120 Gal. Reverse Flow (not your normal build) "DONE"

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JckDanls 07

Legendary Pitmaster
Original poster
OTBS Member
SMF Premier Member
Sep 10, 2011
Tampa area, Florida.
OK... So after reading GEOThernal's (George) build.. I asked him If I could copy his design... He said"GO AHEAD"... His Build .. http://www.smokingmeatforums.com/t/166551/20-pipe-rf-smoker

SO this build started nearly 2 years ago with this 120 Gal. air compressor tank ...

(click on any pic to enlarge)

Removable reverse flow plates

2 slide out grates

Firebox and vents (before handles)

a look inside...

This is what it looks like now...

made a tow bar for it... easy to move ...

Taking it for a test ride...

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

And finally ... ribs were the first cook ... they were really thick ribs.... So at 6.5 hrs of running at 225` I had people yelling they wanna eat... "ARE THEY DONE YET"... NOOOOO they weren't quite done... so unfinished ribs is what they got...

here's the radiator cap.. kinda hard to see it...

So that's it for now.. gonna sand blast and let it rust again (evenly)....

Also... the wheels... I made these myself (home made)
ok.. I think I know the answer ... so I tried using the Guru today... they are recommending 2 blowers for this size firebox... as you can see I'm trying with just one... when I closed the vents and turned on the Guru... temps fell ... the blower wasn't running constantly... just short little bursts ... I would think the blower would run constantly to try to reach set temps.... especially if temps are falling... open vents up a quarter of an inch and temps come right back up ... any ideas.. besides a second blower ...
I'm running my cyberq right now the number of fans shouldn't matter from what your saying. Check your control setup your deviation might be to wide of a range. Also where you place the thermo probe makes a difference my guru and smoker probes rarely match up
That's a great build Keith!

You can be very proud of it!

I wish I had your talent!

Point to you my friend!

I have been using a Guru on my Lang lately. 

I had to buy the Pit Viper fan, because the smaller fan I had on my WSM just didn't put out enough air.

You would have to check with BBQ Guru on this, but I think the Guru learns from each time you use it.

In other words it learns your pit & when to come on & off to keep the temps stable.

Mine was used to the WSM & when I put it on the Lang it didn't work very well the first few times.

I found that if you start your fire & get the temp up to 150 or so, then shut the dampers & let the Guru take over.

It will learn how much air is needed to raise the temp in your pit.

I also found that I use a lot less wood when the Guru is controlling the pit.

The other thing I notice is your Guru port seems a little high.

I have mine below the grate in the firebox, so the air comes in under the wood.

I also have it on the opposite side of the door in the firebox.

Thanks Y'all.. I'm having a blast with it...

So here are my thoughts... when running on vents I have to keep the vents closed down to about a 1/4 of an inch (exhaust wide open) to run at 225` ... I'm using whole logs as that's all I have... ranging from 2" - 6" , 12" - 16" long ... I assume If I want more air to flow through I would have to maintain a smaller fire ? ... It just seemed like the smoke flavor was a little musty/heavy/strong/almost creosote .. was thinking it was from not much airflow ... I'm pretty sure it's gonna be fire size which means smaller wood added at more frequency ?? The fire had flames (not smoldering) pretty much the whole time .. Yes.. I understand I need to learn fire management as that is what I'm trying to do... This was my first cook on it so it's a learning experience..
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My blowers are pretty much even with the grate. If temps are falling that fan should be blowing pretty constant. You've used mine plenty and I keep the dampers closed all the way when I use it. The only time I get a lot of small puffs is when the temp is on and it's trying to hold it. Love the build!
Yes you're on the right path as far as your ideals of fire control. I try to leave my firebox and stack wide open and control temps strictly by controlling the amount of fuel. This allows the fire to burn as freely as possible giving you a very clean smoke, almost invisible. You'll notice once your coal bed is set the time between refueling will become longer and longer.


Learned my fire control the hard way, was very frustrating but makes cooking on the big boy a breeze.

OK.. so I did another burn with it today... using only the DigiQ DX2 (guru) ... I placed the probe for it in the dead center of the smoker and left it there ... I used my Thermoworks "Smoke" to move all around the chamber to compare temps (all probes were tested in boiling water before starting)... The firebox end was 15` hotter than the center... The far end was 15` cooler than center.. so a 30` difference from end to end...

I tried with all vents (except exhaust) closed... then I opened the top intake vent about a 1/4".. it seemed to raise the far end temp a couple of degrees ... and the blower didn't seem to have to work as much...

Question about blowers.... when the blower is off... does it still draw air through it ?? If so maybe this is why they suggest 2 blowers for this size firebox ... The blower never stayed on continuously.. so this makes me think one blower is enough... unless it needs more air when blower is off (through 2 blowers) ...

Adding wood... I have been preheating wood on the firebox before throwing them in... I don't imagine there is much that can be done about this but... when you throw splits on it put's out the nasty white smoke for 5-10 minutes... normal ??

As for the temp being hotter at FB end... will a baffle plate about an inch or 2 above the RF plate going about a 1/3rd of the way into the chamber help with that issue ??
Evening Keith....   May I suggest one more test run.... Exhaust wide open...   Upper air inlet wide open....  lower air inlet wide open.....

Get a good fire going... maybe 8-10 of those hunks of firewood you've got in the picture.....   get them burning well so they are starting to glow like turning to charcoal....

Start closing down the lower air inlet...  about 1/4" at a time...  follow the temps...   If you can, have a couple extra remote therms to follow the temps...   The temps "should be" close to the same across the meat screen...    When the temps get down to maybe 200 ish, start closing the upper air inlet and see what happens....   You need good air flow to get even temps..   Lower air inlet adjusts the heat... upper air inlet moves the heat through the smoker body...  It is similar to the fan and ductwork on a home furnace....     You need a large bed of coals to make these smokers work... skimping on the wood makes temperature control difficult....  When all is working correctly, the firebox temperature should be close to the CC temp...  that indicates you are not burning wood needlessly ....   soooooo, lots of air flow from the upper air inlet while the wood fire is idling along just doing what needs to be done to maintain temp.... 

Oh yeah, leave the Guru unplugged......
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I would try a dry run with firebox open and smoke stack wide open and play with that. Let that fire burn as freely as possible. If too hot, use less wood. Your RF plate prevents the fire and direct heat from scorching the meat so let her breath.
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