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View Full Version : Newbie self builder reverse flow, two cooks, two fails.


Blondy_UK
06-07-2017, 02:40 PM
Hi i am new to the site and new to smoking, i have just built my first reverse flow smoker after watching many youtube vids on building smokers and using them over the past year. after seasoning the smoker i tried my first pork shoulder, i used charcoal briquettes to start with then added small logs that i had in my shed 1 at a time. after a couple of hours i foiled it then kept up the heat for another 3 hours. then removed the pork to rest a while and upon trying the the meat i was disapointed with the well over smoked taste and bitterness, i later found out that it could have been creosote.

This weekend i thought i would give it another go but leaving the chimney fully open and using more charcoal and only adding oak splits one at a time to keep the temperature up. i wrapped the pork at 90 minutes this time but although not as bad of the first smoke it still ended up in the bin. i tried to keep the thin blue smoke but when adding a log or split there is always some initial white smoke that i am getting for some time after.

I dont want to give up on this just yet so i am asking for some advice on what i might be doing wrong, i have some pics in my welcome call if anyone can look at to see if there is anything obvious in them that would not help me. the air inlet and chimney are both 4 1/2" pipe and the chimney extends down to the cooking rack. thanks for any suggestions or help.

Zak
06-07-2017, 03:11 PM
If you could post pics that'd be great!!! Read this thread since it's very similar to your situation.

http://www.bbq-brethren.com/forum/showthread.php?t=247475

smoke ninja
06-07-2017, 06:03 PM
Are you familiar with the term thin blue smoke?

Nuco59
06-07-2017, 06:14 PM
I cast another vote for needing pictures- since they are worth a thousand words and all. There are some pretty smart fellas on this site- they will get you squared away in no time.

SmittyJonz
06-07-2017, 06:17 PM
When was the wood cut.?

Rockinar
06-07-2017, 06:24 PM
Here's a link to the welcome page showing the home built smoker.

http://www.bbq-brethren.com/forum/showthread.php?t=247564

I wonder if the exhaust is too tall, the smoke is cooling as it rises and it's not pulling a good draft? Other than that, I don't see anything really obvious.


My unprofessional opinion is the exhaust is too tall or your wood is too green (not dried out yet).

Nuco59
06-07-2017, 06:25 PM
Are you familiar with the term thin blue smoke?

I'd say he had at least a passing familiarity with the term.
He might not have had enough practice getting there but he did use all those words: thin, blue and smoke. :-D

I'd be sort of interested in the type of wood or if it had been seasoned or how long. He did mention having his exhaust come down to grate level- if he's getting stagnant nasty smoke...

SmittyJonz
06-07-2017, 06:34 PM
Yup exhaust looks too tall. Cut a foot off, maybe even 16"-18"......

smoke ninja
06-07-2017, 07:17 PM
I'd say he had at least a passing familiarity with the term.
He might not have had enough practice getting there but he did use all those words: thin, blue and smoke. :-D

I'd be sort of interested in the type of wood or if it had been seasoned or how long. He did mention having his exhaust come down to grate level- if he's getting stagnant nasty smoke...

Sorry. Im under the weather and will admit to not completely reading the op

Nuco59
06-07-2017, 07:27 PM
Don't feel sorry about being sick- get well and back to your old Ninja self. I never can remember "feed a cold or starve a cold- so I just eat" :-D

m-fine
06-07-2017, 08:16 PM
Unless it is losing a lot of heat, a taller exhaust creates a stronger draft, not a weaker one. If you want to be sure, you can wrap the chimney in a blanket to insulate it a bit and quickly see that it won't solve your problem.

I suspect the issue is with the fire, or possibly green wood, with airflow the third choice.

Assuming the wood is seasoned, your description screams not enough coal bed in the fire box. To start the fire, you can use a little charcoal, but then add several splits. Maybe 3-5 depending on size, not the one at a time you are describing. With exhaust and intake vents wide open, and maybe the cook chamber door also open at first, get a good fire going. The logs should be well engulfed in flames with little visible smoke. Shut the doors if open but leave the vents for now. If it is too hot, let it burn down for a bit. Once you have a good base, add one or two splits at a time to maintain temperature. If your splits take a while to light and give off a lot of smoke when you add them, they are too green or your coal base is too small.

Instead of wasting meat, try a fire with the smoker empty. If it is still giving off white smoke try heating logs in the cook chamber (while maintaining a fire) for a couple of hours before throwing them on. That should help "kiln dry" them and if not, you will see moisture coming out of the end grain if the wood is too green. Adjust until you can maintain a clean burning fire with thin blue smoke before adding meat.

The other potential issue is the outlet from the firebox to the main chamber. The air flowing through there is at its hottest and its density will be much lower than the intake air or the air leaving the chimney, so it needs the largest cross sectional area. If you rule out green wood and you still can't get the fire to burn cleanly, you have an airflow issue and we can look into smoker design issues to try to address it.

I often do pork butts on a stick burner for 10-12+ hours without wrapping them. They are never over smoked or bitter. If you have a good clean burning fire it should never be bitter and it should be very difficult to oversmoke pork or beef on a stick burner.

SmoothBoarBBQ
06-07-2017, 08:20 PM
Hey Blondy_UK,

Smoker looks good but your exhaust stack is WAY too tall for such a small cooker. One thing you have to remember is that the exhaust stack will draw the hot air out of the smoking chamber, but if it's too tall the smoke will cool and no longer be buoyant so it will fall back down your exhaust stack and your smoke will become stagnant and bitter.

There are quite a few calculators out there which will take the dimensions of your smoking chamber, firebox, and exhaust stack and it will tell you what you need to alter. Your firebox looks good like it's a good size for your smoking chamber, but your stack is quite a large diameter pipe and I believe it's quite a bit too long.

http://www.feldoncentral.com/bbqcalculator2.html
Give that a try and see if it will help you out.

As for your firebox, make sure that you've got a fully oxygenated and energetic fire, and not a bunch of smoldering wood.

Good luck!

m-fine
06-07-2017, 08:54 PM
Where are you guys coming up with this nonsense about the chimney being too tall? Yes it is possible, but it would need to be much taller than I see in the pictures.

Stick a heat probe in the chimney at different points and let us know how much the air is really cooling per foot. It only takes a fraction of a degree difference in temperature for the chimney to draw air up, so unless he is trying to cold smoke in there, the flow rate should keep the exhaust temp at the top of the chimney over 100 degree F hotter than ambient. FWIW, with steady weather, the tiny heat output of an AMPS is enough to keep a draw going through my Lang 84 with the chamber temp 1 degree or less above the abient air temp.

m-fine
06-07-2017, 08:55 PM
BTW, Feldon is complete bunk.

sleebus.jones
06-07-2017, 09:03 PM
Where are you guys coming up with this nonsense about the chimney being too tall? Yes it is possible, but it would need to be much taller than I see in the pictures.

Agree 100%

McSpazatron
06-07-2017, 09:07 PM
Hmmm. Im also in the camp of kinda thinking the stack is too tall. Not only is it tall, but it seems to be a fairy large diameter which would compound the problem. Not sure though, would hate to cut it off for no reason. When you have your fire established, do you feel good airflow? Weak? Does it come out in waves or burps? Im just taking stabs in the dark. Nice job on the build though. Im betting you can sort this out.

SmittyJonz
06-07-2017, 09:12 PM
I'd cut it down just so it looks Normal....... :twitch:

How big is your end gap at end of reverse flow plate.?
.

m-fine
06-07-2017, 09:18 PM
I wonder how my wood burning stove could possibly work with an 18 foot tall chimney? Oh that's right, the specs call for a 15 foot minimum chimney rise. But what do the engineers, testing labs and building code people know anyway?

SmoothBoarBBQ
06-07-2017, 09:37 PM
Where are you guys coming up with this nonsense about the chimney being too tall? Yes it is possible, but it would need to be much taller than I see in the pictures.

Stick a heat probe in the chimney at different points and let us know how much the air is really cooling per foot. It only takes a fraction of a degree difference in temperature for the chimney to draw air up, so unless he is trying to cold smoke in there, the flow rate should keep the exhaust temp at the top of the chimney over 100 degree F hotter than ambient. FWIW, with steady weather, the tiny heat output of an AMPS is enough to keep a draw going through my Lang 84 with the chamber temp 1 degree or less above the abient air temp.

This is a good post but you're also comparing a Lang versus a homemade project. We know the Lang is built to specific specifications and has good airflow, and those things are unknowns right now on OP's smoker. I will also point out that the smoke stack on OP's cooker appears to be of a similar diameter to your Lang, but is obviously MUCH longer. Just things to keep in mind and if OP is stating that they are having an airflow issue it's certainly something to look into.

You put forth a great course of action though to temp the airflow in the stack and see if it's actually pulling any air. OP is saying they are getting TBS, so if that is correct, and they are still having food come out so bitter it's inedible what do you think the problem might be other than airflow? The firebox looks adequately sized for that smoker and it appears to be in an appropriate place to allow for the heat and smoke to rise up and over into the smoking chamber. All in all the exhaust stack appears to be comically out of place on such a small cooker so I think reasonable deduction points there.

As for Feldon being bunk, if that's true, then good heads up. I just googled something so that OP had a place to start.

SmoothBoarBBQ
06-07-2017, 09:40 PM
I wonder how my wood burning stove could possibly work with an 18 foot tall chimney? Oh that's right, the specs call for a 15 foot minimum chimney rise. But what do the engineers, testing labs and building code people know anyway?

Now you're just getting crazy by comparing a vertical burning stove against an offset reverse flow smoker. As for the engineering component OP stated they just made it as they went and had no idea about which kind of dimensions would be appropriate. It doesn't sound as though OP consulted any engineers or blueprints while making their smoker... kind of really shocked by the lack of thought in your post.

Here's what OP said in their Welcome Post about this smoker :
"I had not realised that there were rules and calculations that went into these machines"

Blondy_UK
06-08-2017, 02:51 AM
Wow, thats a lot of response and some good sugestions.

I will try to add some more info, the wood had been gathering dust in my shed for probably 3-4 years which went onto a chimney full of glowing coals and left it to burn down and for the cook chamber to get hot before putting in the meat. At that first time i only had dial meat probe which i left on the shelf so not that accurate. I have a twin probe wireless thing now but did not arrive untill the day after my second cook.

I did look at a calculator regarding the dimensions and such and it recomended a 6 1/2" tall chimney. When i built it i thought that a larger stack would get the smoke out quicker and being that high would keep the wood smoke out of my face and off of my clothes. I think i will do another dry run and probe the chimney at different levels just to see whats going on there before i get the hacksaw out, but if thats going to help then it will have to be done.

The space at the end of the RF baffle plate is comparable with the opening to the firebox/ cook chamber ang bigger in area than the stack, i did cut a piece plate to close it of a bit as i read somewhere that it could be putting too much smoke into the cook chamber and not being able to leave quick enough.

I was getting the TBS a lot of the time but it was when i was adding wood the keep the temp up i was getting some white smoke . So was wondering if its possible to do long cooks on wood but as one of the coments said the can do 10-12 hours without wrapping. Thats what i'm after.

There are some picks on my welcome call page also whats OP mean?
I hope i have given all the extra info, there were a lot of suggestions to try but if i have missed any replys out let me know and i wil try to give more info but thanks again for all of your suggestions. Weather permitting i will be burning again at the weekend. PJ

SmoothBoarBBQ
06-08-2017, 05:31 AM
Blondy_UK,

OP means "Original Poster" so in this instance you're the OP. I certainly believe the culprit is the excessively long and large diameter smoke stack. I agree that you should probe it and if the air coming out isn't very hot then you should go with your instinct and cut it down quite a bit. You say you think 6.5" is what your calculations gave you and that sounds pretty good, though I'm not sure if you need to go quite that low to start. Maybe cut it down a bit, do a burn and see what's going on.

Thin Blue Smoke (TBS) is ideal but you will get a bit of white smoke when you put a new log on the fire. This is nothing to worry about when the airflow is good, so I believe once you make some adjustments you'll see that white smoke will come and go very quickly. Something to think about while you're messing around with the smoke stack and what not is to put a few balls of foil (just sheet foil balled up) in a few different places on your cooking grate, just like you would meat. Those balls of foil should be very clean after a long smoking session... if they are black then you know you're still having serious airflow issues. If they are slightly dark that's probably OK, but you're looking for them to look VERY clean, almost as clean as when you pulled them off the foil roll. This way you can see what's really happening in your cooking chamber while you're working on your exhaust stack adjustments without wasting good pieces of meat.

The biggest thing about an offset cooker is that you can get that TBS and keep a super clean fire for a very long cook. On my new reverse flow offset smoker I run a very clean fire and I will leave an entire brisket on there for 12+ hours and it comes out with just a nice kiss of smoke. Proper airflow does that for you so the smoke is just kissing your meat as it is pulled gently through the smoking chamber. So this is what you're talking about with a long cook without wrapping and for that to happen you really need good airflow.

I hope I helped you out a bit but I'm very glad you've crunched some numbers and realize your exhaust stack is likely your issue. Post updates as you move forward and I'm pretty curious about the temps you're going to get in that exhaust stack as well. If you desire keep us posted, and good luck! I certainly hope you can make this the cooker you wanted it to be. Cheers!

m-fine
06-08-2017, 07:01 AM
A restriction on the reverse flow is not going to help at all. At this point you want to maximize airflow and avoid any restrictions.

I will repeat it again. Shorter chimney = LESS DRAFT!

The problem is either insufficient fire or not enough draft. Cutting the chimney is only going to make things worse. If you guys want to put your money where your mouth is, I will add 10-12 feet of additional chimney pipe to my Lang and demonstrate that the smoke will not cool off and fall back into the cook chamber. Raise $1000 to bet against me and I'll give you 2:1 odds. Word of warning, my degree in aerospace engineering comes from a real acredited university. I learned thermodynamics and fluid dynamics from text books and professors, not Internet forums. You will lose.

For the OP, build a bigger fire and see if it will burn clean. If not, post the dimensions of your openings, and pictures of your fire. Also what temperatures you are seeing. If the wood is 3+ years old and your fire has a sufficient coal bed, I am concerned that the firebox exit and RF are too small. Also, space in the firebox may be an issue.

Kmm
06-08-2017, 08:03 AM
After looking at your pics, I am seeing something different. The height of what appears to be your intake/ clean out pipe is below your fire grate. There is another pic showing some unburnt wood on the far end of the firebox. Look closely at that same pic and you will see the ash clean out is nearly full. My suspicion is that puppy is drafting just fine.....perhaps too well such that it is pulling ash out of the fire box into the smoking chamber. I suspect you will need to find a way of bringing air in over the top of the ash bin so it creates a dead air space below the fire grate. Ash could well be responsible for the bitter taste that is rendering your meat to the dust bin.
Some are going to argue that their air intakes are below the fire grates and they don't have any problems....however, I'll bet they have more room between the bottom of the fire grate and floor of the ash bin which keeps the ash from choking the fresh air.

Yellowhair42
06-08-2017, 08:38 AM
BTW, Feldon is complete bunk.


Why is that? Is there one better?

pjtexas1
06-08-2017, 08:59 AM
After looking at your pics, I am seeing something different. The height of what appears to be your intake/ clean out pipe is below your fire grate. There is another pic showing some unburnt wood on the far end of the firebox. Look closely at that same pic and you will see the ash clean out is nearly full. My suspicion is that puppy is drafting just fine.....perhaps too well such that it is pulling ash out of the fire box into the smoking chamber. I suspect you will need to find a way of bringing air in over the top of the ash bin so it creates a dead air space below the fire grate. Ash could well be responsible for the bitter taste that is rendering your meat to the dust bin.
Some are going to argue that their air intakes are below the fire grates and they don't have any problems....however, I'll bet they have more room between the bottom of the fire grate and floor of the ash bin which keeps the ash from choking the fresh air.

^^^let's run with theory for a second...
on my rf if the wind is blowing too hard into the intake it will definitely pull ash under the rf plate and into the cook chamber. i wonder if the op has tried choking down the exhaust to slow down the air flow? i also wonder if the op can see ash blowing thru the cook chamber if he opens the cook chamber door? i sure can and that's how i figured out that i need to block off the wind from blowing into my intake on windy days. example: at the spring bash we spun my cooker around and away from the wind. the other 2 stick burners there did not have to do this. my rf pulls hard and the wind is not my friend.

the other thing mentioned is the space below the fire grate. i would get that raised up higher just to give the fire more room to breathe. i know franklin runs his cookers with no fire grate but i would try it anyway.

SmittyJonz
06-08-2017, 10:06 AM
Maybe......Nuttins wrong with it and OP just Don't like Smoked meat........
He could try a pellet smoker.

Do some video of your next cook.

Smilerb
06-08-2017, 10:15 AM
Welcome to a great site, looking at your photos, especially the one showing unburnt wood and charcoal in your fire box seems to me to indicate a fire management problem. I agree with what has been said before. I would raise the height of the fire grate. I would guess that air from your intake is passing over the top of your fire into the cooking chamber and really itís a case of getting air to flow through the fire which is one reason a UDS are so efficient. I would try raising the height of the grate and also moving the fire away slightly from the transfer port to the cooking chamber.
When I was testing my recent build , I started with all briquettes because they are quite predictable, after 7 hours all ash nothing else left , my next run was a mix of briquettes and lump wood, again just ash left but not such a long burn but I did find adding lump wood created white smoke but a couple of minutes with the fire box open when I added new wood sorted that out, next will be all wood so a definite case of learning to control the fire before getting into some serious smoking.

m-fine
06-08-2017, 10:37 AM
Why is that? Is there one better?

I have not seen a good one yet, wish there was one I could point people to.

The problem with Feldon is it uses the wrong inputs. The calculations are based on volume and ignore surface area, R/K value of the material, and other factors that will more directly drive BTU and airflow requirements. Much of it looks like it was developed by looking at a few designs that worked and trying to come up with some formulas, rather than actual engineering calculations as it is purported to be. The formulas will result in a smoker that works within certain size and shape ranges, but they will not scale well outside of those (undefined) ranges. It also does nothing for you in reverse. Many designs that violate the Feldon ratios work very well, and the calculator will not find the problem(s) with a design that does not work.

JackW
06-08-2017, 11:48 AM
"the chimney extends down to the cooking rack" If so there can't be much room between the bottom of the stack and the top of the reverse flow plate. Maybe that is causing a backup of smoke in the cook chamber. My stack does not extend into the cook chamber at all. All in all agood discussion,

Jack

m-fine
06-08-2017, 12:13 PM
"the chimney extends down to the cooking rack" If so there can't be much room between the bottom of the stack and the top of the reverse flow plate. Maybe that is causing a backup of smoke in the cook chamber. My stack does not extend into the cook chamber at all. All in all agood discussion,

Jack

Good catch. That could definitely cause problems.

BurntOffering
06-08-2017, 12:27 PM
So in one of your pictures I see fire in your cooking chamber.
Is there a baffle plate in there?

pjtexas1
06-08-2017, 12:55 PM
"the chimney extends down to the cooking rack" If so there can't be much room between the bottom of the stack and the top of the reverse flow plate. Maybe that is causing a backup of smoke in the cook chamber. My stack does not extend into the cook chamber at all. All in all agood discussion,

Jack

i had to go back and look...totally missed that. :tsk:

weave1499
06-08-2017, 01:26 PM
void

sleebus.jones
06-08-2017, 01:36 PM
I think what's happening here is that everyone talks about TBS, but newbies to this hobby haven't seen it. A picture is worth a thousand words, so a video must be priceless...

(this is not my video)

Blue Smoke - YouTube

So, if you see smoke bellowing continuously out of the chimney, you ain't got TBS.

m-fine
06-08-2017, 01:55 PM
Yep, smoke out of a stick burner running cleanly should be nearly invisible as it is exiting the stack.

I am thinking if the OP built a fire and showed us some pictures or even a video it would be helpful. What does the fire and coal bed look like? What does the smoke coming out of the chimney look like? What happens when the cook chamber is opened? How far into the smoker does the chimney extend? What do the splits look like and how big are they?

Blondy_UK
06-08-2017, 03:50 PM
Again, lots of replies and ideas. There is no baffle plate under the RF plate by the opening from the fire box. The chimney goes down to the cooking grate as in the picture but it is cut at an angle, i could easily take some out with a grinder if that would help. I have also see other cookers with an extra air inlet
vent higher up above the height of the coal grate which i can also put in without too much hassle. The TBS i was referring to was more of a clear heat haze coming from the chimney but at times it did have a blue tint to it.

I also had thoughts about perhaps i didn't like the taste of smoked meat but i hope thats not the case as i have been teasing my taste buds all this time watching youtube vids of people slow cooking these ribs and beef brisket.
I will see about getting some video clips or pics this weekend when i try again maybe just a dry run.

m-fine
06-08-2017, 04:08 PM
Here is another thought. Is it definitely wood smoke? See post 7 in this thread where someone complains about fat drippings on the reverse plate smoking.

http://www.bbq-brethren.com/forum/showthread.php?p=3809284#post3809284

You need to get the plate close to 400 to do that, but that could be an issue with your design and how you are running it.

THoey1963
06-08-2017, 04:45 PM
Very interesting thread. A bit contentious at times, but interesting. Remember, we are here to help the OP. Any discussions that side track from that (i.e. is Feldon crap or not) should probably be in a different thread.

I agree the fire grate seems to need to be lifted up. Maybe just raise it up on some cans to see if that helps (a quick test, not an extended burn). More pictures of the inside would help too.

m-fine
06-08-2017, 05:19 PM
Very interesting thread. A bit contentious at times, but interesting. Remember, we are here to help the OP. Any discussions that side track from that (i.e. is Feldon crap or not) should probably be in a different thread.

I agree the fire grate seems to need to be lifted up. Maybe just raise it up on some cans to see if that helps (a quick test, not an extended burn). More pictures of the inside would help too.

The issue with Feldon is not when people use it to design before they build. The problem and reason I brought it up here is that when someone has a problem with a home built, there is often a knee jerk "does it follow Feldon? If not, that is what is wrong" response.

I hate for a guy to go chopping his chimney or get out the saws and welders before we know what is really the problem.

Blondy_UK
06-09-2017, 02:04 AM
I forgot to mention the wrap foil was a bit 'bronzed' after about 2 1/2 hours and the unburnt wood in the firebox might have been me closing the chimney and air inlet after i took off the meat and finished cooking.

Zak
06-09-2017, 08:31 AM
From what i've seen it looks to me like it's a decent setup with plenty of room for a fire, decent air intake, large enough opening into cooking chamber, decent length cooking chamber, ok exhaust layout(although i prefer to have the exhaust exit at the highest point to promote air flow) so i'm not exactly sure where to problem lies. Could be operator error, bad wood, bad thermometers, bad meat etc. What i'd try is to run it with just splits and no food just to see if you cant get things to run right. Exhaust wide open, only use splits, air intake wide open and only start closing when temps get over 250 then watch temps and adjust every 15 minutes. With practice i'm sure you'll figure it out.

SmittyJonz
06-09-2017, 09:51 AM
I'd trim up the exhaust inside the smoker. Try different wood or a charcoal only cook.
Could be drippings burning like already said. Maybe cook in pans.

Kmm
06-09-2017, 10:58 AM
Blondy,

Thanks for the pics they each tell a story. Before you get all medieval with a cutting wheel, it would be best to do some science to see what you have. Hopefully you have (or know an engineering friend with) a set of thermocouplers and a data recorder? If not, can you get something like a Weber "igrill2"? You need to understand what is happening inside the closed lid during a burm cycle.
Based on the discoloration of the plate at the throat of the cooking chamber ( just below the stack) I suspect you have some hotspot issues. Is your plate angled down towards the far end of the cooking chamber or setting flat? If it is flat, the oils will not drain off of the plate properly to avoid burning! Further, if it is flat and the cooker is oriented with the firebox slightly downhill, oil will be running directly into the hotspot. Burning oils would account for the "bronzed" aluminum foil as well as the dark psoot on the bottom of the stack pipe.
If the unit is sucking ash and making soot, it is no wonder the meat is about as pleasant as a chunk of tender asphalt!

SmittyJonz
06-09-2017, 11:24 AM
My drippings burning experience :
http://www.bbq-brethren.com/forum/showthread.php?t=223436
.
.

DaveAlvarado
06-09-2017, 01:19 PM
I wonder how my wood burning stove could possibly work with an 18 foot tall chimney? Oh that's right, the specs call for a 15 foot minimum chimney rise. But what do the engineers, testing labs and building code people know anyway?

How to make a smoker that looks funny, apparently. :crazy:

My thoughts are:

1. How green is your wood?
2. How sure are you it's oak?
3. What does your smoker smell like when there's nothing in it and no fire?

I'm thinking it's either the wood or residue from the propane. It's certainly not nonsense like "smoke falling back down the chimney". :doh:

Blondy_UK
06-09-2017, 02:19 PM
From what i've seen it looks to me like it's a decent setup with plenty of room for a fire, decent air intake, large enough opening into cooking chamber, decent length cooking chamber, ok exhaust layout(although i prefer to have the exhaust exit at the highest point to promote air flow) so i'm not exactly sure where to problem lies. Could be operator error, bad wood, bad thermometers, bad meat etc. What i'd try is to run it with just splits and no food just to see if you cant get things to run right. Exhaust wide open, only use splits, air intake wide open and only start closing when temps get over 250 then watch temps and adjust every 15 minutes. With practice i'm sure you'll figure it out.

quite possibly user error, i haven't got a problem in cutting the chimney inside the cc or just cut some vertical slits, as for thermometers i had only the dial ones installed on the second cook and there was a difference 50f being 250f at the firebox end, but there seems to be a hotspot on the reverse plate above the firebox entrance. I have now received my Thermo Pro TP20 wireless probe so will use this over the weekend with just charcoal and splits to get an idea on chamber temps and chimney temps too.

Blondy_UK
06-09-2017, 02:25 PM
I'd trim up the exhaust inside the smoker. Try different wood or a charcoal only cook.
Could be drippings burning like already said. Maybe cook in pans.

Would putting slits or even holes in the chimney inside do they same as trimming off?
I was using shallow pans beneath the cook grate to catch anything but they were sitting on the reverse plate. I will also jack the firebox end up very slightly when i cook with meat again to drain any grease if any down to the opposite end and may install a drain valve.

Blondy_UK
06-09-2017, 02:31 PM
Blondy,

Thanks for the pics they each tell a story. Before you get all medieval with a cutting wheel, it would be best to do some science to see what you have. Hopefully you have (or know an engineering friend with) a set of thermocouplers and a data recorder? If not, can you get something like a Weber "igrill2"? You need to understand what is happening inside the closed lid during a burm cycle.
Based on the discoloration of the plate at the throat of the cooking chamber ( just below the stack) I suspect you have some hotspot issues. Is your plate angled down towards the far end of the cooking chamber or setting flat? If it is flat, the oils will not drain off of the plate properly to avoid burning! Further, if it is flat and the cooker is oriented with the firebox slightly downhill, oil will be running directly into the hotspot. Burning oils would account for the "bronzed" aluminum foil as well as the dark psoot on the bottom of the stack pipe.
If the unit is sucking ash and making soot, it is no wonder the meat is about as pleasant as a chunk of tender asphalt!

mmm, tender asphalt sounds good compared to my first try.
There is a hotspot as you say but there shouldn't have been any drippings as i had 2 trays under there but one of them may have been sitting over the hotspot slightly.

Sucking soot, would that be the lack of space beneath the fire grate?

Blondy_UK
06-09-2017, 02:40 PM
How to make a smoker that looks funny, apparently. :crazy:

My thoughts are:

1. How green is your wood?
2. How sure are you it's oak?
3. What does your smoker smell like when there's nothing in it and no fire?

I'm thinking it's either the wood or residue from the propane. It's certainly not nonsense like "smoke falling back down the chimney". :doh:

Hi, first time cook was definitely dry but not oak, some sort of maple i think front my front garden about 4 years ago.

I did set fire to both chambers after i finished building, the cooker smells smokey but when i rub my hand around the bottom or inside the stack there is no soot residue on my fingers but the too smell smokey.

Kmm
06-09-2017, 03:34 PM
Yes sir, it may me sucking grayish ash out of the fire box.....soot is the black stuff burning oil (rendered fat) produces. Indeed, if the pan was on on very near a hot spot, the oils can still get hot enough to burn. Only way is to know is to probe it up. Good luck

Blondy_UK
06-09-2017, 03:55 PM
Sorry folks, just seen the multi quote option. That will make replying to all of these great suggetions easyer.

m-fine
06-09-2017, 03:59 PM
The flavor problem may just be the wood. Some sort of whatever is not good. I don't know what you can get locally, but look for fruit or nut trees, white or post oak, hickory, or sugar maple. There are others, but at least know what it is. Split it to coke can/beer bottle thickness. Make sure it is seasoned but not too old and decaying either. The wood I use is usually 6 months to a year old, not multi year old (unlike what I burn for heat which I like more seasoned and lower moisture content).

I would give yourself a clean start. Raise your fire grate so there is at least 2" under it, 4+ is better. Build a nice big raging wood fire and get the cook chamber up to about 500* F. If there is any spilled drippings they will give off white smoke and then eventually it should burn clean. If there are a lot of drippings it could take an hour or more at high temp before the smoke clears, very little and it should clear up quickly. If you can get it up to 500 and the fire isn't smoldering, you should have enough airflow to smoke. If not, we have some design debugging to do.

Once it has stabilized around 500 for a bit and the smoke is clean, spray the insides down with a garden hose a steam clean it well. Let the fire die back a bit but maintain a pile of coals that will ignite a new split quickly. See if you can stabilize the fire between 225 and 300 adding a split or two every 30-60 minutes. Splits should ignite fairly quickly and burn clean. Try to keep most of the fire toward the end away from the outlet to the cook chamber. Keep the vents open for now and try to maintain a lower temp with a smaller fire NOT with choked back airflow. You can learn to dial back the air for later cooks after you verify that everything else works, but air is never a primary temp control on a stick burner, control comes from managing the fire. Smoke should be very thin and flowing steadily out of the chimney in a fairly smooth continuous stream. If you can smell it, it should smell pleasant, not bitter or harsh or chemically etc. If all goes well to this point, then try throwing on a pork butt. Otherwise come back here and report.

Once on to the pork butt cook, If your RF plate is over 370 give or take fats will smoke. Give yourself 1-2" or more of an airgap between the drip pans and the RF plate to keep the pans from over heating and to let the RF plate work. Any clean non-combustible spacer should work (tuna cans, brick pieces, cooling rack, whatever. Keeping a bit of liquid in the pan should also prevent any fat smoke. If the RF plate is below 350 and it drains, you will not need drip pans, but stick to them for now to help debug. BTW, an RF thermometer gun would be the best tool to check RF plate temp in different locations. Cook a pork butt unwrapped for 6-12 hours at 225-300 (time depending on size temp etc.) until it is soft enough to pull easily. You can wrap when done for resting/holding, but the key is it should easily be able to cook that long unwrapped without any hint of bad smoke flavor. This is a cut that is hard to screw up so it is a good test meat.

What is the chimney diameter and what is the cross sectional area of the space below the RF plate? What are the dimensions of the fire box and the cook chamber?

Blondy_UK
06-11-2017, 07:48 AM
The flavor problem may just be the wood. Some sort of whatever is not good. I don't know what you can get locally, but look for fruit or nut trees, white or post oak, hickory, or sugar maple. There are others, but at least know what it is. Split it to coke can/beer bottle thickness. Make sure it is seasoned but not too old and decaying either. The wood I use is usually 6 months to a year old, not multi year old (unlike what I burn for heat which I like more seasoned and lower moisture content).

I would give yourself a clean start. Raise your fire grate so there is at least 2" under it, 4+ is better. Build a nice big raging wood fire and get the cook chamber up to about 500* F. If there is any spilled drippings they will give off white smoke and then eventually it should burn clean. If there are a lot of drippings it could take an hour or more at high temp before the smoke clears, very little and it should clear up quickly. If you can get it up to 500 and the fire isn't smoldering, you should have enough airflow to smoke. If not, we have some design debugging to do.

Once it has stabilized around 500 for a bit and the smoke is clean, spray the insides down with a garden hose a steam clean it well. Let the fire die back a bit but maintain a pile of coals that will ignite a new split quickly. See if you can stabilize the fire between 225 and 300 adding a split or two every 30-60 minutes. Splits should ignite fairly quickly and burn clean. Try to keep most of the fire toward the end away from the outlet to the cook chamber. Keep the vents open for now and try to maintain a lower temp with a smaller fire NOT with choked back airflow. You can learn to dial back the air for later cooks after you verify that everything else works, but air is never a primary temp control on a stick burner, control comes from managing the fire. Smoke should be very thin and flowing steadily out of the chimney in a fairly smooth continuous stream. If you can smell it, it should smell pleasant, not bitter or harsh or chemically etc. If all goes well to this point, then try throwing on a pork butt. Otherwise come back here and report.

Once on to the pork butt cook, If your RF plate is over 370 give or take fats will smoke. Give yourself 1-2" or more of an airgap between the drip pans and the RF plate to keep the pans from over heating and to let the RF plate work. Any clean non-combustible spacer should work (tuna cans, brick pieces, cooling rack, whatever. Keeping a bit of liquid in the pan should also prevent any fat smoke. If the RF plate is below 350 and it drains, you will not need drip pans, but stick to them for now to help debug. BTW, an RF thermometer gun would be the best tool to check RF plate temp in different locations. Cook a pork butt unwrapped for 6-12 hours at 225-300 (time depending on size temp etc.) until it is soft enough to pull easily. You can wrap when done for resting/holding, but the key is it should easily be able to cook that long unwrapped without any hint of bad smoke flavor. This is a cut that is hard to screw up so it is a good test meat.

What is the chimney diameter and what is the cross sectional area of the space below the RF plate? What are the dimensions of the fire box and the cook chamber?

The chimney is 4" diameter as is the air intake. The rf plate is 13" across and there is probably 4-5" gap underneath. The cook chamber is about 15"x 39" the firebox is14"x 22".

I had a dry run yesterday and got the cook chamber upto 480℉ and sprayed it with water/steam, then got it back upto temp for a while with wood chunks. I probed the chimney at 3 places and they were between 380℉-450℉ and plenty of draft with a big fire but it seems when trying to bring the fire down later it would not hold 230℉ very well, couldnt get a decent coals bed but maybe the 1" square grate is to big and the smaller coals were dropping out. When i put another wood chunk on it would take time before it caught and i would blow on it to get it to light, perhaps i need another air inlet. Also i had to have the lid open for the wood to catch properly which would the bring the temps down.

I havent cut anything yet but may add an air inlet somewhere unless i get advised against it.

Kmm
06-11-2017, 09:49 AM
smaller coals falling through. Two things
1) When you were blowing on the firebox to get the new stick lit, did you happen to notice how full the area below your fire grate was? If it was full, did you try cleaning it out to see if air flow improved?
2) I realize what I am about to suggest will probably sound counterintuitive, but the 1" fire grate spacing might be a big part of the problem.
Minus any sort of mechanical agitation, as your burn progresses, ash will tend to bridge on the top of the fire grate effectively blocking the fresh air from reaching the embers.

Before you fire up the cutting wheel, please run one more test burn just like the last one.....only this time when it gets to the point you are having a hard time getting a new stick to light, use a sturdy rod of some sort to reach through the air inlet and bang on the bottom of the fire grate. The shaking action will knock any bridged ash down, and you should see an immediate improvement in the fire due to the increased air flow. If this plays out like I think it will, you will need to find some grating with larger openings or build something out of rod and/or bar stock. This was a lesson I learned the hard way many years ago during one of my early builds.

Blondy_UK
06-11-2017, 03:19 PM
smaller coals falling through. Two things
1) When you were blowing on the firebox to get the new stick lit, did you happen to notice how full the area below your fire grate was? If it was full, did you try cleaning it out to see if air flow improved?
2) I realize what I am about to suggest will probably sound counterintuitive, but the 1" fire grate spacing might be a big part of the problem.
Minus any sort of mechanical agitation, as your burn progresses, ash will tend to bridge on the top of the fire grate effectively blocking the fresh air from reaching the embers.

Before you fire up the cutting wheel, please run one more test burn just like the last one.....only this time when it gets to the point you are having a hard time getting a new stick to light, use a sturdy rod of some sort to reach through the air inlet and bang on the bottom of the fire grate. The shaking action will knock any bridged ash down, and you should see an immediate improvement in the fire due to the increased air flow. If this plays out like I think it will, you will need to find some grating with larger openings or build something out of rod and/or bar stock. This was a lesson I learned the hard way many years ago during one of my early builds.

Hi, every now and again i was poking into the inlet and scraping out the ash although there was an air gan beneath the grate, there were small glowing coals as well that were falling through and thats why i thought that i may need a smaller mesh grate to keep the coal bed above.
As for blowing on the coals i did this through the top lid. The first ever cook that i did i was able to keep the temp at 230℉ ish with a bigger fire but closing the input vent a little.
I will do another burn in the week sometime do you think another low down air hole would help?

m-fine
06-11-2017, 03:39 PM
The total airflow is going to be limited by the chimney if it is the same size as the intake. A second intake may help with air distribution but won't increase the total amount of air going through the firebox. If you have enough air to run at 480, you have enough to run at smoking temps.

If you are having a hard time maintaining coals, that could be overly dry wood, or too much falling through the grate, or simply part of the learning curve. You can lay another layer of mesh across the grate and then just watch for them getting blocked with ash. I would also suggest looking for wood that was cut and split between 3 and 12 months ago.

Blondy_UK
06-11-2017, 04:07 PM
The total airflow is going to be limited by the chimney if it is the same size as the intake. A second intake may help with air distribution but won't increase the total amount of air going through the firebox. If you have enough air to run at 480, you have enough to run at smoking temps.

If you are having a hard time maintaining coals, that could be overly dry wood, or too much falling through the grate, or simply part of the learning curve. You can lay another layer of mesh across the grate and then just watch for them getting blocked with ash. I would also suggest looking for wood that was cut and split between 3 and 12 months ago.

What would stop the coals dropping through the mesh? I know that in the US a lot of people use expanded steel but its harderto find here or too expensive. What do you most people have as a grate?

Kmm
06-11-2017, 10:55 PM
Hey Blondy,

Those small coals falling through the grate are not really producing all that much heat. (Small surface area, limited fuel left to burn). Controlling the burn on top of the grate is going to get you there. There seems to be a lot of advise about the wood you are burning...so for the sake of consistency perhaps you should try a burn with some nice fresh, dust free lump charcoal. If lump burns steady and clean, you will need to focus on your current wood pike. If during the lump burn, the same issues persist, we will keep looking at the mechanical systems. Just out of curiosity, what are you using to get your fire started? Personally, I use a propane torch (either small plumbers model or a full out weed burner depending on my mood and sense of urgency). Highly seasoned, unsplit, bark on chunks can be a bear to start even in something that breathes as freely as a fire pit. Sometimes I will cheat a bit and use a leafblower or air compressor to speed things along.
Don't despair, you will eventually figure out most of the quirks and be driving the neighborhood crazy with the smell of finely smoked food.

Blondy_UK
06-12-2017, 02:29 AM
Hey Blondy,

Those small coals falling through the grate are not really producing all that much heat. (Small surface area, limited fuel left to burn). Controlling the burn on top of the grate is going to get you there. There seems to be a lot of advise about the wood you are burning...so for the sake of consistency perhaps you should try a burn with some nice fresh, dust free lump charcoal. If lump burns steady and clean, you will need to focus on your current wood pike. If during the lump burn, the same issues persist, we will keep looking at the mechanical systems. Just out of curiosity, what are you using to get your fire started? Personally, I use a propane torch (either small plumbers model or a full out weed burner depending on my mood and sense of urgency). Highly seasoned, unsplit, bark on chunks can be a bear to start even in something that breathes as freely as a fire pit. Sometimes I will cheat a bit and use a leafblower or air compressor to speed things along.
Don't despair, you will eventually figure out most of the quirks and be driving the neighborhood crazy with the smell of finely smoked food.

To start the fire i fill a chimnet with briquets and stuff some rolled up newspaper under and light with a blow torch, then when going well tip it into the firebox and add se chunks of wood.
But i will try just a lumpwood fire next time and go from there.

Notorious Q.U.E.
06-12-2017, 08:29 AM
A restriction on the reverse flow is not going to help at all. At this point you want to maximize airflow and avoid any restrictions.

I will repeat it again. Shorter chimney = LESS DRAFT!

The problem is either insufficient fire or not enough draft. Cutting the chimney is only going to make things worse. If you guys want to put your money where your mouth is, I will add 10-12 feet of additional chimney pipe to my Lang and demonstrate that the smoke will not cool off and fall back into the cook chamber. Raise $1000 to bet against me and I'll give you 2:1 odds. Word of warning, my degree in aerospace engineering comes from a real acredited university. I learned thermodynamics and fluid dynamics from text books and professors, not Internet forums. You will lose.

For the OP, build a bigger fire and see if it will burn clean. If not, post the dimensions of your openings, and pictures of your fire. Also what temperatures you are seeing. If the wood is 3+ years old and your fire has a sufficient coal bed, I am concerned that the firebox exit and RF are too small. Also, space in the firebox may be an issue.

Damn! Stick it to 'em m-fine!!

Smilerb
06-14-2017, 02:51 AM
The total airflow is going to be limited by the chimney if it is the same size as the intake. A second intake may help with air distribution but won't increase the total amount of air going through the firebox. If you have enough air to run at 480, you have enough to run at smoking temps.

If you are having a hard time maintaining coals, that could be overly dry wood, or too much falling through the grate, or simply part of the learning curve. You can lay another layer of mesh across the grate and then just watch for them getting blocked with ash. I would also suggest looking for wood that was cut and split between 3 and 12 months ago.

Hi Blondy,

I meant to send this earlier this week, I use one of these in my smoker

http://www.ebay.co.uk/itm/NEW-Open-Fire-Basket-15-Cast-Iron-Heavy-Duty-Grate-Log-Coal-Wood-/182608105752?hash=item2a844a9118:g:wmEAAOSww5hZNY3 c

If it fits your fire box it would cross off a number of possible problems that have been raised.

Gavin

Blondy_UK
06-14-2017, 06:06 AM
Hi Blondy,

I meant to send this earlier this week, I use one of these in my smoker

http://www.ebay.co.uk/itm/NEW-Open-Fire-Basket-15-Cast-Iron-Heavy-Duty-Grate-Log-Coal-Wood-/182608105752?hash=item2a844a9118:g:wmEAAOSww5hZNY3 c

If it fits your fire box it would cross off a number of possible problems that have been raised.

Gavin

Looks good and size wise wood fit in but i dont think i will go through the lid so i will make another basket with sides on it that will just fit in and have another burn. Cant wait for that first 'mmm that tastes good moment.'

sleebus.jones
06-14-2017, 09:30 AM
That cast iron grate is a bit overkill. I'd just put a sheet of heavy duty expanded metal in there...takes up way less space and is cheaper.

SmokinJohn
06-14-2017, 12:10 PM
I think we forgot to ask some REALLY important questions:

How big were those butts?
What was the temp and IT when you foiled them?
Why foil after 3 hours?

SmittyJonz
06-14-2017, 01:20 PM
That cast iron grate is a bit overkill. I'd just put a sheet of heavy duty expanded metal in there...takes up way less space and is cheaper.

He's in UK - said expanded metal is $$$$ over there

sleebus.jones
06-14-2017, 01:49 PM
He's in UK - said expanded metal is $$$$ over there

Ah, whoops. My bad. :doh:

unzippy
06-14-2017, 02:28 PM
Expanded metal in teh UK - https://www.google.co.uk/search?q=expanded+metal#q=expanded+metal&tbm=shop

Doesn't look that bad online and I'm sure builders merchants will do it cheaper if you walk in..?

Blondy_UK
06-15-2017, 03:21 PM
I think we forgot to ask some REALLY important questions:

How big were those butts?
What was the temp and IT when you foiled them?
Why foil after 3 hours?

Hi they were small about 4lb, i didnt want to waste a big cut on my first attempts.
I wrapped after an hour and half the temp was around 165℉ and still after that short smoke time and i think another 3-4 hours cooking it was nasty, realy moist though.
I have a few things to try this weekend and see how i get on.

Blondy_UK
06-19-2017, 03:12 PM
I have had a better weekend for smoking, i made a basket for the coals out of 1" square mesh. I started the fire with briquettes in a chimney the added them to the firebox with some splits of wood and got the temp up to over 300 f then reduced it back to around 250f and added a small pork shoulder and a small rack of pork ribs that had been marinated overnight in the fridge.

I kept the next pieces of wood on the firebox to preheat before adding when the temp started dropping i was using my Thermopro T20 duel probe thermometer to keep an eye on temps, and kept the lid of the fire box open a while every time i added wood so that i would catch without smoking and then close lid to bring temp up again which resulted in a much cleaner burn with hardly any visible smoke from the stack, mostly it was clear with just a heat haze.

The results were much better with nothing going in the bin, ribs for breakfast this morning and pulled pork sandwiches for lunch tomorrow. Still getting to know the pit as i found it unstable at lower temps so maybe will try using smaller chunks of wood but more often. Its gonna be a learning curve but glad to get some good results and know that it does work it was just user error.

Thanks for all the comments and suggestions that helped to understand that it is not a light and forget operation but a more involved hobby.

SmokinJohn
06-19-2017, 04:13 PM
Hi they were small about 4lb, i didnt want to waste a big cut on my first attempts.
I wrapped after an hour and half the temp was around 165℉ and still after that short smoke time and i think another 3-4 hours cooking it was nasty, realy moist though.
I have a few things to try this weekend and see how i get on.

I think you got bad smoke/creosote on those butts.

But I normally don't pull my butt (SILENCE!!) until the IT is 190F. At 165, it is still fighting the stall.

sleebus.jones
06-19-2017, 04:17 PM
Good to hear you've had some better luck there, Blondy!

SirPorkaLot
06-19-2017, 04:24 PM
The issue is not the chimney height as much as the diameter

From the photos..it looks like too small of an intake for the size of the cooker and not a large enough diameter om the chimney.
Stick burning is all about airflow (draft).

You want your cook chamber to be tight (no air flows except where you want it to).

If it is sealed up tight, then the exhaust stack (chimney) should pull a negative air pressure across the cook chamber, literally pulling the air from the intake vent.

If the chimney is obstructed (or too tall/small), it won't pull enough draft (negative air pressure in chamber).

As an experiment; Try putting a small fan at the intake vent (outside the firebox), so that the fan will pull airway from the firebox. I think you will find you have a much stronger draft then, which will help to keep creosote forming on the meat

Bob C Cue
06-19-2017, 04:30 PM
A restriction on the reverse flow is not going to help at all. At this point you want to maximize airflow and avoid any restrictions.

I will repeat it again. Shorter chimney = LESS DRAFT!

The problem is either insufficient fire or not enough draft. Cutting the chimney is only going to make things worse. If you guys want to put your money where your mouth is, I will add 10-12 feet of additional chimney pipe to my Lang and demonstrate that the smoke will not cool off and fall back into the cook chamber. Raise $1000 to bet against me and I'll give you 2:1 odds. Word of warning, my degree in aerospace engineering comes from a real acredited university. I learned thermodynamics and fluid dynamics from text books and professors, not Internet forums. You will lose.

For the OP, build a bigger fire and see if it will burn clean. If not, post the dimensions of your openings, and pictures of your fire. Also what temperatures you are seeing. If the wood is 3+ years old and your fire has a sufficient coal bed, I am concerned that the firebox exit and RF are too small. Also, space in the firebox may be an issue.


Sounds like you know your hot air!

m-fine
06-19-2017, 08:30 PM
I have had a better weekend for smoking, i made a basket for the coals out of 1" square mesh. I started the fire with briquettes in a chimney the added them to the firebox with some splits of wood and got the temp up to over 300 f then reduced it back to around 250f and added a small pork shoulder and a small rack of pork ribs that had been marinated overnight in the fridge.

I kept the next pieces of wood on the firebox to preheat before adding when the temp started dropping i was using my Thermopro T20 duel probe thermometer to keep an eye on temps, and kept the lid of the fire box open a while every time i added wood so that i would catch without smoking and then close lid to bring temp up again which resulted in a much cleaner burn with hardly any visible smoke from the stack, mostly it was clear with just a heat haze.

The results were much better with nothing going in the bin, ribs for breakfast this morning and pulled pork sandwiches for lunch tomorrow. Still getting to know the pit as i found it unstable at lower temps so maybe will try using smaller chunks of wood but more often. Its gonna be a learning curve but glad to get some good results and know that it does work it was just user error.

Thanks for all the comments and suggestions that helped to understand that it is not a light and forget operation but a more involved hobby.

If it is too difficult to smoke at 250, try 275. You can also try smaller pieces of wood to maintain a lower temperature, but you may find it challenging to maintain a bed of coals and a lower stable temperature at the same time.

mrbill
06-19-2017, 09:09 PM
Its gonna be a learning curve but glad to get some good results and know that it does work it was just user error.

Thanks for all the comments and suggestions that helped to understand that it is not a light and forget operation but a more involved hobby.


glad you're getting it down and producing some good food.


there is always a learning curve with any new cooker. how steep that curve is depends on many variables. if you want set it and forget it cooking, go with a wsm or insulated vertical paired up with a pit controller. if you want to have a hand in the process and don't mind stirring coals, tapping dampers and otherwise tinkering with the cooker for hours on end, then a stick burner is what you seek.