12 replies to this topic

[MakeMeHoppy]

I finally broke down and collected what I need to make a stir plate. Anyone know where you can buy stir bars other than online? I don't want to pay shipping that will likely cost more than the bar.

[MakeMeHoppy]

Actual I have another problem. Got my PC fan and my variable voltage DC adapter and the fan spins great. I got my rare earth magnet from the hard drive and placed it on top of the fan and now it no longer spins. Looks like the rare earth magnet field is too strong for the fan motor. I saw many online 'build a stir plate' projects and they all say to glue the magnet onto the fan. Anyone else have this problem? Looks like I'll need a 2" spacer to allow the fan to spin.

[ncbeerbrewer]

Actual I have another problem. Got my PC fan and my variable voltage DC adapter and the fan spins great. I got my rare earth magnet from the hard drive and placed it on top of the fan and now it no longer spins. Looks like the rare earth magnet field is too strong for the fan motor. I saw many online 'build a stir plate' projects and they all say to glue the magnet onto the fan. Anyone else have this problem? Looks like I'll need a 2" spacer to allow the fan to spin.

I control the speed of the fan with a potentiometer. If I plug it in the fan does not spin. If I turn the potentiometer all the way up the fan starts to spin then I turn it down and it spins the stir bar no problem. Just an idea to help you out.

[Fatman]

It could be that the rare earth magnets are messing with the electromagnet in the fan. I gorilla glued a big washer to my fan hub and placed the magnets on top of the washer (no glue) and that problem went away. Also, you might want to stick with an octagonal stir bar. I had issues with the square ones.

[MolBasser]

Triangular ones work well.Where do you live? There might be a scientific supply store...BrewBasser

[ThroatwobblerMangrove]

I control the speed of the fan with a potentiometer. If I plug it in the fan does not spin. If I turn the potentiometer all the way up the fan starts to spin then I turn it down and it spins the stir bar no problem. Just an idea to help you out.

If you have an old HD those have a piece of magnetically shielded metal in them that might help you out.

[MakeMeHoppy]

Thanks for the posts. Yes, I'm sure the magnet field is interfering with the fan motor. I did try running at 12 volts and hand starting the fan, but it stopped right away. Glad I checked in before work today, it was a shallow dumpster dive to retrieve the hard drive from the garbage to try out the non-magnetic shield that I bet will work.

[Stout_fan]

Just a guess, but the magnet is probably overloading the Hall effect sensor.The MuMetal will probably do the trick

[MakeMeHoppy]

The shield that came with the hard drive worked perfectly. Funny that I didn't see this problem in any of the articles I read on stir plates.

[DubbelEntendre]

Back to the OP. McMaster Carr has stir bars. This could be incentive for an order with some additional supplies.

[djinkc]

VWR Lab58948-950If you get more than 1 it's probably cheaper than buying locally. I'm pretty sure this is what I have and they have worked great. You will want more than one, they seem to jump into fermenters........

[Jimmy James]

That's where I got mine too. www.vwrsp.com If you know someone who works in a lab at a University or company they may be able to order it on their acct but pay with your cc and thus avoid shipping charges if they have an institutional discount with VWR.

VWR Lab58948-950If you get more than 1 it's probably cheaper than buying locally. I'm pretty sure this is what I have and they have worked great. You will want more than one, they seem to jump into fermenters........

[MakeMeHoppy]

Thanks all, I got one on order. I was just wondering if a local store may stock something like this and the answer to that is no.