First ~160 gallon build starting in Finland

[Big T]

I would weld up any pin holes that I could see and there's nothing wrong with welding from the inside.

[forty_creek]

I've welded inside and out on all seams that I can so far on my build. Just so I felt good that it was sealed off.


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[rikun]

I think I'll just weld it from outside as well as I can. I can't really fit inside the FB so welding from inside would be a major pain...

Is it a good idea to grind down the first pass before welding subsequent passes? I think grinding it a little bit down to uniform thickness is usually done...?

[bluecatfish]

If I were doing it I would make sure all the slag was chipped and bushed of and then weld over the first pass without grinding. Just the way I do it. Others may think differently.

[rikun]

Ok, it's been a while once again

Progress has been made, got the fb welded to the cook chamber, rf plates (3 sections) are almost welded and the drain is in. Will post some pics after tomorrow's progress.

As I've been building this thing my catering business has taken off, so now it almost feels like it's going to be too small to begin with. I'm trying to rectify this by putting in three grates for flatter meats.

I'm just wondering could I cause some airflow issues by cramming the smoker very full of meat? I'm planning to have my second grate 4" from the first grate, that way brisket flats will just fit. The 3rd grate will be also 4" from the second and there will be 6" of space from the third grate to the tank. Refer to pic:



I'll probably weld in additional angle irons between those three, so I can get more space between my grates if I choose to use only 2 of them (or cooking butts, etc)

[rikun]

Oh heck yeah, it cooks! It's been a long project, still some things left to do but it cooks.

Cooker

However, there's a major temp problem, it's hotter on the far end away from the firebox! And I can't get that end to settle with the firebox end, even if I dip it a lot lower than my firebox. The difference is at least 40-50 F and very noticeable with real world use.

Any idea what could cause this? All the openings have been made according to the calculator and then some leeway to allow good airflow. And I don't think I have any airflow problems.

I have a theory that the firebox ends cools down because my doors currently are very very leaky. Hot air coming from the far end has enough opening on the first door to leak out causing the FB end to cool down. I think I'll need to get new doors rolled, since I made my flanges too small to allow any gaskets. That way I could get the new doors on top of the openings and also install gaskets.

Any ideas if the leaky doors could cause this?

[Rodcrafter]

The better the cooker seals the better everything works, that is true. Now one thing that is also true, there is a lot of steel to heat up. It will take some time to heat all the baffle plate from end to end. When the whole thing is operating temp, it should level out the temps very close. Each cooker takes some experimenting with to learn how to run it correctly. The fire itself is a learning process, to get the thin blue smoke verses white smoke that will make everyone dislike the "Q". When you fire her up, build an very hot fire with charcoal because it putts out lots more BTUs than wood. Don't put any meat in it until the outer shell of the CC is 225* then you have it up to temp. You can add meat and manage fire with wood.

jm2cw

[rikun]

I know fire management very well. I've done three cooks on it already, all hot and fast at 275-325F range.

It takes about an hour to hour and half to get the BP and the whole chamber to heat up nicely. But still there is a big temp difference that can't be corrected.

Never had anything other come out of the stack than thin blue New splits ignite in seconds with good coal bed going on.

[Rodcrafter]

You know I don't run that hot, but if I did I would open my BP opening some to slow down the velocity of the air/smoke. I would say that is what you are experiencing. The air is intensified by its speed. So it is hotter than the BP. Have you tried running it like an normal smoker 225/235? I think you will find a big difference.


Making memories.

[bluecatfish]

I see a lot of black soot at the ends of the doors. Is that from the burnout or is that coming from the cooks you have done?

[Fishless Mickey]

Maybe tip the trailer tongue down a little to slow the velocity and let heat build up near the firebox?

[Fishless Mickey]

After re-reading I see that you already tried that.

[rikun]

I see a lot of black soot at the ends of the doors. Is that from the burnout or is that coming from the cooks you have done?

From both I guess. The doors leak so much that smoke rolling out of the sides taints the tank black. I've never had any creosote taste from any of the cooks and the smoke is invisible to light blueish so it shouldn't be an airflow issue.

And I did a test with the doors taped 100% air-proof with aluminum tape, didn't make any difference for the temps...

I've ran it at 225 F range, and it runs more stable. I think my first test I ran it around 180 F and both ends were pretty dead even. But I don't cook anything at 225 range, except fish at less than 200 F

I somehow think my BP opening might be too _big_ after I read this post from Frank: http://www.smokerbuilder.com/so-talking ... ebox-size/

My BP opening is 100% of my throat, which is also oversized a bit from what calculators suggest as a starting point...

Oh yeah, I measured my smoker with IR thermometer, here are the results:

Hottest part of the smoker: almost 400 F (top shelf farthest from FB)
Coldest part of the smoker: 250 F (lowest shelf next to FB)

BP right side closest to firebox: 392 F.
BP center: 302 F.
BP left side away from FB: 275 F.

I also measured the temp of my cook chamber's outer surface from the top where the hinges are:

Right side closest to firebox: 199 F.
Center: 219 F.
Left side away from FB: 251 F.

To my uneducated mind those numbers look pretty ok, BP is clearly hotter at FB end and cook chamber is clearly hotter at the other end. Shouldn't they pretty much cancel each other out and even out the temps?

I guess the next test it to mount some 1/4" scrap to make the BP gap smaller and see if anything changes...

Also, might be worth mentioning, I need to run my intakes very choked to keep reasonable temps when having a decent coal bed. Still have no issues with incomplete combustion, though, splits keep on burning happily with very little air getting in.

[rikun]

Okay, been doing some testing, thinking and measuring...

Smoker seems to run very consistent as previously, however I used more probes and discovered that from left to right the temp difference is only around 30F, which in my books is fine. After all the CC is 6.5 feet long.

But the big problem is from top shelf to bottom grate, temp difference is around 100 F or more and nothing I do changes that. Except extending my stack a little further down, it helped to level the difference maybe around 10-20 F.

I measured my baffle plate again with the IR meter and it's at 300 F on bottom right when my top right grate air is 300 F.

So I guess my BP should be way hotter, since air is poor conductor of heat and there is 4" of distance between BP and the bottom grate...?

I'll try to extend my stack all the way to the lowest grate next cook, but I'm betting I should be doing something to get the BP hotter...

[mp4]

Did you close up the baffle plate gap? I did mine and my temps settled in quite a bit. The last cook I was within 5-10° left to right and center.

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[Rodcrafter]

Heat/smoke travel like water with gravity pulling up instead of down. So if you can imagine that the air moving from the FB is hitting the BP not really even touching the bottom of the tank, moving quickly to the other end of the tank because of the quantity of air being moved. Then it goes through the BP opening very quickly straight up now hitting the top of the tank and moving across as fast as it can to get out the stack. So the temp you are changing when putting the stack opening at the bottom cooking grate is caused by the turbulence created by the air trying to find its way out of the stack. I don't think you can get even temps and a clean airflow at the temperature you are trying to run. The vertical cabinet cookers don't have the same problem you have with an offset RF trying to maintain that high temperature in every area because with one of those all the fire is on the bottom and all the cooking racks are straight above it. There's things about an offset RF that the cabinet can't get and vise versa. So I think you should cook low and slow on this one and build another cabinet for the high temperatures you are trying to attain.

jm2cw


Making memories.

[rikun]

Did you close up the baffle plate gap? I did mine and my temps settled in quite a bit. The last cook I was within 5-10° left to right and center.
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Not yet, that's what's I'm doing next. Any idea how big your gap is percentage wise from the FB throat size? Have you measured temp difference from bottom rack to top rack (if you have one) ?

I got the smoker settle pretty nicely from left to right just by having a large coal bed and using only very small splits burning very slowly. Like two apple splits sized a little bigger than my thumbs combined.

If I built a larger fire or had bigger splits, the end away from FB started to heat up more. Also with the very small fire, the BP clearly got hotter near the FB, I started to hear grease drippings and sizzle from that end.

Intake was just barely open, but still all I got from the stack was thin blue or just heat distortion after the splits ignited in about minute.

I don't really buy that thing about RF being only good for low and slow, plenty of people run their RF/standard offsets at 275-300 without problems.. But it's possible of course, after I all I have three grates so the bottom and top have quite a bit of space in between..

And anyway, the problem between bottom and top rack persists when cooking low and slow, only left and right equalize a bit better. If I cooked at 225F on top shelf, bottom shelf would be cruising around 150F

[mp4]

I closed mine up 20-25%. I measure temps left to right and center with the sensor hanging on the bottom of the top rack. In the past the center temp stayed in line with the left temp gauge and the right one would be higher when I had too big of a fire and lower when the fire was dying down. I might try smoking a turkey for thanksgiving so I'll do some more checking.

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[rikun]

Okay, I'll close mine a little bit. Currently my gap is actually a bit bigger than the throat at 132 sq inches vs throat at 128 sq inches. Not by design, though Maybe I'll close it 50% and see if there is change.

Which side you have your firebox on? Left or right?

[mp4]

Right side.

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[mp4]

Here's my smoker so you get an idea of where I'm at. I hope it helps some...it's 180 gallons so we're both in the same ballpark size wise.

viewtopic.php?t=4558

[rikun]

Great looking build you got there

The funny thing is, my FB end is always cooler than the other end. I tried to close my BP gap some with a temporary square plate, that didn't really help too much. Did you try yours with squared plate or did you went with curved straight away?

Also, I don't think tilting my smoker either way affects the temps at all, which seems strange.

I think I'll need to bring my stack further down after looking at your build. Mine's cut at 45 degrees miter from the top, so the lowest point it drafts is around 6" from top.

How long is you CC chamber? I see it's "fatter" in shape than mine. Did you size your throat based on the calculator or did you oversize?