How powerful is too powerful when building stir plate?

[autonomist3k]

I way over engineered the stir plate that I just built, at its lowest setting with 4000ml in a 5000 flask I get a vortex that goes half way to the stir bar, I can only imagine how crazy it would be with only 2000ml or less.

So can a starter be stirred too much?
I know that you only need a small divet, but if it looks like a tornado in your flask will it hurt anything?

 

[jammin]

Pulling a vortex in water is quite a bit easier than through wort with active yeast. You might find it will be just right.

 

[dude_brewery]

Having excessive vortex can provide detrimental stresses to your yeast. I'm not sure that a stir plate vortex can produce the shear stresses required to rupture yeast cell walls (I read an article a while back saying that it was unlikely to reach these values with a stir plate set-up). But, there is a point where the force causes damage to the yeast. (http://www.mbaa.com/districts/MidSo...11_06_11Centrifuges_in_Brewing_PAUL_CHLUP.pdf)

After initial aeration, the smaller the dimple the better. Just enough to keep the yeast in suspension and knock CO2 out of the liquid. But, my opinion is that if the vortex goes somewhere less than to the bottom of your flask, your yeast should be fine.

 

[autonomist3k]

Having excessive vortex can provide detrimental stresses to your yeast. I'm not sure that a stir plate vortex can produce the shear stresses required to rupture yeast cell walls (I read an article a while back saying that it was unlikely to reach these values with a stir plate set-up). But, there is a point where the force causes damage to the yeast. (http://www.mbaa.com/districts/MidSo...11_06_11Centrifuges_in_Brewing_PAUL_CHLUP.pdf)

After initial aeration, the smaller the dimple the better. Just enough to keep the yeast in suspension and knock CO2 out of the liquid. But, my opinion is that if the vortex goes somewhere less than to the bottom of your flask, your yeast should be fine.

Interesting article, I think I'm going to get a smaller stir bar and see what happens.
At this rate, it's way too powerful haha.

 

[AkBrew907]

Pulling a vortex in water is quite a bit easier than through wort with active yeast. You might find it will be just right.

This. I was able to get one hell of a vortex with my setup using a mason jar and water



But once it's a flask full of wort I couldn't get the same vortex. As long as it's moving things around and keeping it mixed up you are good to go.

 

[autonomist3k]

I realize that with water it will stir much easier, but I have a huge vortex with 4000ml, imagine a 2000ml starter.
I ordered another stir bar to see what happens.

The first picture is at it's lowest speed with a 2" stir bar.

The second is it's highest speed with the 2" stir bar LOL!!!!!

 

[AkBrew907]

This is the stir bar I use. Smaller one might help you out View attachment ImageUploadedByHome Brew1454527521.133344.jpg

 

[autonomist3k]

Dammit, I bought a 1.5" bar for about $14 last night.
Although if that one is too big still I'll get this one.
Thanks for the suggestion.

 

[Hobo]

I'm able to get very good speed control using this circuit taken from the following source, I agree a larger stir-bar may help slow it down:
http://stirstarters.com/instructions.html

 

[Gavin C]

(http://www.mbaa.com/districts/MidSo...11_06_11Centrifuges_in_Brewing_PAUL_CHLUP.pdf)

.

The paper you linked does not relate to the forces and scales in a stir plate. It discusses the effects of centrifuges on yeast when separating the cells from the beer. It is simply not applicable to the homebrew scale. Also much of the data is equivocal in answering the studies' proposed objectives. I don't see any statistical analysis of the data that supports the conclusions the paper makes. That being said it is not applicable to the question of a stirplate.

This. I was able to get one hell of a vortex with my setup using a mason jar and water
View attachment 335013



But once it's a flask full of wort I couldn't get the same vortex. As long as it's moving things around and keeping it mixed up you are good to go.
View attachment 335014

How can you compare the two. One is clear water the other is an opaque liquid (cloudy starter beer) covered with foam. I see no difference in the vortex between water and wort. The difference in viscosity is simply not significant enough to make any difference.

The vortex is identical. The visualization of it is very different.


In answer to the OP. The stir speed is too much if your bar is getting thrown. There is good data to support rapid spinning of a yeast starter. The more the better with the simple stirplates we use. (ie not centrifuges to separate yeast from beer)

Braukaiser's summary of data in support of rapidly stirring a starter.

 

[autonomist3k]

That was a cool experiment, makes me feel better about the stir plate I built.
I'm curious about his method of cell counting though, I wonder if he was just eyeing it or if he was using lab equipment of some sort.

 

[autonomist3k]

Update:
I bought a 1.5" stir bar and set up some magnets for it and it's much more moderately powered than the 2".
Here it is on its lowest setting.
View attachment ImageUploadedByHome Brew1454995365.530721.jpg

I set up some magnets for my 1" stir bar also, here it is in my 2000ml flask on the lowest setting.
View attachment ImageUploadedByHome Brew1454995462.536064.jpg

After this I don't see any reason to have a 2" stir bar unless you're doing huge starters in a 10,000ml flask or something.

 

[bionut]

That's the speed regulator scheme that i used: http://sash.bgplus.com/lm_317/tutorial-full.html
It works like a charm.

 

[autonomist3k]

That's the speed regulator scheme that i used: http://sash.bgplus.com/lm_317/tutorial-full.html
It works like a charm.

That's more wiring than I wanted to do, I just got one of those variable voltage dc plugs, I just reposition the switch between 12 and 3 volts, works great.

 

[bionut]

I bet it works if you want more control you can buy this

 

[autonomist3k]

That seems pretty cool, have you used it for a stir plate with success?

 

[bionut]

Not really, i soldered some components on a pre-drilled circuit board before i found this on ebay. If i will ever need more than one stri plate i will order this from ebay.
I don't see any reason for it to not work, PWM is preferd, but is's harder to solder yourself without some electronic knowledge (wich i don't have).
BTW, that's the first result on ebay, if you search you can find some even cheaper.

 

[autonomist3k]

If I ever decide to update mine, or make a stir plate for someone else I think I'll go that route, I can imagine that being a pretty nice addition.

 

[AkBrew907]

No need to do any fancy wiring. Just get a thermaltake fan off amazon with the speed controller. Runs off USB and the dial is already included
View attachment ImageUploadedByHome Brew1455076066.470692.jpgView attachment ImageUploadedByHome Brew1455076079.321035.jpg

 

[Bigdp228]

Akbrew, I love that clear box, where did you get it?

 

[Stillraining]

Is this the one your talking about...if so how do you go about powering it? I see you have some small power device on the table.

 

[jammin]

How can you compare the two. One is clear water the other is an opaque liquid (cloudy starter beer) covered with foam. I see no difference in the vortex between water and wort. The difference in viscosity is simply not significant enough to make any difference.

The vortex is identical. The visualization of it is very different.

In every starter I've made its always been true for me (that the vortex isn't as strong compared to straight water). It's especially true when the yeast is as peak activity and lots of C02 is being forced out of suspension.

I'm shocked you haven't experienced these results as well.

 

[AZCoolerBrewer]

Here's mine. I still need to put the "science" in it.

 

[AkBrew907]

Akbrew, I love that clear box, where did you get it?

Amazon.

Is this the one your talking about...if so how do you go about powering it? I see you have some small power device on the table.

Yup. It's USB so any cell phone charger that you can plug a cable into. I was just using a battery pack in that picture to try it out. Any universal USB wall charger will work though

 

[AkBrew907]

View attachment ImageUploadedByHome Brew1455439972.111219.jpgthis is the box