Advise on a magnet for a DIY Sitrplate

[DRoyLenz]

Hey All -

I'm in the planning stages for building a stirplate, and I was hoping for a recommendation on which magnet I should use. I have a bunch of harddrives, but they all have data on them, so I don't really want to scrap any of them. I was looking at Forcefield Magnets but was unsure of which magnet I should get. I have got all of the other parts (or at least I know where I'm going to get them). The only thing left is the magnet and stirbar, but I think I'm going to go with the 2" Magnetic Stirbar from AHS.

Any thoughts?

 

[DRoyLenz]

bump.... let's try this again people

 

[Surly]

Go to a computer shop. Tell the good people there what you want magnets for. Computer geeks are not that far from beer geeks.

They will become interested in your project and you will have plenty of magnets. Drop off a six pack some Friday afternoon.

 

[knownikko]

Go to a computer shop. Tell the good people there what you want magnets for. Computer geeks are not that far from beer geeks.

They will become interested in your project and you will have plenty of magnets. Drop off a six pack some Friday afternoon.

+1

Or just post on Craigslist looking for a dead hard drive. Someone will oblige for far less than any fancy magnet will cost you.

 

[DoubleXL]

I tried 2 local PC shops one just said he couldn't help the other said it was illegal for him to sell me a "used" hard drive so I'm looking also.

 

[jackson_d]

1" stirbar. 2" are tuff to get to spin, seriously, dont do the 2". get the 1"..

https://www.homebrewtalk.com/f51/my-stirplate-cheap-easy-build-86252/

on this site- easy instructions for stirplate. look through that, you'll find the link for the good magnets

 

[krops13]

I called up a computer store asking for any old hard drives. He was very inquisitive about why i would need the magnets from a hard drive. 1 22oz bottle of beer later I'm leaving with magnets in pocket.

 

[keiths]

I am one of those computer GEEKS and I have as many magnets as U need.How many do U want.

 

[smizak]

In my local hardware store, i found some neat little neodymium button magnets, smaller than a dime. They work great for me. I tried hard drive magnets and the stirplate was super sketchy and would barely hold a bar for more than a minute.

 

[buffalobrewer]

harbor freight has button magnets that I am using in mine. Work great.

 

[homebrewer_99]

1" stirbar. 2" are tuff to get to spin, seriously, dont do the 2". get the 1"..

https://www.homebrewtalk.com/f51/my-stirplate-cheap-easy-build-86252/

on this site- easy instructions for stirplate. look through that, you'll find the link for the good magnets

I built a homemade stirplate that worked great for about a year.

Later on, I purchased a new stirbar. It wouldn't stay centered and kept getting tossed to the side of the flask. I did a side-by-side and realized it was longer than the first and was probalby the source of my problem.

I took the box apart and pulled the magnets off (they were glued on).

I then repositioned the magnets further apart (about 1/2" or so) and glued them back into place. I placed a small piece of wood between them to keep them sperated until the glue dried (they kept sliding toward each other and the center of the fan).

Now it works great again.

What I'm trying to say is the length of the stirbar isn't as important as the distance between the magnets that's going to make it work better.

 

[remilard]

I bought a box of like 30 stir bars (3 of various sizes) in various sizes on ebay for $20 shipped. That is a little more than 2-3 stir bars run you at a home brew shop.

This accomplished two things for me. First, I could try out various sizes and see which worked best. Second, I had three of the one that worked best, which I couldn't have bought for less than $20 individually anyway.

 

[SpanishCastleAle]

What I'm trying to say is the length of the stirbar isn't as important as the distance between the magnets that's going to make it work better.

I think it's the combination of the magnet distance AND the stirbar length.

Take a stirbar that's too long and place it on the stirplate (no flask or nothing) and you'll see that one magnet 'grabs' one end of the stirbar and the other end of the stirbar extends past that second magnet. So now the magnet is not centered about the rotational axis of the motor.

Take a stirbar that's too short and place it on the stirplate (no flask) and again one magnet will 'grab' one end of the stirbar but the other end doesn't even reach the second magnet. So again, the magnet is not centered about the rotational axis of the motor.

It seems the 'magnet length' needs to be relatively close to the length of the stirbar (actually the magnets inside the stirbar) otherwise the magnets will always be tugging the stirbar one way or another such that's not centered about the rotating axis of the motor.

I figured by the time I sourced/scrounged everything and put the time in it to build I'd have spent at least $45 so I just bought a stirplate.com model.

 

[homebrewer_99]

...I think it's the combination of the magnet distance AND the stirbar length...

...It seems the 'magnet length' needs to be relatively close to the length of the stirbar (actually the magnets inside the stirbar) otherwise the magnets will always be tugging the stirbar one way or another such that's not centered about the rotating axis of the motor...

I totally agree.

I think a wide space between the magnets will get results with either a long or short stir bar.

 

[Mirilis]

Try going to radio shack.. they sell Rare Earth Magnets.. its the same thing thats in your hard drive except its a cylinder shape.

 

[raceskier]

On my homebrew stirplate, I first tried the Radio Shack NdFeB magnets: http://www.radioshack.com/product/index.jsp?productId=2102642&filterName=Category

They proved to be much too small. Not enough remanence (magnetic force) to hold a 1 inch stirbar. I ended up with some ebay NdFeB's closer to this size: http://69.175.14.181/catalog/product_info.php?cPath=23_37&products_id=32
(That's a great price BTW.)

 

[Sacdan]

*edit* already covered above

 

[HSM]

http://www.supermagnetman.net/index.php