Thrown Stir Bar - in water

Hello,

I have read the other similar threads but didn't see anything the same. My home built stir plate spins fine when the magnet is on the plate as well as when the bar is in an empty flask. When I tried with water it gets thrown every time so I have no confidence of it working in my wort.

any suggestions?

Is it the speed?

 

I usually get it going slow and ramp the speed up once it seems to be stable. You'll get the hang of it, keep practicing with water, gets even trickier with wort thats hard to see through.

 

its on the slowest speed

 

Hmm.... Try a smaller bar?

 

You can also try putting it on the stir plate with it OFF so the bar jumps onto the magnet, then turning it on. Not all stir plates have enough power to get spinning with the agnet already attached but worth a shot.

 

also make sure the stir bar is centered by moving it around once it start spinning, slow small movements of the flask kind of in a circle to find the sweet spot.

 

I have homemade stir plates and had the same issue when i started using 1 gallon growlers for my starter vessels. At the time my magnet was about 1/4 to 3/8 inch below the vessel. So I raised the magnet up so it is almost flush with the base of the stir plate housing. Now all i do is drop the stir bar in, let the magnet get a hold of it, center it then turn the stir plate on and have not had a thrown magnet since.
I think if you had a flat bottom vessel that might do the trick as well.

 

Couple of questions:

1. What type of magnet(s) did you use?
2. What type of speed control are using? What size of power supply do you have?

It sounds to me that either your magnets are not strong enough or they are spinning too fast. Both of which could cause the bar to de-couple from the stirplate.

A little more information on your build will help everyone give some better recommendations.

 

Or the magnets are not centered on the stir plate.

 

I have been agonizing over the same problem.....I had a cheap plastic container that worked alright with water but I decided to upgrade to an earlenmeyer flask....

My problems were that I had never bought any speed control....just never made it to a radio shack...

And I also just ordered one of the stir bars with the middle ridge that should help reduce friction for spinning but increase friction on the ridge (like tire tread) to keep the stir bar centered...

We shall see.

 

I like the (American) football-shaped stir bars. They look too stubby to work well, but they do a good job. The shape makes them very stable.

 

I had the same problem and went through a couple of stir bars trying to figure it out. I have a square shaped stir bar that works great on my 2000 ml flask. It has a concave bottom and the square side prevent it from being thrown.

 

I bought 3 or 4 different lengths of stir bars. Found one that works--on my 2L flask (it throws constantly on my 3L flask). It's kind of hit and miss. But you should be able to find something that works.

Just don't buy one of those cross-shaped stir bars. There is no nub in the center, and the arms of it grab and throw it right away. Total waste of $$.

 

I agree, beef up the stirplate magnets, use a shorter bar, or slow the spin and slowly ramp up.

 

Mine was throwing the bar until I raised the magnet another 1/4 inch, works like a charm now. It even handles my biggest stirbars without an issue now. I just need to get speed control at this point so I can get it working on a 5L+ starter.

 

I got a variable voltage wall wort instead of a speed controller.

 

Where do you get them? I would be interested in trying one.

 

I had to increase the distance between the magnets and my 2L flask.

 

They call them egg-shaped in this catalog.
http://www.belart.com/shop/371300038-eggshaped-spinbarreg-stir-38x316-p-371300038.html?y=5&x=80

 

Thanks for all the replies. I have a starter in my 2000 ml flask right now so I will take a look when i am done with that and try some of the other suggestions. I do know the fan / magnets are as flush as possible without touching. The magnets are about the same size (2 small round ones) as the length of the stir bar(s). The bar has flat ridges.