bfesser - 26-12-2010 at 10:17
I'm considering purchasing an overhead stirrer for use with my 24/40, 19/22, and 14/20 glassware. Is a stirrer with a minimum speed of 500 rpm too
fast? If so, what minimum rpm should I look for?
Magpie - 26-12-2010 at 21:00
I have an overhead stirrer but have not used it much. It's a Wheaton that I won on eBay. It needed a chuck and shaft adapter so the price was good.
I just measured it's low speed at no load at 120 rpm. For our kind of work I think it is desirable to have one which will turn at low speed under
load.
How's the weather in the Northland? 
aonomus - 27-12-2010 at 07:49
What you ideally want is a stirrer with closed loop speed control so that the load can change while maintaining RPM, say if your reaction mixture
becomes thick as it cools, stirring is maintained.
Bear in mind you will also want to consider the type of shaft adapter and shaft (ground glass vs non ground glass vs teflon).
Protip: once you get your stirrer, detach the chuck and toss it. Slip a piece of vacuum tubing over the shaft, and whenever you need the stirrer, just
shove the stir shaft up into the vacuum tubing. Its flexible enough to allow for some mis-alignment.
bfesser - 27-12-2010 at 13:39
Magpie, it's bitterly cold and we're balls deep in snow--so, perfect. 
Thanks for the tips. I already have some vacuum tubing on my stirrer shafts, in anticipation of getting a motor. As for the cloosed loop controller,
I guess I'll have to watch the auctions for mis-categorized items. Most of what I've seen is way too expensive!