Sciencemadness Discussion Board - overhead stirrer wattage?

overhead stirrer wattage?

Funkerman23 - 21-10-2012 at 10:01

Generally speaking: what wattage overhead stirrer do you out there recommend for a 3 to 5 liter flask setup? I am considering one of these as my hotplate, while very helpful, is only good to about 2 liters or so of liquid. I thank you for your comments as always and I wish you the best.

Lambda-Eyde - 21-10-2012 at 10:20

I'm also interesting in hearing some input on this. I recently found an old overhead stirrer outside the chemistry department which seems to be functioning, but it seems to be very weak and it's only 25 (!) watts. I'm wondering how much it could take.

edgecase - 21-10-2012 at 15:06

I'm more interested in knowing the RPM range. There are surplus motors of many types, which could be adapted, some with gearing reductions etc. I wonder if automotive types such as power-seat might be in the right range?

CaliusOptimus - 22-10-2012 at 20:41

As a home chemist, I've found that a $20 chinese cordless drill makes a rather perfect overhead stirring motor. The torque and speed is significant enough to turn any sized stirring setup, and it's got a torque limiter in case of a jam!

You can either hold the drill with clamps (likewise for the trigger as a speed control), or you can remove the motor from the casing like I did, and wire it to a bench power supply. The whole drive train from motor to chuck should come out as one unit.

[Edited on 23-10-2012 by CaliusOptimus]

Funkerman23 - 23-10-2012 at 04:13

Quote: Originally posted by CaliusOptimus

As a home chemist, I've found that a $20 chinese cordless drill makes a rather perfect overhead stirring motor. The torque and speed is significant enough to turn any sized stirring setup, and it's got a torque limiter in case of a jam!

You can either hold the drill with clamps (likewise for the trigger as a speed control), or you can remove the motor from the casing like I did, and wire it to a bench power supply. The whole drive train from motor to chuck should come out as one unit.

[Edited on 23-10-2012 by CaliusOptimus]

I myself would go this route EXCEPT for fear of vapor ignition. I can't recall exactly where but I saw a thread here on the matter and more than a few posts warning that using a re purposed motor could cause problems either from the sparking( hence the fume issue) or the rotor's wobble.But for all I know i could be dead wrong on both points. Still any help, comments and remarks appreciated greatly.

[Edited on 23-10-2012 by Funkerman23]

watson.fawkes - 23-10-2012 at 05:51

Quote: Originally posted by Funkerman23

You can address the vapor issue in two ways, depending on your relationship with time, money, and tools. The first is to build a box around the whole drive train, including the motor, and separately ventilate it in a positive pressure mode (that is, blower on the inlet). The second way is to replace the motor with a TEFC version (Totally Enclosed Fan Cooled). These aren't nearly as cheap to buy new, though; expect USD 200-300.

As for the wobble issue, it's a good idea to use any one of the parts available to deal with misalignment and runout (the machinist's slang for non-axial rotation). I'm partial to Lovejoy couplers (named after the manufacturer); they have the advantage that simply raising and lower the quill can disconnect and connect, though you would need to rig up a stop to keep the quill down.

paw_20 - 23-10-2012 at 11:49

I'm no expert, but an IKA RW16 has a motor output rating of 55 watts, and they say it has a ten liter capacity. It's power input/consumption is 75 watts

CaliusOptimus - 27-10-2012 at 17:59

Quote: Originally posted by Funkerman23

I haven't had to use it with any flammable vapors so the thought hadn't crossed my mind, but in that case I have a suggestion. A stepper motor would be a non-sparking option, but it would require a drive circuit (google 'velleman k8005' for a cheap kit). That and a flex coupler (or even a piece of rubber tubing) would make for a cheap and effective stirring setup. I considered this for myself at first, but the only motors I have laying around are monsters.

Funkerman23 - 18-10-2013 at 19:00

Bump? Not trying to perturb the mods but with the holidays looming I might be able to score one and a (much needed) mantle and I haven't had much luck jury rigging so far. On a related note: should I stick with glass( jacked or non jacketed) stirrer bearing or will the Chinese PTFE ones hold out?My gut says go ahead and find a jacketed stirrer bearing but I hope you good folks will have an answer on that matter as well.

Funkerman23 - 26-10-2013 at 17:55

Update: while this isn't much progress, I've found that the YouTube channel : myst32YT in 2(that I know of) videos he uses a 25 watt overhead stirrer from Changbio on eBay( another eBay user; comewithstyle has an overhead stirrer but they appear to either be made by the same factory or on similar tooling). Granted his is an earlier version but in the two videos he stirs a slurry of calcium hypochlorite/water, acetone mix as well as uses it to prepare hydrobromic acid. The haloform mix was in what looked like a 500Ml( maybe a 1 liter) flask . Now I know this isn't exact or even formalized in any real way but hopefully this is a possible start to answer the original question. Yes these are Chinese, not ideal by any means, but it's an option.

jamit - 29-10-2013 at 20:12

I have an extra overhead stirrer by Sargent welch if anyone is interested. It will have no problem stirring anything you can throw at it. U2u me if anyone is interested. Cost is 75.00 plus shipping.

UnintentionalChaos - 29-10-2013 at 20:31

U2U sent.

Funkerman23 - 29-10-2013 at 21:13

...well it looks like I missed that one..dang

jamit - 30-10-2013 at 05:24

here's some pictures of the overhead stirrer

testimento - 30-10-2013 at 09:15

If the liquid viscosity is close to water, one can easily survive with 25-50 watts maximum for up to 10 liters. I used times ago an electric fan with 30W three-phase power switch for 10 liters batch max and it survived good as long as the fitting was made properly from teflon to minimize friction. I have 300W ball mill and its actually way too overpowered for the 2kg maximum mass it has to rotate.

On the other hand, I've had many batches where I was glad to use that 300watts to stirr the crap out of it.