Make my stir plate work

[BackBayBrewing]

Anybody know any good tricks for getting my stir plate to function properly. I built a stir plate over the weekend, and it seems to work great. Until I put my beaker on it and try to use it that is. The magnet will move the stir bar, but it won't seem to get it spinning in place. Is there something that I need to know or do I just need to experiment with magnet placement? Thanks.

 

[Schnitzengiggle]

Placement of the magnet is crucial, as well as how close the magnets are to the stirbar itself. I built a stirplate about 2 months ago, and it has worked great, I basically followed the instructions from https://www.homebrewtalk.com/f51/my-stirplate-cheap-easy-build-86252/?highlight=anthony's+DIY ,however, I did not use hard drive magnets. I opted to purchase magnets for better performance, and I didn't want to dilly dally with placement of the HD magnets because of their odd shape.

I would say to make sure your magnet polarity is right, placement is crucial, and how close the magnets are to the stirbar itself.

I placed my stirbar onto my magnets before epoxying the magnets to the fan to see where the optimal placement would be to catch the stirbar. After that all I needed to do was adjust the height of the fan in the box and voila, really had no issues.

FWIW I ordered my magnets from K&J magnetics (http://www.kjmagnetics.com), and I use a 2" stirbar in a 1/2 gallon growler.

 

[BackBayBrewing]

hey giggle, do you happen to have any pictures of how your stir plate and your magnet placement. That might really help me. I am not using a HD magnet either. The magnet seem to be very much strong enough, and it is about as close to the stir bar as is possible. Do you use one magnet or two? Thanks for the reply.

 

[Catt22]

The magnet alignment is critical. Even a slight misalignment will cause the stir bar to wobble and it will be more susceptible to being thrown. My solution is to precisely mount the magnets on a wooden flywheel. There are two major advantages to doing it this way. It's easier to properly position the magnets and the density of the wood is close to the density of the magnets making perfect alignment less critical. IMO, it's nearly impossible to get the magnets aligned perfectly for a DIY'er. The strength of the magnets is also important. I'm using a 110v AC muffin fan and here's the latest version:

Here's a pic of the wooden flywheel w/magnets mounted from the previous version:

With the magnets placed at 1-1/2" center to center, any stir bar up to and including the 50mm or 2 inch size work well.

You could also try my O-ring trick which may help with what you currently have.

The O-ring mod isn't necessary if everything is aligned and adjusted properly, but if not, it's worth a try and it's cheap to implement.

 

[eriktlupus]

you might look into how much speed your trying to turn the fan at also. mine don't seem to work for **** at 12v but work great either with 200ohms of resistance or drop the voltage down to 6v. at 12v it just seemed to dance the bar around with no concerted spinning action.

 

[Schnitzengiggle]

hey giggle, do you happen to have any pictures of how your stir plate and your magnet placement. That might really help me. I am not using a HD magnet either. The magnet seem to be very much strong enough, and it is about as close to the stir bar as is possible. Do you use one magnet or two? Thanks for the reply.

I'm at work at the moment so I do not have the plate or camera nearby, but basically I mounted them to a SS washer ontop of the fan, I am using round/disk magnets wit a bout 5lb of pull each.

Check this out, it is almost exacty what I did.

http://davidtrumbell.com/Beer/Setup/StirPlate/StirPlate-Pages/Image6.html

Here is this guy's whole project:

Stir Plate

 

[BackBayBrewing]

Thanks for all the help. I got it working. I just needed to spread out my magnets a little further. I think I need a little bit more power however, because even with the power turned all the way up I can't get the vortex to come down more than a few inches. Thanks again.

 

[BackBayBrewing]

It's Alive... but you can see the vortex is not very deep even at full power.

 

[Catt22]

Thanks for all the help. I got it working. I just needed to spread out my magnets a little further. I think I need a little bit more power however, because even with the power turned all the way up I can't get the vortex to come down more than a few inches. Thanks again.

That's all you need. Even less of a vortex is fine. The objective is to stir the wort so that it "turns over". The gas exchange occurs primarily at the air/wort interface. A strong vortex may draw more air down into the wort, but there will be more than enough gas exchange with just gentle stirring. A vortex that reaches all the way down to the stir bar can interfere with it and it can get noisy too. I can use a tiny 1 inch bar which will produce a narrow vortex to the bottom, but it doesn't stir the entire volume as well as a larger bar moving more slowly. You can visually demonstrate this with some food coloring added while the bar is spinning. You can see how the dye diffuses really well.

You are good to go with what you have, provided it will work as well with actual wort in the flask which will have a higher viscosity. The viscosity will increase even more as the yeast propagate. So long as you have some stirring action and it doesn't stall, it will work well for you.

 

[Schnitzengiggle]

Thanks for all the help. I got it working. I just needed to spread out my magnets a little further. I think I need a little bit more power however, because even with the power turned all the way up I can't get the vortex to come down more than a few inches. Thanks again.

The vortx doesn't need to make it to the bottom, most of the gas exchange takes place on the surface, as long as it is stirring it is doing what it needs to.

I used to think the same thing, that the vortex needed to extend to the bottom of the vessel, but it isn't necessary. I can get a vortex to the bottom in a flat bottom vessel, but not im my growlers, I am happy with it.

Congrats!

 

[Munsoned]

Your vortex also won't be as strong once there is wort/yeast in there. It gets thicker and slows down the spin. In fact, that's one of the signs I use to tell how far along the yeasties are in the process...

 

[HarkinBanks]

I just built a very simple stir plate with a computer fan, HD magnets and a cell phone charger. I put it on plexiglass and got a fairly small vortex with a 1 inch stir bar. It worked pretty good for my last starter, which was in a 2L flask and a 1.5L starter volume. A 2 inch stir bar would spin, but no vortex. I decided to remove the plexiglass and seat the flask right on the screws of the fan raised up just a bit, with the flask as close to the magnets as possible. This worked like a charm, now I have a great vortex with a 1 inch stir bar. You can easily make stir bars yourself with cut down steel nails and some small plastic tubing from Home Depot. You can seal the sides of the plastic tubing over your gas stove. I made a few of them and tested them out to see which size worked best with my setup. Proximity to the magnets and size of the stir bar were the key for me.

 

[jrfuda]

Great info guys. I finished my stirplate build yesterday and had the same concerns about the size of the vortex and ordered some stronger magnets so my 2" stirbar would work (1" works fine). I was using some cheap (12 for $2) magnets I picked up at Lowes and ordered some strong neodymium rare earth magnets to get the 2" to work, however, now I see that the vortex I'm getting in my 2L flask is good enough.

Of course, that won't stop me from trying the stronger magnets when I get them!

 

[jtrainer]

I agree the vortex depth is not critical. However in goof ing with my DIY stir plate I found my magnet distance to the stir bar was crucial.

I used an older HDD magnet, cause I'm cheap!

 

[StirStarters]

Yeah, a "Wizard Of Oz" vortex is cool to watch, but not really necessary.