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Old 04-24-2013, 08:31 AM   #1
Majd
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Default My Stirplate does not work properly

I did build a new stirplate using a good quality potentiometer and a motor that is mounted on a metal plate that is mounted on 4 screws that are setting through the bottom of the box (see the picture). I mounted two earth magnets on a plastic disk that is mounted on the rotating axle. The distance between the two earth magnets is equal to the length of the stir bar that I’m using, 1”. Al spins fine with slight wobbling, but in all it spins fast and slow and it does fine without water. However, when I put water in the flask, the bar will spin fine at slow speeds but when I increase speed (slowly or fast) the bar spins out to the side of the flask. The best I could get is a start of a vortex. I even have put two earth magnets at each end which did help little bet but not good enough. Any thoughts?

Cheers

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Old 04-24-2013, 10:51 AM   #2
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do not use stir magnets with the hub in the middle. This allows it to wobble until it finally spins off to one side. If you have one of those magnets put a small o ring on each end and it will be fixed.

see my thread

http://www.homebrewtalk.com/f51/stir...magnet-404859/

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Old 04-24-2013, 11:08 AM   #3
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Have you tried playing with the position of your flask relative to the magnets? Mine has to be off-center or the bar will spin off...something to do with the slight dome in the bottom of the flask.

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Old 04-24-2013, 01:53 PM   #4
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I had the same problem with similar sized rare earth magnets. So I tore open a hard drive and put the hard drive magnet on top of the existing magnets and problem solved. It has not thrown the rod one time since I did this. Attachment is easy because the origional magnets hold the hard drive magnet in place.

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Old 04-24-2013, 09:43 PM   #5
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Quite genius fix, I like it particularly because I have two of those computer disk magnets available. I just want to know how did you position those crescent shapes over the earth magnets? Do you have a picture or a diagram?

Thanks

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Old 04-25-2013, 01:54 AM   #6
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Quote:
Originally Posted by Majd
Quite genius fix, I like it particularly because I have two of those computer disk magnets available. I just want to know how did you position those crescent shapes over the earth magnets? Do you have a picture or a diagram?

Thanks
I don't have a picture right now. I can take one on Friday if you need one, But I don't think you will need it. The magnets naturally centered themselves on the rare earth magnets. I had to help them move around, because of the friction, but they sort of wanted to to rest in the correct position. Try it and if you need it I will post some pic's over the weekend.
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Old 04-25-2013, 04:37 AM   #7
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Quote:
Originally Posted by unclevername

I don't have a picture right now. I can take one on Friday if you need one, But I don't think you will need it. The magnets naturally centered themselves on the rare earth magnets. I had to help them move around, because of the friction, but they sort of wanted to to rest in the correct position. Try it and if you need it I will post some pic's over the weekend.
Thanks a lot. I will try it and let you know.
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Old 04-25-2013, 05:01 AM   #8
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I have a, "cow magnet". Once my wort is cooled and ready for the stir plate I pitch the yest. I then tip the flask so the stir bar that has been in the flask for before the boil drops. At that point I use my external cow magnet to grab that stir bar and I can now see clearly see it.

I then remove my cow magnet and lower & move the flask over my stir plates magnet. I can hear the stir plate magnet, "grab" the stir bar and I position the flask and bar over the center of the stir plate. I then slowly turn the plate on and I get the result I need.

Play with it.

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Old 04-25-2013, 05:09 AM   #9
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Simple solution. Put an o-ring on the stir bar in the center. I had a lot of issues with my stir plate throwing the bar until I out on an o-ring. Try it. I'll bet it fixes your issue.

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