Flat Damper


 

Benjamin Thibault

TVWBB Member
I designed this damper some months back, with a little input from SteveCK. My intention for it was to be small, and most importantly not stick out very far. I wanted to be able to drill a hole in the middle of the bottom of an UDS, and have it fit nicely between it and the ground without needing to lift it very far off the ground.

I don't actually own a 3D printer, but I sent a couple revisions of it to 3D hubs and had prints sent back to me. I haven't printed off a copy of the current (hopefully final revision), but I think it will work just fine.

It is a Rack/Pinion type damper. A gear pressed and glued onto the servo splines moves a door with a built in rack sideways uncovering the path to the cooker and a fan (which is optional I guess). It's designed around a 40x40x15mm fan (I used http://www.digikey.com/product-detail/en/AFB0412SHB-SP04/603-1486-ND/2560610) which significantly outperforms the blower recommended as the stock Heatermeter fan. Though, for most cookers I don't think the added airflow and static pressure is required.

It's designed to accept the 4 pin Phono Jack that was talked about in the MicroDamper thread (Shamelessly stolen idea). You will need to print the Main portion of it, and drill a hole through the opening for the wiring into the fan housing area. The hole for the servo wiring should print just fine though.

I know there was talk of linear surface area, cross sectional area and airflow and the whole nine yards. I believe this is a significantly larger cross area (40x40=1600mm) than other dampers and being as it's an expanding rectangle the opening is linear.
Thingiverse Link


http://i.imgur.com/4pQNpTs.png
http://i.imgur.com/qcB4wCv.png
http://i.imgur.com/T7foE2Y.png
http://i.imgur.com/EFclXuE.png

YouTube Video of early prototype work. The gear and rack were bought off eBay before I got around to modeling some. I think they work better, and would prefer to see if I could find an elegant way of using them instead of the printed one.

The design is by no means complete, but it should be functional. I do not know when I'll get around to finalizing the design, and I release the files freely to the community to do with as they want under the Creative Commons - Attribution - Share Alike license.
 
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SteveCK

TVWBB Pro
Looks good Ben. Did you get this to work without modifying the servo to run full rotation?

I don't mind you "stealing" the TRRS jack idea at all. You can even feel free to link my brief instructions on how to wire the jacks found here. I'll be making a more detailed PDF - not because it's difficult but when it comes to fabricating the cable it's easy to leave something out.
 

Benjamin Thibault

TVWBB Member
Yeah the Gear and Rack is enough to open the door fully with the normal rotation of the MG90S servo. You have to tell the heatermeter to output it to 100%, and then put the door on and tell it to close it to bring it in. I think it's actually a bit less than the full range, so you can edit the opening and closing positions of the servo to accommodate the actual needs of the door.
 

Bryan Mayland

TVWBB Hall of Fame
Yeah this is really cool! I've always considered trying to rig something to slide the actual door of my BGE open and closed but this seems like a better idea, creating something that is easily controllable and bolting that to the opening. How do you attach it, and do we have to worry about the plastic melting at the attachment point? My testing indicates that an inch away from the grill the temperature doesn't get above 60C, but at the door itself it can be 200C.

I'd love to see this with an easily made rectangular fitting that can somehow take 300-400C temps, with the full door opening passing through to the grill and no fan at all. Just like a person opening and closing the damper manually!

These ideas are great and I can't wait to see where your design goes, keep us posted!
 

Tom Kole

TVWBB Pro
Very nice design. I really like the rack and pinion mechanism. I've been working on a milled aluminum attachment for my BGE that uses a sliding door, but the servo attachment was through a lever arm which I've never liked. Your idea is much better and is going to finally allow me to finish this (I think). Thanks!
 

RalphTrimble

TVWBB Diamond Member
I like it, definitely earns points for originality.
I had thought of doing something similar initially but my fear was the unit would want to bind when moving the cover in an air tight slot. Your mech seems to move really nice so perhaps it will push the cover just fine, IDK...
Also, it's gonna open up rather quick, cause even a small crack the length of the body will allow a fair amount of air through. You could make a taper in the body on that end so you can achieve a smaller opening in the lower percentages, unless you are hung up on linearity, which IMHO is not important or even practical in the lower range of a grill damper because the more you clamp down on the damper the more the rest of the grill leaks...
 

SteveCK

TVWBB Pro
linearity is not important or even practical in the lower range of a grill damper because the more you clamp down on the damper the more the rest of the grill leaks...

This is true. If you have a very inefficient pit. In cases like a drum or a kamado (minus the Akorn) if you have a leaky area it's high up on the pit where you will leak hot air, not air that fuels the fire. The heat produced in the pit creates it's own natural drafting from bottom to top unless you snuff out the fire to the point where it's so desperate for air it overcomes that natural drafting - which would take some time to do. An Akorn, however, is a leaky SOB in the bottom but can be sealed up fairly well with enough nomex and tightening of the bottom clips. WSM are prone to leak at the joints but this is also about the point where they would naturally draw air, plus a large number of people with WSM also seal their rig up with nomex.
 

WBegg

TVWBB Pro
You could make a taper in the body on that end so you can achieve a smaller opening in the lower percentages, unless you are hung up on linearity, which IMHO is not important or even practical in the lower range of a grill damper because the more you clamp down on the damper the more the rest of the grill leaks...

Maybe I'm missing something, but wouldn't a linear design cause less "clamping" at the lower percentages? And wouldn't a tapered design cause more "clamping" in the lower range?
 

Benjamin Thibault

TVWBB Member
Thanks for the support everyone.

Bryan - I guess it would depend on the type of plastic you're printing with as to how it handles the heat. I know ABS has a higher melting point than PLA does. I'm not sure of any of the other plastics used in printing. I connected my MicroDamper to my Kettle with a piece of 35mm hydraulic tubing. I designed the FlatDamper around the same connection method (because I designed it for myself - lol).

Tom - If it helps you finish your own design, awesome! Look forward to seeing your finished product.

Ralph - The door piece slides relatively easily in and out of the slot. I had the same fear of it wanting to bind, and am fully prepared to use some kind of Graphite or Molybdenum dry lubricant to assist it in sliding if necessary. The test pieces I had printed weren't exactly smooth, but I used some sand paper and a file to smooth it out. That seemed to make it slide nicely. I also adjusted the tolerances of the slot parts (male and female) to give a little bit more clearance. I don't think the door is 100% air tight, but I would expect it to be tight enough to choke off the pit if closed all the way.
 
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Bryan Mayland

TVWBB Hall of Fame
Yup, I hear ya. My go-to connector is a 1" EMT conduit connector just because I have a plate with one of those in it so it is really easy to swap something onto it. I feel like the inner diameter of the hole could be larger though to reduce the restriction and your 35mm pipe has roughly twice the area of mine. I just have a hard time cutting round holes in sheet metal to mount to my vent so the 1" I can use a conduit punch I had on hand.

I use ABS for everything as well, but not in contact with the grill because it most likely will melt if I do a higher temp cook (600-700F). So far, having at least 1 inch of distance from the grill has proven to not be an issue with the plastic becoming soft enough to deform at all.

What I really like about this design, in addition to its giant surface area, is that you can look and see exactly how wide open the damper is without needing any indicators on the damper body. Did you have any problems with the 3D printed gears not being high enough resolution to be good gears? I know printing smaller gears can sometimes cause the teeth to be too round to engage tightly.
 

SteveCK

TVWBB Pro
My go-to connector is a 1" EMT conduit connector just because I have a plate with one of those in it so it is really easy to swap something onto it.

I shiver anytime I see someone use these. That galvanization can cause you some serious harm. I know, I know, "it doesn't got hot enough to vaporize the zinc"... but it wouldn't be an outrageous occurance to have your lump charcoal pop and a piece lands on it causing the zinc to go. Please please people, if you insist on using these put them in a full charcoal chimney and burn off the zinc. Make sure you stand far back while you do it!

BTW Bryan, these work great for cutting holes: http://www.harborfreight.com/titanium-nitride-coated-high-speed-steel-step-bit-set-2-pc-69088.html
 
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Bryan Mayland

TVWBB Hall of Fame
Oh I have a set of those as well, but they only go up to 1 3/8" and can make some gnarly holes in thinner sheet metal unless you're also cutting a giant hole into some support material.

If you don't like the conduit, you'd love knowing that my plate is galvanized steel as well. Is there a better sheet material that can be purchased from Lowes / Home Depot that doesn't cost more than $10?
 

SteveCK

TVWBB Pro
You could always burn that off too, but I'm sure you're looking for something that won't rust. Go to homedepot.com and search for "aluminum sheet" (may need to remove quotes, not sure how their search feature works), you'll find some for <$10.
 

Steve_M

TVWBB Guru
You'll probably have done more damage to your health by playing with toy cars made out of zinc vs the almost nill amount of zinc oxide you'd get from an EMT connector.
 

SteveCK

TVWBB Pro

Thats cool. I prefer to choose when I put toxins in my body though. Southern Tier IPA is my prefered choice.

Sorry for going off subject Ben. When I do my next cook, I'll use my infrared thermometer and check out what the temp is on the bottom of my UDS.
 

Steve_M

TVWBB Guru
If you don't live in a bubble, you're not really in control of what toxins you're choosing to put in your body anyways!
 

Benjamin Thibault

TVWBB Member
1 3/8" is 34.92mm. I take the tubing from work, and slap it on the lathe. Turn a small amount off to make it fit the 1 3/8" hole from my step drill.

The gear set that I had printed wasn't crisp. The corners were rounded on both the rack and gear part. It still worked though. I'm not sure about longevity of it though which is why I said I liked the ones I got off eBay better. They're molded with sharp corners. I guess you could print a slot instead of the protruding gear rack and fit the eBay rack into it. That might be a solution worth looking into. I was hoping (and suggested by Steve) to not have people need to buy something else when they're paying for a print anyway. When I modeled them I tried to make the teeth large enough so the printer didn't have trouble. Maybe the guys printer wasn't very well calibrated?

I put the Thingiverse link up. If anyone wants to print the gear, since it's so small, and let us know how it prints that'd be sweet.
 

 

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