Magnetic stirrer construction (with pictures)

[demorol]

This link might be useful for all DIY bees. Check it out:

http://www.lce.org/equipment/stirrer/stirrer.html

Life without chemistry would be a mistake.

[goiterjoe]

What size motor would be recommended for a stirrer for a 5L flask?  The stirrer I used to have started struggling to keep a good vortex going with anything over 3L.
All paths are the same: they lead nowhere

[UTFSE]

Most important and difficult part is
centering the magnet- balancing the motorshaft/magnet combo

1- get a blown speaker - look around there are thousands of them out there
disassemble and retain the round magnet and the "keeper" portion - looks like a hat of ferrous (magnetic) metal

if its riveted bust is loose carefully

if its glued soak it in a solvent

seperate the back magnet and keeper from the front metal structure that surrounds the now defunt speaker cone.

2- remove the "keeper portion" from the round magnet

the magnet material is very brittle and will cut your paws not to mention ruin its value

3- drill a hole in the center of the "keeper" - there is usually an indentation already there. make the hole the size of your motors shaft.

4- firmly attach the "keeper" to the motor shaft. this can be done a variety of ways. epoxy will work if high speeds and vibration can be avoided. otherwise drilling and placing a pin across both pieces or tapping and threading both keeper and shaft.  a machine shop could mount it for you.

5- go to the approipriate place and purchase a fan/motor control speed controller.
 
6- balance the round magnet originally removed from the keeper back on the keeper.  by   spinning the motor and making slight adjustments in the magnets position until it no longer vibrates or the amount of vibration is acceptable.

Mount the whole thing in a non-magnetic enclosure. Vertically.

No belts,simple components OTC and easy to maintain the balance and repair- spin it baby!!!





OTEECEE & meeeee!!!!

[humidbeing]

Does this thing take into account the degree of heat it
can withstand?
 Although a mantle with it's glass housing puts off
very little ambient heat, SWIMS set up gets very hot to
the touch. but seems to take it well.
CG I miss you sweety, I really do.

[SaintCyril]

Making things is awsome, and aquiring otc is cool too, but check your phone book for surplus and industrial surplus stores, they are getting rid of extra stuff, and half the time they don't even know what it is, there is a store in my area with unlimited mag stirred/hot plate combos for $15, and there are three other of these surplus type stores in my area that also have similar, but slightly higher prices.

Anyhow just trying to help
cy
So you need a precursor to a pecursor, just to make a precursor thats what the people told me . . .

[ylid]

If you bust open a defunct microwave oven you will find a fan and a plate-spinning device, either of which might do for a stirrer motor. More interestingly if you break apart the magnetron you will also find 2 very powerful ring magnets. Fix magnet to fan, insert underneath hotplate, cross your fingers and hope it doesn't melt... voila.

[raffike]

I don't think this HDD motor stirrer is any good for volumes over 1 liter.100 wt stirrer is enough for every purpouse,for example IKA maxistirrer that stirs upto 130 liters or so...

[Organikum]

of a microwave has 5 Watts and makes 5 to 8 rpm. How to get a vortex out of this? Forget it.

Harddiskdrives - the old ones 5 1/4" full height contain very useful strong neodym magnets - first choice for such a project. (also cheap at surplus). For harder jobs like Goiterjoe mentioned, make a full electromagnetdriven one - principle of a linearmotor. Seven to nine electromagnets working push-pull. The trick is: You can without any problems overload electromagnets up to an 100x nominal load if the pulse is short. All starters of automobiles work by this idea. Stirrs everything - power depends on your stirrbar alone - best made from plain transformer iron - not magnets. Flux is the key!