I pulled the pump head off of my March pump and noticed that it is a magnetic coupled pump head. I am considering testing to see if it can be used as a yeast stir plate motor. I can install a reostat to control the pump speed. I am interested in purchasing a magnet that is used in the flask for such a project. Has any one tried this before? If so did it work adequately to stir the yeast? Where can I purchase a magnet for the flask?
It’s called a “stir bar” and I’d suggest eBay, where you can probably find one for less than $5 including shipping. The more usual sources would be retailers like coleparmer.com and fishersci.com.
You can put together a stir plate for less than $30 though (link). It might be worth it, especially if your pump has the plastic head. Eventually you’ll just strip the threads.
Also, if memory serves the magnets in the March pumps surround the impeller. I’m not 100% sure they’d turn a bar that was a few inches removed from the hub.
On ebay under “stir bar.” Get something like a 2" bar. The one inchers won’t stir much liquid. Up to you to build the stir plate tho.
Definitely get a big stir bar, 2 inch or plus. I use a 3 inch in a 6L flask.
I’m not really sure the March pump will be able to do what you’re asking. And on top of that, the rotation speed will almost certainly be too high. You can actually throw the stir bar if you spin too fast. I don’t think a reostat will be able to turn down the power enough to work correctly.
I once got a package of I think 8 sizes of stir bars and 3 of each for $20 on ebay. About 3 of the sizes are useful to me but I do find that different size flasks sometimes work better with a different size bar so I like the flexibility and I definitely like having three of each. Never lost one, have dumped in the fermenter once or twice. I brew often enough that is problematic.
I have two stir plates now, both computer fan types but neither made by me. Even with the 2 liter flask I usually use I find one works better with a bigger bar and one with a slightly smaller.
You can find ceiling fan speed control units on ebay. Those will work with shaded pole motors. I use one for a BIG stirplate (think 3 gallon carboy) and one to control the pump on my rims.
My concern would be that if you slow the pump down using a rheostat it isn’t going to cool the motor properly and it would fail prematurely. That’s why homebrewers use a ball valve on the output of the pump to control flow vs. slowing down the motor.
One option for stir bars:
How about stirbar.com?
http://www.stirbar.com/
They have any stirbar you could imagine.
Bad thing is that they have minimum order.
Just a thought thou 