My stir plate works but throws the bar

[codyjp]

I've put together a stir plate but if I turn it up too fast it throws the bar. I used a 3/4" of PVC as a standoff for the magnets and then glued the magnets to the top of that. I think my stir bar is 1 1/2" or so. Do I need to get a smaller stir bar so it will bit in between the magnets? Do I need to find a way to get the magnets further apart?

Should I just let it be? It will stir up the yeasties fine but there is no chance for a vortex and a big krausen has formed. If that is fine I'll just stop worrying.

Lastly, would it be wise to ventilate the box so the fan doesn't get hot or does it matter?

 

[deremer]

I would think a stronger magnet. My is from a hard drive that I got for free from a computer repair shop.

 

[shelly_belly]

I just used a single hard drive magnet on mine and it throws everything bigger than a 3/4" stirbar. However, that 3/4" stirbar can pull a big vortex on even a 1 gallon starter. I would try a smaller size.

 

[g8tor]

Mine did the same thing when I was using only one hard drive magnet. Once I added a second magnet right on top of the first the problem ended.

Scott

 

[EdWort]

Check your flasks to make sure they have a flat bottom. Any convex bottom can cause a bar to be thrown.

I used to have one and got rid of it.

 

[Catt22]

Should I just let it be? It will stir up the yeasties fine but there is no chance for a vortex and a big krausen has formed. If that is fine I'll just stop worrying.

Lastly, would it be wise to ventilate the box so the fan doesn't get hot or does it matter?

1. Yes

2. Yes, particularly if it's running hot. It can't do any harm that I can see.

IMO, you don't need a big vortex. Gentle stirring gets the job done just fine.

 

[Flomaster]

placement of magnets
strength of magnets
type of flask being used
speed of fan spinning

all these things play a factor in your stir plate

any one could be causing a problem or several one could be to blame

-=Jason=-

 

[discooby]

Making sure to magnetize the stir bar helped with mine; it was magnetized but weak… I now always run it over the magnets several times before dropping it in

 

[rockytoptim]

Check your flasks to make sure they have a flat bottom. Any convex bottom can cause a bar to be thrown.

I used to have one and got rid of it.

+1 on checking flask flatness. I have a 2000ml flask and it worked great but when I bought a second one it would throw the bar and I notice the bottom wasn't flat. I only had one bar at the time so it wasn't the bar. I took my second flask back and exchanged it for one that looked flat and it works like great now.

 

[beertastic]

I use this one with a hard drive magnet and it *never* throws:

http://www.amazon.com/gp/product/B002VBW5FY/?tag=skimlinks_replacement-20

I remember thinking my stir plate didn't work (was using screws, etc.) until I got a real stir bar, so I think they make all the difference.

I use either a glass gallon jug or a growler. I'd like to upgrade to a 2000mL flask so I don't have to transfer the wort starter between containers, but there's a few other items with higher priority.

 

[tknice]

Few things:

1. +1 on flat surface. The flatter your surface, the smoother the spin will be. Avoid curved surfaces if possible.

2. +1 on slow stir. I only spin fast for the first 10 minutes to add some oxygen. The rest of the time set it just fast enought to keep the yeast suspended. You do not need a vortex.

3. Smaller stirbars throw less often.

4. For curved surfaces (like a many half gallon jugs), if you keg and have extra dip tube o-rings, put one on each end of a longer bar to keep it from throwing. Move the rings closer together until it spins smoothly.

5. When finding a new favorite container, look for something wide. More surface area propagates yeast better than something (like many flasks) with less surface area. I found an old glass stovetop popcorn maker that is around 6-7 inches across at the base. The sides come straight up to a nice lip that is great for pouring. It's my favorite but the bottom has ridges in a swirl pattern to match many electric stoves. The bar still spins great but I do wish it was perfectly flat.