Stirplates: Where on the fan should the magnets be placed?

[Smellyglove]

Should the magnets be placed on the outer edges, or more towards the center?

I have two "sticks" or what you call them. One is longer than the other one. My stir plate cant utilize the shorter one. The shorter one is shorter than the distance between the magnets, while the longer on is about the same length as the distance between the magnets.

Will placing the magnets further towards the center make the "stick" stick better to the magnets?

 

[day_trippr]

The "sticks" are "stir bars". They'll perform best when the centers of their magnetic poles are lined up with the centers of the magnetic poles on the driving magnet(s). If you are using "button" magnets on the fan, you're kind of stuck setting them up if you have significantly different length stir bars. You pretty much have to decide which bar you want to work, and set your button up to match the spread of the poles. In your case, you have one bar that works with the current spread. If you'd rather use the shorter bar, you're going to have to move the magnets closer to the center of the fan hub.

fwiw, if you use bar magnets with their poles on their broad surfaces, you can put two bars end to end and accommodate many different length stir bars. I have 1 inch and 2 inch bars and they work great with this setup. I'm pretty sure I could go down another size on the short end and up a size on the long end and they'd still work great...


Cheers!

 

[Smellyglove]

Thanks. Maybe I should swap out my button-magnets for bar-magnets then.

 

[mikescooling]

I was messing around with little earth magnets and it was not working for me. I got the block magnets form Radio shack. I used two side by side. Everything was great from then on. And yes put them on the center or your stir plate will also be a shaker.

 

[ClaudiusB]

Thanks. Maybe I should swap out my button-magnets for bar-magnets then.

Look what I did.
Works with all stir bars



ClaudiusB

 

[banks412]

Check this guy's website out. He uses a small piece of PVC to standoff the magnets from the fan to protect the fan motor from damage and to get the magnets as close to the top of the box as possible. I recently bought one of his sitrplates and used it for a brown ale I brewed last week - couldn't be happier with it.

http://www.stirstarters.com/index.html

Cheers!

 

[day_trippr]

Seen it. It's clearly limited to a specific length stir bar that matches the spread of the two button magnets...

Cheers!