Stir plate not working.

[MrFeltimo]

I had built a stir plate many moons ago, design based of internet searches and HBT.
This little diddy worked wonders and never had to worry.
However this past weekend i made my starter and fired the old girl up, it spun, but kept throwing my stir bar off the magnet, hours i tried to get it to work but alas, no go.
Any thoughts on what could have happened?

Computer Fan; 110 volts with speed controller
Rare earth magnet
2L earlymyer flask
1 inch stir bar. I also tried with different sized bars. 1/4 inch to 2 inch with every size in between.

Nothing has changed in the set up.

Thanks
Dan

 

[antony]

Usually the speed is too fast or the surface isn't flat, but it seems like you have both of those covered. One of my homemade plates only works if I fit an o-ring over the bar to act as a fulcrum, you may wanna give that a shot (btw, I have to do this for the plate that doesn't have a speed controller, I'm assuming you've already tried at the lowest setting). Best of luck.

 

[MrFeltimo]

Thanks for the reply.
My speed setting is usually set to slow, but have tried differently.
Also the bars i have, have the center raised pivot point built in..

 

[logdrum]

I did not build my stir plate, it's a "Stir Starter"-practically identical to the DIY ones. That being said, I've run into the same issue with mine. I can only stir at very low speeds, and with the clumpier English strains the magnet will often get bogged down. If I try to go faster, it throws the magnet. I'm getting ready to upgrade-it seems pointless to compute cell counts but not have a reliable stir plate. This is the model I'm looking at:

http://www.brewinternational.com/magnetic-stir-plate/

Wish I had a better solution for you...

 

[MrFeltimo]

The one thing i might have to consider is getting a bigger magnet, maybe this will help hold the bar in place.
it still don't answer WHY it not longer works correctly.

 

[RM-MN]

I did not build my stir plate, it's a "Stir Starter"-practically identical to the DIY ones. That being said, I've run into the same issue with mine. I can only stir at very low speeds, and with the clumpier English strains the magnet will often get bogged down. If I try to go faster, it throws the magnet. I'm getting ready to upgrade-it seems pointless to compute cell counts but not have a reliable stir plate. This is the model I'm looking at:

http://www.brewinternational.com/magnetic-stir-plate/

Wish I had a better solution for you...

Before you buy the next stir plate, take a good look at the research done by WoodlandBrews on yeast propagation. http://www.woodlandbrew.com/2015/02/yeast-starters-stirred-vs-not.html

 

[RobbyComstock]

I had the same problem with mine. The magnet on the computer fan needs to be the right distance from the stir bar. I had to make some spacers for mine to get it just right.

 

[MrFeltimo]

I've just fitted a more powerful magnet and are using a larger stir bar.
Seams to be working for now.
I simply don't know why the original set up all of a sudden stop working.
Most annoying.