So a few reactions I needed an overhead stirrer instead of my magstirrer/hotplate for various reasons; however, many decent ones I saw were
prohibitivly expensive and the tape-a-dremel-to-your-stand idea wasn't of much appeal to me. So I decided to build my own. It consisted of the
following:
I went with an internal power supply because the last thing I wanted was another power brick waiting to have something nasty spilled all over it, not
to mention in the way. I would of gotten a higher RPM motor but that was all they had in that brand (which I had previous positive experience with).
Everything fit pretty snug but it is real solid and the motor has a lot of torque. Also used Flouropon PVDF paint which is pretty chemical resistant
(really resistant compared to standard enamel) but required good metal surface prep, etching, priming, and a a baking to cure. However it seems very
resistant to nicks and adheres much better than standard paints to aluminum. I did not do the best on color choice; I picked the first thing I saw
that was not white or light-colored in the Sherwin Williams Color palettes, but oh well. All in all spent around $125-$150 which is much less than the
$400-$2K ones I saw advertised.
Btw I plan to just secure the SS rod out the back in to a heavy duty bosshead
[Edited on 14-2-2021 by thermochromic]Johnny Cappone - 13-2-2021 at 23:12
Congratulations on the great job!
I am on a similar journey, working on a magnetic stirrer hot plate. All the ones I found here are very expensive for me. Have you had electronics as
a hobby before or, like me, some needs of home chemistry led you to learn it?XeonTheMGPony - 14-2-2021 at 08:44
I would recommend for making set up more convenient to decouple the motor from the controller, this way it will be protected from vapors entering it
over time and corroding or doing other unwanted things.RogueRose - 14-2-2021 at 11:15
I would recommend for making set up more convenient to decouple the motor from the controller, this way it will be protected from vapors entering it
over time and corroding or doing other unwanted things.
What do you mean by decoupling the two? Do you mean to leave the motor to be mounted above the stirrer and move the control module elsewhere &
then run wire to the motor? I think that is a good idea as well, especially if dealing with certain chemicals.
I was looking at doing something like this and I found some 90 degree drill extensions (sometimes called right angle drill extension) which would
allow to mount the motor away from any possible fumes coming out directly above it. You could use any piece of either tubing or solid rod (1/4"
probably is fine) and some coupler's or weld it.
ya make the motor in its own sealed enclosure. Mateo_swe - 15-2-2021 at 10:36
I also have a overhead stirrer project.
But i have looked at brushless outrunner motors because i thought quite high torque was needed.
I have this really big outrunner made for electric skateboards that is way overkill but it seems run fine with a controller i have and i might not
need a gearbox.
The controller have a potentiometer for speed and a direction switch.
I even bought a shaft connector 10mm to 7mm, a couple of PTFE stirrer rods with paddles and some PTFE stirrer bearings.
Only some soldering to do and how i mount the motor to some stand left to figure out.
Well, a box for the on/off switch, direction switch and the speed potentiometer would be nice.
I have not thought about an enclosure protecting the motor from vapors.
That might be a good idea.
[Edited on 2021-2-15 by Mateo_swe]NaK - 15-2-2021 at 13:33
Oh that is fancy! I thought about making one myself but I never really had the need. Great to have an illustrated guide!thermochromic - 16-2-2021 at 08:11
I am on a similar journey, working on a magnetic stirrer hot plate. All the ones I found here are very expensive for me. Have you had electronics as
a hobby before or, like me, some needs of home chemistry led you to learn it?
Thanks. I already have an electronics background with my job. Chemistry is just a hobby I dabble with. I guess you could call me a maker and chemistry
is more of a hobby but I often find myself using knowledge I learned in the process of researching some chemical synthesis at my job in ways I never
would have thought; however, I think that is true of most scientific fields, there is always some overlap.
I would recommend for making set up more convenient to decouple the motor from the controller, this way it will be protected from vapors entering it
over time and corroding or doing other unwanted things.
Ya I definitely am a little concerned about corrosion. You can't really see it in the pictures but there is a circular mesh air vent hole in the top;
other than that everything is decently sealed. I am hoping the polyvinylidene difluoride coating will protect all the internals. The bearing housing,
drive shaft, and chuck are exposed but I am hoping they wont be affected too bad. The reason I built it the way I did was that my first version was
more as you describe, with the controller separate. Not only that but it had a big power brick transformer that was also "separate" and this often
caused a mess as far as wires getting tangled or getting in the way when trying to assemble or disassemble glassware. More than one flasks have been
knocked over by the cords when trying to quickly move the stirrer so the basic design idea was to make it as integrated as possible. I will let
everyone know how this works in practice.
[Edited on 16-2-2021 by thermochromic]
[Edited on 16-2-2021 by thermochromic]monolithic - 16-2-2021 at 10:26
Nice project. I have a similar setup but the motor (a low rpm 775 variant similar to what you have) is direct drive with a PWM controller. They put
out a surprising amount of torque, even direct drive. https://www.sciencemadness.org/whisper/viewthread.php?tid=15...Fyndium - 30-4-2021 at 10:49
For the record, vacuum distillation with overhead stirring seems to work actually great. I was lazy and just tested how it behaves in vacuum, against
presumption that it doesn't, and to my surprise it leaked very little. The lube oil I administer to the O-ring bearing, remained as a small pool,
indicating little leak, and stuff boiled at desired temp. When using overheads, it is anyway a good idea to stock a bag of fluororubber O-rings,
because they are the expendable part, the PTFE shaft seems to hold on well.
Bin the magstirs, for good. Finally.
Just make sure that the coupling with the motor is good, because the vacuum creates axial load, and if it lets loose, it shoots to the bottom of the
flask, and if cracking it in ntp isn't bad enough, releasing the two tons of compressive force under vacuum on large rbf half-full with 150C boiling
liquid, and add to that a heating bath with dual the amount of at least 20C hotter liquid is a good reminder to double check the fittings.
Trust me, I blasted one flask with my improvised thermowell setup which did exactly that. The vacuum was created by the cooling reaction liquid after
reaction completion, which I did not take into consideration. It was 300€ flask.
