Does your stirbar sing? Video!

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cannman

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Just finished my DIY stir plate and in my testing with water and a 2000ml erlenmeyer flask... and it sounds like my stirbar is banging slightly on the bottom of the glass creating a vibration that changes as the funnel inside the flask grows and shrinks... is this normal? or am I not level??? Does it matter?

Video of my stirbar song here

Thanks.

2014-09-23 19.03.14.jpg
 
yes, that makes complete sense. the stirbar is constantly bouncing off the glass bottom of the flask creating the high pitched frequency! all is well...enjoy the music of yeast multiplying!
 
Well, I guess I feel a bit better. My worst fear is the stirbar cracking my 2000ml flask right before brewday....
 
While I'll occasionally have a starter that's a little noisy, none have been that noisy. I find even the "little noisy" ones to get really annoying after a short time.

What I find generally solves the problem is one of two things:
1. Different length stirbar, or just a different same-length stirbar
2. Increased distance between stirbar and magnet

Both are easy to test. #1 is obvious, try a different stirbar. #2 is also easy to test by using layers of cardboard under the flask until you find a distance that doesn't have quite the magnetic attraction.
 
The bottom of my flask has a bump which makes my stirbar rattle loudly when I have it spinning. Thats what I get for not looking at it closely when I bought it. I can often make it silent by rotating my flask so that the bar spins free of the bump but it can be a PITA to find the sweet spot. I may just end up getting another flask and hope that the next one has a flat bottom.
 

While I'll occasionally have a starter that's a little noisy, none have been that noisy. I find even the "little noisy" ones to get really annoying after a short time.

What I find generally solves the problem is one of two things:
1. Different length stirbar, or just a different same-length stirbar
2. Increased distance between stirbar and magnet

Both are easy to test. #1 is obvious, try a different stirbar. #2 is also easy to test by using layers of cardboard under the flask until you find a distance that doesn't have quite the magnetic attraction.

Very cool vid passedpawn. Your stir bar is longer than the one I'm using in the 2000ml flask, so perhaps that's what I need to do, is either a)buy a longer bar or b)higher quality stir bar?

Time to go shopping!

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stpug, you really think INCREASING the distance of the magnets will work? i thought it was not enough magnetic pull that was causing the bar to lift and separate :)confused:).

When the new bars arrive next week, I'll post an update.

Thanks everyone.
 
Very cool vid passedpawn. Your stir bar is longer than the one I'm using in the 2000ml flask, so perhaps that's what I need to do, is either a)buy a longer bar or b)higher quality stir bar?

Time to go shopping!

#################

stpug, you really think INCREASING the distance of the magnets will work? i thought it was not enough magnetic pull that was causing the bar to lift and separate :)confused:).

When the new bars arrive next week, I'll post an update.

Thanks everyone.

I went back to a shorter stir bar. That long one works great until a lot of yeast has grown in there. Then, it gets thrown a lot. The shorter ones work just as well at moving the beer, and they will run longer without getting thrown.

There are stir bars with a little ridge in the middle, and ones shaped like a football. I think they both keep the arms of the bar off the bottom. You might give one of those a shot. It's probably easier to just get another flask though.
 
If I have mine running at a higher speed, when it pulls the vortex to the bottom it will make a little noise.
It can also make some stir bar noise if it's not centered. after you start your stir plate, set it so the vortex doesn't go all the way to the bottom, you only need a slight vortex. Then, slowly move the flask around and see if you can find a sweet spot.

I don't think your bar length has any thing to do with it. move the flask around on the stir plate and see if it changes things.
 
stpug, you really think INCREASING the distance of the magnets will work? i thought it was not enough magnetic pull that was causing the bar to lift and separate :)confused:).

It's counter-intuitive for sure, but it has worked for me. I now keep three "sheets" of cardboard with my stirplate in case I run into a noisy starter in which case I'll start adding them one by one until I find a distance that works for my ears. Like I said, it's easy to try :mug:
 
The bottom of my flask has a bump which makes my stirbar rattle loudly when I have it spinning. Thats what I get for not looking at it closely when I bought it. I can often make it silent by rotating my flask so that the bar spins free of the bump but it can be a PITA to find the sweet spot. I may just end up getting another flask and hope that the next one has a flat bottom.

Yep that's exactly what I have too. I think the idea is that it has less friction with the bottom of the erlynmeyer and can spin easier that way.


I quite like the eerie sound.


Adam
 
When building and testing mine, ( with water, have not made a starter yet), it was noisy, even the ones with the rib in the middle.
I slipped a small o-ring over each end, equidistant from each end, and now it rides on the rubber.

I used DME flavored o-rings..............:D
 
AAAAH the sweet sound of yeasty-beasties, mine has the same sound with a 3/4", 1", or 1.5" bar. All of mine have the ring in the middle of the bar. Will have to try one of the suggestions of layers of cardboard or the o-rings to see if that makes a difference to mine. Thanks to all for the suggestions.
David.:)
 
As a sound engineer I just wanted to answer the OP's question.

The reason the sound changes is that when the vortex alters so does the accoustics in your flask. The "swooshing/sweeping" sound is relative to how big the vortex is. At any given time one frequency will be louder than others. When the vortex changes so will the frequency which sounds the loudest. Since the vortex changes continiously a different frequency will be the loudest, which will give this swooshing or sweeping sound. The speed of this effect is relative to how fast the vortex changes in size and form. It's like a natural phaser effect. If you know a guitar player maybe he has a phaser-pedal.
 
The o ring worked! It's now very much a soft hum, pleasant like.

The only issue I've found with the o rings is that it raises the stir bar off the surface of the glass just enough to reduce the efficiency of the spin and the quality of the vortex. Before, at max speed, I could get the vortex to reach the stir bar and toss it. Now at max speed, the vortex reaches 3/4 of the way down to the surface at best. I'm sure I don't need such a bad-ass vortex but I think it's important to note just incase we have some small rpm devices out there.
 
Just finished my DIY stir plate and in my testing with water and a 2000ml erlenmeyer flask... and it sounds like my stirbar is banging slightly on the bottom of the glass creating a vibration that changes as the funnel inside the flask grows and shrinks... is this normal? or am I not level??? Does it matter?

Video of my stirbar song here

Thanks.

That's normal. The bottom of your flask is not flat and the stir bar is bouncing between the high spots and low spots.
 
Mine has the silence. It used to be loud enough to hear clear across the house. Now I sanitize a short length of vinyl tubing and slip it over the stir-bar. Ninja quiet.
 
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