Attaching a Fan


 
D

Darren C.

TVWBB Pro
I have been trying to come up with an elegant way to attach my fan to my WSM. I'm still looking. But, I have a working prototype that I thought I'd share in case anyone could use the idea as is or improve it. Discaimer, it's still ghetto but way less ghetto than my first attempt.

Anyway, I wanted to make it out of metal. But, I don't have tools or skills with sheet metal. So, I thought I'd start out making a template out of cardboard, find my mistakes and then I'd only have to bend and cut the metal once. I quickly realized that I just couldn't bend the metal by hand. And, I also realized that the cardboard was pretty dang rigid. So, I ended up just using the cardboard today. I have to say, although I'm not particularly proud of how it looks, it did the job. So, here's how I did it.

Here's an action shot.

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I started by creating a template in LibreOffice Draw. If you are not familiar with LibreOffice, it's a free alternative to Microsoft Office and runs on Mac, Linux and Windows. Here's what it looks like on paper. I printed it and glued it to a piece of cardboard. Then, I cut it out with a box cutter knife/razor. I can make the file available. But, I don't really have a good place to store it where I'm sure it will remain available. So, for now, I'll just have to email it to those who might want a copy.

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After cutting it out, I had to glue pieces of wood (popsicle sticks I got from a hobby store) in places to keep the CAT5 jack a litle more stable.

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Here's a shot of it from inside the dish. I cut a square hole in the dish and pushed the tabs from the template through and folded them back. Then, I "secured" them with foil tape.

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Yep. It's pretty ghetto. I know. But, it worked okay today. I hope someone can think of a way to improve it more.
 
I made a change to my setup. I got tired of dealing with the bolt. One problem was that I could only close the vent so much before it started hitting the bolt. Sometimes, that wasn't enough. Also, once attached, I couldn't determine how open or closed the vent might be. I didn't have those problems with my sink drain. I decided to combine my original sink drain with my new fan housing. So, I wanted to update my thread.

What I have here is a sink drain with some Nomex around the edge to help seal. The seal is pretty tight. But, I'm not terribly concerned about the seal because I'm allowing some natural convection anyway. The sink drain is held in place by the tabs of the vent. It's easy to push on and pull off for storage. If fit becomes too loose, the tabs can be slightly bent outwards or inwards to adjust the pressure on the sink drain, making it easier to get on and off or more securely attached as needed.

Note that I have 3 marks on the drain. If you look closely, there is one mark on the smoker, too. The marks like up with 0, 1/2 and 100% open. This refers to the actual vent itself. The drain can be turned during the cook and the threads help keep it cool to touch, too. The cardboard in which the fan is mounted is taped with foil tape from inside the drain, exactly the same way I have it attached to dog food bowl in previous pictures. Having the ability to adjust the vent during cook is nice. If I see the fan is working too hard or not hard enough, I can tweak the vent. And, with the marks, it's pretty precise. Tiny adjustments make a huge difference.

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Here's graph from a recent cook. The temp is not perfectly steady. But, you know, it is just bbq. So, rather than chasing a perfectly flat line on my pit temp, I'm pretty happy. I can cook with the confidence that my temps aren't going to swing wildly. I'm not saying I'm not going to try to improve it. But, I'm a lot more content with this and if it never improved from here, I'd be satisfied. Having said that, I do have 2 questions about the graph.

First, see how the temperature swings got wider as the cook progressed? What would cause that? I'm using my default pids. Could I adjust the pids help with that?

Second, see the drop in the Set Temp (red line)? Unless I accidentally hit something, that wasn't anything I did. I opened the lid for some reason, but then I noticed the set temp had changed. I changed it back and all was good. But, it looks like instead of lid open mode, the set temp dropped. Weird.

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I kind of like the cardboard, actually. You could always skin the whole thing with your foil tape. If you want metal, have you tried roof flashing? Home Depot has small sheets for about a dollar each and you could probably hand shape them and snip them with utility shears.

As for your set temp drop, did you configure an alarm and specify a new set temp? That resets the set temp after you hit an alarm so you can do things like shut off the grill once you reach your meat target. I did the same thing on my test cook.
 
The cardboard was supposed to be an easy way to prototype. But, after forming it into this shape, I felt like it was actually quite sturdy. And, if I need another one or slight variation, it's not difficult to print another template and cut it out. I'm going to use this set up for at least awhile. A friend suggested painting it to protect it from moisture, which I think is great idea.

I originally intended to bend this out of metal. But, the edges were so sharp and my metal fabricating skills so poor that I decided to stick with the cardboard. I thought about getting one printed. That would probably be my preference if I end up liking the overall setup. That would allow an improved connection between the sink drain and the fan, too.

I'm also interested in a servo design. I have an idea for that in mind. But, I haven't taken time to work on it. I'm thinking I'll use the servo to operate the existing vent. I don't see any reason to come up with another vent design when Weber's works perfectly fine. They move quite easily and I don't believe it would put strain on the servo at all.
 
I also thought I would make a fan mount prototype out of cardboard then immediately make a metal one. I also failed spectacularly at making the metal version (over and over again). I ended up using the cardboard prototype for years and it was perfectly sufficient.

As far as the setpoint dropping. It's got to be an alarm unless someone else did it. There's just no other way to change the setpoint (unless a magic bullet somehow can press the right menu button once, then down a bunch of times).

EDIT: Is there somewhere that has the source for that home screen style? I'm going to be adding user styles tonight and I want to compare it to the original.
 
Bryan Mayland said:
I also thought I would make a fan mount prototype out of cardboard then immediately make a metal one. I also failed spectacularly at making the metal version (over and over again). I ended up using the cardboard prototype for years and it was perfectly sufficient.

As far as the setpoint dropping. It's got to be an alarm unless someone else did it. There's just no other way to change the setpoint (unless a magic bullet somehow can press the right menu button once, then down a bunch of times).

EDIT: Is there somewhere that has the source for that home screen style? I'm going to be adding user styles tonight and I want to compare it to the original.
Click to expand...

I don't have the source posted anywhere. But, I can get you whatever you need. I can't recall exactly what I modified. I think it was a few places in one file, with the addition of an image. I probably saved the original file. If so, I can send you a diff (and the image if you want it).

Do you have any suggestions on the temperature oscillations? They seemed to amplify over time. Is that something PID tuning would help with?
 
The oscillations, I can't really say without watching it happen live. The interaction between the three components can really help tell what's not working properly. Generally you want the D term to cut/power up the fan as the temperature begins to change. The amount of which would be dependent on the P term and how much I term buildup you have. It could be as simple as upping your D, but it might be because your P or I is too high.

If you can just forward your modified index.htm to me bmayland@capnbry.net, I'd appreciate it.
 
Bryan Mayland said:
The oscillations, I can't really say without watching it happen live. The interaction between the three components can really help tell what's not working properly. Generally you want the D term to cut/power up the fan as the temperature begins to change. The amount of which would be dependent on the P term and how much I term buildup you have. It could be as simple as upping your D, but it might be because your P or I is too high.

If you can just forward your modified index.htm to me bmayland@capnbry.net, I'd appreciate it.
Click to expand...

Thanks for your thoughts on the PID. I'll send the index.htm file asap.
 
I wanted to update this thread with a graph from yesterday's cook. I'm using the sink drain as seen in the second post in this thread. I upped the PID D value +1 (to 6, I believe). I don't know if that helped or not. I also set the max fan speed to 50% and opened the vent a bit wider. I couldn't be happier with this setup. I love being able to turn the vent with this set up.

From 8:45 to 1:45, the pit temp just barely strayed from 250. I'm not sure what made it start climbing at around 1:45, though. Maybe my vents were open just a tad bit too much.

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Darren C. said:
What I have here is a sink drain with some Nomex around the edge to help seal.
Click to expand...

Darren,

I could've sworn that you posted what sink drain this is, but I can't find it for the life of me.

I grabbed one at Lowe's today, only to get it home and realize it's not completely open on the bottom. It's a strainer type drain. To fit the fan outlet through, I'd have to cut the metal to open it up.

Can you let us know what you bought and where you found it?

Thanks!
 
Mine was not cut out when I bought it either. My fan does not extend into the drain. So, it was not necessary to remove the metal crossing the hole. However, I did remove mine to improve the air flow and make it easier to tape. I used a pair of snips to cut it. It was easy to remove.
 
FYI.......for a WSM 22.5 the daisey vent is bigger, I picked up the drain today and it fits between the tabs on the vent, not big enough to cover it. I added the gasket to drain and it fits quiet well, for solid fit just bend down the vent tabs. Will post a pic tomorrow.
 
I got mine off ebay, 2 sizes for WSM, 1/2" wide and 1". Thought there was a thread awhile back about the gaskets in the mod section.
 
Well, for me the gasket was primarily to prevent scratching the paint on the WSM. Making it air tight really had little to do with it. A little natural convection seems perfectly fine to me. You can close the vent if it gets excessive. The only downside I see is you may lose some blower air.

Why don't you try what you have and see how it works for you? Maybe just a little tape on it would help prevent scratching.

Oh. And, I used gasket material because I had some left over from sealing my smoker. I do recommend that. But, I'm not sure I would go out of my way to put it on my sink drain because I'm not sure it matters. And, it's going to leak some anyway. The seal is not that tight between the smoker and the Nomex.

I forget where I bought mine. But, try searching the forums for Nomex.
 
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