INTRODUCING: the "Roto Damper"



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*Update, 2015:

The RD3 came together this summer and I think it's the best Roto Damper yet!

It's built around the 50mm Delta blower, model BFB0512VHD (Digikey, Mouser), it can only run this blower, no substitutes. That's good news though, since the Delta BFB0512VHD blower is now the default blower for the Heater Meter.

Since the addition of the Thermocouple Pit Probe high heat cooking has become a part of the HM world, so I set out to redesign the Roto Damper to maximize the top end air flow capabilities for high heat cooking. At the same time I wanted to reduce the amount of moving parts/wires to increase the long term reliability. The blower is inside the RD3 as are all the wires, none of the electronic parts or wires move, the only moving part is the outer damper disc. The blower output shoots directly into the grill unobstructed, no twists and turns or valves to travel through, with the 1" conduit adapter there is a full open path from the blower output into the grill. Due to this design change and the larger opening of the valve itself the RD3 is capable of achieving much higher air flow than the original Roto Damper, yet still maintains low and slow like a champ.

"and so, without further adieu, I present to you, the "Roto Damper 3"" (Code Name RD3)

The RD3 shares many of the same elements with the orininal Roto Damper. It uses the same Tower Pro MG90s servo, it also uses the same removable control/wiring box as the original RD. There are two options for wiring (both the original RD and RD3), either hand wired or the Aux Thermocouple "RDTC" board that John Bostwick and I worked together on.

The hand wired RD(3) uses the CAT5 jack from Home Depot that will snap into the RD(3) control box. You punch down the wires from the servo and blower to this CAT5 jack, Here is a link to the HM Wiki that shows what pin number on the CAT5 jack you punch each wire to. You can also install up to 3 (optional) panel mount probe jacks in this control box and punch those wires down to the 4 spare wires on the CAT5 jack. You will also need to add some jumper wires on your HM board from the CAT5 jack to the probe jacks before the probe jacks will function.

The RDTC is a small all SMD circuit board that has the CAT5 jack (the same type used on the HM board, NOT the Home Depot type), a Thermocouple Amp, Thermocouple Jack, and two standard food probe jacks on board. It also has a 3.3v regulator on board (to free up a wire for the second food probe) and an optional "REF Offset" circuit. The REF offset circuit will allow you to tune the TC to register temperatures below the natural bottom end of the HM at about 37F. The TC will function below 37F without the REF offset, but it will flat line at 37F until the pit temp rises above. This would only be needed if you wanted to have the ability to monitor very cold temperatures and see how miserable things are in the winter... lol

Here's a couple pics of the RD3 parts, including the RDTC board and hand wired control box:


...and a handsome shot of the RD3 assembled and ready for action...

The above picture also shows the standard output cap with the 1" conduit adapter from Home Depot attached, the other end of the conduit adapter goes through your kamado vent plate or "dog bowl" and secures with the ring nut provided to make the connection to your grill. The RD3 to original RD output adapter is also pictured above. The orRD adapter is ideal for someone who may have both, it is also nice because the RD3 will pop on/off the round output cap from the original RD much easier than the square RD3 output. This is also a good option for someone who has a couple grills they want to use the RD(3) on, just put an original RD output cap on each grill and you can move the RD(3) from grill to grill with ease.

If you have a 3D printer and are interested in getting the RD3 stl's just shoot me a PM or email...

*The first post about the Original Roto Damper has been moved down a few posts to allow room for the above information about the RD3.
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Looks nice. Good luck with your cook. I bought a servo. But, I haven't come up with a way to use it yet. I'll be anxious to see a video of it.

Just a quick question, why not do a second half moon? So, looking at your last image adding a half moon to the right of where the servo is attached, just like the one on the left side of where it attaches. You could get better natural aspiration that way.
Original Roto Damper UPDATE 1-3-15
Here are some pictures of the standard Roto Damper parts as of now. The four printed parts are the Body, Barrel, Blower Mount and Output Cap. The standard Output cap has a hole that fits a 1" conduit connector and also the BBQ Guru grill adapters, the standard blower mount cap fits the standard Heater Meter blower, however both the Blower Mount and Output cap can be customized to accommodate just about any I/O option. All parts press fit together securely and can be popped apart simply with a thin wedge inserted and twisted in the space where the parts mate.



The servo required is the Tower Pro MG90s (not MG90 or MG90D) which can be found at Amazon, Ebay and hobby outlets. The Body has a slot to snap fit the "CE-TECH" CAT5 jack found in Home Depot and 3 holes for (optional) panel mount probe jacks that can be found at Mouser or Digikey. (Alternate more expensive but in stock jack from Mouser) (note image on Mouser catalog page does not match the product, look at the DATASHEET for proper information) The conduit connector pictured can be found at Home Depot, they should have any number of connectors that will work in the electic isle. The side with the conduit ring nut goes through the metal plate that fits into your grill vent, the other threaded end will press fit into the standard Roto Damper output cap. The standard Heater Meter blower will press fit into the blower mount cap.

End Edit...

I broke the flap on my servo valve last week when I emptied the ash pan and accidentally let some chunks of coal get down into the valve. I could have just printed another flap, but I have been tossing around this idea for a different kind of valve so I thought I would give it a try. It seems to have worked out really well....

INTRODUCING the "Roto Damper":


(in the background of the picture above you can see the smaller prototype valve that I created as a proof of concept)

The idea was to create a direct drive damper made of two discs so you can see the movement and position of the damper. The design is very simple and I think it should be quite durable, it is made from just two printed parts which you can see pictured below. I printed a rectangular base under the parts to assure the two mating surfaces were completely flat (since this particular filament I have right now tends to bow up on the edges more than most), the rectangles may not be needed with other filament or when made on a printer that has a cooling fan attached.

Here are the parts trimmed up and split open so you can see the mating surface and valve opening.

Above you can see the bottom side opening where the CAT5 jack is located which connects the valve to my HM via standard CAT5 cable. The whole unit is held together with the one screw that holds the lever onto the servo. I used a Tower Pro MG90s servo for this design, the one with the metal gears. I had to cut the mounting tabs off the servo so it would fit through the hole for the blower, the way the servo mates to the part you don't need them anyways. The mini-headphone jack you see hanging out there is to connect the blower, I decided to use that connector so I can remove the fan if I ever want to use just the valve alone.

I had a misprint the first time around when my blue filament spool tangled, so I cracked that one open so I can show you the insides. Here is a shot from the bottom showing the servo mounted and the valve fully opened.

Below is a picture of the inside of the top of the valve, you can see how the lever from the servo fits into the damper. I have the valve propped open just a little bit so you can see how small an opening the valve is capable of creating. The valve opening can go from quite small to fairly large, the arrow on the front will show you clearly what position the valve is in. When the valve is closed it closes very tight, if I blow through either end while closed my cheeks puff up and there is very little leakage.

One thing I really like about this design is you can manually operate the valve very easily. So if you feel you need to pull your HM out of bad weather, or just don't want to bother pulling it out for a short cook, or if you disconnect the HM before you tell it to close your damper.... you can always turn the damper by hand. It makes very accurate vent adjustments from very small to fully open, much better than the slider vent I had originally.

Below is a short video of the damper in action, this is my prototype unit that I had running out in the rain 24/7 for the last 4 days, so far so good! During this video the Roto-Damper is being run through a CAT5 cable (~50ft) with two probes and the servo/fan all running through the CAT5 cable. I started the video while the HM was in "lid open" mode so you can see the valve jump into place when I disable lid mode. I was using the default PID values and had the fan set to run at 100% only, which is my typical setup for low and slow cooking.

Here is a graph of the first test burn...

I started the pit with an alcohol soaked cotton ball and lump coal, the HM was set in damper mode (with fan assist at 100% only) and a setpoint of 175 degrees. There was a short 5 degree overshoot then she settled right in on 175 degrees and held steady. Then I upped the temp to 225, the pit responded quickly due to the fan assist, then I bumped it to 250, then bumped back down to 225 to test the rise and fall with the valve. Finally I set the pit to jump way up to 375, the blower kicked on and you can see the super fast rise up to 375 on the graph, most excellent!
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Wow this is really cool! I really love 3D printers because four of us have come up with four different mechanisms. I had been planning to add an arrow to my design as well but got sidetracked with my printer upgrades. Can't wait to see it in motion.
Yah, for someone like me/us who likes to tinker and fix/create stuff, 3D printers represent a sea change event, almost like the advent of the internet. I just love being able to ponder something like this and then actually CREATE it!
I just got done attempting a short video, daylight was waning so I'm not sure how good it came out, I haven't gotten a chance to review it yet. TBHWY I don't even know what format this camera shoots video in, so I still have to look into making it viable for the web and posting it, if it goes well it should be added to the first post soon...
Bryan, does a video have to come from youtube to post in the forum, can I link right to a mov file or mpg file from a web server instead?
Bryan, does a video have to come from youtube to post in the forum, can I link right to a mov file or mpg file from a web server instead?
Ralph, MOV files are several times larger than mp4's. I would think your best bet would be to post the mov file to youtube and let them convert it for you. If you post it on your own server, it's only going to be available as long as your server is online. Plus, it would eat up your bandwidth.
I can convert to mp4, and I don't think bandwidth would be an issue for this one file, but I decided to just go the youtube route cause that's the easiest thing to do...
The video should be posted now...
i want one!! you gonna sell them ?

Well, I just got mine done yesterday so I haven't thought that far ahead yet, and I am running low on filament at the moment but my order is in for 2 spools that should be coming soon... but I might decide to make some to sell eventually. I really have no idea what I would charge for one though... both pieces print together in about 5 hours, then I have to clean out all the support material, trim off the pad, and then wire the thing up and make an adapter plate for your grill. So there is a fair amount of time involved in getting it all together. I also have yet to make an actual mount for the blower, right now the hole for the blower is made tight enough so when I force it in there it holds pretty solid, but if I were to sell one I think I should print an actual mount for the blower so I know it is going to stay put for you without fiddling with it (though I have never had a problem with the force fit on my adapters, I wouldn't want to sell one and let the owner have a problem)

What kind of grill do you have? I am wondering what kind of adapter you would need to attach it to your grill? I have been using copper pipe and plate to make my grill adapters (because copper can be soldered and doesn't rust, and making right angles is easy), it works out well on my FauxMado grill but I haven't made one for another grill yet.
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I have an XL big green egg (also have a small bge that i would also like to use) but the xl is my main grill.... i would be fine with just the valve as i could fab up the adapter etc.... let me know
I just tracked the shipment of my filament order and it says it wont be here until Tuesday (guess I should have shelled out the $5 extra for faster shipping, cause I thought when ordering Sunday it would arrive by this weekend with standard shipping) BTW, the colors I ordered are Orange and "Glow in the Dark" Blue. I thought glow in the dark might be cool for the damper, but I will have to see how well it prints. I almost ordered a color changing filament that goes from Green to Yellow at about 91F but decided to try the glow in the dark first. The Orange I have used before, it printed very well and has a nice bright color...

So I wont be able to print any jobs this large until next week when I get my filament (and I will only have those two colors to offer, I have a few more colors I can offer for the arrow and marker lines).

Meanwhile I am making a few tweaks to the design.... One thing I am working on now is adding 3 probe jacks that I will connect to the CAT5 connector so (theoretically) we can make the probe connections on the back of the damper and connect them to the HM through the CAT5 cable if you like... I haven't tested this yet (connecting the probes through the CAT5 cable) so I am not sure if it will work well, or if long CAT5 cable runs will effect the probe accuracy or not. If it works out you will be able to run three probes, the servo damper and the blower over a standard CAT5 cable which will allow you to keep the HM further away from the pit in case of bad weather/winter etc.
You should have no problem running the probes over cat5 cable.

Great, thanks for that reply. I am working out the mount for the probe jacks right now... Winter seems to be coming on now and I would like to get this working before it gets too cold. I will have to do some experimenting on how long the CAT5 cable run can be before it causes an issue (if at all), I've been thinking of building in a CAT5 jack box on my deck with a wire that runs into my house so I won't have to prop a door or window open to let the cable in... Wireless sure would be easier, but if it will all work over a long CAT5 cable that'll work too. I guess it would be kinda cool to plug my grill into a CAT5 wall jack on my deck to control it, really nice for winter cooking....
Juan, what did you have in mind to use for your grill adapter? Square, Round? I could make the output of the valve be whatever shape/size, but I would prefer to test the fit before I send it out to you.
if it will all work over a long CAT5 cable that'll work too. I guess it would be kinda cool to plug my grill into a CAT5 wall jack on my deck to control it, really nice for winter cooking....
100Mb Ethernet runs at 100 meter segments before requiring a repeater, I think you'll be fine unless you're pushing much less power than Ethernet to your probes to your buddy's house all the way down the street.
100Mb Ethernet runs at 100 meter segments before requiring a repeater, I think you'll be fine unless you're pushing much less power than Ethernet to your probes to your buddy's house all the way down the street.

Just remember that the 100 meter limitation is for solid core cat5, not the stranded stuff that patch cables are made from.
The cat5 distance limitations only apply because of the fast signaling rate being transmitted across the wires. The signals from the servo/blower/probes are extremely slow, so that is not a concern at all. What could be more of a concern is the resistance of the wire since it will be in series with the thermistor, but unless you're running extremely long distances with really thin gauge wire with a thermistor that has a low nominal resistance value it shouldn't be a concern.
I've been running the servo damper and blower through a CAT5 cable for a long time now, it was the resistance of the wire and possibly the connectors that I wasn't sure about having an effect on the probe readings/resistance.