High School Shop- Reverse Flow Build

[Bearcarver]

I personally would recommend going with a Small unit first.
That way if they wanted to, the students could each build their own personal smoker.
Then after most of them learn a bit about using them, they can all get together with you (Teacher), and build a big one that could be used for some type of School Shindig, as a celebration of completion. Naturally the big one would need to be trailer mounted to move it, but being also the Auto Teacher should make that easy enough for some more instructive classes along the way.

Bear

 

[Gijoe985]

I think we are going to stick with the 120 gallon unit for now. We've got the tank. It'd actually take less metal to build then trying to fab up one from scratch. Though a smaller unit would be great for the future.

 

[Gijoe985]

Anyone have good pictures of their firebox? I'm just trying to make sure we include all the needed features.

Also, what are the specs on the expanded steel you guys usually use for the grating?

 

[JckDanls 07]

I made my FB the same width as the tank where it was going to connect to it... pretty sure it was 22" ... my tank is also a 120 gallon.... I believe my FB ended up being 22" cubed ... Here's a couple of pics... they don't really show where it's connected/welded to the tank though ...

Tractor Smoker 013.JPG

• JckDanls 07
• Dec 18, 2016

Tractor Smoker 018.JPG

• JckDanls 07
• Dec 18, 2016

As for the grates.. luckily I had some heavy duty 1" sq stainless screen that I used... but most use the #9 (3/4") flat expanded metal for the grates.. For my FB grate I used 3/4" catwalk expanded metal (I'm sure that's not the proper name for it) ... but ended up laying a piece of the #9 flat expanded on top of it...

This is where the vents like to be to run at 225`

This is my preheating method.. I let this burn down to coals.. that way my chamber is about 350`.. I then spray water all around the inside of the chamber for a steam clean... it also brings temps back down for smoking

 

[Bigmark1127]

I am following the guide and had all the numbers I am getting tripped up on the stack or stacks if you will I came up with1718.5 ESV and to run 4 inch I'd pipe and I come up with 108 inches above the c.f. can I cut this half if I put 2 4 inch stacks on?
Thanks for any help

 

[Gijoe985]

What's the optimal distance from the RF plate to the lower cooking rack? I'm seeing 4-5" from what I've found via searching, but others have said closer.

On a 5ft long smoker, 1 big door, or two smaller doors? Pros/Cons?

 

[motocrash]

On a 5ft long smoker, 1 big door, or two smaller doors? Pros/Cons?

To whole hog,or not to whole hog?

 

[Gijoe985]

4-5" up sound good for the lower grate? I need to figure this out before we cut the door.

Also, is there any reason why would wouldn't want the bottom of the door to be about even with the bottom of the grate? That way the grate can slide out. I figure the door doesn't need to be any lower than that.

 

[Gijoe985]

Follow this build tutorial.... It will get you a great smoker.....

https://www.smokingmeatforums.com/t...eady-to-use-rev5-6-19-15.172425/#post_1264161

If I make the stack drop down into the smoker like in the "alternative" stack picture in the link, do I calculate the total height of the metal, or just what it above the smoker? For a 4x4 smoker stack it told me that I need a 40.75" stack. Sound right?

 

[JckDanls 07]

Measurement is from the TOP of the tank/smoker... does not include what protrudes down into the tank/smoker or a plenum out the end/side ...

 

[Gijoe985]

Can anyone elaborate on the benefits to having the stack protrude down into the tank more or less? My only thought is that more smoke would linger in the smoker if the stack went further down into the smoker.

 

[Gijoe985]

We're trying to use materials that we have on hand. We have 2.5" exhaust pipe that we could use for the stack(s). From the math provided, we'd need 132" of pipe. What I thought would look cool (and give us that volume [~650cu in]) would be cutting 4 different lengths that add up to the 132. Then bunch them together, but they'd be unequal at the top. I thought that'd look cool, but maybe the different lengths would be less efficient.

Thoughts?

 

[Gijoe985]

Ok, and not after doing more reading, it seems that more stacks = more friction. We just don't have anything else that size. Our best option B is to weld some 4" wide flat stock to make a 4" square exhaust.

 

[Bigmark1127]

We're trying to use materials that we have on hand. We have 2.5" exhaust pipe that we could use for the stack(s). From the math provided, we'd need 132" of pipe. What I thought would look cool (and give us that volume [~650cu in]) would be cutting 4 different lengths that add up to the 132. Then bunch them together, but they'd be unequal at the top. I thought that'd look cool, but maybe the different lengths would be less efficient.

Thoughts?

I have 1079 escape I want to run two 4” pipes because that’s what I have coming up with 42” tall above CC does seem right?

 

[daveomak]

Something to remember, or learn....
2.5" = 4.9 sq. in. area... X 4 = 19.6 sq. in. X 34" height = 666 cu. in...
However, 2.5" dia. X 3.14 = 7.85 circumference... X 4 = 31.3 in. of circumference total..

A 5" D pipe = 19.6 sq. in. area X 34" = 667 cu. in.
5" D X 3.14 = 15.7 circumference

The thing to note here is... FRICTION from the pipe interior...

31.3 cir. inches compared to 15.7 cir. inches is twice the friction...
Friction is a killer in a gravity smoker....

Now, make a 5" square exhaust...

 

[Jonok]

What would happen if you took some of your 2” exhaust pipe, ripped it in half lengthwise, and welded it back together like a 5 or 6 leaf clover? Seems to me you’d be able to achieve more than enough cross sectional area, and you’d have a great math and fabrication project to boot.

 

[Gijoe985]

That may be better than what I had been dreaming up. We are low on 1/8"x 4" flat... lots of 1/4", but that'd be a very heavy stack!

 

[Jonok]

If you've got any budding tig welders, "walking the cup" in a groove like that over a 5' stack 6 times would be a dream.

 

[Gijoe985]

Ok, we did a quick test burn (just using 2x4 wood we had at the school shop.).

We have two thermometers. The one closer to the firebox quickly climbed to 300 while the further one slowly raised to 200-225.

Suggestions?