smoke ring here it is at the 3.5hr mark, took 5 hrs to reach the internal temp I was looking for.




Offline sawdstmakr

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Re: Reverse flow offset build.
« Reply #16 on: December 25, 2017, 03:36:39 pm »
Wow that looks good.
I will be butchering a steer in 2 weeks. He has been being fed and tenderizing for the last 3 months. I'm told by an expert friend of mine that the meat will be real tender, like RuthChris'. I'll let you do the cooking at the bee fest if you want. I was thinking of a full rib roast. That way we will have the ribs and the prime rib. What do you think.
Jim
"If you don't read the newspaper you are uninformed.  If you do read the newspaper you are misinformed."--Mark Twain