My buddy and I are making our first stir plate but the only stir bars we have been able to find typically have something called a pivot ring on them. Is this a big deal or should we keep looking to find one without the ring?
One of these stirbars and 2 magnets (links below) make for an incredible noise-free setup that will stir anything (expecially glass gallon jugs with curved bottom). I've tried other computer hard drive magnets and there's no comparison to a pair of these.
The pivot ring in the middle is a GOOD thing. It helps the ends of the stir bar stay off the bottom and helps it run more quietly. I don't have the pivot ring on my stirbars, but I have added a silicone o-ring to the middle of each one.
I bought a stir plate and lost the original magnet that came with it. I bought a six pack of magnets (same size as the original) but the new magnets were octagonal and they had a pivot ring on them. They didn't work well at all. Turning the stir plate to anything higher than about 25% speed threw the bar.
Solution: I took a razor blade and sliced off the pivot ring. Worked like a charm.