Building a stir plate, check out this USB adjustable computer fan

[HopsMan]

that sounds reasonable...I'll see what I find. Thanks!

 

[junior]

Sure Westphalen, I was going to post pics of the whole process, but forgot. Here we go:

Shopping List:

• Bel-Art 371100002 Scienceware Teflon Octagon Spinbar Magnetic Stirring Bar with Integral Pivot Ring, White, 2" x 5/16" Size - $8.17
• Magcraft NSN0674 5/8-Inch by 1/8-Inch Rare Earth Disc Magnets, 8-Count - $10.39 (Amazon currently lists this product as unavailable)
• Thermaltake Mobile Fan 12 External USB Cooling Fan 12CM AF0007 - $16.90
• DAP StrongStik or any other adhesive that doesn't set immediately (Don't use epoxy).
• 2" steel washer

The parts of the fan after it has been disassembled:
(I already glued the washer on here, pretend it's not there)

The glue I used:
(It doesn't set immediately, this is useful for centering)

Centering the washer:

1. This is the same technique for centering a thrown pot on a potter's wheel for trimming.
2. With the fan spinning, hold the pen steady and bring it towards the washer until it just touches.
3. Turn off the fan and look where the mark is. If the mark is equal all around, you're done. If the mark is only on one side, nudge the washer in the opposite direction of the center of the mark.
4. Repeat until the mark is equal all around.

Affixing the magnets:

I didn't permanently attach the magnets because I wanted to allow for adjustments. I just put a drop of Loctite on the washer beneath each magnet. This worked so well that I didn't need to permanently attach them.​

Et voila :rockin:

Matts, thank's for the fan link. I know this is an old thread but, I just received my fan after doing a stir plate search and your post seemed the easiest, so I purchased the 120mm fan when I received it today I quickly put it together to see how it would work. I had some 2" fender washers and some ceramic magnets around the house, I used a glass of water with a nail to see what it would do, it spun the nail but not with very a big vortex,I cant imagine it will do a good job when I use a heavier 2" stir bar and 2L flask which I have on order. I notice in your material list you used the same washer(you used the smaller fan), but you used Rare Earth Disc Magnets not the ceramic ones that I used, my questions are, do you think the magnets will make a big difference in performance ? Second question, do you think I should use a bigger washer to spread the distance of the magnets to get a better result? If there are any other suggestions you have I would appreciate them.

 

[matts]

Hi Junior. The rare earth magnets make all the difference. I don't think it will work otherwise, especially once your starter is full of yeast. I used the same 120mm fan as you. It still works flawlessly. Get the rare earth magnets and you're golden.

Edit: As for the washer, I don't think you should go bigger, just get smaller and stronger magnets.

 

[junior]

Hi Junior. The rare earth magnets make all the difference. I don't think it will work otherwise, especially once your starter is full of yeast. I used the same 120mm fan as you. It still works flawlessly. Get the rare earth magnets and you're golden.

Edit: As for the washer, I don't think you should go bigger, just get smaller and stronger magnets.

Matts, Thank's for the fast reply and the good news about the magnet issue. I thought you purchased the smaller fan?

 

[matts]

Matts, Thank's for the fast reply and the good news about the magnet issue. I thought you purchased the smaller fan?

Hi Junior, sure thing, glad to help. The first link I posted to start this thread had the link for the smaller fan, but then I found the larger one and went with that. I figured the larger unit would have more torque. Flomaster bought the smaller one and I think it's working for him.

 

[junior]

Have a question, here is my prototype, would this work better with a hole cut into the base? Once again, thank's to all for the help.

 

[matts]

Have a question, here is my prototype, would this work better with a hole cut into the base? Once again, thank's to all for the help.

Junior, I like your design. Fans are designed to have air moving over the motor. In your design, the fan motor will get good ventilation for releasing heat. I didn't have a problem with this in my enclosed box, but I have wondered if the unventilated enclosure will shorten the lifespan of my fan.

You don't need to cut a hole in the top, the earth magnets' power will go straight through that cardboard. Even if you made it plastic or wood, it will still be fine.

Edit: One thing I would change is to figure out a way to get those mounting screws flush to the surface. You are going to want to get a good flask for your starters. They have pretty wide bases and won't be able to sit properly with those screws sticking out.

 

[junior]

Junior, I like your design. Fans are designed to have air moving over the motor. In your design, the fan motor will get good ventilation for releasing heat. I didn't have a problem with this in my enclosed box, but I have wondered if the unventilated enclosure will shorten the lifespan of my fan.

You don't need to cut a hole in the top, the earth magnets' power will go straight through that cardboard. Even if you made it plastic or wood, it will still be fine.

Edit: One thing I would change is to figure out a way to get those mounting screws flush to the surface. You are going to want to get a good flask for your starters. They have pretty wide bases and won't be able to sit properly with those screws sticking out.

Matts, thank's for the quick reply. I plan on using some plexiglass I have laying around, I will also counter sink nuts,have a flush base for the flask. If you know,what would be the dimensions of the base that you would recommend for a 2liter flask?

 

[junior]

Hey Matt's, Here is my latest version, all I have to do is get a piece of glass or plastic, I figure a piece 7"x7", for a 2liter flask. Once again, thank's for the link for the fan and all the advice.

 

[junior]

Matts, final version, I am so anal.Once again thank's for the link for the fan, made this build easy for a handy but electrically illiterate brewer. Can't wait for my first starter attempt!
#1 Low
#2 High

 

[drewmedic23]

Just finished getting my 2 stir plates together and tested with water. I threw in some pepper so I could see how well it would suspend the yeast AND looks like it will work wonderfully! Just curious how to be sure not to drop the stir bar into the fermenter? I almost lost it down the drain when pouring out my pepper-water...




Well that answers that.... Pretty Slick!

Grab an extra magnet and stick it to the bottom of the flask before pouring...the stir bar wont move

 

[emjay]

Grab an extra magnet and stick it to the bottom of the flask before pouring...the stir bar wont move

That'll work but it can be awkward.

As we all know, stir plates are commercially manufactured and used in all sorts of actual laboratories. So obviously, there should also be a solution for this issue that's manufactured and used in actual laboratories. There is, and they're called retrievers:

They're basically just long sticks with a magnet at the end. The magnets are coated with an inert substance, usually Teflon, which allows it to remain food-grade. It doesn't take a genius to see that you can make one by using an extra stir bar for the magnetic tip, using something like small-diameter stainless steel pipe for the shaft. Or you can save yourself the trouble and just buy one... they're not that expensive. You just stick it in the flask and pull it out with the stir bar. It's easier than trying to hold the stir bar in place with a magnet on the outside while simultaneously pouring it out... it's the standard for a reason.

That being said... I don't have any problem at all keeping the stir bar in the flask while completely pouring it out. The only time it will end up in the fermentor is if I forget the bar is in there, in which case no magnet or retriever would be of any help anyways.

 

[thadius856]

A little thread necro to recommend a different type of product. That lab-grade retriever sure is cool, but probably pricy. Automotive shops have been using telescoping poles with magnets on them for years.

Here's one for $5 at Harbor Freight before coupons. I think I'll be picking one up soon.

 

[emjay]

A little thread necro to recommend a different type of product. That lab-grade retriever sure is cool, but probably pricy. Automotive shops have been using telescoping poles with magnets on them for years.

Here's one for $5 at Harbor Freight before coupons. I think I'll be picking one up soon.

You didn't actually include a link, but that could be a good thing as I doubt an automotive retrieve has a food-grade coating, and magnets themselves are not considered food-grade.

 

[thadius856]

Yup. Not food grade. Stay away from it if you're the type that can't trust a cooler mash tun because it contains plastic.

If you're that worried about piece of non-food-grade steel that touches your beer for at most 5 seconds, consider this: touching a wrench, door knob, or car key, then making hand-to-mouth contact (eating a sandwich, biting a fingernail) without washing your hands first will give you a larger dose of nastier chemicals and we do it constantly.

Unless you're auto-immune compromised, it's not going to harm you. And really, if you're going to go all-out, you'd probably be better off having your stir bar tested for residual lead from the Chinese factory that made it.

 

[mracko]

Don't want to start up and old thread, but I may have some useful information. I have been looking into getting a magnetic stirrer and in most of my searches all I could find were stirrers from ~$90 to $200...not gonna happen. In one of my searches I came across: the Bell Brewery stirrer. I was going to go with the DIY stirrer. I really like the design, but then I added up the cost. For $40, the Bell Brewery stirrer isn't much more than building your own. Granted you don't get the satisfaction of a DIY project and I don't know what, if any, shipping costs are, but it is another option.

 

[pbnj]

I figured one way to show my appreciation for all the great reads here is to post something that might encourage someone else to take a shot at building one of these.

I used the 120mm fan from Amazon, but I might use the 80mm for my next one.

This couldn't have been easier--all told this cost me around $30 but I had to acquire everything from scratch. Made my first starter for a batch of saison over the weekend. If you're on the fence just do it.

A couple of photos:

 

[thadius856]

Intense vortex. I'm amazed it has that much power as the 120mm fans are typically lower speed and torque, but I've seen it suck vortexes in 5L flasks filled to the 5.5L mark to the point that air bubbles hit the stir bar.

 

[JohnnyO]

Just ordered the 80mm fan and some stir bars. Excited to finally build a stir plate. I harvested magents from a laptop almost two years ago now.

At this rate, I might have this project done by 2020.

 

[lcrai321]

pbnj-
i'm attempting a DIY with a gallon glass wine jug like i see in your picture. With the bottom of the jug beveled, I was hoping you could tell me how you are keeping the stir bar centered. once i get it there, it is flying off. different type of stir bar?

 

[tenthletter]

Thanks to this thread I ordered the 80 mm fan. I was not sure what to use for a case, so I used the Amazon box it shipped in. I still have to dial in the height of the fan, but looks like it will get me by until I get a more suitable enclosure.