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Old 07-25-2013, 03:06 AM   #1
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Default Do I need a new stir plate?

I made my own stir plate a while ago and it works somewhat well with 1 L starters. It puts a decent dimple on the top, but no major vortex like I see others getting. I know that the dimple is all you need though.

Anyways...

I'm looking to start doing huge starters so that I can pitch half in the beer and save the other half as fresh yeast to use at a later time. I just bought a 5 L Erlenmeyer flask. Will my stirplate still be fine since as long as the surface is spinning, it is still working. I will probably do 4.5 L starters. Is that too much liquid to the point that it won't work? I can test it in a couple days when I get the flask in the mail, but if I NEED to beef up my stir plate, I might as well do it now. Thanks everyone.

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Old 07-25-2013, 03:15 AM   #2
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What are the specs on your power supply? Maybe you just need more juice to get a faster spin.

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Old 07-25-2013, 04:34 PM   #3
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Your stir plate is probably just fine.

The vortex is purely bling. Dimple is all you need.

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Old 07-25-2013, 09:42 PM   #4
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I honestly couldn't tell you power supply info. I'll check when I get home. Old cell phone charger. Is there a suggested type of power supply that works well?

I should be receiving the flask either tomorrow or the next day. I'll test it out when I get it and fill you in on some results.

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Old 07-25-2013, 09:48 PM   #5
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Quote:
Originally Posted by MedicMang View Post
I honestly couldn't tell you power supply info. I'll check when I get home. Old cell phone charger. Is the power supply what makes the difference in speed then?

I should be receiving the flask either tomorrow or the next day. I'll test it out when I get it and fill you in on some results.
When I made my stirplate I had several of the block power supplies from old answering machines, etc. I tried 3 with different amperages? I think? until I found the one that worked the best.

A stirring (slight dimple on the surface) is all that you need.
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Old 07-25-2013, 09:56 PM   #6
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If you made your stirplate with a DC PC fan like most of us did then you can run that fan anywhere from 5V (quite a few won't start this low) all the way up to 12V. At 12V it will be spinning as fast as it can. Check your cell phone charger to see what it puts out. Also keep in mind that all fans are not created equal. I have Noctua fans that run at 900RPM at 12V and I have Corsair SP120 HPs that run at 2350RPM at 12V. I used a Scythe SFlex fan to make mine because the FDB bearing will run for a very long time and I didn't want to rebuild the thing.

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Old 07-27-2013, 08:50 PM   #7
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Well poo. I got my MASSIVE 5 L flask. Have I mentioned its MASSIVE? Well it is.

I think I am going to need to rebuild. The stir bar keeps getting thrown. Is there a difference in rare earth magnets in their strength? Any suggestions of where I can find some really strong ones? Is there such a thing as "too strong"?

Also while I have it open, I may just replace the power cord. I looked at my present one and it is only 5v. Ill find a stronger one and replace that too.

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Old 07-28-2013, 04:13 AM   #8
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Yes, there are big differences in magnets. Most newer hard drives have much thinner and weaker magnets. I recommend K&J Magnetics, fast shipping and good prices. You don't have to use monster magnets though. The ones I used for my stir plate were so strong I had to put washers on top of them to dull the field a bit. They were pulling so strongly on my stir bar that it was making the fan slow down quite a lot from so much load on the bearing. There is definitely a balance there, but you can fine tune that with distance from magnets to flask. I recommend you go with a 12V power source and then use a fan controller (rheostat) to control the speed of your fan. You can really dial it in at that point no matter the volume of liquid in your flask.

I don't think your massive 5L flask will be a problem. I use a 2L and even with it full I can get a vortex that goes all the way to the stir bar, 1/2" wide column of nothing at the stir bar, it looks like a tornado and sounds like a blender. This is obviously overkill but I don't think it would have any problem getting a dimple on a 5L flask with 5L in it. My point is that it is definitely possible to do on the cheap with a computer fan and some hard drive magnets. I think 12 volts would probably solve your speed problem, but I'm not sure about your magnets. I would replace the power supply first. If you have a power supply for an old wireless router that will do the job very nicely. They are almost always 12V.

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Old 07-28-2013, 04:21 AM   #9
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Wow. Thank you man. Very informative. Will definitely be looking into all of that. I do have a rheostat on there already so this will be quite an easy operation.

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Old 11-13-2013, 07:12 AM   #10
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So check this out guys. I went to the thrift store today and found a 12v power supply and this sweet wooden box for $1 a piece. Seems to have fixed my problem. I used the parts from my first one to remake it. Ordered a new stir bar with the ring in the middle, hoping that it will quiet it up a bit. The magnet seems slightly off and is making a lot of noise on the glass. Thank you to everyone who helped. Oh and that's my new 5L flask that I am using to test it.

img_0715.jpg   img_0714.jpg  
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