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General Category => Yeast and Fermentation => Topic started by: jgourd on February 19, 2010, 08:17:46 PM

Title: stir plate vortex
Post by: jgourd on February 19, 2010, 08:17:46 PM
First homemade stir plate in a cigar box.  Cost: $5 (the 1" stir bar).  Computer PSU fan with hard drive magnet.  Powered by another computer PSU converted to a benchtop PSU.  Current output voltage to fan is 7V (10V is too fast; the stir bar spins off).  Does this look like enough vortex for a 2L sample (in a 1gal. jug)?

(http://www.artificial-stupidity.com:4352/beer/vortex2L_1.jpg)

(http://www.artificial-stupidity.com:4352/beer/vortex2L_2.jpg)

And this vortex for a 1L sample in a 1L flask?

(http://www.artificial-stupidity.com:4352/beer/vortex1L.jpg)
Title: Re: stir plate vortex
Post by: Thirsty_Monk on February 19, 2010, 08:22:36 PM
Does this look like enough vortex for a 2L sample (in a 1gal. jug)?

Yes you do not need to have big vortex. All you want is small dimple (1" or so) in the top of liquid.
Title: Re: stir plate vortex
Post by: eric on March 22, 2010, 09:04:20 AM
Do you need to use a food grade stir bar? Or will any magnet do?
Title: Re: stir plate vortex
Post by: dhacker on March 22, 2010, 11:15:51 AM
Do you need to use a food grade stir bar? Or will any magnet do?

Stir bars are designed to be nearly friction free devices. They are Teflon coated for a reason! The bars with a ring in the middle or the dumb bell variety providing the least friction. Doubtful you'd ever get just any dual pole bar magnet to turn. Plus, a raw ceramic magnet could shed and sanitizing heat for any other type of magnet could damage the magnetic field.

Bottom line . . Just spring for the right device!  ;)
Title: Re: stir plate vortex
Post by: jgourd on March 22, 2010, 12:45:15 PM
I use a 1" stir bar I bought for about $4.  It works great!  I tried a paper clip when testing and it didn't always work; I was worried.  In any event, once I tried the stir bar, all was fine.  I've never had a problem with mine, and I've made 10 starters with it so far.
Title: Re: stir plate vortex
Post by: a10t2 on March 22, 2010, 06:28:23 PM
What style stir bar are you using? The only thing holding me back from building a stir plate was that I'd have to get a big ol' flask, but if there's one that will stay centered on a convex bottom...
Title: Re: stir plate vortex
Post by: dhacker on March 22, 2010, 07:03:30 PM
What style stir bar are you using? The only thing holding me back from building a stir plate was that I'd have to get a big ol' flask, but if there's one that will stay centered on a convex bottom...

These dumbbells stay centered perfectly in a gallon jug. No need for a 4 or 5 liter flask. Problem is it's $85 for 10 of them. A group of 5 brewers went in a couple of months ago to split up a 10 pack purchase of two each. Perhaps others here would want to do the same. 

 http://www.stirbars.com/magnetic-stirbar-prices.htm#barbell
Title: Re: stir plate vortex
Post by: yugamrap on March 23, 2010, 02:09:29 AM
What style stir bar are you using? The only thing holding me back from building a stir plate was that I'd have to get a big ol' flask, but if there's one that will stay centered on a convex bottom...
I have a 2" bar with the ring in the middle.  It works fine in a cheapo 1-gallon Carlo Rossi wine jug with a convex bottom.  This pic is just a 1.75 L starter, but it works fine all the way up to a full gallon.

(http://i49.tinypic.com/2q2ejo0.jpg)
Title: Re: stir plate vortex
Post by: a10t2 on March 23, 2010, 03:07:59 AM
Awesome. I put together the LM317 circuit tonight, and got a set of 1"-2.5" stir bars on eBay. Now I just need to decide which hard drive to pull apart, and find/buy a box to put the thing in.
Title: Re: stir plate vortex
Post by: jgourd on March 23, 2010, 12:45:45 PM
What style stir bar are you using? The only thing holding me back from building a stir plate was that I'd have to get a big ol' flask, but if there's one that will stay centered on a convex bottom...

One like this one (http://www.northernbrewer.com/brewing/micro-stir-bar.html).
Title: Re: stir plate vortex
Post by: a10t2 on April 26, 2010, 05:39:16 AM
After trying and failing to get good results with a HDD magnet, I broke down and bought a pair of neodymium magnets that are roughly the size of watch batteries and rated for 4 lb of lift apiece. Works like a charm now.

The photo is with a 1" stir bar with ring, running at about 6 V.

(http://seanterrill.com/wp-content/uploads/2010/04/IMG_2325-288x384.jpg) (http://seanterrill.com/2010/04/26/build-a-better-stirplate/)
Title: Re: stir plate vortex
Post by: jgourd on April 26, 2010, 12:33:36 PM
After trying and failing to get good results with a HDD magnet, I broke down and bought a pair of neodymium magnets that are roughly the size of watch batteries and rated for 4 lb of lift apiece. Works like a charm now.

The photo is with a 1" stir bar with ring, running at about 6 V.

(http://seanterrill.com/wp-content/uploads/2010/04/IMG_2325-288x384.jpg) (http://seanterrill.com/2010/04/26/build-a-better-stirplate/)

Ha!  I love your container!  Looks good.
Title: Re: stir plate vortex
Post by: Thirsty_Monk on April 26, 2010, 05:04:29 PM
After trying and failing to get good results with a HDD magnet, I broke down and bought a pair of neodymium magnets that are roughly the size of watch batteries and rated for 4 lb of lift apiece. Works like a charm now.

The photo is with a 1" stir bar with ring, running at about 6 V.

(http://seanterrill.com/wp-content/uploads/2010/04/IMG_2325-288x384.jpg) (http://seanterrill.com/2010/04/26/build-a-better-stirplate/)

I also have questionable results with HD magnets.
It sort of works but not that well :)
Title: Re: stir plate vortex
Post by: a10t2 on April 27, 2010, 01:54:49 AM
Ha!  I love your container!  Looks good.

I actually had a moment of embarrassment about using a clear container because of the blue LEDs in the case fan (while I don't think I ever deliberately bought one, all three I had laying around had LEDs). But now I kind of think it looks cool, and spared me three extra solder points for a power indicator. ::)

Plus buying a new piece of Tupperware would have doubled the cost of the project.
Title: Re: stir plate vortex
Post by: roffenburger on April 28, 2010, 04:02:38 PM
I was surprised to find neodymium magnets at michaels craft store for only about a dollar each. I bought 2 two-packs and use two (stacked) on each side of the fan.

Edit: I guess it was a 4-pack for a a couple dollars. Here is the link.

http://www.michaels.com/art/online/displayProductPage?productNum=gc0468