thrown stir bar!!

Brewer's Friend 728
Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Seawolf

Seawolf

Well-Known Member
Joined
Feb 24, 2008
Messages
223
Reaction score
7
Location
Alexandria, VA
Is there a fix for a stir plate that keeps throwing the stir bar? I can't get the bar centered, and it doesn't spin for more than 10 seconds or so.
 
Can you slow it down? That is the only way I can get mine to spin well, too fast and its off.

I also saw someone who had good luck with a + shaped stir bar.
 
Do you keg?

Try placing a o-ring at the center of the bar as a pivot point. Works for me and I use the curved bottom 1 gallon jugs.
 
GilaMinumBeer said:
Do you keg?

Try placing a o-ring at the center of the bar as a pivot point. Works for me and I use the curved bottom 1 gallon jugs.
Click to expand...


Not a bad idea! It kind of seems like it doesn't even want to stay centered in over the stir plate though. The bar tends to favor 1 or the other magnet at rest. Is that normal for you guys?
 
Mine would throw all the time on my home built stirplate.

I had two hard drive magnets close together on the hub of the fan (differing poles facing up). I ended up putting a thin piece of pressed wood across the hub of the fan and gluing the magnets to the end of that so they were about 1" apart.

I've also heard that if you go down to having one magnet it can work as well.
 
conpewter said:
Mine would throw all the time on my home built stirplate.

I had two hard drive magnets close together on the hub of the fan (differing poles facing up). I ended up putting a thin piece of pressed wood across the hub of the fan and gluing the magnets to the end of that so they were about 1" apart.

I've also heard that if you go down to having one magnet it can work as well.
Click to expand...


Interesting..... I have two hard drive magnets, and the same polarity is facing up on both magnets. Are they supposed to be different?!?! I'm gonna get a smaller stir bar as the one I have is 2". If the smaller bar doesn't work, I can reverse polarity, or reduce to one magnet.
 
Should be differing polarities facing up. If you take your stirbar and touch opposite ends to one pole of a magnet you will see that (normally) its just a bar magnet inside a plastic shell, so to get the maximum attraction between your bar magnet and two hard drive magnets you would want opposite poles facing up.
 
Also, try a smaller stirbar. I switched to a smaller one AND one that did not have the ring in the center and have not had a problem.

And your magnets should be aligned so that both poles of the stirbar are matched with the poles of the RE Magnets....
 
I originally had 2 of the kidney shaped magnets from a hard drive on my fan. No matter what polarity NN/NS/SS and spacing or stacked, I could never get it to grab as well as if I only had 1 magnet.

I recently moved the fan a little closer to the bottom of the plexiglass, and now can pull a vortex in 1.5L of wort in a 2L flask with my 2" bar. I have 2mm spacing above my magnet to the plexiglass which the flask sits directly on. Moved it closer by 2mm, and it made a huge difference in stability at speed.
 
Typically, a thrown bar is from trying to spin too fast. If you can't slow down the spin, then put some kind of spacer between the top of the stir plate and the flask. Plexiglass would be ideal, but you could use wood, cardboard, etc. Just experiment with materials and thicknesses until you get what you like.
 
s3n8 said:
I originally had 2 of the kidney shaped magnets from a hard drive on my fan. No matter what polarity NN/NS/SS and spacing or stacked, I could never get it to grab as well as if I only had 1 magnet.

I recently moved the fan a little closer to the bottom of the plexiglass, and now can pull a vortex in 1.5L of wort in a 2L flask with my 2" bar. I have 2mm spacing above my magnet to the plexiglass which the flask sits directly on. Moved it closer by 2mm, and it made a huge difference in stability at speed.
Click to expand...


Where did you put your one magnet? centered?
 
The one my son and I bilt, We use 1 magnet on a center line of the fan. It seems to work better then when we had 2 spaced acrossed from each other.
 
I have a single hard drive magnet centered and balanced (placed in the best location to reduce shimmy) and get a full vortex in 3 quart 1.040 to 1.060 starters using the o-ring center pivot at full speed start up and it doesn't get thrown. Ever.

Before I added the pivot ring it got thrown ewven at the slowest speed.
 
I had similar problems with two magnets. Pried them off and centered one. Works much better.
 
david_42 said:
I had similar problems with two magnets. Pried them off and centered one. Works much better.
Click to expand...


It sounds like the pivot ring is crucial. As soon as I get the new bar, I'll play around with the magnets. It sounds like I only need one. I can't wait to get this thing working!
 
slyngshot said:
Where did you put your one magnet? centered?
Click to expand...

Yes, centered. try to find the center of gravity on the magnet, and put that directly on the center of the fan. Mine sticks without glue, so I guess I got lucky.

Also play with the spacing between the magnet and stirbar. I have the fan mounted on long machine screws, so i can raise and lower it easily. I found that the closer I got the magnet to the stir bar the faster i could spin up to a point. Takes a bit of tweaking to get it just right.
 
If the bottom of the vessel is not flat it can make the stir bar wobble and get throan. Flasks usually have a nice flat bottom.
 
When I built my stirplate the first time I used hard drive magnets as well. They were super strong, but I think something about the shape of them does not serve well for use as a stirplate, as I threw the bar after awhile, even in plain water.

So I bought a package of round neodymium magnets at my local hardware store for $4, the small button shaped ones about a quarter inch in diameter. I glued them on the fan(opposite polarity of course) so they were exactly the same length apart as my stirbar(1.5") and I have never thrown it, even after three days spinning in wort.
 
smizak said:
When I built my stirplate the first time I used hard drive magnets as well. They were super strong, but I think something about the shape of them does not serve well for use as a stirplate, as I threw the bar after awhile, even in plain water.

So I bought a package of round neodymium magnets at my local hardware store for $4, the small button shaped ones about a quarter inch in diameter. I glued them on the fan(opposite polarity of course) so they were exactly the same length apart as my stirbar(1.5") and I have never thrown it, even after three days spinning in wort.
Click to expand...


That sounds like some sound advice!! I'll give that a shot too!
 
Someone never took chemistry lab. This is a really common problem. My students crank the stir rate and wonder why the stir bar just broke through an erlenmyer.
 
I used my stirplate for a year without any problems. Now it throws the bar every time after about 2 seconds.

I may have to remove one of the magnets and center the other.

FWIW, my flasks are not flat bottomed.
 

Similar threads

Nagorg
Stir Bar Size for Maelstrom Stir Plate
Replies
17
Views
2K
wepeeler
wepeeler
M
For Sale Maelstrom stir plate & Conductivity Tester
Replies
7
Views
505
MrCheezle
M
olie
How to help hop-cake not "melt" after whirlpool (during knockout)?
Replies
5
Views
689
Broken Crow
Broken Crow
bweinel
For Sale Variable Speed Magnetic Stir Plate w/flask and stir bars - Raleigh NC
Replies
0
Views
424
bweinel
bweinel
P
Bar Gun equipment guidance.
Replies
3
Views
205
whoaru99
W
Brewer's Friend 300

Latest posts

Back
Top