Sciencemadness Discussion Board

An Affordable Modular Rotary Evaporator

smaerd - 23-1-2013 at 09:23

Here's my first write-up it's far from complete but I could use some input. The original work done was being done here:

Any suggestions on things to add or test please let me know.

Attachment: write up.doc (30kB)
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[Edited on 25-1-2013 by smaerd]

[Edited on 26-1-2013 by smaerd]

[Edited on 27-1-2013 by smaerd]

smaerd - 23-1-2013 at 09:54

Okay added some pictures here's the next one sorry for posting twice so fast.

[Edited on 23-1-2013 by smaerd]

Attachment: write up.doc (536kB)
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smaerd - 23-1-2013 at 16:23

Alright tidied up some of the grammar and redundancy. Put in a circuit diagram heres the latest.
edit - prices updated due to this thread

Is this an acceptable idea for a publication submission?

Edit(woelen): Removed uploaded file, it is replaced by newer version on request of smaerd.

[Edited on 25-5-14 by woelen]

smaerd - 26-1-2013 at 09:06

Alright, got new bearing today and ran some trials! Results are in and two more pictures were taken. I was actually surprised the rotary evaporator beat out the vacuum distillation in all of the trials. Though it was close where there was more solvent per surface area.

This is it, The project is done. :)

Edit(woelen): Removed uploaded file, it is replaced by newer version on request of smaerd, which can be found near the end of the thread.

[Edited on 25-5-14 by woelen]

Magpie - 26-1-2013 at 11:35

Very nice smaerd! This would be a nice project for those who like to build things.

The pictures didn't show for me.

[Edited on 26-1-2013 by Magpie]

smaerd - 26-1-2013 at 11:48

Thanks for letting me know I'll try and put them in another way :)
Does the PDF work?

Edit(woelen): Removed uploaded file, it is replaced by newer version on request of smaerd.

[Edited on 25-5-14 by woelen]

Magpie - 26-1-2013 at 15:02

Yes the pdf and pictures are good. However, the electrical circuit diagram is unreadable due to the black background.

smaerd - 26-1-2013 at 15:52

Thanks for the input. Changed the circuit diagram to a lighter scheme and provided the tool that was used to make it in the references.

Edit(woelen): Removed uploaded file, it is replaced by newer version on request of smaerd.

[Edited on 25-5-14 by woelen]

smaerd - 27-1-2013 at 05:30

Added standard taper symbols to the joint sizes to be more official or whatever. Also fixed up some of the wording. I'm really bad a proof-reading and catching errors sorry... Anyways I think this is actually the last one, at least it's the one going on my web-site hehehe.

Edit(woelen): Removed uploaded file, it is replaced by newer version on request of smaerd.

[Edited on 25-5-14 by woelen]

watson.fawkes - 27-1-2013 at 08:55

Quote: Originally posted by smaerd  
I think this is actually the last one
I would really recommend putting in dimensioned drawings for, at the very least, the two machined PTFE pieces. The lack of dimensioned drawings makes it harder for someone else to make use of this document as it is.

For example, in a photo you show a Keck clip. In order for that clip to work, the shaft has to be a particular diameter. Nowhere that I saw is there mention that this dimension is important. If someone already had 1-1/4" ID pillow blocks in their parts bin but no 1" ones, it would be more economical to use a 1-1/4" shaft. But the clip wouldn't work naively, you'd need to turn down the shaft for a bit to allow the clip to fit. So the dimensions of the taper matter, and it's the kind of thing drawings are for.

Another thing I was looking for was a picture of how this was set up with the distillation head in place, just to see how everything is arranged on the bench.

I would recommend taking a look at an issue of Home Shop Machinist or Machinist's Workshop (both by Village Press) for examples of how other people write project articles.

smaerd - 27-1-2013 at 09:03

The shaft is actually just 1" outer diameter for the keck clip. The keck clip doesn't do too much holding to be honest but I put it there for good measure I guess. I really appreciate the advice I will get to work on drawing up some more exact dimensions for the teflon attachments and reading some more about the article format. I'll also take a picture of how I had it set up, the reason why I did not was because the way I had it set up was very ... sloppy... The rotovap was simply placed onto a pile of wood and the glass attachment was clamped via a ring stand, stainless steel measuring cup for a water bath, etc. I'll work on making it's implementation more practical as well. Thanks for being critical.

smaerd - 27-1-2013 at 15:41

Okay I added two schematics I drew in LibreCad and added the information using Gimp image editing program. That was not fun. I'm not an engineer, I don't think I should have to adhere to a machinists type article base while sticking to a chemistry article. I thought about it, and my write-up includes way more information then many of the ACS published roto-vap designs do if not the majority of them. Several of them are maybe five paragraphs long with a picture, no tests done, no parts list for amateurs to look into let alone a redundant circuit diagram, or any explanation of what goes where or how to improvise a pulley, etc.

I'll wait to get enough money to buy a decent metal bowl/pot and a cheap hot-plate I can dedicate to this as well as build a stand for it so it is aesthetically appealing in use. For that final picture. Probably will be a month or so.

Anyway's here's the latest including the schematics of the teflon pieces.

Edit - I'm also not using a real roto-vap distillation head, I'm just using a 18/9 ball joint "blank"( with a bit of hose leading to a vacuum take-off(connected to a friedrich and a flask)

Edit(woelen): Removed uploaded file, it is replaced by newer version on request of smaerd.

[Edited on 25-5-14 by woelen]

smaerd - 28-2-2013 at 13:55

Okay finished product. Got the pictures up of the whole thing working.

Attachment: An Affordable Modular Rotary Evaporator.pdf (908kB)
This file has been downloaded 2392 times

smaerd - 18-5-2013 at 05:22

The design is still holding up and working fine :). Hasn't been used a tremendous amount of times but has removed some liters of solvent now of several varieties. If I had to improve on this design here is what I would do and may very well do in the future. Have to comment and say how refreshing it is to want solvent to be evaporated under mild conditions and 10 minutes later be back at work.

I would use a servo motor to drive the rotor. I would have a thermostat going into the bath. I would use an arduino microcontroller to read out the bath temperature and an LCD to display this information as well as the RPM's. I figure it would cost another 60 dollars or so but would provide very similar functionality to a commercial rotary evaporator without too much more work.

[Edited on 18-5-2013 by smaerd]

A couple suggestions

Nitrous2000 - 16-4-2014 at 17:55

Hi there,
Really, a very nice and ambitious project. On that theme, well done.
Now, a couple suggestions.

You've clearly identified the biggest challenge in this project, and that is the rotary vacuum joint. Unfortunately, it is the weakest part of your write up. I've looked through countless (as in...."too many to bother counting" :) ) pdf's that you've uploaded, and not one of them actually shows the connection to the distillation column with the clear tube. You come close, but no cigar!

So, I'd suggest the following. First, get a moderator to delete all but your final version. I suspect more than a few have download some, but not all of your files. The second point would be to include a photo of the link between the condenser assembly and the teflon ball joint as it attaches to the aluminum tube.

Finally, it would really add to your instructable if you actually diagrammed, in a linear fashion how all the parts fit together (including the vacuum line and the ground glass flask that goes into the water bath). Ok, if you really want to polish it up, replace that out of focus picture of the teflon/ground glass joint adapter! I think I see some o-rings....but I'm not sure ;)

Anyway, please don't take the above as anything but constructive criticism. I think you've accomplished a lot.

Oh, the following patent refers to the Yamato Scientific version of a Rotovap sealed joint. Very interesting. US005919339 dated July 6, 1999

My experiences with Rotovaps go back to my grad Chemistry days in the early 1980's. This may be a way more modern version. ;)


Steam - 16-4-2014 at 19:49

I agree with Nitrous, The vacuum joint is not clearly defined at at, yet it is the most critical aspect of the design. It would be super nice if you posted a close-up picture if it!
That being said am really liking what you are doing here, I have been thinking about building a rotovap for some time and your document is definitely going to help!

Keep up the good work! :)

smaerd - 25-5-2014 at 06:26

Hey Nitrous2000. Really sorry I will request a moderator to get on that. I will take a picture of the connections and diagram it more appropriately. It still is running to this day. I have to admit the vacuum seal is not perfect and the set-up is kind of crude. There is definitely a better solution but mine was to take the ground glass ball joint and 'mate' it with the teflon ball joint using some faucet grease to create a seal. A ring-stand clamp holds the ground glass ball joint into place I'll work on that either today or tomorrow.

Edit - Okay asked Woelen if he would be so kind as to remove all of the attachements except for the final one. I have a bad habit of editing things a hundred million times :P.

Edit(woelen): I removed all uploaded versions, except the last one. For all other versions I placed a remark in the message, telling that there is a newer version.

[Edited on 25-5-14 by woelen]

smaerd - 26-5-2014 at 08:38

As promised I added the picture of the connection. Please note I temporarily have wrapped the glass joint connection to the tubing in duct tape for classiness. No, okay, well simply sticking tubing into the glass joint wasn't air tight after a few runs. Anyone experimenting with this who has decent materials could concoct a much better connection. Viton + epoxy to a valve, etc... I am embarrassed that I haven't yet but I have been incredibly busy and the duct tape is working fine.

It's kind of cute to revisit my writing style from 2013. I have drastically improved at technical writing, although I have no desire to improve the text of the document anytime soon. Should be clear enough to understand what is happening without over-complicating things.

I would love to revisit this project knowing what I know now. Make a better glass to Teflon seal, do the electronics properly, create a better stand. However, I am buried in other projects, school, and soon a temporary 'professional' research position. It still works, and doing the chemistry(when I have the time which is rare now) means more to me than the device as of right now.

Attachment: An Affordable Modular Rotary Evaporator.pdf (979kB)
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[Edited on 26-5-2014 by smaerd]

smaerd - 10-2-2015 at 06:19

I finally have a camera that can do short lengths of video.

Would anyone be interested in an operational video for this device?
How about a better write-up?

Zombie - 10-2-2015 at 06:44

You sir have inspired me.

A roto-evap. is one of the tools I would love to have, and your method here is, for lack of better words... Cool as hell!

I will not even begin to critique any aspect of what you have accomplished in this project BUT I do have a technical question.
Once your product has been separated, how do efficiently you recover it from the RBF? Noob question, yes. Obvious answer, no.

Great project. I'm very happy to have seen it.

smaerd - 10-2-2015 at 07:19

That's actually a great question that stumped me until I toyed with it.

In an academic setting usually rotovaping is performed to remove ~98% of solvent. Then the flask is taken to a highvacuum line and sucked down for an hour or so to get rid of 1.99% of solvent/volatiles. After that, a lot of people will store intermediates in the respective rbf. If the compound is realllly dilute in solvent it will be spun down to like ~80% on the rotovap in a big flask, then transferred to a little flask and spun down 98% so there isn't a tiny amount of compound in a ginormous flask.

At home, my rotovap yields are my yields I don't really have a means to get things any drier. In that write-up I was spinning down a sample of an attempted indolinene imine hydrolysis I believe (was a while back), so it was pretty oily. Oils I tend to dissolve in the smallest amount of volatile organic solvent such as DCM or acetone and transfer to a semi-closed vial to evaporate on their own. Or I'll recrystallize them in a dish -> filter paper -> vial (some people prefer flask recrystallizations). Solids I break them up and transfer the powder/clumps via spatula, sometimes I get the traces with DCM and do the semi-closed vial thing but usually the solid mass is good enough (the traces are great for TLC standards). Edit - I should mention sometimes it's a ridiculous pain in the ass to scrape flasks via spatula depending on the compound, so just hitting it with solvent can save 20 minutes of scraping, but adds a few hours of evaporating.

So there are a few options when working under normal atmosphere. Vial storage, or RBF storage. RBF storage is real easy, rubber septa make it convenient but you know as an amateur scientist I only have maybe 10 rbfs? Edit - and it always turns out that the flask I need for something else is a baby chemical's home. A weird form of Murphy's Law. So I prefer little screw top vials even if it means using a little solvent, I have yet to run a reaction that was effected by trace DCM.

[Edited on 10-2-2015 by smaerd]

Also thanks for the congratulations. It's been I think a year since I posted this up and still haven't seen anyone build one themselves yet. I really hope that happens soon. I know Aga was working on something not sure if he's still in the process or not. Inspiring other's to either innovate and/or reproduce the result was the goal.

[Edited on 10-2-2015 by smaerd]

Zombie - 10-2-2015 at 09:32

Thanks for explaining that. I was looking up tons of Evap. set ups, and very few went as far as recovering the product.

I like the idea of transferring to a smaller flask as the process is nearing completion. I think a couple cases of 10 - 50 ml RBF's are in my near future.

See? Another project... Making a rack to store RBF's containing products... Inside the storage cabinet I still have to make... Under the bench I am making... under the fume hood I am going to make... In the lab I have made.
And this is just the beginning???

I hope I live long enough to do you all proud. Thanks for helping. (no sarcasm, really) Thanks!

smaerd - 10-2-2015 at 11:39

Hahaha, That's amateur science for you. A list of never ending projects. The trick is to start them while another project is nearing completion. Things do get done and before you know it you'll be so consumed in things you are still working on that you won't even recognize how much you've built/accomplished. At one point I didn't have a lab bench, or cabinets, or glass-ware aside from 10 test-tubes and some mason jars. It takes a life-time to build a lab from the ground up, and the Work is never finished.

Any dope can buy equipment, but it takes a hobbyist to turn that equipment into laboratory. I've spent the last what, 5 years cultivating my work-space and life-style into something formidable and there's miles to go. When people post pictures of their laboratories it's hard not to appreciate all the sweat and effort they put into it.

So many unspoken and under-noted achievements have been made by this community :). It's the projects people don't talk about that are the most interesting. That's kind of what makes it fun though right? Excited to see what 2015 has in store for us all.

akok - 8-8-2016 at 04:15

Smaerd that's a good project and effort on this rotovap!!! But it can be unproved a lot if we can find someone with 3D designing software skills. Many parts can be made cheaply by 3D printer if there is a 3D design. Let's try to find someone that it can an upload an .stl file of the project on
I believe the following pdf manual would be a good guide for a designer to replicate the basic mechanism.

FYI his is a example of magnetic stirrer.