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Need some help with a couple of issues on my wood smoker.

post #1 of 16
Thread Starter 

It's a Lang model 60.  I've been running it all summer.  Have 20 or 30 runs on it so far.  The problems I'm seeing are this:

 

1.  Uneven temperatures across the smoking chamber.  At the firebox end it's almost 100 degrees hotter than the end furthest from the firebox.  The middle seems to match up with the thermometer.  Below is a Rock's Stoker temperature chart from a test run I did with no meat in the chamber.  The temp was set at 280 degrees and it was maintaining that in the middle of the graph.  The pit temp probe was clipped onto the Lang thermometer.  The smoking chamber was 310 degrees on the firebox end, 280 in the middle and 220 on the end furthest from the firebox.

 

 

bbqemptysmoker.jpg

 

Is there anything I can do to even out the temperatures on this thing?

 

 

 

2.  I cannot get the temperatures as high as I want with just a coals fire (using firewood but when it's burned down to no flames left).  I've had large glowing beds of coals in the firebox and the temp stays below 200 degrees.  In order to run higher (250 to 280) I have to keep the fire flaming, which means I have to keep fresh wood in the box.  Not a problem, but I can't get the good thin blue with flaming wood.  I get more of the billowing white smoke.  If I was to try to use the burn barrel method to preburn the wood and put coals in the firebox, I would never get enough heat.  Is this something that can be overcome or is it simply a characteristic of this type of smoker?

post #2 of 16

Try raising and lowering the tongue end of the smoker using the jack this will change the heat from end to end. As for the wood what size splits are you using most people I know use splits about the size of a magnum beer can

post #3 of 16
Thread Starter 

Pineywoods,  Thanks for the tips.  As far as wood size, I've got a variety from standard cord wood to smaller pieces.  Told my supplier that I was willing to take the stuff that might be too small for his firewood customers. 

 

I did catch a video from Ben Lang showing how he starts his smoker.  It was informative and I used some of his tips.  The best tip was to get a good fire going, take the temp above what you want and then slowly feather the vents closed until the fire damps to the point that you have steady heat.   That worked well for having good smoke at my last cook.

 

I also read a tip about closing the grease drain valve.  I tried that and I tried changing the tongue level.  Neither seemed to have any effect on the temperature spread from front to back.  Here's a graph.  (I know I didn't wait very long between making changes, but being there live, you can see changes pretty quickly on the stoker temp probes)  Here's the stoker log data:

 

bbqnofoodexperiment.jpg

 

 

The red line on top is the pit temp measured at the stock thermometer location (top of smoke chamber).

The other three are measured at the lower grate level.

Blue is right of pit

Brown is middle

Green is left.

 

Note that the temps remained pretty much 100 degrees apart right to left regardless of what I was trying.  I went from the tongue at its lowest point to about 20 turns above level on the jack (the toungue was pointing up at a very significant angle)

 

Note that at 8:00am, I started choking the fire back to be able to put the meat in.  When I didn that, the right temp approached to within 50 degrees of the left temp.  That's the closest it ever got.  This tells me that when the fire is really cranking, the flames and likely infrared radiant heat are hitting the baffle plate directly from the fire.  When I choked the fire back, the flames and IR dropped and the right side cooled.

 

Some things I want to try.

1st (and likely most important) it seems there's a bad weld on the right side.  I think I see smoke coming from right to left at the right side (firebox end) of the smoke chamber when I first start the smoker.  Obviously, that's going to need to be fixed as hot gases right from the fire will keep that end of the smoker at a higher temp.

 

2nd, If rewelding the right side plate doesn't help, I'm considering putting a baffle in the firebox to block heat/infrared energy from the baffle plate on the right side of the smoker.  I might make something out of firebrick to reflect heat back into the fire and possibly get a more complete burn and less 'bad' smoke.

 

3rd.  I want to try adding a baffle to the left side of the plate that extends down into the lower chamber.  My idea is that it will help back up the heat and smoke under the plate and help raise the right side temperature.

 

4th, Modify the stack.  I want to raise the stack about 60 inches for two reasons,  1, better draft and 2, get the smoke above my canopy so it doesn't irritate me or any neighbors I might have at an event.  I'm also considering extending the stack downward into the chamber to cause it to draw heat from the grate level and possibly force the heat to even out in the chamber.

 

Any thoughts on my ideas?

post #4 of 16

I have seen Ben's video as well but I don't start with a big hot fire unless I'm gonna steam it I start with a smaller fire I have found that if I get the firebox end temps off by 50-75 degrees I never really get them back to close. Seems once that metal plate gets too hot it takes forever to even the temps back out if I even can do it during the smoke. Raising or lowing the tongue does take awhile to take effect again the plate has to adjust and that 1/4" steel takes time to cool

post #5 of 16


 

Quote:
Originally Posted by Smokeon View Post

Pineywoods,  Thanks for the tips.  As far as wood size, I've got a variety from standard cord wood to smaller pieces.  Told my supplier that I was willing to take the stuff that might be too small for his firewood customers. 

 

I did catch a video from Ben Lang showing how he starts his smoker.  It was informative and I used some of his tips.  The best tip was to get a good fire going, take the temp above what you want and then slowly feather the vents closed until the fire damps to the point that you have steady heat.   That worked well for having good smoke at my last cook.

 

I also read a tip about closing the grease drain valve.  I tried that and I tried changing the tongue level.  Neither seemed to have any effect on the temperature spread from front to back.  Here's a graph.  (I know I didn't wait very long between making changes, but being there live, you can see changes pretty quickly on the stoker temp probes)  Here's the stoker log data:

 

bbqnofoodexperiment.jpg

 

 

The red line on top is the pit temp measured at the stock thermometer location (top of smoke chamber).

The other three are measured at the lower grate level.

Blue is right of pit

Brown is middle

Green is left.

 

Note that the temps remained pretty much 100 degrees apart right to left regardless of what I was trying.  I went from the tongue at its lowest point to about 20 turns above level on the jack (the toungue was pointing up at a very significant angle)

 

Note that at 8:00am, I started choking the fire back to be able to put the meat in.  When I didn that, the right temp approached to within 50 degrees of the left temp.  That's the closest it ever got.  This tells me that when the fire is really cranking, the flames and likely infrared radiant heat are hitting the baffle plate directly from the fire.  When I choked the fire back, the flames and IR dropped and the right side cooled.

 

Some things I want to try.

1st (and likely most important) it seems there's a bad weld on the right side.  I think I see smoke coming from right to left at the right side (firebox end) of the smoke chamber when I first start the smoker.  Obviously, that's going to need to be fixed as hot gases right from the fire will keep that end of the smoker at a higher temp.

 

2nd, If rewelding the right side plate doesn't help, I'm considering putting a baffle in the firebox to block heat/infrared energy from the baffle plate on the right side of the smoker.  I might make something out of firebrick to reflect heat back into the fire and possibly get a more complete burn and less 'bad' smoke.

 

I built a reverse flow recently and had similar problems, I had temp variations as high as 90 degrees, however unlike yours the difference got greater with the increase in temps.

 

I put a second baffle that went halfway under the RF plate then welded another piece to the top inside of the firebox but under the secondary baffle.on a slight sloped angle towards the smoke chamber, now I am getting an average of about 15° difference.

 

3rd.  I want to try adding a baffle to the left side of the plate that extends down into the lower chamber.  My idea is that it will help back up the heat and smoke under the plate and help raise the right side temperature.

 

4th, Modify the stack.  I want to raise the stack about 60 inches for two reasons,  1, better draft and 2, get the smoke above my canopy so it doesn't irritate me or any neighbors I might have at an event.  I'm also considering extending the stack downward into the chamber to cause it to draw heat from the grate level and possibly force the heat to even out in the chamber.

 

Any thoughts on my ideas?

post #6 of 16
Thread Starter 
Quote:
Originally Posted by Pineywoods View Post

I have seen Ben's video as well but I don't start with a big hot fire unless I'm gonna steam it I start with a smaller fire I have found that if I get the firebox end temps off by 50-75 degrees I never really get them back to close. Seems once that metal plate gets too hot it takes forever to even the temps back out if I even can do it during the smoke. Raising or lowing the tongue does take awhile to take effect again the plate has to adjust and that 1/4" steel takes time to cool


 

Ok.  I can understand that if one end of the plate gets too hot it won't come back down.  So you start with a small fire and work your way  up to temp?

I usually have my fire up next to the back of the firebox, do you keep yours closer to the door?  I was thinking that might help keep the plate from overheating at that end.

I'm assuming the tongue adjustment is to raise the tongue to increase heat on the end away from the firebox, is that right?  How much do you find you have to raise the tongue?  One or two turns or half a bubble over level?
 


Edited by Smokeon - 12/18/10 at 7:58am
post #7 of 16
Thread Starter 

Ok.  Some positive news to report.  I wasn't able to get the plate welded on the right side, RE item 1 above.  So I started with item 2 -- a shield in the firebox.  The temperature was 22 degrees F yesterday and I had 2 fatties I concocted that I wanted to try out.  So I added the mod to the firebox that I've been considering, hooked up the stoker and log and fired her up.  Here's the log data from the initial fireup.

 

12-19-10bbqtest2.jpg

 

Remember that before the mod, the smoker was running with a 90 degree difference right to left.  With the mod in place the difference dropped to 40 degrees.  I started with way too large of  a fire and experienced a lot of smouldering smoke at the begining.  But after I let it burn down a bit, the fire got way more efficient and the smoke cleared up to a very nice TBS.  In fact, at some points during the process. the smoke was invisible.  My wood usage is WAY down now with this mod.  The flavor of the fatties was excellent with no hint of creosote bitterness.

 

Here's a pic of the log of the entire run.

 

 

12-19-10bbqtest.jpg

 

 

In the middle I experimented with half closing the damper (from verticle to 10:00 position).  The response of the smoker was immediate and negative.  The temp dropped as soon as I did it.  So then I opened it 1/4 of the way to open (11:00 position) and the temp started to recover.  There's no lable but before it fully recovered, I opened the damper all the way.  Proof to me that the stack needs to be unencumbered for this thing to draw correctly.

 

There is one encouraging spot just before 18:00 where you can see the temp dropping because the fire needed fuel.  After I added the fuel, the pit temp came up and started servoing on the set temp, and the right side stayed within 10 degrees.  I'm not sure if I can repeat that.  Next time I run it (Christmas Day) I'll start with a smaller fire and see how that goes.  After 18:00 I was done and I let the fire die out.

post #8 of 16
Thread Starter 

Ran it again yesterday for the Christmas ham.  Reconfigured the baffle to eliminate some heat leaks that were allowing flames to hit the plate on the right side.  That adjustment with no other changes tightened up the temps even more.  Here's the temp chart for the initial fireup. 

 

12-25-10bbqhamwithfirebox2.jpg

 

 

This time instead of going with a big fire to start with, I decided to start small and build up.  After I got it to temp, I wanted to let it run a while to warm everything up thoroughly.  The longer it ran, the closer the temps were getting to each other.  Just before I loaded the meat in the smoker the temps were the same from the right side to the middle and the left side was 12 degrees cooler.  Once I loaded the meat in the smoker, I did not move the temperature probes for the entire smoke.  The right side cooled off and the left side caught up to it.  I think it was likely due to the extra thermal load of the meat.  There was no meat in the left side of the smoker.  Here's the graph for the entire smoke.

 

12-25-10bbqhamwithfirebox.jpg

 

The temps across the smoker stayed close for the whole time.  The right side of the smoker had 2 hams in it, there were two chickens nect to the hams and two pastramis next to that in the middle of the smoker.  If there were something in the left side of the smoker the temps might have been further apart.  I am happy with the results so far.

post #9 of 16

Glad your getting it closer!!

post #10 of 16

Just curious smokeon,  the right axis is labled fan rate,  I am assuming that is just an embedded label in the plotting software?  Most of the Lang users I know just use splits, they don't preburn the wood.   I know that allowing the smoker to come to even temp before loading is extremely important.  That heavy steel holds a lot of latent heat and works to smooth out the temp swings.

 

You shouldn't need to be making mods to a Lang, I would call them and ask their advice first.  If they are not able to help you let me know, I'll have to think twice before I place an order with them this spring.

 

Al

post #11 of 16
Thread Starter 



 

Quote:
Originally Posted by Pineywoods View Post

Glad your getting it closer!!



 Thanks.  It was your idea about starting the fire off small and working up to the proper temp that I tried this time.  It did seem to help a lot.

post #12 of 16
Thread Starter 



 

Quote:
Originally Posted by alblancher View Post

Just curious smokeon,  the right axis is labled fan rate,  I am assuming that is just an embedded label in the plotting software?  Most of the Lang users I know just use splits, they don't preburn the wood.   I know that allowing the smoker to come to even temp before loading is extremely important.  That heavy steel holds a lot of latent heat and works to smooth out the temp swings.

 

You shouldn't need to be making mods to a Lang, I would call them and ask their advice first.  If they are not able to help you let me know, I'll have to think twice before I place an order with them this spring.

 

Al



 Yes it is.  I believe that some models of Stokers can vary the fan speed.  The model I have (25cfm) only runs at one speed.  The blue trace on the bottom is the fan trace.  It really only tells 'on/off' state of the fan so the right axis is not used.

 

As far as Ben Lang goes.  Please do not use this thread as an indictment against Ben Lang and his product.  The product he builds is great and I would recommend anyone buying one.  Some background on my case.  I bought the smoker second hand off E-bay and I do not want to needlessly bother Ben with questions from someone who has not spent money directly with him.  So my learning curve has been a little steep on using this smoker.  That's why I've turned to this forum for input.  I'm an engineer and a tinker-er.  I cannot leave well enough alone and just because I want to modify a product does not mean the product was defective.  I'm just trying to tune the performance and get more out of it. 

 

I'm using a Lang 60 and I have a Rock's Stoker connected to it with 4 temperature probes.  I felt I needed the stoker for two things. 

1) I didn't feel I was getting enough heat out of the fire for what I wanted to do.  I was likely not using the vents properly. 

2) I wanted to free up time spent adjusting and tending the fire to be able to fix other dishes during catering.  (something that I'm easing into.) 

 

So far my tinkering has yeilded the following results:

1) It's easier to get higher temperatures.

2) It's a lot easier to maintain the desired temperature.

3) Wood usage is down by half without a stoker.  (That's a pretty impressive endorsement of the Stoker)

 

The most recent changes I've added have given me the following:

1) Tighter temperature spread from left to right.

2) Wood use is down by half again (I'm using 1/4 of the wood I was using when I started)

 

This is just the way I operate.  I like to learn how something works, theorize how I can improve it, and then execute an experiment to see the results.   Other people prefer to have the temperature spread and once they learn it the use it to their advantage.  That's fine too.

 

Once again, the Lang is a superior product.  I like it a  lot and would recommend anyone considering one to get it.  Once I learn more about it, I might go to Ben with some of my ideas and see if he'd like to incorporate them.

post #13 of 16

I wasn't fully familiar with a "Stoker".  Did not realize off hand that it runs a fan in your smoker.   I guess you installed the Stoker because you where not getting high enough temps without it.  I personally would remove the Stoker and try to get the Lang working properly without the mods.  That was the point of my comments,  I would be pretty confident that the smoker, as is from the factory, would give you the proper temps.  That's the kind of reputation the Lang has.  I would be curious how the smoker would perform with no modifications.  Baffles wide open to light the fire, temp brought to at least 300 for 10 - 15 minutes, firebox dampers closed down to about 1/4 open to get temps to 280, meat loaded and temps allowed to moderate at 250-260.  Just guessing?

 

 

Al

post #14 of 16
Thread Starter 
Quote:
Originally Posted by alblancher View Post

I wasn't fully familiar with a "Stoker".  Did not realize off hand that it runs a fan in your smoker.   I guess you installed the Stoker because you where not getting high enough temps without it.  I personally would remove the Stoker and try to get the Lang working properly without the mods.  That was the point of my comments,  I would be pretty confident that the smoker, as is from the factory, would give you the proper temps.  That's the kind of reputation the Lang has.  I would be curious how the smoker would perform with no modifications.  Baffles wide open to light the fire, temp brought to at least 300 for 10 - 15 minutes, firebox dampers closed down to about 1/4 open to get temps to 280, meat loaded and temps allowed to moderate at 250-260.  Just guessing?

 

 

Al



Here's a link to the thread that shows what I got from Rock's BBQ.

 

http://www.smokingmeatforums.com/forum/thread/92476/just-ordered-a-rock-s-bbq-stoker-for-my-lang-60

 

 

Yeah, part of the reason for the purchase was to get a higher stable operating temp.  The other part was to get a much more stable temp over a run.  I'd like to see someone be able to maintain a +/- 2 degree stability over an hour without some sort of controller.  It might be possible, but the amount of attention it would take is large.   And of course the other reason was the bling/tinker/cool factor.

 

I would be willing to run another experiment without the stoker to see if what I've learned so far about its operation would allow me to run it as well without the stoker as I can with it.  There's actually a few advantages to having that skill set and knowledge ready to fall back on if needed.  I have no doubt that the Lang will run without the stoker.  Ben didn't build his reputation on a smoker that won't perform.  But the Stoker's data logging ability has allowed me to learn an immense amount of how the smoker runs very quickly.

 

Some things I would try if I do the no Stoker experiment would be to use the Stoker in a data logging function without running the fan.  I would actually start with a smaller fire with smaller splits and build up to a temp higher than what I wanted to run at.  I would also keep the fire away from the back of the firebox and closer to the door.

post #15 of 16

All good, if you follow Piney's advice.   A 2 degree delta for temp at one testing thermo site is quite a feat.  Keeping a 2 degree delta between the two ends of the smoker would be even more amazing.  I would think that there are just too many variables,  moisture in each stick of wood, variability of wind, how much of the firebox load is actually burning. 

 

Does the stoker actually replace one of the dampers in the firebox?  Have you reduced the amount of fresh air available to the fire by having the stoker installed but not on?

 

Interested in what you find,

 

Al

post #16 of 16
Thread Starter 
Quote:
Originally Posted by alblancher View Post

All good, if you follow Piney's advice.   A 2 degree delta for temp at one testing thermo site is quite a feat.  Keeping a 2 degree delta between the two ends of the smoker would be even more amazing.  I would think that there are just too many variables,  moisture in each stick of wood, variability of wind, how much of the firebox load is actually burning. 

 

Does the stoker actually replace one of the dampers in the firebox?  Have you reduced the amount of fresh air available to the fire by having the stoker installed but not on?

 

Interested in what you find,

 

Al



Just so we're on the same page and I really don't want to sound condescending.... when I refer to delta, that would be the total difference in the system.  When I stated +/- 2 degrees, that was the range of temperatures.  +/-2 degrees gives a delta of 4 degrees.  Now having said that, and looking at the charts above, +/-2 is too tight.  However, if you look at the first chart in post numbe 8, the stoker is keeping the temperature steady state with less than a 10 degree delta (+/-5 degrees).  The trace that the Stoker is servoing on is the red line at the top of the graph.  That temperature probe was clipped to the stock analog Lang thermometer in the top of the smoker well above the grates where the other probes were located.  The delta in temp between the top located pit temp probe and the grate was about 70 degrees.  Good reason for Ben to have moved the thermometer location closer to the grates in the new smokers he's building. 

 

If you look at the second graph in post 8, the smoker is maintaining between a +/-5 and +/-10 degree range left to right.  That's probably as good as it will get.  Though I'd like to be able to keep it closer to the +/-5.  So it is possible to tighten the left/right temp delta up considerably.

 

As to the variables, differences in wood, wind, etc, the stoker takes those out of the equation.  It fans the flames when it needs more heat and shuts off when it doesn't. When it's stabilized and in full servo, the fan turns on and off about every 10 seconds.  That is totally dependant upon how the smoker is behaving.  The stoker will learn how the smoker responds every time it is used and adjust to compensate.  The graph in post 3 shows this.  At around 10:00, the fire died down and I added some wood.  You'll see after that the Stoker recovers temp but over shoots some and there's a ringing in the trace as it relearns the pit's behavior but then the trace settles down and locks into temp.  One thing new users might have to get used to is letting the stoker self adjust and not fiddle too much with the air vents while it's learning.  There's no 'learning mode' nor an indicator that's what it's doing.  It's just something it does on the fly.

 

 

 If you go to the link I provided, it shows the adapter I got with the stoker.  It is intended to replace one of the stock wheel dampers.  That's how I installed it but it wasn't blowing directly on the fire so I wasn't getting the response I wanted.  I've tried a few things since.  Right now what's working best for me is to have the stoker mounted on the door of the Lang blowing straight onto the fire.  I was finding that I'd have to open one or more of the wheel dampers to get enough of a baseline oxygen level and then the stoker would provide enough additional to kick the temp up to the specified level. During the last two smokes with the baffle that I designed in place, the fan has provided all the air the fire needs and I keep the wheel dampers fully closed.  Also, the thin blue has been very easy to obtain with the baffle as well.  I'm pretty close to the optimal setup for me, though I might never stop tinkering with it.  Something else I'm thinking about is mounting the fan adapter on the opposite end of the firebox from the door so that the fan is out of the way when adding wood.  In order to do that though, I think I'd need to add a pipe to the adapter to route the air into the fire.  Not sure if I'm going to go with that one yet.

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