Sciencemadness Discussion Board

Home-made rotary evaporator

micron - 30-9-2012 at 10:56

I have pondered that thought almost a six month by now. First I thought I would buy it, but they are not very common in European different ebay markets for some reason for a quite a while by now and if they are avalaible they are too expensive (my limit would be about 200-280EUR max) as I'm poor university student. As I don't know what parts are needed I really don't know is it worth to start buying rotavap pieces to put it together myself. The heating bath wouldn;t be no problem as I can do it myself very easily, nor the stand. Now there are some buchi motors for sale in ebay and quite often a condensators also(and of course the flasks). But I don't know exactly in what size condensator I need that would fit and what other little parts I would need. If I would know all the needed items I can calculate the total sum and buy the needed pieces and put it together. Can someone who knows all the rotavap principes could help me here what adapters and other small items I would need beside motor, condensator, flasks, metal clips for joints. I have asked from sellers but they say that they don't know nothing. Big thanks for all those who can help me out and others who might have interesting ideas and comments.

Here are motor that are for sale:

the price is 80EUR
rotavap motor 2.jpg - 83kB

Hexavalent - 30-9-2012 at 10:59

Have you tried looking through manuals and technical spec sheets first?

micron - 30-9-2012 at 11:03

yeah that would be good idea for first, but I;m sure there are many ways how to put it together, maybe someone knows the most straightforward way. I'll check out some sheets. I have looked before some patents only and they contain lots of different small items but they have been quite an old also.

Hexavalent - 30-9-2012 at 11:11

a) Have you checked eBay recently? Sometimes you can get professional models at great prices.

b) If you're at university, have you looked in the waste/refuse centre? A few members here have scored some nice stuff that would otherwise have been thrown away.

Lambda-Eyde - 30-9-2012 at 11:24

One possible solution would be to have a glassblower make an adapter for you, so you can fit a standard ground glass condenser to the threaded port on a rotavap. Büchi condensers can be had on eBay for several hundred €, while a standard condenser (think large dimroth with cooling jacket) can be had for much less.

kristofvagyok - 30-9-2012 at 12:26

I would mention two little but important things about rotavaps.

We have currently 2 non working rotavaps in the lab and this causes a lot problem. Why are they not working? One has an old PTFE sealing (between the rotator motor the "steam pipe" -or how it's called and the condenser), the other one has a fixed steam pipe and the result is: both are rotating, but there is NO vacuum in them.

The PTFE sealing costs 50-80Euro the steam pipe is at 150-200euro and these are the cheapest part of the rotavap.

If you want to make one at home from differently purchased parts with a low budget like this, then you have to be really lucky to get perfect, well sealed, not damaged parts, elseway it won't work.

Lambda-Eyde - 30-9-2012 at 12:32

Quote: Originally posted by kristofvagyok  
I would mention two little but important things about rotavaps.

We have currently 2 non working rotavaps in the lab and this causes a lot problem. Why are they not working? One has an old PTFE sealing (between the rotator motor the "steam pipe" -or how it's called and the condenser), the other one has a fixed steam pipe and the result is: both are rotating, but there is NO vacuum in them.

The PTFE sealing costs 50-80Euro the steam pipe is at 150-200euro and these are the cheapest part of the rotavap.

If you want to make one at home from differently purchased parts with a low budget like this, then you have to be really lucky to get perfect, well sealed, not damaged parts, elseway it won't work.

If a glassblower could make a custom adapter like I mentioned in my previous post, I think that such a part could be modeled around a much cheaper and readily available PTFE seal serving the same purpose (I'm guessing the steep price is due to Büchi's "monopoly" and not the actual price of PTFE...), or a skilled machinist could make this seal himself.

[Edited on 30-9-2012 by Lambda-Eyde]

kristofvagyok - 30-9-2012 at 13:27

Quote: Originally posted by Lambda-Eyde  

If a glassblower could make a custom adapter like I mentioned in my previous post, I think that such a part could be modeled around a much cheaper and readily available PTFE seal serving the same purpose

The adapter what we have problem with is a repared one by our best glassblower (more than 50years doing it), so if I wouldn't use it I would say that there is no problem. But there is a less than half mm angle in it (where it was broken) and there is 0 vacuum with it.

The PTFE sealing is also not a thing what I would make with OTC methods, because if the rubber gets old, or any else problems, then also 0 vacuum will be in the apparatus.

Dr.Bob - 30-9-2012 at 15:19

Yes, unless you have parts for a pieced together rotovap, then it will be very hard to make the parts work together unless perfect. They used to sell the pieces as separate items, where their was the rotary vacuum adapter as one piece, then you could supply your own condenser and water bath (often heated with steam via a coil of copper). Those were easy to put together as they were designed with simple fittings at each end. Newer parts like the RE 120 are designed only to fit and work with Buchi parts, and thus are a pain, unless you have more Buchi parts. And the few glass blowers I know left alive charge $100 / hour to fix things, so that is much more expensive than buying the parts used. You can buy many of these parts on Ebay used for cheap, but this only works if shipping is not too much, you read the manuals so you know which pieces fit together, and you trust the seller on Ebay.

leu - 1-10-2012 at 06:40

If you would have used:

http://www.sciencemadness.org/talk/search.php?fid=5

you would have found:

http://www.sciencemadness.org/talk/viewthread.php?tid=7128

reading which could prove illuminating :) The end results from the effort applied :cool:

chemrox - 1-10-2012 at 10:37

Although the search engine here does not always yield the results it should - I nominate this reply as a sticky! I further suggest it be a global sticky; if there could be such a thing. It is perfectly concise and utterly to the point. Thanks, leu.

I edited to add:
There are a number of cheaper options for making a rotary evaporator. I've go the glass parts for a simple one that runs on an aspirator and a motor. I had one that was a motor with a 24/40 pass through to an aspirator. I can think of no cheap way to build one from Buchi parts but there could be if you are a good machinist and have lots of seals lying around. The problem with the cheap solutions is the solvents go down the drain. As soon as you incorporate a trap you've likely gone to more expense than buying a decent used evap from me for $1800.

[Edited on 1-10-2012 by chemrox]

smaerd - 2-10-2012 at 13:44

We have a thread on this with a hand-full of articles describing some designs. Hopefully I'll be finishing my build by the end of the month. Depends on the pay-check and time available.

Buying a motor and putting it on a stand isn't really what I'd call 'home-made'.

[Edited on 2-10-2012 by smaerd]