Author Topic: Stir Plate Question  (Read 4432 times)

Offline GoodBeer

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Stir Plate Question
« on: December 29, 2012, 05:24:15 PM »
OK so I built myself a stir plate and bought a little stir bar.  But I am having a dickens of a time getting it to spin.  When I tested it with water it seemed to little tough kept throwing the stir bar to the side but I could see the stir bar.  Once I made my starter and could not see the stir bar without lifting the flask man did I have a hard time.  Maybe my stir plate magnet is spinning a little to fast?  I changed to a 6 volt power source and that seemed to help some, I like look of the whirlpool better but still hard to get started.  It seemed that if I titled the flask just a bit seemed to help, but I may have just finely got lucky. LOL  I don't know but is working now.

So what's the trick?

Cheers  Tim

Offline tom_hampton

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Re: Stir Plate Question
« Reply #1 on: December 29, 2012, 05:52:26 PM »
Tim-

Did you install a speed control in your stir plate?  A simple potentiometer (250 ohms or so) will do the trick.  Add it between the (+) terminal of the battery and the fan.

You generally need to start the stir bar on slow and then increase the speed just until the water surface dimples.  You don't need a wild vortex. 

Also, stir bar size can have an impact on how it gets thrown.  I have better luck with my larger bar.  I also have better luck with pivot ring type bars, vs. straight bars. 

http://www.stirbars.com/list.php?category=Stir%20Bars&subCat=Pivot%20Ring%20-%20PTFE&sessionID=dad2c05b87e8e6b8846de3716f2fee3f

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Offline GoodBeer

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Re: Stir Plate Question
« Reply #2 on: December 29, 2012, 09:41:05 PM »
Thanks for the reply,  The stir bar with the pivot ring looks like it might be a good idea but kind of expensive.  I do have a potentiometer installed, it was one I had on the shelf and I don't remember the resistance value.  I had to add a resister inline to slow it down but it was plane to see today that it was to fast on the slowest setting.

It worked good or at least looked good with water and 1500 mL of water but with only 900 mL of wort I had to much of a vortex going on.  When I went to the 6v power supply that helped a lot.  My stir bar is the little 1" bar that I got from More Beer.

Here is a picture of my starter and my messy work bench.

Cheers
« Last Edit: December 29, 2012, 10:01:50 PM by GoodBeer »

Offline tom_hampton

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Re: Stir Plate Question
« Reply #3 on: December 30, 2012, 12:34:56 AM »
Yikes! I didn't look at the prices. Just an example. Try these:

http://www.cynmar.com/SearchByKeyword?word=Stir%20bar

$5 or so.

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Next Up: PtE(1.1), Belgian Dubbel?

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Offline mbg-bs

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Re: Stir Plate Question
« Reply #4 on: December 30, 2012, 01:52:48 PM »
Yikes! I didn't look at the prices. Just an example. Try these:

http://www.cynmar.com/SearchByKeyword?word=Stir%20bar

$5 or so.

The prices in  the link I think are for 10 pieces.

Mike

Offline Humble Brewer

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Re: Stir Plate Question
« Reply #5 on: January 02, 2013, 10:28:38 AM »
Try changing the distance between the stir plate and the magnet.  There is a youtube video out there where I guy spins a stir bar in a bowl.  He used cardboard spacers to raise the bowl further and further off the stirplate.  When the bowl was too close it threw the magent, when he backed it off a bit it spun great, when he backed off further it couldn't spin.  It was a video about building your own stirplate mount and he was illustrating that the distance between the plate and the magent was important.  Maybe its part of your issue.
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Offline GoodBeer

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Re: Stir Plate Question
« Reply #6 on: January 02, 2013, 09:07:48 PM »
That maybe, I was thinking maybe I have to much of a spacer from my magnet to the base but maybe it's the other way like you mentioned.  I did notice that if I tilted my flask a little it seemed to start a little better.  Anyway time for some more testing.

Thanks for the input.

Cheers