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Home Brew Forums > Home Brewing Beer > DIY Projects > Why does my stir magnet fly to the side of the flask?
 
 
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Old 02-28-2012, 06:24 PM   #1
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Default Why does my stir magnet fly to the side of the flask?

I built a stir plate with the magnet of a hard drive like so many. I used a pot and everything I saw in a couple of videos and threads. As soon as I turn on the fan the bar flies to the side of a 2000 ml beaker. Any Ideas why? Thanks.

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Old 02-28-2012, 06:31 PM   #2
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I built a stir plate with the magnet of a hard drive like so many. I used a pot and everything I saw in a couple of videos and threads. As soon as I turn on the fan the bar flies to the side of a 2000 ml beaker. Any Ideas why? Thanks.
There are a few reasons this can happen. Normally it's because the bottom of the container isn't flat which shouldn't be the case with your beaker. You can also try using a smaller stir bar. From my experience, larger bars throw a lot more easily than smaller ones.

Also, the speed should not be going full bore. I'd set it just fast enough so that the yeast is suspended. Certain yeasts will begin to clump after some time, especially with larger starters, so you may need to speed it up if you see this happening.

-TK
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Old 02-28-2012, 06:33 PM   #3
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magnet and stir rod are deflecting each other?

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Old 02-28-2012, 06:34 PM   #4
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How well does it work if you eliminate the beaker and just place the stir bar on the plate? My initial guess is that the plate material is too thick or you've got too much space between the HD magnets and the pot (plate surface). In either case, a weak magnetic field acting on the stir bar. Assuming you're not just cranking up the fan full bore of course.

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Old 02-28-2012, 06:34 PM   #5
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Another problem may be that you don't have the magnets' polarity correct on the fan. If you have both of them oriented the same it will throw the bar every time, I learned this the hard way.

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Old 02-28-2012, 06:39 PM   #6
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My initial guess is that the plate material is too thick or you've got too much space between the HD magnets and the pot (plate surface).
That was the problem with mine. I adjusted it about 1/16" and now there is no spin off. It doesn't take much.
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Old 02-28-2012, 06:47 PM   #7
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I have also had the space between the magnets not enough. I have to use two pieces of cardboard on top of the stir plate to make it work well. Getting stir plates to work correctly takes a lot of tinkering.

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Old 02-28-2012, 07:03 PM   #8
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so I've made a few stir plates now, all with HD magnets, and I can't get them to work well when the I leave the curved HD magnet in one piece. I have to break them in half, which allows me to line them up straighter. I think the curved shape makes it difficult to get the stir bar to line up with the center of the fan.

Here's what I do. Break the magnet in half to make two, equal sized pieces (if the magnets are smaller sized ones, then break two of them and keep the big ends of each break). Use your stir bar to check the polarity of the magnets and line the magnets up under the stir bar so that each end is being pulled down by the respective magnet. Now, you should have two pieces of magnet lined up together and stuck to the stir bar. Then place them all on the center of your fan--the magnets should stick to the fan and, with a little help from spare fingers, you should be able to remove the stirbar and keep the magnets stuck to the fan. Test it out and make adjustments as necessary. When things are right you should be able to start the fan full-bore without throwing the bar. Once you get it right, glue down the magnets with some super glue. I drop super glue around the edges, so I don't have to pick up and move the magnets, which might make me lose the magic spot.

Hopefully, this makes sense--it does take some tinkering. Good luck!

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Old 02-28-2012, 07:10 PM   #9
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Tagged for future reference -- desperately need to adjust my stir bar plate as I'm constantly have to fool with it to get it work properly.

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Old 02-28-2012, 07:38 PM   #10
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Ok, Yes the bar jumps right where it should before I start. As soon as it starts it throws the bar. I will try some of the suggestions here. Thanks for the quick help and reply.

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