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Author: Subject: Using an Electric Drill as an Overhead Stirrer
JJay
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[*] posted on 25-12-2015 at 17:50
Using an Electric Drill as an Overhead Stirrer


I have been looking at purchasing an overhead stirrer, and it looks to me as though they are outrageously priced. For this reason, I am thinking about using an electric drill as an overhead stirrer.

I plan to mount the drill in a condenser clamp and put a PTFE stirrer paddle in the chuck, using a tapered PTFE stirrer bearing. The particular drill I plan to use will allow locking the trigger in the on position. I can modulate the drill speed with a triac dimmer.

I think this setup will function ok for a short while, but I'm not sure how long an electric drill will last when used as an overhead stirrer. Has anyone ever used a drill as an overhead stirrer before?
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hissingnoise
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[*] posted on 26-12-2015 at 03:23


Have you considered a magstir?

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JJay
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[*] posted on 26-12-2015 at 03:40


Quote: Originally posted by hissingnoise  
Have you considered a magstir?



Sometimes, mixtures are too thick for magnetic stirring.
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[*] posted on 26-12-2015 at 06:24


I've been thinking about getting one of these from a second hand/thrift shop and modifying it, I see them quite often, I wouldn't mix anything flammable with it though

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[*] posted on 26-12-2015 at 06:47


I was thinking of the same exact thing, but instead of a electric drill use a pnumatic type drill, That way no boom.
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JJay
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[*] posted on 26-12-2015 at 07:38


Quote: Originally posted by skip  
I was thinking of the same exact thing, but instead of a electric drill use a pnumatic type drill, That way no boom.


I like that idea... I see a lot of sparks inside the drill I have been thinking of using. I don't have a good source of compressed air, though.... Putting an electric drill at the top of a column of refluxing ether might not be such a great idea... but I could lead the vapors outside pretty easily.

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[*] posted on 26-12-2015 at 08:19


There is a discussion of this in EM, as part of a nitroglycerin synthesis thread.

http://www.sciencemadness.org/talk/viewthread.php?tid=949&am...

It worked. But you should think through the ramifications if setting up improvised equipment... Here are a couple, off the top of my head:

Pneumatic drills are capable of very high RPM but have very low torque @ low speeds, in my experience. Also consider how adding several cubic feet/minute of exhaust to your hood might change the airflow, as such drills are not usually plumbed for an air exhaust hose to take the spent compressed air elsewhere-

Non totally enclosed, fan cooled electric motors are obviously bad for an explosive or flammable environment. Such devices were also not designed to protect bearings and electrical contacts from corrosive atmospheres, so they may have a shortened service life.

A lot of electric motors are NOT designed to run with a "wave chopper" as a speed control. If dropping the voltage increases the curent in the circuit (motor winding), you will have an overheating issue- especially if your process runs continuously for a longer time than a homeowner grade tool was designed for. Such tools are designed around "duty cycles", homeowner grade may be only intended to run 20% of the time or so over a 10 minute interval. The expensive professional grade ones may be needed for a 100% cycle.




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[*] posted on 26-12-2015 at 10:31


Here's some bedtime reading for you:

http://www.sciencemadness.org/talk/viewthread.php?tid=41539




The single most important condition for a successful synthesis is good mixing - Nicodem
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[*] posted on 26-12-2015 at 12:51


According to the manual, the drill I have been considering for this application (a $20 Ryobi drill) is designed for continuous duty but only at high speed. It recommends running the drill at top speed if there are any issues with high temperatures. It does work at lower speeds with a triac, but I think overheating could be an issue if run at low speeds for long periods of time.

I don't relish the idea of using a stepper motor in a stirrer, but I do have some gear motors and components that could be used to wire up control circuitry... as well as stepper motors. Stepper motors do have an advantage in that they don't give off sparks, which is probably a good thing in environments with explosive vapor, and I'm not sure about my gear motors... I'll check when I get back to the lab.

Of course, none of my motors are designed for corrosive environments... TBH, I don't think most stirrer motors really are either.
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[*] posted on 26-12-2015 at 13:27


I have used my stepper motor stirrer once since assembling it. It performed well but I could have used more rpm - its limit is 220rpm using 12vdc. With an 18vdc I could get 700rpm which would surely be enough for most all of my syntheses.

I would feel comfortable using it in an application with an ether solvent as long as my hood fan was on.




The single most important condition for a successful synthesis is good mixing - Nicodem
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[*] posted on 27-12-2015 at 14:53


Quote: Originally posted by JJay  
Quote: Originally posted by hissingnoise  
Have you considered a magstir?



Sometimes, mixtures are too thick for magnetic stirring.

What's an example? I've never come across a solution that couldn't simply be thinned out by adding a solvent+ larger reaction vessel. Or in turn, heating it.




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[*] posted on 27-12-2015 at 16:26


Quote: Originally posted by JJay  
Putting an electric drill at the top of a column of refluxing ether might not be such a great idea... but I could lead the vapors outside pretty easily.



Ever had a fire? I have. Scary shit. An induction (brushless) motor would be the way I tried to go and with a semi Rube Goldberg-ish linky set of pulleys and a belt (think drill press) the speed could slowed way down and torque increased to usable amounts. I've been thinking of needing stirring too, and hotplates are ridiculously priced, especially when one can get "obtanium"




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[*] posted on 27-12-2015 at 20:19


Quote: Originally posted by arkoma  
Quote: Originally posted by JJay  
Putting an electric drill at the top of a column of refluxing ether might not be such a great idea... but I could lead the vapors outside pretty easily.


Ever had a fire? I have. Scary shit.

I'm still cleaning off the residue from the fire extinguisher off my glassware.
It's more annoying than anything. :(




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[*] posted on 27-12-2015 at 23:39


.....even overhead stirrers get contaminated and begin to malfuntion, i've considered an air drill with a small roofing compressor, running it, this way no electrilcal contacts , no danger of explosions and it would last longer as for the torque, it would depend on the air pressure running it.......solo



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[*] posted on 28-12-2015 at 00:18


Oh you compulsive diy types..doesn't the synthesis offer enough challenge? I've got a spare conical drive stir motor you could buy for lab trader prices



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JJay
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[*] posted on 28-12-2015 at 06:31


Quote: Originally posted by dermolotov  
Quote: Originally posted by JJay  
Quote: Originally posted by hissingnoise  
Have you considered a magstir?



Sometimes, mixtures are too thick for magnetic stirring.

What's an example? I've never come across a solution that couldn't simply be thinned out by adding a solvent+ larger reaction vessel. Or in turn, heating it.


Seriously?? Aren't you a professional chemist?
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[*] posted on 28-12-2015 at 06:38


Quote: Originally posted by arkoma  
Quote: Originally posted by JJay  
Putting an electric drill at the top of a column of refluxing ether might not be such a great idea... but I could lead the vapors outside pretty easily.



Ever had a fire? I have. Scary shit. An induction (brushless) motor would be the way I tried to go and with a semi Rube Goldberg-ish linky set of pulleys and a belt (think drill press) the speed could slowed way down and torque increased to usable amounts. I've been thinking of needing stirring too, and hotplates are ridiculously priced, especially when one can get "obtanium"


Yeah, I've had some small fires but never one that got out of hand. IMHO, the best kind of motor to use would be an oil-filled one.
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[*] posted on 28-12-2015 at 07:00


Vogel suggested using a flexible shaft to protect the stirrer from fires and corrosive vapors.

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[*] posted on 28-12-2015 at 08:05


hope this helps
https://www.erowid.org/archive/rhodium/chemistry/equipment/o...
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[*] posted on 28-12-2015 at 10:29


Quote: Originally posted by CuReUS  
hope this helps
https://www.erowid.org/archive/rhodium/chemistry/equipment/o...


Some kitchen mixers spark so much that they could probably be used as part of an ozone generation apparatus....

Using a cork lubricated with glycerine is a bit ghetto for my tastes... I plan on using a PTFE bearing unless I need something that is really tightly sealed... Vogel recommends a mercury-filled bearing.

I wonder if a kitchen mixer would hold up better under continuous duty than an electric drill. The rubber tubing coupling is a good idea.
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[*] posted on 28-12-2015 at 18:13


The Parr pressure reactor utilizes an offset motor, several feet lateral to the reactor itself.

This works well and provides lots of torque, but it is not inherently explosion proof. In theory, flammable or explosive vapors, are isolated inside of the sealed reactor itself.

Still, a drill press could be re-purposed to become an overhead stirrer. It has an offset motor-mount.....AND, a higher speed air motor, could be geared down to provide lower speed and higher torque, via the drill press's pulley system. Static discharge might still be a concern, but compared to the hazard a sparking, standard AC motor produces, danger is vastly decreased.

Got a good sized, standard, un-motored, drill press you can modify? Of course, as a propellant, an explosion proof DC motor would also serve, in lieu of an air motor. http://www.harborfreight.com/8-in-5-speed-bench-drill-press-...

Oh, yeah, Parr....once upon a time, such systems were available used, on e-bay, at reasonable prices. Haven't seen a decent offering in a while. Quite possibly, private individuals are being blocked from freely selling these items.


http://www.ebay.com/itm/Parr-Reactor-System-500-ML-Hast-C-10...

[Edited on 29-12-2015 by zed]

[Edited on 29-12-2015 by zed]

[Edited on 29-12-2015 by zed]
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[*] posted on 29-12-2015 at 04:21


I found an oil-filled stepper gear motor, 12 volts, 1/64 step, 19:1 gear ratio. I'm a little concerned that it might overheat, but other than that it looks sufficient.

I'm going to try the drill first since it is so easy to rig and if it starts to overheat, I'll prepare a controller for the motor.
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[*] posted on 29-12-2015 at 08:51


Quote: Originally posted by zed  


Still, a drill press could be re-purposed to become an overhead stirrer. It has an offset motor-mount...


A variable speed tabletop drill press plus a flexible shaft might be a really good stirrer set-up (throat clearance would generally be insufficient without). Torque galore.

There is of course the famous Chinese 5-speed drill press sold by many companies but cheapest from Harbor Freight for $70 or less (depending of coupons and special sales), and often available on Craig's List. It has a 1/2 HP motor and speeds from 760 to 3070 RPM. That slowest speed is not real slow, but within the range of overhead stirrers. If you are mechanically inclined perhaps you could set up a speed reduction gear linkage.

When we people start discussing explosion-proof set-ups, of course everything in the vicinity has to be "explosion proof": all connections to heaters, lights, etc. have be secure from sparking in the "vapor zone" to prevent ignition.

[Edited on 29-12-2015 by careysub]
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[*] posted on 31-12-2015 at 15:09


I stirred a refluxing mixture with a drill held at 25% power with a triac dimmer for about an hour. The drill became perceptibly warm but not hot. I conclude that a drill does indeed make an effective overhead stirrer, if proper precautions are taken.
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[*] posted on 1-1-2016 at 14:38


I use glass shafts with PTFE shaft holders and flexible shaft through glass adapter. Both work depending on the conditions. Some mixture are too dense to work with stir bars and some reactions require constant effective stirring. Using silica substrates are one example; STAB works better when well stirred. We should stir more and use less solvent IMHO.



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