DIY Stir Plate. HELP!

[ThePwnStick]

So I tried building a stirplate out of 2 neodymium magnets glued down onto a PC cooler fan, but the short metal rod I use for my stir bar just keeps wobbling instead of spinning. What am I doing wrong?

 

[bdupree]

if you mean that you glued down 2 of those magnets on the actual fan blades, then you probably have a pretty equal amount of force on teh stir rod from each magnet. put one magnet on the center of the fan blade and it might spin then

 

[camiller]

if you mean that you glued down 2 of those magnets on the actual fan blades, then you probably have a pretty equal amount of force on teh stir rod from each magnet. put one magnet on the center of the fan blade and it might spin then

I think he is talking about the button/disk magnets not like a hard drive magnet. Although he doesn't really say.

How about a little more detail ThePwnStick? Maybe pictures.

Educated guess #1 -- You have the same magnetic poll pointed up on both magnets.

 

[ThePwnStick]

I think he is talking about the button/disk magnets not like a hard drive magnet. Although he doesn't really say.

How about a little more detail ThePwnStick? Maybe pictures.

Educated guess #1 -- You have the same magnetic poll pointed up on both magnets.

I don't have my camera right now, but yeah, I used those button magnets, glued down onto a small wooden plank, which in turn is glued down onto the fan. The magnet polarity is opposites up. I think the problem is in my stir rod, which is just a little metal bar.

I've heard that I can magnetize it my rubbing a magnet on it.

Or is it better to get an actual stir rod? Can I get one from a pharmacy or someplace other than ebay?

 

[azscoob]

I got my stirbar from my LHBS, the price was quite reasonable if I recall.

 

[CodeRage]

Magnets too far apart can do this. The magnets should be pretty close together. Id says 1/4 to 3/8 apart.
Also, if you turn the fan on at 100% speed odds are the stir bar wont be able to couple to the spinning magnetic field. You would see a wabbling if this were the case.

I would get a stir bar, the wort from the starter and all that o2 in suspension would cause anything ferrous to rust. could add some contaminants or nasty off flavors to your starter. You are using some kind of iron or steel bar right?

 

[camiller]

Magnets too far apart can do this. The magnets should be pretty close together. Id says 1/4 to 3/8 apart.
Also, if you turn the fan on at 100% speed odds are the stir bar wont be able to couple to the spinning magnetic field. You would see a wabbling if this were the case.

I would get a stir bar, the wort from the starter and all that o2 in suspension would cause anything ferrous to rust. could add some contaminants or nasty off flavors to your starter. You are using some kind of iron or steel bar right?

Disagree with the distance thing. Most of the folks that use magnets like that suggest a center to center spacing the same length as the stir bar itself.

Also, all the larger online homebrew shops have them, so if your ordering supplies add on a stir bar.

 

[CodeRage]

How big of a stir bar are you using?

Oops, bad explanation. You're right. I meant to say the distances are from center. I use a 3/4" stir bar with the magnets centered on a 3/8s radius.

 

[ThePwnStick]

Yay! I fixed the problem by replacing the two magnets with one hard drive one. My stirbar is stainless steel, which doesn't rust, so I think I'll be OK. Maybe I'll coat it with silicone rubber. Will that be better or worse for it?

 

[CodeRage]

Lol, Stainless doesn't have the best magnetic properties. Depends on the alloy.

 

[Catt22]

A real stir bar has a magnet embedded inside the teflon cover. Buy a real stir bar and position the magnets to match the bar. IMO, it's best to mount the magnets so that the ends of the magnet inside the stir bar line up with the centers of the magnets mounted on the fan (assuming you are using two magnets and not a HD magnet). It's trickier getting the HD magnets properly aligned due to their curved shape.

 

[AluminumGerbil]

If it's truly stainless steel it's not magnetic. None of my piercings will stick to a magnet anyway because they're 100% stainless.

 

[ThePwnStick]

If it's truly stainless steel it's not magnetic. None of my piercings will stick to a magnet anyway because they're 100% stainless.

There's no such thing as 100% stainless steel as it is an alloy, and steel is generally iron and coal, so if your piercings are non-magnetic, they are made of chromium, aluminium, nickel, etc, or an alloy of said metals.

 

[AluminumGerbil]

I won't pretend to be an expert, I know jewelry is made from 316L Stainless. I guess now that you mention it I did know it was an allow, I wasn't thinking the best when I posted that response. But to the best of my knowledge if it's magnetic wouldn't you have to worry about it rusting because of the amount of ferrous material?

 

[completegeek]

When I just used a metal bar as my stir bar I had the same problem. When I got the stirbar (which is a magnet coated in teflon, btw) my problem was solved.

They only other thing I could think would be the problem is that your RPMs are too high. I had to add a few resistors inline to slow my computer fan down enough not to fling even the correct stir bar.