Project Brinkman SnP Update w/phase 2 mods

[OkieJay]

[bigabyte]

This weekend, time permitting, I will clean out my cooker, install the removable upper racks and the adjustable stack extension per the Alien design in this thread, season the cooker, and then do some temperature testing (front to back temp difference) using the various setups available to me. Here's a breakdown of the temperature tests I will be running:

1. Original pit design with no mods.
2. with Alien simple baffle (from another thread http://www.thesmokering.com/forum/viewtopic.php?t=925 )
3. with Alien stack extension (from this thread)
4. with Alien upper level racks installed (from this thread)
5. 2 and 3 together
6. 2 and 4 together
7. 3 and 4 together
8. 2, 3 and 4 together

Wow, that's looking like a pretty good list, I may have to break this into a couple weekends!
_________________
--Chris Baker
--Mad BBQ Scientist
--When my lab fills with smoke, that means it's working!

[Alien BBQ]

WoooDoggy,

I had a thought,
I am assuming that you will not have the newly designed baffles in place so a temp experiment of both the ends and the three zones (lower rack) (original rack) and (new upper rack) might lend some good data as to the variations to be found and the effect of the extension on the smoker.
_________________
https://www.linkedin.com/in/michaeloberry

[bigabyte]

I was thinking the same thing. I'm not sure I trust the results I got though. I want to test again with two thermos in each location to verify the accuracy of the thermos, and with a little more precise placement of the thermos between experiments. For each test, I placed the thermos in the middle of the racks where you are most likely to put meat. I used two thermos for each test, one for forward temperature, one for back. Again, I question some of these results, but I think I have some reasoning behind some of the differences I observed. With another round of testing I can see if I get the same results, or if something was wrong with these tests and these results should be thrown out. I used the original charcoal grates in the firebox for the testing, but turned them sideways to get the extra airspace below the coals. I used B&B Lump Charcoal and the Minion method to keep the fire going through the tests. I was measuring for temp variation while keeping the back thermo reading between 200 and 250. I observed each setting for 15 minutes and observed the highest and lowest temperature variations and rounded the average of these numbers to the nearest 5 degrees.

Test #1 was with the original design where the cooking grates are mounted in the middle of the cooker on the mounting brackets. I got a 20 degree temperature variation, which was quite surprising. I suspect one reason could be that with the thermo in the middle of the grate, the majority of the heat was rising before it reached the thermo.

Test #2 was with the new upper racks installed and the forward thermo placed on the top front rack. I got a 70 degree variation with this setup. This may confirm the idea of the heat rising before hitting the thermo in the last test.

Test #3 was with the racks back in their original position and with the adjustable stack extension extended down to the grates. I got a 40 degree difference which really surprised me. I am wondering if when I moved the forward thermo back down to the original cooking grate if I placed it perhaps a bit closer to the firebox than in test #1. Wish I had taken pictures. Oh well, I plan on retesting anyway.

Test #4 was with the simple baffle (heat shield) and the racks in their original position. I got a 5 degree variation (actually the average was 7 but I rounded down to 5). This is far more balanced than I expected, so I suspect there was something wrong with either the thermo or its placement. I know the heat shield works, but I don't think it should be THAT big a difference.

Test #5 was with the upper racks plus the simple baffle (heat shield). I got a 60 degree variation. This confirms that the heat shield is making a difference when compared with test #2.

Test #6 was with the racks in their original position but with the adjustable stack and the heat shield. The temp difference was 10 degrees. This showed the heat shield still making a big difference over test #3, but showed a bigger variation over using just the baffle alone in test #4. This may have been thermo placement again.

Test #7 was with the upper racks installed along with the adjustable stack. This time I got a 65 degree variation. Again, placement of thermos may be why these results are so weird compared to tests #2 and #3.

Test #8 was with the upper racks, adjsutable stack and the simple baffle (heat shield) all in at the same time. I got a 25 degree difference.

I plan to do retesting on all of these. In the future tests I will make sure I place the thermos a pre-determined distance from the firebox for each test to ensure consistency. I am also going to use two thermos at each position so I can validate the readings. Before cooking, my two thermos read the same temperature, so I was happy assuming they were synchronized. They are older thermos and I plan on using 4 new thermos for the next round of tests, and checking each one for accuracy before testing.
_________________
--Chris Baker
--Mad BBQ Scientist
--When my lab fills with smoke, that means it's working!

[Alien BBQ]

Chris,

Yes, it looked like you were all over the chart. I read and reread some of your findings and can confirm some of the variations observed. With no baffle in place there can be a 50 – 70 degree difference between the two opposite ends. The round pie plate baffle is suppose to do three things:

#1 prevent some of the direct radiant heating from line of sight with the fire.
#2 Prevent fire lap into the cooking chamber. Fire lap can cause your temps to swing wildly and spike.
#3 Slow down the heat as it travels from the fire box to the exhaust.

By slowing the heat at it passes from box to chamber, induced heat is retained better. I really don’t expect the pie plate baffle to do much more than that. Again, it is still 100% better than running without one, but you should still get three zones in the chamber with different heats:

Zone #1 Bottom rack (coolest)
Zone #2 Original rack (med heat)
Zone #3 Upper rack (hottest)

The ratio from the fire box end compared to the stack end should remain constant and be reflected as a percentage of the zone chosen.

When the exhaust extension is installed, it will slow down the escaping gasses by requiring them to collect along the top of the chamber until they reach the level of the opening. With this being said, the difference between zone #3 and zone #2 should be less and the variation in temp from firebox end to exhaust end should be less (in zone #3 initially and then zone #2. You should see a jump in zone #1 range due to convection from the upper 2 zones, but I have not tested to see if the percentage holds true.

The bottom line is that with the pie plate baffle in a offset smoker, you will always have a hot end, a cold end and three zones. This is why I designed the baffles in the Alien SnP to direct the heat to the bottom of the chamber, move along the tuning plates and exit in multiple areas. It’s not a perfect setup but the temps are more predictable and stable.

I did not want to say anything earlier, because I did not want to influence your results. Some of your results are in-line and some (as you said) need to be redone. One suggestion I might add is 15 minutes is a bit premature. I believe you would still have thermal eddy currents in the smoker going on and they would never allow you to produce the same results twice. Another problem is both of us are using wood and charcoal to do the experiments. It would be better if we were using gas top produce a constant firebox temp each time, because when you raise the cover to check the probes, you change the air/fuel ratio and the temp in the firebox and in the smoker. I don’t have a gas system and don’t plan to install one in the immediate future, so all of my experiments will have an “i” factor in the formula.

Thank you again for your devotion to explaining “why” thing happen when we decide to smoke some meat. We are all a lot more knowledgeable due to your efforts.
_________________
https://www.linkedin.com/in/michaeloberry

[bigabyte]

Thanks for the input Alien, I hadn't thought about having all three levels of racks installed throughout each test. That would save a lot of time and with a sturdy installation could ensure consistent thermo placement for each test, but would require a lot more thermos! I'm just enough of a geek about this stuff that I probably will buy all those thermos anyway! I'm figuring 12 total thermos. Two for top rack firebox side, two for top rack stack side, and then doing the same thing on the two lower racks. Since all the rack configurations are installed, I would only need 4 tests:
No Mods
Heat Shield only
Stack only
Heat Shield and Stack

For the temperature readings, I will wait until 15 minutes after closing the lid to start gathering data, and get 15 minutes of data at 1 minute intervals.

Do you think I'm missing anything with that plan?

And before anyone says anything.... CAN YOU REALLY HAVE TOO MANY THERMOS?????

I don't know how I'm gonna explain this one to the wife. I told her I was re-seasoning the smoker and since I was simply heating it with no food in it I was taking advantage of the opportunity to see what the new modifications did to the temperature. She has now coined me a "Food Geek"!
_________________
--Chris Baker
--Mad BBQ Scientist
--When my lab fills with smoke, that means it's working!

[sledgehammer03]

Try a bit of the KISS priciple.

Keep
It
Simple
Stupid

It seems like you are going through too many itterations in your experiments. ther other thing you have to ask yourself is, "What do I want to know about my smoker?" or " What do I want from my smoker?"

If you are cooking a full load of meat, do you want it to all finish at once? I think that would be difficlut as each piece is different, shape and size. If you are doing 1 butt or brisket at a time, you will know what the temp is where meat sits on the racks.

Or do you want to reduce the smoker's reliance on you for fire management?

My feeling is that the baffle or heat shield is going to help you tune your smoker and the chimney is going to help reduce your fuel comsumption.

Don't get me wrong, I like the work that you are doing, but I feel that you are making too many changes in each experiment to draw proper conclusions as to what you are seeing. Also, unless you see something that tells you there is a problem with the thermo, I would take what they are reading as good. You use this thing all the time and they either work right, or are way off.

If you want to do it hard core, get strip chart recorder, with 8 or 12 inputs. Thsi will give you a record of how things are changing. Then you can make little changes and watch the reaction. that or just use bisquits.

Rock On

Sledge

[Alien BBQ]

Even though they are not as nice, the Pyrex digital thermometers are only $13 at Walmart. I agree that you can never have too many thermometers. This week on my trailer mounted smoker, I have installed two grate level auxiliary heaters. Basically they are two pieces of 8 inch pipe that just sit on the grate and have an open bottom. The trailer smoker is made out of 3/8 inch steel and is a bear to heat on a cold morning. The guys who built this knew nothing about building a smoker and I have been modifying it, trying to get it to work better. I have installed an exhaust extension to retain more heat and a heat plate in the bottom to disperse the heat coming up from the bottom. The idea with the rings is that they should hold about ½ a load from a chimney starter each. If I need extra heat in the cooker section, I just fire up a starter and dump the lit coals in the rings. They sit on top of the cooking grate so they are easy to load and move around. They are made out of 3/8 pipe so I won’t have to worry about them warping.
_________________
https://www.linkedin.com/in/michaeloberry

[Alien BBQ]

Sledge,
I think I can speak for Chris and say that it sometimes is not the end result, but the journey. When I put my keys in the ignition of my car it works or it doesn’t, it doesn’t mean I don’t want to know why or how. I enjoy experimenting and inventing things that help others and I believe Chris does also. So many and I do mean soooo many people write in wondering why their SnP or Chargriller is not working like they thought it should, right out of the box. I have taken it upon myself to find out why, and try and fix it. Fortunately, as a professor of fire physics and toxicology, (among others), my job allows me to do research for the BBQ College class I teach. When my students pay money to take my class, they don’t want to hear that it works by FM. I applaud Chris on his efforts because he does not have a research grant and he pays for his experiments out of his own pocket. I know that the data is all over the board and Chris is making the efforts to limit the variations. I also know that you enjoy reading our post and I thank you for your comments because they are valid. In the end, we will figure this out, and will have an answer for the newbie’s that want to know why their smoker isn’t working.
_________________
https://www.linkedin.com/in/michaeloberry

[bigabyte]

Thanks for the tip on the thermos Alien, I'll check those out.

Sledge, thanks for your thoughts as well. I do trust those thermos, but some of the readings contradict the results other people have seen. In this case I truly believe there was some operator error, and I plan to correct that! The stack extension isn't a new concept and it is posted all over the place and people have used them reporting great success. In my tests I got results indicating that the use of the stack extension made the temperature variation worse than not using it. Thus, I want to verify my results before I go around telling people that extending the stack down to the grate will actually make your front-to-back temperature differences even more erratic. I like to back my words up with proof and not just claim stuff works because I like to think that is how stuff works or it is what some BBQ guy told me once. If you look back at all my posts, I will generally state if what I am saying is based on observations, or backed by facts, or just a simple "this is what I have heard and believe" thing. Whether or not someone listens to me and believes what I say is completely on them, but I take what I learn and build on it in order to make better Q based on the real world, and not the smoke that a lot of seasoned Q'ers like to blow out their stacks when passing on knowledge. The best advice I ever got from a BBQ guy was that the advice you get contains exactly what you need to know, but has just enough misinformation in it to keep you from beating him at a competition. I plan on doing the exact opposite and stating clear as day exactly what I am doing, how and why I do it, and what results you get. I personally don't give a hoot about keeping secrets for my own personal gain, because I don't really have any major aspirations in the field of BBQ other than having fun and exposing the truth about as many BBQ misconceptions as possible.

Now, the reason I am testing so many configurations is that I am trying to determine what effect each common modification on a cheapo offset actually has. Each modification is done to steady the temperature in the cooking chamber. Perhaps some are better than others and if people had some information about exactly what the impacts are from each modification they can make better decisions about what modifications they want to make to their smoker. Perhaps making every mod doesn't give you optimal performance? In addition, Alien has talked about manufacturing a mod kit for the Smoke N Pit smokers. What I am doing is some independent testing to validate the results he saw in his tests. That way he knows that it works so when he starts selling the product he can stand behind the claims he makes about it.

Man, the wife is right. I am a "BBQ Geek".
_________________
--Chris Baker
--Mad BBQ Scientist
--When my lab fills with smoke, that means it's working!

[Alien BBQ]

I prefer the title “enthusiast”.
_________________
https://www.linkedin.com/in/michaeloberry

[sledgehammer03]

From what I have seen on my Char-Grill, the stack extension hurt the temperature gradiant. With out it, the heat passes quickly from the fire box to the exhaust. The cooking chamber was hotter at the fire box, and as you went up. When I added the extension and flipped the charcoal pan the cold spot was actually at the fire box and I had to completely readjust everything.

What I did find the extension did was cut fuel consumption by more htan half, as the hot gasses had to work their way out of the cooker.

My opinion, based on facts if that the tuning plates keep the temperature even. The lower stack intake affets fuel consumption.

I am not sure the guage of the sttel your smoker is built of, but my is very thin and the heat loss through the bottom is tremdous (not quantitative). By adding a couple of bags of ceramic briquettes (Thanks Doc1680) I have been able to keep the grate temperture up a to 240-260, (was about 200-210) and further reduce fuel consumption.

[SDrees]

Alien, I'm a newbie to the ring, and I have a Chargriller that I've been using for about 2 1/2 years with no changes. Never gave it a thought to try and improve it. I've read your posts and it all makes sense. I'll make some mods this week, and I have about 20 friends and family members coming over this Sat. for Ribs and Brisket. I was always wondering why I was having a low temp. problem and consistency issue.

Thanks I'll be posting more for sure.
_________________
It's never to late to start smoking

[SDrees]

Sledgehammer03
It seems to me when you flip the charcoal pan you have made a reverse flow smoker. If that's the case you should move the stack to the fire box end.
_________________
It's never to late to start smoking

[DawgPhan]

[sledgehammer03]

I have it covering half the pass through now. I'm sure you are right about the revese flow. I have her humming pretty good now, for 1 butt or brisket.

[bigabyte]

I'm liking the idea with the ceramic bricks too. It makes me wonder about maintaining sufficient airflow if you later want to add tuning pates down there, but it makes a lot of sense. I'm glad you posted that you have seen a bigger variation when using a stack. I haven't heard anyone state that before. Good to know.
_________________
--Chris Baker
--Mad BBQ Scientist
--When my lab fills with smoke, that means it's working!

[SDrees]

[SDrees]

[Alien BBQ]

They make a fiberglass door seal for wood stoves that works good for sealing doors and such. You can buy it by the foot at Lowes.
_________________
https://www.linkedin.com/in/michaeloberry