The STL file is available for free if you have access to a 3D printer. See the full write up for that file.
The magnet mounting aid is also available for purchase via Shapeways. Check that out – Here
I purchased two of those myself. At some point I went back to Shapeways and added several to my cart to see if shipping is flat rate (it does appear to be flat rate). Anyway, I didn’t check out because I already have two on the way. Within a day or two, I received this email offering me 10% off.
YMMV – Your mileage may vary on this one. I’m not certain you’ll get the 10% off offer. If you do want to try this, I would sign up for a Shapeways account first and then add the magnet mounting thingy to your cart.
I had several people contact me about purchasing one of these or otherwise making them available publicly. Note that I’m already providing the STL file for free to those of you with access to a 3D printer. See the full write up for that file.
A serendipitous reading of an article about a legal controversy regarding a 3D printed “Left Shark” led me to 3D vendor… shapeways. As always… thanks go to “Left Shark”
Shapeways, prints and delivers 3D creations. Whammo.
The HBF Magnet Mounting Thingy is now available on Shapeways. It’s available in white and black. White material cost is $1 lower. I ordered a copy and will see how it turns out.
You probably know that since getting my XYZPrinting Da Vinci 3D Printer I’ve been on a quest to come up with a 3D printed stir plate design. Note that these projects are certainly already out there (including designs specifically for mounting magnets on fans), but these designs are typically – “here’s what I put together with stuff around my house”. That’s great, but it’s hard to nail down what works with what. My goal was to use use known part numbers and a set procedure to come up with an effective design.
Well… I’m not done yet. I am working with Brandon, a very talented Engineer (and HBF Reader!), on the larger project.
But… I can tell you that I’ve come up with a pretty amazing magnet mount, magnet, stir bar and fan combo.
First, the fan…
I sourced this specific cooling fan for the project. I like this model because… 1. It’s a good size (4.7″ square), 2. Is already wired for AC and, 3. Includes a variable speed function.
A close up of the finished piece. I tried several designs. Magnet alignment is an important part of stir plate design. Uneven or mis-spaced magnets mean easily thrown stir bars. That’s not good. I figured that out on my own, trying to place magnets isn’t fun. They don’t want to cooperate. This piece helps mount magnets and do so easily. I decided on the hole in the middle because the fan I purchased has a dimple in the exact center. The magnets are centered and held in place here and alignment on the fan is as easy as lining up the dot in the center of the circle. Note that the two spots for magnets are designed to work with these specific 1/2″ by 1/8″ neodymium magnets.
Although I have Solidworks, I’m still new to 3D designing. I designed this piece in the free version of SketchUp.
Magnets and Magnet Alignment…
About the magnets… I tried three different sizes of magnets. I was about to go with a smaller size that worked okay, but decided I wasn’t happy with their performance. Yes they did work on a moderately sized starter. But, I just wanted more holding power. I didn’t want to have to struggle with thrown stir bars. I decided on these 1/2″ by 1/8″ Neodymimum Rare Earth Magnets. If any magic exists in this design… certainly a good bit of it comes from these magnets. The alignment and fan are both huge parts to the puzzle. But the power of these magnets is central.
Note: Be careful with these magnets. Read the warning on the box and always follow manufacturer’s instructions. Take special care when using these around each other and around metal in general.
You want to line your magnets up so that the polarity is in agreement. I’ve done this a few times now, not always successfully I might add. Now, I start by putting the magnet on a stir bar. Get it placed so everything is nice and happy. I put this on Ritebrew’s Tasting Paddle. I’m working on my deep freeze here and the magnet would prefer to make friends with the deep freeze vs the stir bar. The tasting paddle helps. Note that here and throughout these tests, I’m using this 6 x 25 mm Stir Bar.
Now take the stir bar and magnet combo and place it into the holder.
When you’re comfortable with positioning, glue the first magnet down. I’ve been using Gorilla’s Super Glue. Wait for that first magnet to set up. It’s worth noting that the individual magnet holders are tight enough (at least for me) for this specific magnet to hold them, at least temporarily, in place while you play around with positioning.
Next, I take the other magnet and move it close to where it needs to go. See how the stir bar has moved to the side? That’s because the polarity was incorrect. The stir bar was repelled. Rotate the magnet around until the stir bar is attracted and you’ve found the correct position.
Here, I’ve found the correct orientation for both magnets and the stir bar is attaching perfectly. Glue the second magnet into place and wait for it to set up.
Mounting the Mounting-Thingy on the fan…
Notice the dimple in the middle of this fan. Disregard the scuffing on this. I’ve tried a bunch of things with this fan. The fact that it’s still working well after the paces I’ve put it through is a testament to it’s hardiness.
Add some glue and line up the dimple in the center section and whammo you’re lined up and installed.
Installed and aligned correctly using the center circle as a guide
With a temporary top installed. Note that the actual enclosure for this stir plate is a work in progress. This is a temporary platform and will not be the final design.
With some stir plates, it’s necessary to move the flask around a bit (with the stir bar in it) to train up the stir bar on the stir plates magnets. Not necessary with this design. Drop the stir bar in and the two immediately find each other.
Here is a test of 1.6 Liters of water in a 2 Liter Flask
Here’s another picture of of the same test. This is vigorous and violent. It’s worth noting that this magnet/spacing/stir bar combination doesn’t throw stir bars (at least in my tests) even at top speed.
Here’s a video of the 1.6 Liter Test
This setup is entirely capable of holding a 5 liter Erlenemeyer and stirring large starters. Here is a beautiful vortex in a 4 Liter flask of water.
A video of the 4L Test
How about a full 5 Liter starter? Yup!
I’m very happy with these results. Look for a complete design in the near future. I also plan to develop a non-3D version at some point. The fundamentals of this hold true however they are put together… the fan, magnets and magnet positions are winners. Want to work with me on the traditional design? Send me an email.