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INTRODUCING: the "Roto Damper"


 
Phillip, Don't let my experience and thoughts discourage you. Three dampers did work and I was using the default PID values which were not designed for this application. If you add a fan to one and fiddle with the PID you would probably end up with what you are looking for. Good luck and I would be interested to hear about someone perfecting this idea. Dan
 
RalphTrimble said:
Although I prefer to seal up the bottom vents and run as much air through the HM as possible, this gives you better control of overshoot.
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I too like to seal the puppy up as much as possible.

RalphTrimble said:
I don't think you said if you are using the blower or a damper with the HM? If it's just a blower you might want to try lowering the max speed a bit.
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I am using just the blower going through a copper manifold "air burner" that I have been working on. I bought one of Dave's damper valves a while back but have not figured out a good way to mount it yet. I may try and find a way to mount that puppy and give the blower / single valve a shot.

RalphTrimble said:
Also, if you are getting a lot of overshoot when your lid is open maybe you're building too big a fire for your target temp? Are you using some form of the minion method with the coals?
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I used to use the minion-esque "fuse" method of letting the coals burn in a semi-circle around a rock but it just never worked out. The last time, I dumped a pile of lit lump into the center of a fully loaded charcoal bowl. Worked MUCH better. I don't think that the fire is too large, it is just that the volume of air inside of the WSM is so large that any disturbance just adds tons of fresh oxygen into the mix and the lump just takes off.

I haven't found any briquets that I like and the ones that I do want to try next (Wicked Good Charcoal) are next to impossible to source right now.
 
Dan Francis said:
Phillip, Don't let my experience and thoughts discourage you. Three dampers did work and I was using the default PID values which were not designed for this application. If you add a fan to one and fiddle with the PID you would probably end up with what you are looking for. Good luck and I would be interested to hear about someone perfecting this idea. Dan
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Oh, not at all Dan! In fact, it was very encouraging. If you do find the photos of your setup, I would be very interested in seeing them.
 
Phil, a damper of any sort on the output of your HM blower will help you get control of overshoot, and so will a smaller fire... I say that again 'cause a big pile of coals can use up the large volume of air in your smoker, but a smaller (minion) fire can only burn so much oxygen... The problem with a big fire is exactly as you stated, once you open the lid a ton of fresh air flows in and the fire stokes itself beyond the size you really want it. Even worse, once you close the lid the bigger fire pulls more convection air flow through your smoker and stokes it'self further if you don't have any sort of damper on your HM blower output. That said, on my cheapo thin walled smoker I always just put a big pile of coals in the pan and lit it up and I never had a problem with overshoot (while not running any sort of damper) cause it leaked so much heat, I guess the WSM holds more heat than my cheapo smoker (though the designs are similar really). How are you running the top vents? I would try putting some sort of damper on your HM blower and running your top vent more open, and perhaps lowering the max blower speed in your HM settings. You can also use the PID settings to calm down the amount of air it feeds the pit and how fast it reacts to changes to make your flow more moderate.

It's been a while since I used the old smoker with the prototype "air-burner" since I got the "FauxMado", but I recall the HM action was a little bit more of a puff puff puff because the air-burner stokes the fire so well and the pit reacts really quick, but then the thin walled smoker leaks the heat just about as fast. Although my temps graphs were always rock solid the blower graph was always much more rocky than when I cook in the FauxMado. I don't think you can expect as slow and steady of a blower graph on a thin walled smoker as you see on the ceramic komado's or another insulated grills like my FauxMado....
 
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For what it's worth this is how I made the variable dampers without one of those nice 3D printers. They are made from 3 1/2 inch PVC and the end caps are called Test Caps which I found at menards. You can get the brass sheet from ACE or about any hobby shop.

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Dan Francis said:
For what it's worth this is how I made the variable dampers without one of those nice 3D printers. They are made from 3 1/2 inch PVC and the end caps are called Test Caps which I found at menards. You can get the brass sheet from ACE or about any hobby shop.
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Fascinating! What were the adhesives? Due to some health issues in the family, I am really loathe to start mixing up heat and unknown substances.

Thank you!
 
Phillip P said:
Fascinating! What were the adhesives? Due to some health issues in the family, I am really loathe to start mixing up heat and unknown substances.

Thank you!
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Only adhesive was 5 min epoxy on the servo mount and the arm to brass damper, no heat. Also a ring of silicone around the pet bowl. If you notice, I have installed a muffin fan in this one. I have not tried it out yet and probably won't for a long time as I just ordered Big Green Egg. The WSM will probably only be used once a year now for our big BBQ. Dan
 
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Nice job putting together a rotational damper from common parts! You should probably share it in the "Servo/Damper Pictures" thread where others have posted about their servo dampers, so people reviewing the various damper designs will find it....
 
It FINALLY stopped raining today and I was able to update the video on the first post with better light so you can see the roto-damper in action. The prototype valve in that video had been run non stop for about 4 days out in the rain with temps in the 40's-50's, the HM was inside the house at the end of a very long CAT5 cable. At times the fire was out and the pit probe was dropping on and off with temps in the 40-50's and rain, so the roto-damper was working overtime opening and closing when the pit probe would drop and reappear, so the the prototype valve got a real good workout. As you can see in the video, so far so good, still working fine after all that abuse.

The CAT5 Experiment...

I've had to make some modifications to the wiring on my CAT5 cable, it seems the probes and the servo don't like sharing wires, initially my probe readings were kinda rocky over the CAT5 cable. With the new wiring scheme the probes are very steady although I will only be able to run two probes through the CAT5 cable until the new HM V4.1 board is released (then it can be 3 probes). Here is a graph of a test run today showing ThermoWorks and Maverick High Heat (73) probes run both directly to the HM and over a very long CAT5 cable (~50ft). I let the graph start out with some overshoot so I could see how the probes read when the servo/blower is idle, and then see how they perform when the servo/blower kicks in...
CAT5Test.jpg

For this experiment I have a Thermoworks probe connected to the Roto-Damper as the Pit Probe, as well as a Maverick High Heat(73) probe connected to the Roto-Damper as the third probe. I connect CAT5 cable to the Roto-Damper, the cable runs from my deck into my basement, up through the floor into my kitchen where it comes out a cabinet and for this experiment I have pulled it all the way back out by the grill. Then I connect a ThermoWorks probe DIRECTLY to the HM at the second slot, and a Maverick High Heat(73) probe in the fourth slot. I put all 4 probes in the top vent in the same spot where I put my pit probe. As you can see the probes track very closely over all, the probes did read 3-5 degrees higher over the long CAT5 cable. I think that is close enough to work, you could add an offset for the probes when you run them over the CAT5 cable but I dont think they're off enough to bother with.

Here is a screenshot of a graph showing only a 14 degree temperature range, you can see the different readings for each probe much more pronounced, keep in mind each line in the graph is just one degree in temperature change. I did a few little lid burps so I could watch the probes track up and down...
CAT5TestSM.jpg


...and finally I pulled all of the probes out of the pit and placed them in a glass of hot tap water and let them settle, then I poured out the hot water and poured in ice water. Here is the graph of the water treatment...
CAT5TestWater.jpg


You can see the probes on the CAT5 cable tend to drop off more at very low temps but they're all good from around 40 degrees or so....
 
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Did my first high heat pizza cook last night using the roto-damper (over CAT5) and it worked great. I was able to achieve and hold 500 degrees in my FauxMado and the pizza was excellent. (outside ambient temperature was in the upper 40's) That pretty much covers the bases, the roto-damper will hold steady temps as low as 175 degrees all the way up to 500 degrees without a problem.

For the pizza cook I used "blower mode" letting the fan blow all the time and setting the servo damper for open/closed only, for low and slow cooks I reverse it and use "damper mode", having the fan blow at 100% only and letting the servo damper work the full range. There are a ton of ways you can configure the HM to work with the Servo+Blower but I find these two simple modes are all I need. I like "damper mode" for low and slow cooks because it doesn't force air through the pit, it lets natural convection air flow do the job, for high heat cooks you really need the blower to push the air and stoke the fire. I have used the default PID values for all of these tests and it worked very well.

This is no minor achievement, because unlike a real BGE, my FauxMado grill did NOT want to hold low temperatures before I started using a damper. No matter how tight I kept the top and bottom vents the temp in the pit always wanted to creep up into the mid 300's before it settled down. In the past I had to use minion methods to try and keep the temps low, for these experiments with the roto-damper I just lit a pile of lump coal and let it go... The Roto-Damper is able to clamp down on the air flow and backs the fire down to the size it needs to be for the setpoint, then it starts regulating air flow to keep it right in the sweet spot. It also allows me to run my top vent pretty open now, which I like because I don't want stale smoke stuck in my pit. I've noticed during low and slow cooks, regardless of the chosen setpoint, the damper seems to end up sitting around half open. I've run the pit at 225 and 375, in either case the HM will use the blower to stoke the fire to the appropriate size, then turn the blower off (at 99%) and clamp down on the damper, eventually the damper ends up right around the middle setting for the most of the cook. I couldn't be happier with how it is working...

Speaking of being happy... I'm thrilled at how I've got the HM working over the CAT5 cable now! I know many of you are blessed with good weather year round, but here in the Midwest we get bad winters and the bad weather has already started. This past week has been in the 40's-50's with lots of wind and rain, I've kept the HM and Roto-Damper running through the bad weather the whole time and cooked on it most every night. I plan to continue to cook through the winter on my FauxMado, which is why running the pit over a CAT5 cable is so important to me. I really like having my HM sitting in the kitchen instead of out at the pit, I no longer have to worry about rain, and it's easy for me to glance at to see my cook is on track without stepping outside (or powering up another device), I had been running my laptop in the kitchen in the past so I had a reference there but that's a PITA. Don't get me wrong, there's nothing better than a warm sunny day with the HM sitting next to the pit, but those days are gone for me until next MAY, so in the kitchen is where my HM will be sitting until then... With my initial CAT5 wiring scheme the temps were bouncing around about +/-5 to 10 degrees and the Roto-Damper was very hyperactive (reacting to all those false temperature swings). With the new wiring scheme I can only run two probes through the CAT5 (until the new HM board is released) but the temps are nice and steady and so is the Roto-Damper. When the pit is left undisturbed the damper finds the right position to hit the target and does very little moving, I sometimes find myself looking at it hoping it will move (cause I am still pretty excited about it) but she's moving a lot less now that I have the CAT5 cable wiring dialed in....
 
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RalphTrimble said:
Here is a screenshot of a graph showing only a 14 degree temperature range, you can see the different readings for each probe much more pronounced, keep in mind each line in the graph is just one degree in temperature change. .
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Just curious....how do you change the y axis of the graph to show a much tighter range? Mine always a range down to 40F or so.
 
T Hayes said:
Just curious....how do you change the y axis of the graph to show a much tighter range? Mine always a range down to 40F or so.
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Dont the the probes dip too far down below the set temp. He most likely reset the graph when the probes were at temp.
 
T Hayes said:
Just curious....how do you change the y axis of the graph to show a much tighter range? Mine always a range down to 40F or so.
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You need to adjust the view to eliminate data points that are far out of range of the temps being displayed... (drag and drop on the bottom graph, toggle off probes that are far out of range like ambient and food probes by clicking their color dot on the top half of the HM main screen, select the most accurate 1 hour graph first)
 
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UPDATE:
I've left the prototype "Roto-Damper" out on the grill since I made it, must be a couple weeks now. We've had lots of rain and cold, now it's turned to snow and ice. I did my first "winter" cook last night, the outside temp was in the upper 20's, the grill was covered in snow, the top vent was frozen and the roto-damper was slightly frozen as well. When I powered on the HM it was unable to move the damper, a quick manual twist of the damper broke the ice loose and then it functioned great as usual. I went on to do a high heat cook of steak and baked potato...

It has been my goal to get my system to the point where I can leave the grill hardware out at the grill and just plug in 1 simple cable to the HM when I want to grill, the roto-damper with CAT5 connection does that nicely... I've been wondering how the roto-damper would handle the weather, specially the ice and snow... So far so good! I will continue to cook through the winter so we will see how much abuse she can take...
 
RalphTrimble said:
UPDATE:
I've left the prototype "Roto-Damper" out on the grill since I made it, must be a couple weeks now. We've had lots of rain and cold, now it's turned to snow and ice. I did my first "winter" cook last night, the outside temp was in the upper 20's, the grill was covered in snow, the top vent was frozen and the roto-damper was slightly frozen as well. When I powered on the HM it was unable to move the damper, a quick manual twist of the damper broke the ice loose and then it functioned great as usual. I went on to do a high heat cook of steak and baked potato...

It has been my goal to get my system to the point where I can leave the grill hardware out at the grill and just plug in 1 simple cable to the HM when I want to grill, the roto-damper with CAT5 connection does that nicely... I've been wondering how the roto-damper would handle the weather, specially the ice and snow... So far so good! I will continue to cook through the winter so we will see how much abuse she can take...[/QUOTE


Considering, I have had my first heatermeter that had the linksys router and no premade circuit boards outside over a year and it still works fine.you should have no problems smoking in the winter. I have used the hm in all types of weather without any issues.
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JuanGarcia said:
So you ready to sell these ?
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Juan, I've got a fresh one printed up and assembled right now but it isn't wired up yet. I wanted to test the new CAT5 wiring a bit first to make sure it's reliable before I wire up more than the prototype. Since everything has been working great the past couple weeks I guess I should get moving on that now...
 
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