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Homemade Centrifuge for Five Dollars...

9/11/2012

15 Comments

 
Picture
Video Below:
There are some experiments that require equipment that is either too costly, or may only be used infrequently, as in the case of a centrifuge. Occasionally, I need one, but try to get around the problem in another way. But, I decided that it was time to make one myself and end the "alternative solutions" trying to get around the use of a centrifuge. This is the result of some considered thought and limited resources. For this experiment I wanted to work with extracted chlorophyll and check the fluorescence with a small UV LED flashlight. As you will see in the video, it worked fairly well.
There are many designs on the web but none seemed to be what I wanted. This build is extremely easy and allows for several alternative materials. For example, if aquarium tubing is not available, any flexible tubing from the hardware store will work. It can be purchased by the foot at a really low price. The only important factor is that the tubing has to be sized to be flexible and capable of being a forced fit for the dropping pipette. The other piece of this simple centrifuge is the knurl on the shaft of the motor. The tubing has to have something to "grab onto" and it could be a knurl, a flat spot, or a tiny gear. Balancing can be "trial and error" or small weights that can be moved to compensate. I found that if the tubing assembly is fairly accurate in distance from the shaft, and the fluid in the tubes are close to the same weight, the balance is fine. There are a couple of thoughts before the video and the included links:
I have posted this project in good faith, but there are always safety issues with anything that is spinning at 4000 RPM's. The safe and careful operation of this device is the responsibility of the reader. I can assume no responsibility for your safety. I have recommended plastic pipettes and not glass as there is greater risk with glass. Always use a container of some type to enclose the centrifuge. Now, on with the video:

Almost any 12 volt motor will work but  the link to the motor that I used is here. If the link is broken, the product may not be available, but there are many DC motors  at the Electronic Goldmine. Check the column on the left at the home page. The dropping pipettes can be found at some drug stores but also at American Science and Surplus. I could not link directly to the product, but just type in "plastic pipette" in the search our stuff  here. For the extraction of chlorophyll from spinach leaves, check here. Lets go for a spin!


15 Comments
Dexter
10/12/2013 03:32:31 pm

hey man thanks this helped alot! hey i was just wondering, was that a black light you used at the end? the red peaked my interest. also ive never heard of electronic goldmine, but would princess auto be just as good to get a motor from? and i then id use a potentiometer to deal with speeds. :)

Reply
Ken
10/13/2013 01:44:56 am

Hey Dexter,
Yes, the light was a small UV flashlight and the red is the fluorescence from the chlorophyll found in spinach. Any small DC motor will work, even from a number of toys. But, I would not use a potentiometer for speed control but would use either a variable DC voltage or PWM, (pulse width modulation). Thanks for the comment. Ken.

Reply
Lisa
3/27/2014 10:11:57 am

Hi Ken,
I enjoyed your video. I wondered whether this would be suitable to separate out gold precipitate or other precious metal precipitate from its solution in a quicker way than currently employed? Typically the precipitate is filtered through a Buchner funnel, with filters but the process is very slow. People often used a grooved funnel and employ simple gravity, to separate the solids from solution. I started to think of a bucket and water, spun round and round and I did a search and came across your video. Do you think it would work, separating the solids from the liquids - perhaps bucket, with funnel glued to its inner rim, then filter into funnel, then liquid into filter and spun round and round? My question is do you think, this would make for a quicker filtration as opposed to just letting gravity, do its work, drip by drip? Lisa

Reply
Ken
3/28/2014 08:20:35 am

Hi Lisa,
The short answer to your question is yes but if you are talking large volumes of liquid, it may be more difficult. A centrifuge will work if the speed and duration of spin is enough. I made a larger volume centrifuge using a top loading washing machine. I made some easy fixtures to attach to the inner barrel that would hold large plastic cuvettes. Then, during the spin cycle the force and speed was great enough to do the job. But, I am curious as to why the Buchner does not work well. These typically have a partial vacuum in the flask and flow quickly depending on the filter pore size. Even a hand vacuum pump will work. But I do agree that gravity is way to slow most of the time. Let me know how you solve the problem or have other questions. Ken.

Reply
Lisa
3/29/2014 06:36:19 am

Hi Ken,

Thanks for the response, I hoped I'd hear from you.

We are talking about variable volumes of liquid, but all posing the same filtration problem due to very fine or clogging precipitates from precious metal refining with nitric and or aqua regia.

The Buchner filter is not the problem, rather the fine mesh of black powder which is displaced from acid onto a copper bus bar, cemented silver; palladium; platinum and gold form, before being brushed off. This black powder is so very fine, it clogs the filter.

Again after decanting the nitric, which contains silver chloride, the last part of the precipitate through the filter clogs. If you think it would be beneficial - and If you are willing to provide further details, on your large top-loader centrifuge, then I would give it a try to try and speed up these processes.

Reply
Ken
3/29/2014 09:20:32 am

Lisa,
It seems as though the problem is in the black precipitate so have you identified it? Is it of low density like carbon dust or more dense like a product of an oxidation reaction? This would make a difference as we might be able to sequester or chealate it for removal. It will also make a difference as to how it would behave during centrifuging. If it is small, sub-micron, it might go to the bottom of the cuvette with the desired material. It might also be worthwhile to make a quick and dirty centrifuge as I did in the video by just using a plastic dropping pipette, drilling a hole near the bulb, and attaching it to a small DC motor and try centrifuging before committing to the large version. But, I think that the key is knowing what the black material is. Stay in touch, Thanks, Ken.

Reply
Lisa
3/29/2014 11:05:53 pm

How strange that you received my last post, as their was a message that there was a problem, so I intended to try again another day.

The black precipitated is a combination of palladium, silver and some gold and even platinum where present and where the metals have been previously in contact with HCl (Hydrochloric acid). It is produced when precious metals and base metals are put into solution in concentrated nitric acid. When a copper bus bar is put into the acid, when no further action is showing, the acid displaces the precious metals still in solution, exchanging by attraction to the copper bus bar, where a black precipitate forms. The base metals of copper and iron stay in solution, so this method is great for getting out metals that may contain platinum group metals, where precipitating them individually is very difficult. This way the black can be put through a silver cell and separated, although I have not done this yet.

The website that helps with problems like this, that I use is goldrefining.com which you might enjoy. Thanks again.

Reply
kid
6/6/2014 07:53:46 pm

hello and thank you a lot. your idea is quite good. I need to do a project of making a centrifuge . I am just a kid so I am sorry if this post is bad. thank you very much. I wonder if you could post this video on youtube.

Reply
kid
6/6/2014 08:09:22 pm

I have a difficulty loading and playing the video, the video doesn't play for more than 1:27 minutes and it stops and restarts all over again. I wish you could write the details down and display it , it will be a lot more easier that way.

Reply
Ken
6/8/2014 01:34:44 am

I have checked the video on two different computers with two different browsers and it works without any problem. It may be worth trying a different browser and make sure that Flash is up to date. The project is so simple and the writeup covers all of the elements needed to make the centrifuge. And, the cover photo shows exactly how to attach the tubes. Thanks for the comments, Ken.

Reply
nick link
2/26/2016 07:50:31 am

Great job with this! I'm just setting up a lab in the garage to school the grandkids and wanted to do the chlorophyll process. Actually have an old lab centrifuge but wanted to have them build if for the engineering lesson. Figured I'd let them try longer dongles and walk them through the concept of high tip speed and forces all the way to failure. The cake box was genius.
Your site is also very interesting.
Cheers

Reply
Jackie
10/27/2016 07:25:55 pm

Ingenious!! Very crafty. Do you think this would work to centrifuge blood? Wondering how long it would take to spin.

Reply
Ken
10/28/2016 09:12:29 am

Hi Jackie,
Unfortunately the answer would be no as the speed is too slow and time would not really be a factor. Even micro centrifuges spin at 12,000 RPM's. However, separating plasma may be possible with some modifications. But, safety would be more critical at higher RPM. Thanks for the question, Ken.

Reply
Ophelia
7/8/2017 07:20:24 pm

Hope you still on. I am glad I found your video. Thanks.

Reply
Ken
7/9/2017 08:41:07 am

Ophelia,
Still on and glad you found the video. Thanks, Ken.

Reply



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    The author has an eclectic background in chemistry, electronics, writing, mental health, and community action...Ken

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