Stir Bar Silencer

Occasionally, the stir bar I use on my stirplate will rattle slightly, especially at higher speeds. I also noticed that some stir bars have a tendency to do this and others do not. I'm using a 48mm bar. (2" x 5/16")

So, I've been looking at some alternatives. There are quite a few different stir bar configurations. One design is shaped like a barbell and it's supposed to be more stable and quieter. The problem is that they are too expensive.

Thought I would try an experiment to approximate the barbell shape. I put two O-rings on the stir bar positioned symetrically about 2/3rds out from the center. Works like a charm!

The O-rings I used are the same size used on keg dip tubes, but any 1/4" ID O-ring should work. I've have not tried any other size, so there could be an even better choice on these.

Here's a pic of the stir bar w/-Orings installed:

Thanks for the heads up! I have the same problem.

Yeah I have noticed that the stirbars with the small center band are prone to getting thrown, as opposed to the ones where the center area is at least 1/4inch long.

That's a good rig you came up with.

Another option for those who have this issue, and can't find o rings is to see if the bar will fit snugly in a piece of any of your hoses, then cut off a piece anywhere from a quarter to an inch depending on the length of your stir bar, and slip the bar in there. Your making a sleeve basically.

Or if you can cut the hose into your own o rings and place them in the above configuration.

I forced a piece of vinyl tubing over the bar magnet the same length to keep the noise down, my daughter can hear a mouse fart 100 yards away and complained before this quick fix.

Thanks for the ideas. I have the same bar and it's obnoxious.

I use the o-ring as a pivot point when doing a starter in a 1 gallon jug. Works like a charm.

I use a closet as the silencer.

GilaMinumBeer said:

I use a closet as the silencer.

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I don't think it's so much that it is noisy, in my case the bar like the one in the picture with the small pivot point would get thrown even on the lowest speed of my stirplate.

Revvy said:

I don't think it's so much that it is noisy, in my case the bar like the one in the picture with the small pivot point would get thrown even on the lowest speed of my stirplate.

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It was the occasional rattling that I found annoying, so it was a noise issue for me. The side benefit of using the o-rings is that it also improved the stability of the stir bar.

I like the idea of using a section of plastic tubing over the stir bar, but I would be concerned about cleaning and sanitizing it. I would think it might be a hassle to remove and replace. The O-rings are easy to slip on or off and they are dirt cheap. You can get them at most any hardware store.

Here's a pic using four O-rings. This seems to work even better than two, but two work quite well by themselves:



Stir bars can vary in quality and balance. They can also be damaged if dropped or otherwise subjected to shock. They should be stored stuck together to help maintain their magnetic properties. I've ordered some cross shaped stir bars to play with. I'll report my findings after I try them out.

I've tried several stir bars, and the one that seems to work best and is the most quiet is one that's shaped like a football. The only way I can tell it's still spinning is by checking the vortex, and it's got a great spin to it too. I've tried a couple crosses and liked them the least.

I have a 2" bar with a fairly wide pivot ring, does not get thrown easily and is pretty quiet. I use 1/2 gallon growlers opposed to flasks. they have a slightly concave bottom, when I get it centered up well, there really is no rattle.

XL_Jockey said:

I've tried several stir bars, and the one that seems to work best and is the most quiet is one that's shaped like a football. The only way I can tell it's still spinning is by checking the vortex, and it's got a great spin to it too. I've tried a couple crosses and liked them the least.

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What was the problem with the crosses? Someone else reported good results with them a while back.

Bobby_M said:

Thanks for the ideas. I have the same bar and it's obnoxious.

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Bobby, did you try the O-ring trick yet? I think you may be surprised at the difference they make.

Catt22 said:

What was the problem with the crosses? Someone else reported good results with them a while back.

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They don't fit into as large a variety of containers.

For me the crosses were too noisy and they didn't stay in place as well. I tried a smaller and a larger one and both got throw rather easily. The football was one of the few that stayed put at high speeds but was also the quietest. That's just my experimentation though.

Catt22 said:

What was the problem with the crosses? Someone else reported good results with them a while back.

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I recall the crosses were silent running this from a reply about a year ago vs a straight sided and a center ringed magnet.

The solution I came up with is to simply use an X-acto knife (or razor blade) and cut off the ring. I tested several different bars (I got a pack of 5) from 1/4" to 2+" before and after cutting off the ring and they ALL performed much better and were SILENT. I can crank up the speed to full without throwing any of them and if I listen carefully, I can actually hear the yeast scream as they fly by. It seems to me adding o-rings would greatly increase friction between the bar and the container reducing performance of the plate, but that may not be a problem with 120mm fans and may help cover up the effects of misaligned magnets. I think removing the problem is a better solution than covering it up.

Revvy said:

I don't think it's so much that it is noisy, in my case the bar like the one in the picture with the small pivot point would get thrown even on the lowest speed of my stirplate.

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Same here. I built a stir plate and haven't been able to utilize it due to my stir bar constantly being thrown even at its lowest speed.

Thanks for this thread. HBT does it again.

Hey, Catt, big ups for this idea. I put a couple diptube o-rings on mine last night, tried it out, and it's a world of difference. Not only does it keep it from rattling, it also is less likely to throw the bar, because it doesn't wobble, even at high speeds. Thanks, yo.

Oh, and to the above: I guess it depends on how your stirplate is built, but I have a cross-shaped stirbar, and it gets thrown if I use it on any speed higher then medium.

Glad to hear that it worked for you guys. I just got a bag of the cross shaped stir bars and they work pretty well for me.

Yes, I've built a number of these stir plate for my fellow brewers and I've experimented with various combinations of muffin fans, magnets and stir bars and learned that there are a number of variables that determine how well they operate.
I want to try the oval football shaped stir bars next. I've heard that some have had good results with those. The cross and straight bars work, but I'm curious to see if the footballs work any better.

The strength of the magnets, the stir bar configuration, the distance from the magnets to the bottom of the flask and the muffin fan design all come into play. It often takes some trial and error work to find the right combination.

The most important factor IMO, is the alignment of the magnets on the fan. Even a very small misalignment will cause the bar to wobble and at higher speeds, get thrown. I have my magnets positioned very close to the underside of the platform. The clearance is only about 1/16" and I'm using some very strong rare earth magnets on the fan.

Oh, one other thing. You can also do some trial and error testing to determine the best position for the O-rings. Seems to be that about half way out from the center works best, but out near the ends works well too.

anybody get a bar to stay spinning past 900 rpm? i got some 2" bars off ebay that once i cut the ring off and put orings on, are quite but the usuable range is 400-900 rpm. below doesnt make visible movement, if i spin up to 1600 it gets launched. what does it take to spin a bar at 1600rpm?

mordantly said:

anybody get a bar to stay spinning past 900 rpm? i got some 2" bars off ebay that once i cut the ring off and put orings on, are quite but the usuable range is 400-900 rpm. below doesnt make visible movement, if i spin up to 1600 it gets launched. what does it take to spin a bar at 1600rpm?

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Something doesn't seem right. Maybe I'm not understanding you correctly. You should be able to see a lot of stirring action at much lower speeds than 400-900 rpm with a 2" bar. I estimate that I'm usually running about 200-300 rpm which is more than sufficient. I don't know the exact rpms as I have no way to measure the speed, so that's only an estimate. Should not be too far off though, +/- 100 rpm maybe.

Running up at 1600 rpm is very, very fast. You would need to have everything balanced near perfectly at that speed which is very difficult to achieve on a DIY level. The other problem is that the stir bars themselves are not always balanced perfectly, so even if the stir plate magnets are well balanced you may still have problems at very high rpms. Then there is the issue of the fluid itself not always spinning with perfect uniformity and this can interfere with the stir bar enough to throw it at higher speeds. Everything becomes more critical at higher rpms. What size is your flask or container? I can stir very well with a one gallon jug and a 2" bar at somewhere in the range of 300 rpm with no problem at all. I don't understand why you are not able to do the same.

How are you measuring the rpms?

i tested a 2L with 2L water in it. my plate is rated 60-1600rpm. its a lab plate so it has a speedo. perhaps i got cheap bars. as far as problems: i had my plate resting so the glass wasnt parallel to the counter. it turns out when i give it longer then a minute 200rpm does make a current. now i can get to about 1050 stable before it gets thrown. that is one hellova vortex! i guess i need to buy an expensive bar since my plate magnets were affecting the spare bar resting about 6in away on the counter.

You shouldn't need an expensive stir bar. It is important to store them properly in order to avoid them becoming demagnetized. It's suggested to store them in pairs stuck together or alternately, resting on the stir plate itself where it will align with the plate magnets.

Yes, it may take minute or two for the liquid to get moving well. The bar will tend to spin faster as the liquid catches up and provides less resistance. It doesn't happen instantly. Try letting it run at around 300-400 rpm. Put some food coloring in the water and you can see how it mixes. A strong vortex is not necessary. All you need is to keep the liquid moving. I run mine at a speed that causes a dimple about an inch deep at the surface and no deep vortex at all. A vortex which reaches all the way to the bottom touching the stir bar can interfere with the bar and sometimes cause it to get thrown. IMO, a moderate stirring rate is the best way to go and I lean to the slow side of that. Actually, I like to run at just above the stall speed. This permits it to self start in case of a power interruption or temporary voltage fluctuation. As the yeast reproduce the viscosity of the wort will increase and this may require you to boost the power some to stay at the same speed.

the orings added resistence but it sure is silent.

your the brass balls guy i saw the other day in a post. i cut the rib off but it still made racket. obviously the teflon wont mar the glass, its just annoying. id like to have the plate on the kitchen counter where temps are in the 60s-70s and i can monitor it. it gets 35f at night so my garage in the 50s is too cold for ale growth. the orings get loose, so im going to try a length of tubing if i have a size that fits.

mordantly said:

your the brass balls guy i saw the other day in a post. i cut the rib off but it still made racket. obviously the teflon wont mar the glass, its just annoying. id like to have the plate on the kitchen counter where temps are in the 60s-70s and i can monitor it. it gets 35f at night so my garage in the 50s is too cold for ale growth. the orings get loose, so im going to try a length of tubing if i have a size that fits.

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Interesting. Why "brass balls"? Really, I'm serious. I have a stir plate that i made myself from stuff anyone can buy cheaply that runs quietly and stirs 50Ml to 4 gal., but, you say "brass balls". Please explaine.....

a full carboy on a stir plate is not an average occurance. if i did it, id be worried the sucker would fall over or get to vigorous of a ferment and make a big mess. perhaps my cat would nock it off the counter. as interesting an idea as it is i know something would bite me in the ass if i attempted it. you havent said what type of bar you have that runs so nice aside from it doesn't have orings. so is it the ring type, non ring, or some weird shape like a cross or football a square?

FWIW, I don't use O-rings either. I came up with that idea in the course of the R & D and it seems to have helped with some who have had problems with noisy stir bars. I use a 2" (50 mm) stir bar and it runs silently. I've also experimented with various other bars including a 1-1/2" cross shaped type. IMO, the 2" works best all around for any size flask or jug. I haven't tried to use a carboy, but I'm pretty sure it could handle one of those as well.

I have two stir plates and two 2 liter flasks. I typically only make a single 2 liter starter for a six gallon batch of average gravity brew or double that for a twelve gallon batch. I will step them up for high gravity brews and lagers. The starters usually finish out in 24 hours, so I can propagate a bunch of yeast fairly quickly.