Stir Plate Problems

So I've made the step up to making starters. I've got most of my stir plate done but I'm wondering what you guys are doing for magnets. I got some magnets from work but hey don't seem to be strong enough. Question 1 is where are you guys getting these magnets locally? Question 2 what strength are they? I'm thinking my problem is with the magnet strength but it could be how fast my fan is spinning. I had a 9v power supply that was spinning the fan fine but sometimes it wouldn't start the fan until I turned it up. My new power supply spins the fan fast and faster but it seems like magnets are the issue. Help me out. If you need pics of my set-up let me know I'll be happy to show them. I want this thing done so I can get on to my next beer. Thanks in advance for your help

A lot of folks are using magnets out of a computer hard drives...They are pretty strong... I am in the midst of a stirplate project and I used two on mine... Check out my-stirplate-cheap-easy-build...
Good luck...

I used two little round ones that I got online but it would keep throwing the bar at the speeds I wanted. Just slapped on a hard drive magnet I ripped out of an old defunct hard drive I had sitting around and it works perfectly now.

Here ya go:

MAGCRAFT® Neodymium Magnets

IMO, cheap and much better than screwing around with salvaged hard drive magnets.

Rare earth magnets is your best bang for the buck.

Some people harvest them from old hard drives as I did. They can also be readily found on Ebay as little button magnets. Just search them on Ebay or Google. Many of the ones on Ebay are sold in lots bigger than what you need though.

I'm in favor of the rare earth magnets as well. I don't know where you can find them locally though.

I finished my stir plate a few days ago and found that you really need to have the magnets aligned correctly to not have the bar thrown at decent speeds. I also found that you need to have "a bit" of separation between the fan motor and the magnets for it to work. Looking back, I'm actually a bit surprised at how many stir plates are functional with a hard drive magnet glued directly onto the fan hub. Maybe it didn't work for me because I'm using a 70mm fan and very powerful magnets.

I figured I'd update this a little bit. I scavenged a computer for it's magnets and I have my 1 inch bar working good. It pulls a vortex all the way to the bottom and shoots air bubbles all over the place. But I think since my magnets are a smaller then the flat spot on the fan my 2 inch bar will always get thrown. The magnets aren't 2 inches long so is that my problem? I think that it may be so do you guys think that I could add some smaller magnets on either side to help get the 2 inch bar to work. Since the 1 inch bar seems to work well what are the benefits of using a 2 inch bar if anything? I'd like to get it to work with both just in case I need to use them. I'll try to take a little video to post up to see if what I have is enough cause I have nothing to base it on. Thanks again for all your help and keep it coming

What you have is enough IMO.

Got my rare earth magnets from Harbor Freight--can't remember how much, but they were cheap (and no shipping costs if you have one local).

Edit:
$2.00
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=98371

I just stopped into ACE hardware and they have a ton of different magnets I picked up a six pack of small ones and they are every bit as strong if not stronger than the hard drive magnets. I'm going to try to get these to help out what I have on there now as the hard drive magnet is cured to the fan and I don't want to shell out any cash for another one now as I'd rather put it to ingedients for my next batch

The other thing that might have worked is breaking one of the crescent moon magnets from the hard drive in half. I acyually broke 2 of them removing them from a hard drive before I got a couple out clean from another one. The two halves would work as smaller magnets.

The best way to make sure you get the best magnet alignment to the stir bar using multiple smaller magnets is to figure the spacing you want then magnetically stick them to the stir bar. This way you know they are set up with the magnetic poles the right way. While they are magnetically stuck to the stir bar put your glue or epoxy on the other side of the magnets and mount them to your fan. When the glue is dried slide the stir bar off the magnets and the fields should line up perfect to spin the stir bar.

So this is how I ended up, do you guys think its enough or should I try some of the other power supplies I have around? Sorry for the crappy video but it does the job. I may try to make another one with some more spare parts if I can get it to work with my 2 inch bar. And thanks again to everyone and the orignator of the cheap and easy stir plate thread



http://s814.photobucket.com/albums/zz61/krelja/?action=view&current=beer008.flv

I dont think you'll ever need to spin it that fast..?

FWIW, get rid of the airlock and replace with an open cell foam stopper or loosely cap it with aluminum foil. You want to faciliate the gas exchange. ie. O2 in & CO2 out. Using an airlock will prevent this from happening.

Otherwise your stirp plate is more than adequate. A big walking vortex that reaches all the way to the bottom can often interfere with the stir bar and sometimes will cause the stir bar to be thrown. IMO, a big vortex isn't at all necessary. The gas exchange occurs primarily at the surface air/wort interface. The key is to keep "turning over" the surface through stirring. Air bubbles drawn down into the wort through the vortex have relatively little surface area relative to the total surface area, so it's not a big deal one way or the other. Running the stir plate slower can reduce stir bar noise and it's less prone to throwing the bar. I usually run mine just a little above the stall speed.

Looks good. +1 on using a breathable cap for the flask. I just use loosely attached aluminum foil.

Also your wort will be denser than water and you might not hit the same speed without throwing the bar, but based on what you have there you should get a plenty fast stir to keep the liquid in motion which is your goal.

So the way to do it is just have the vortex barely hitting the stir bar. Now the airlock was just there to keep things quiet while I was cranking it. I was going to cover it with foil. Can I just take the airlock out and leave hole open or just loosely cover that as well. Can I just buy a breather stopper

Krelja said:

So the way to do it is just have the vortex barely hitting the stir bar. Now the airlock was just there to keep things quiet while I was cranking it. I was going to cover it with foil. Can I just take the airlock out and leave hole open or just loosely cover that as well. Can I just buy a breather stopper

Click to expand...

You could run it even slower than that and get the same results. All that is needed is to keep the wort moving. I don't know if the small stopper hole would inhibit the gas exchange or not. Probably not, but I would just put the foil loosely over the mouth of the flask. Leaving the stopper hole uncovered is probably not a good idea. Dust and such can fall directly down into the flask which could harbor mold and bacteria. They can't crawl, but they can hitch a ride easily. Put a roof over your wort. That's basically what you are doing with the foil. Yes, you can buy a breather stopper. That's the open cell foam stopper mentioned earlier. They are designed for this purpose.