Air movement advice needed - Ok Joe/Mod/Auto fan

[happy2meatu]

Just got an Oklahoma Joe's Longhorn 3-1. Side firebox with smoke chamber. I've already taken steps to seal up gaps, cracks, seams. I ran one test burn so far, concerned about air movement. I checked the Feldon calculator for air inlet and exhaust sizes, and it is clear that the firebox is way too big (round 19" x 17"). It has 230% larger volume than recommended for the cook chamber (cook chamber is round 20" dia x 20" long). Also the fresh air damper and exhaust are too small. Exhaust is 3" dia x 7" long, calc says it should be 34" long. Fresh air inlet is approximately 50% too small.

I'm considering purchasing a Lavalock automatic blower system - I'm wondering if having the forced air in will compensate for these volume shortfalls?

 

[skunkwerx]

Based on my experience with the OK Joe Highland, your 3" chimney, is probably 3" outside diameter, less inside.
I fabricated a new chimney, to fit around the round outlet hole in the cooking chamber. so it increased the volume exiting. As well, I made a baffle on the inside, lowering it down near grate level, which effectively increases the length of the chimney, it helped, but did not completely solve the air flow issues.
Next, I changed the firebox air inlet, increasing it.....it helped also, but still did not solve the overall problem.
I was smoking and BBQing, but knew it wasn't as balanced as it should be.
One day while BBQing, with the smoker up at 225F, I used a Harbor Freight handheld thermometer (gun) and sampled temperatures all over the unit. I found that the firebox was plenty hot!! Really hot! But it seemed that the heat was trapped in the firebox and not wanting to easily go into the cooking chamber. It was as if the heat was bottled up in the firebox, radiating everywhere but less so where it needed to be, and that was into the cooking chamber.

So last winter I wheeled the OK JoeH into the workshop, and cut a larger opening between the firebox and the cooking chamber. This made a world of difference. Now I can actually exceed temps, and regulate the heat much better using the firebox air inlet...as it should be, much like a wood stove operates. If you want more heat, open the air inlet, less, close it down a bit.
What I learned were good improvements.... Increase chimney volume/height, increase open area between firebox and cook chamber, and, not sure if this is needed, but modified firebox air inlet to my liking.

It was a lot of work, and, this is sometimes what happens with lower priced smokers.

 

[skunkwerx]

To answer your actual question (sorry), the blower would likely increase the flow, move heat from inlet, into cooking chamber and out the chimney. You would be "forcing" past the problems. Just my opinion.

 

[happy2meatu]

This is what I thought too - by adding the blower fan, and with my efforts to seal up every potential leak point, the fan will be effectively pressurizing the chamber, and forcing air flow. It is computer controlled to set the temperature where I want it. However, I wonder, if the proportions are far enough off from optimal, maybe the fan will still not be able to produce good results...?

 

[gnarlykaw]

I will be testing this theory myself, in the coming months. I got the cable and the fan for my fireboard for Christmas, and will adding it in a month or two. Volume from the fan id perfect for controlling temps, as the wood begins to turn to coals.
I’m not going to add it from the damper port though. I’m going to pipe in in via a 1” black iron pipe attached to the FB.
I have not decided on what angle to put it in at yet, been sick since Xmas, and it’s the last thing on my mind right now!

 

[gnarlykaw]

yeah, its still not installed yet. I am still considering my options... I had another Idea.
https://www.smokingmeatforums.com/threads/i-have-an-idea.283700/

 

[AllTuckerdOut]

I added what turned out to be a 4-1/4"x2' exhaust pipe and a plenum and it pulls a lot better. Not as good as my custom built reverse flow. But way better than the stock.

 

[AllTuckerdOut]

skunkwerx do you have a pic of your firebox inlets?

 

[gnarlykaw]

and no damper for the stack? I need to post my pics of what i ended up doing with the blower...
I went with the venturi effect... Im blowing air straight up the exhaust stack. ive only got a handful of cooks on it since the mod, but from a temp graphing point, it appears to be doing pretty good.

 

[AllTuckerdOut]

gnarlykaw no damper, I want it to flow as much as possible

 

[daveomak]

Try an upper air inlet to the FB... Directly across from the FB/CC opening... It will move heat from the FB to the CC without adding air to the fire and increasing the heat...
https://www.smokingmeatforums.com/t...eady-to-use-rev5-6-19-15.172425/#post_1264161

 

[Berettaclayshooter]

I have a jighland reverse flow and it too suffered from poor air flow. I also made a new stack. 3" x .065" stainless tubing which is 36" end to center. I used a 90 as well. It works like a charm. I also made a real baffle plate from 1/4" steel 2/3s of the length now it holds temps much more even and uses less fuel.