DIY Stir Plate works without a flask but not with one - Home Brew Forums
Register Now For Free!

Home Brew Forums > Home Brewing Beer > DIY Projects > Chillers & Stir Plates > DIY Stir Plate works without a flask but not with one

Reply
 
Thread Tools
Old 10-15-2013, 07:20 PM   #1
giz
Recipes 
 
Oct 2013
Posts: 3



Let me preface with I am new to the forums. This place seems nice.

I'm running into an issue with my stir plate. When I rest my stir bar on top of the stir plate it will spin freely, and quickly, but when I place the stir bar into a flask with a liquid, the bar will not spin and throw to the side.

So, all of that being said, here are my stir plate specs.

Stir Plate Specs:
  • 25 Ohm Rheostat
  • Fancy switch thingy with red light
  • Computer Fan
  • 12v Power Supply
  • 3/8" round rare earth magnets with 10 lbs. of pull force
  • 1" stir bar with pivot ring
  • Pyrex 2000mL flask - flat bottomed
  • Project box

2 magnets are mounted on a steel washer than has been epoxied to a small section of PVC pipe mounted to the fan. The poles are correctly setup so the stir bar will attach once brought into the magnetic field. The magnets are as close as you can get to one side of the project box that will allow the magnets to spin without rubbing on the top.

So here are my questions:

1. Should I swap my 12v power supply with a 6-9v range?

2. Does my fan spin fast because the 25 Ohm rheostat isn't doing much good? (Assuming so because at the lowest speed it seems to travel like a pack of gazelles)

3. Would adding more 3/8" round magnets to the magnet stacks increase the magnetic force/pull on the stir bar?

4. Does the added thickness of the flask really negate the magnetic attraction so much it causes the throwing?

Any help is greatly appreciated.

 
Reply With Quote
Old 10-15-2013, 07:23 PM   #2
funnycreature
Beer Crafter, Metalhead \m/
HBT_LIFETIMESUPPORTER.png
 
funnycreature's Avatar
Recipes 
 
Mar 2013
Harpers Ferry, West Virginia
Posts: 1,059
Liked 190 Times on 161 Posts


Sounds like your rotor is spinning too fast. The liquid is too viscous for the bar to spin fast enough. There are a lot of discussions here how to throttle a fan correctly as a rheostat does not do a good job. Look also here: http://braukaiser.com/blog/blog/2013...ed-stir-plate/
__________________
Brütal Brews - Infüsing Craft Beer with Metal since 2013

Check out my wife's etsy store where she offers soaps made with my beer!

giz Likes This 
Reply With Quote
Old 10-15-2013, 07:37 PM   #3
FuzzeWuzze
I Love DIY
HBT_SUPPORTER.png
 
FuzzeWuzze's Avatar
Recipes 
 
Jun 2012
Newberg, Oregon
Posts: 3,109
Liked 426 Times on 312 Posts


I only use a 9V supply for this very reason. No need for fancy switches and knobs, i put my flask on my stir plate, ensure its centered as best as i can and plug it into the wall. Then recenter as needed for no other reason than when its properly centered it will be dead quiet, if its off a bit the stir bar rattles against the glass constantly.

 
Reply With Quote
Old 10-15-2013, 07:51 PM   #4
brewkinger
AdirondacKinger
HBT_LIFETIMESUPPORTER.png
 
brewkinger's Avatar
Recipes 
 
Sep 2012
NEK, Vermont
Posts: 2,284
Liked 345 Times on 282 Posts


Quote:
Originally Posted by FuzzeWuzze View Post
I only use a 9V supply for this very reason. No need for fancy switches and knobs, i put my flask on my stir plate, ensure its centered as best as i can and plug it into the wall. Then recenter as needed for no other reason than when its properly centered it will be dead quiet, if its off a bit the stir bar rattles against the glass constantly.
I switched from 12V to 9V supply as well.

I also spent a decent amount of time "tweaking" the correct distance between the bottom of the project box and the magnet.

Keep tinkering, it will all come together eventually.
__________________
Blackbird Brewing

PRIMARY: Northeast Style IPA aka "Roscoe"
PRIMARY: Centennial '75 Session IPA
BOTTLED: Razapple Wine- Vintage 2014
BOTTLED: Orange Haze Blonde
BOTTLED:
KEGGED:
PLANNING: Centennial Orange Blonde
PLANNING: Roscoe V.2
Do not mistake my kindness for weakness. I am kind to everyone, but when someone is unkind to me, weak is not what you will remember about me.

Stealthcruiser Likes This 
Reply With Quote
Old 10-15-2013, 11:01 PM   #5
60sd
Recipes 
 
Jun 2012
Manteca, CA
Posts: 86
Liked 5 Times on 4 Posts


I had the same issue with mine, but the problem was the round heads on the screws that I used to attach the fan to the box set the flask up too high. I changed to tapered or bugle heads and counter sunk them so its completely flat across the top of the box and it works fine now. Doesn't sound like thats your problem, but I figured I'd throw it out there in case someone else is having that problem.

 
Reply With Quote
Old 10-16-2013, 01:01 AM   #6
giz
Recipes 
 
Oct 2013
Posts: 3


Thanks folks. I'll give these ideas a shot and let you know how it works.

 
Reply With Quote
Old 10-16-2013, 04:06 AM   #7
giz
Recipes 
 
Oct 2013
Posts: 3


Quote:
Originally Posted by funnycreature View Post
Just nerdgasmed reading this site. Thanks for the link.

 
Reply With Quote
Reply
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
My Stir Plate Works Better as a Blender WoodlandBrew Fermentation & Yeast 6 02-23-2013 04:36 AM
Stir plate actually works. mopillar Chillers & Stir Plates 3 05-17-2012 05:19 PM
My stir plate works but throws the bar codyjp Chillers & Stir Plates 10 07-25-2011 01:08 AM
Why do I need a flask for my stir plate? Kayos Equipment/Sanitation 18 01-11-2011 01:22 AM
My Stir Plate...IT WORKS!!! CyclingCraig Chillers & Stir Plates 4 03-27-2008 05:52 PM


Forum Jump