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starman
Hazard to Others
Posts: 318
Registered: 5-7-2008
Location: Western Australia
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Mood: No Mood
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@kalacrow,thanks for the ideas.I have actually already built one a few years ago using an AC fan motor(they are after all made to run
continuously)With the aid of some thread tape a 10mm drill chuck went on the shaft nicely.However without the fan attached the motor gets incredibly
hot within half an hour,I wasn't game to run it longer than that and only ever used it on aqueous solutions.Additionally the torque isn't great.(can
be stopped by hand).I will research the suggestions (particularly the automotive side) and hopefully see some more contributions to this thread.
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S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
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For years I used a drill and paint stirrer when I could (sucks to rig, useless for flasks), and later got real lab stirrers and blades and glass
shafts for use with real glassware. I still have to improvise some there because my stirrers go back to the 70's at least and one may be from the late
50's even, and these use 1/4" steel shafts, which are inconvenient for adapting to my 10 mm glass shafts. I've never seen a small electric stirrer
using a 3/8" metal shaft at any of the auctions I go to.
I bought a paint stirrer at Lowes or somewhere a couple months ago that could be useful for anyone that uses a container that these will fit in for
reactions, and has an old 1/4" stirrer: see at squirrelmixer.com. These have 1/4" steel (which can obviously be coated for use with acids) shafts, in
the gallon/quart size. The 5 gallon size has a 5/16" shaft. This is still useless for flasks, and the shaft could be longer, but that's how it goes.
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densest
Hazard to Others
Posts: 359
Registered: 1-10-2005
Location: in the lehr
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Mood: slowly warming to strain point
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For this sort of application you want a "gearmotor". Little electric motors want to go very fast - much too fast to be useful as stirrers. Little
motors typically go 10000-30000 RPM. You want 30-600 RPM to stir things. Electronic surplus houses and robot suppliers and RC car suppliers sell
various gearmotors for $US 3-10. They typically run from 2-24VDC, easily available from very cheap "wall wart" power supplies. I took one such from an
old printer, a piece of heavy teflon tubing for a shaft, and made a crude paddle on the end. 5VDC was slow, 12VDC was medium, 24DC was fast. Total
outlay was $0 since I already had a roll of Teflon tubing from EBay ($10 or so, a -real- bargain), old power supplies from dead computer gear, and the
motor came from a printer I scrapped. The hardest part was making a "bearing" to run the shaft through a stopper for the flasks. A piece of HDPE made
a slippery block to put the shaft through which didn't wear the soft teflon to shreds.
Cheap, worked fine, still have it & use it.
You could use a glass rod for a shaft, for instance, and mold a paddle onto the end.
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Cloner
Hazard to Others
Posts: 150
Registered: 7-12-2004
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Mood: apocalyptic
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A quick and dirty way to build a stirrer is to use a ventilator and tube. You remove the fan and put a few cm of tough rubber tube (propane burner
tube does the job, or vacuum tube) on the rotating bar. On the other side of the tube you put the stirring bit which can be a wooden kitchen spoon or
whatever is inert to your reaction mixture. Rubber tube can transmit rotation in angles but don't expect it to last if the angle is too great.
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chief
National Hazard
Posts: 630
Registered: 19-7-2007
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A drilling engine at reduced voltage will run slowly ... and more silent ...
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peach
Bon Vivant
Posts: 1428
Registered: 14-11-2008
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Yeah, I agree with the others, you'd be better going with something featuring gears.
A microwave turntable motor is remarkably strong, but it does have a fairly low RPM.
Be extremely careful with your solvents, things like cheapo electric whisks can put out some serious sparks from the brushes.
For the coupling, you can buy plastics that melt at 60C and thermofom. You could easily use some of that to custom build a chuck for just about
anything.
As for the bearing, just buy a rubber stopper and drill out the center to roughly fit the rod. Line it with some grease to smooth things out.
If you don't need it to be gas tight, which will be difficult to achieve with just about every home made option, then having a tiny amount of freedom
in the position of the rod may actually help it deal with bumps.
On the subject of PTFE collars, this gimp once purchase around $200 worth of them to fit specialized glassware, only to have said glassware perish at
a later date.... ho hum...
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