my DIY stir plate is worthless

Cigar box, 92 mm-3 speed CP fan, 2000 ml flask, and 2 inch stir bar from northernbrewer.com

Can't get this to spin at all, not even on low. just kinda jiggles for a second and stops moving. I could get the stir bar moving manually by creating a vortex and it looked like the magnet was gonna pick it up but it always just stops moving! ah im so pissed off I waited a week for my flask and stir bar to arrive so I can test it out and now im just disapointed. What could be the problem

Could be your magnet is not strong enough or its not close enough to the base.

so my magnet, one side is stronger than the other. following the tutorials i read, the magnet was attracted to the fan, which left the not as strong side facing up, towards the stir bar. Is this my cause? Do i need my magnet flipped around?

Probably. These things aren't terribly complicated. Start troubleshooting:

Does the fan spin without the magnet?
Does the fan spin with the magnet?
Does the fan spin with the stir bar on the lid of the cigar box? If so, does the stir bar also spin?

If one of these is no, you found the problem.

If you answered yes to all of those, your magnet is too far from the stir bar when it's in whatever vessel you have it in, or you need a stronger magnet.

two inch stir bar? Mine is like 1/2 inch.

Is your flask flat on the bottom? I have a one liter flask that is flat it works great, my 2 liter flask is concave and it will not work.

The stir bar should the the same length as the magnet, if it if too small or too big it can throw the stir bar off the magnet, I had the same problem until it got a stir bar that matched my magnet.

You probably need to move the magnet closer to the lid of the cigar box. I had the same problem with mine. After tweaking the fan magnet, more than a couple times, it works fine. Much like being with a woman, you just need to find that special spot, and it'll all work out for you.

After looking at some other DIY's, I noticed my magnet is different than others. This came out of an old hard drive, you can see the part that is the magnet and the other part it is stuck to. I tried to get them seperated but couldn't, they're welded together or something.



And if the stir bar shouldn't be bigger than the magnet, then it looks like I need a smaller stir bar.

And connected to the fan:


So the strongest part of the magnet isn't facing upwards but I dont know if this is normal or not. Either way the stir bar is attracted to the weaker side, however, on the lowest speed it never gets going. Just starts to jiggle and dance a bit. Stir bar too big? Bad magnet? I dunno what to do..

The magnet is glued onto that other metal piece, not welded. You need to get a flat head screwy and a plier or hammer. Its a pita, but you need to bang the flat head between the magnet and that metal plate. Stand it on end and give it a good whack.
Be careful, the magnet is delicate. When you get it free, make sure its centered on the fan. Once its centered, glue it down, test it, adjust it, and leave it to dry. Then you need to mess with the distance between the magnet and the top of your enclosure. Its a lot of tweaking and fiddling, but it'll be worth it.

Ok ty.and what do you think about the stir bar? Should I get a smaller one from the LHBS

Negative, I think that stir bar will work for you. But it never hurts to have a couple of sizes of stir bar around. I have a half inch and a 1 inch stir bar. The half helps keep things moving without creating a huge vortex, the 1 inch one usually gets things kickin' pretty fast if I need a bigger starter.

Be careful when seperating the magnet from the backing. I shattered two magnets trying.

I've had luck slightly bending the backing. Then you'll have space to get a flathead under it.

I had good luck using a razor blade. Slide it under the magnet, then it's flexible enough to get the screwdriver under without damaging anything.

seabass07 said:

I've had luck slightly bending the backing. Then you'll have space to get a flathead under it.

Click to expand...

Do this. Get two pairs of pliers, one on each end of the bracket, and bend the bracket away from the magnet. It will come right off.

I left the metal piece connected to mine and just turned it so it was facing up towards the flask. I also have to start my plate with the flask and stir bar in place. I can't just set it down on an already spinning plate.

I built one with the same kind of magnet. It throws everything larger than 3/4 inches. The 3/4 inch one works great on mine.

I'm gonna get this magnet seperated and reassess everything. And might be getting a smaller stir bar from the LHBS. 10+ bucks for a 1" stir bar, ehhh..

When the magnet is too close to the fan, it will affect the fan's performance as well.

A spacer between the magnet and the fan would be good, and the magnet facing the thing you are trying to turn (stir-bar). Those magnets pop right off the backing, it's just that they're so strong. I pinch mine in a vice and tap it with a mallet and a putty knife - voila...

I spaced my magnet off the fan with a block of plastic, so they all turn, but the magnet is 1/8" off the bottom of the flask. My best-performing stirbar is 1"

You always have to start them at a dead stop, match up the magnet and bar by twisting the flask around until they "lock" then turn the speed up VERY slowly.

good luck

Update:

Got the magnet off the metal backing. Put the magnet on the fan with the strongest side facing up for the stir bar. the connection between them now is very strong. However I'm still having troubles with the bar getting thrown.

My fan is a 3 speed. I start it from stop on the lowest speed with the stir bar locked on the magnet. I even switched up wall worts and used a 9v as opposed to the 12v. it was a little better but still can not get going in water. I put the stir bar on top of the box by itself and turned the fan on and i could get it spinning nicely, But inside the water, it turns a time or two then gets thrown. I am thinking maybe the stir bar is too big but im going to play with the magnets. My hard drive had 2 in them so im gonna see if another placement works.

Thank u for all the responses ill update again, hopefully with a video of my stir bar creating a vortex!

Is the bottom of the flask flat? (Sorry if I've missed that)

I used a 1 gallon jug for a flask and had the same issues. On a whim, I applied a kegging dip tube O-ring to the center of the bar for a pivot and after that it worked wonderfully.

Might even solve the issue if the flask is flat bottomed.

and now for the update we've all been waiting for



This is on low with the 9v wall wort. Unfortunately it gets thrown as soon as I go to medium speed, and also on low with the 12v. This is the only way I was able to get it to work for me and the vortex doesn't get as big as I had hoped for. But either way I think this will work fine so I'm satisfied

well, then, keep it on low! there is absolutely no need for a vortex. You are only keeping the yeast from settling to the bottom - keeping it in suspension.

congrats on fixing this! Now, test with wort - it's thicker than water and doesn't work quite the same.... If the "instant on" of a three speed switch doesn't work - change switches - get a potentiometer (variable resistor) from Radio Shack instead, and you can ease that fan on slowly.

Thehopguy said:

the vortex doesn't get as big as I had hoped for.

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You don't want a big vortex, all you need is a small dimple on the surface.

Kudos on the fix... I used the exact same magnet you used on your stir plate. I have two of those hard drive magnets stacked on top of each other and it holds well to all stir bar sizes. I have thrown a couple of stir bars when the water levels are too low and i get it going too fast. Hang Glider is right, you don't need a huge vortex, just the swirling action will keep things moving and do what you created it to do. You don't need a spacer under the magnet, just try to get as close to your base without touching. If a spacer helps then I guess that would be fine. Or you could slap another magnet on top of the one you already have. I didn't even have to glue it down. Those suckers are super strong.

SOB_OCDAVE said:

Kudos on the fix... I used the exact same magnet you used on your stir plate. I have two of those hard drive magnets stacked on top of each other and it holds well to all stir bar sizes. I have thrown a couple of stir bars when the water levels are too low and i get it going too fast. Hang Glider is right, you don't need a huge vortex, just the swirling action will keep things moving and do what you created it to do. You don't need a spacer under the magnet, just try to get as close to your base without touching. If a spacer helps then I guess that would be fine. Or you could slap another magnet on top of the one you already have. I didn't even have to glue it down. Those suckers are super strong.

Click to expand...

I also stacked two hard drive magnets. After doing that I had to change from a 1/4 inch stir bar to a 1.5 incher. It made it a million times easier to get my stir bar going.