Hillbilly Engineering- A Homebuilt Kugelrohr

In the mid 1990’s I had the good fortune to do a 1-year sabbatical replacement teaching gig at Ft Lewis College in Durango, Colorado. Of the several colleges in which I was lucky enough to be a faculty member, this school was absolutely the best. The chemistry department had a vitality that I had not experienced elsewhere, and sadly, would not be fortunate enough to repeat.

From my office high up on the mesa next to town I could hear the whistle of the steam locomotives of the Durango-Silverton Narrow Gauge Railroad. On friday afternoons a campus Native American group would sit around a single drum outside of Berndt Hall, each striking a hypnotic beat on the preserved skin while chanting and singing in the Ute language. While they were chanting the steam locomotives in the town below would blow their whistles, announcing their arrival for the tourists. The sound of it was an otherworldly experience I have not forgotten.

A prof I got to know at Ft Lewis, Dr. Irwin “Ike” Klundt, was a retired VP from Aldrich. He was to become a mentor and friend. It turns out that Ike was the inventor of the coffee pot kugelrohr that Aldrich offered in its catalog. West Bend, the appliance company, had a coffee pot manufacturing operation in Milwaukee, WI, where Aldrich was then headquartered. Ike learned that they would always have a few off-spec units coming from their mfg line, so he arranged to snag a few of these units. He recognized that these pots were built to contain heat and would be dandy ovens for his application. The large metal coffee pots were delivered to a one man shop somewhere in Milwaukee where the they would be converted to ovens for the Aldrich kugelrohr still, or “bulb-tube” short path distillation device to be more precise.

To provide agitation around the axis of the distillation train, an automotive pneumatic windshield wiper motor provided the needed reciprocating motion. It had a built-in tube that would serve to couple the bulb tube train to the vacuum line. The reciprocating motion of the motor removed the need for a sealed bearing as in the case of a rotary evaporator.

Aldrich sold a geat many of these units. In later years the kugelrohr was modified to enhance safety and ease of use. Aldrich has never been shy about pricing, so the price went way up as well.

I was thinking about this bit of history yesterday as I was operating my home-built kugelrohr. Sometimes shortpath distillation is needed and yesterday was the day for it. Using Ike as my inspiration, I horizontally configured a Buchi rotovap into a kugelrohr distillation unit with a still pot and a bulb tube receiver.

On a hotplate with a temperature indicator, I placed an 8 inch diameter sheet metal 90 degree elbow from Home Depot. The elbow, modified with a bit of aluminum foil, would serve as my hot air bath. The elbow and hotplate assembly is scooted over to the rotovap so that the still pot bulb is isolated in the “oven”.  A dry ice/acetone cooling bath for the receiver bulb was made from the bottom of a plastic jar. It was notched on opposite ends to accomodate the receiver joints.

The setup works just like a Buchi-brand kugelrohr, but doesn’t carry the price of a luxury ocean cruise. I know that larger companies would not allow this kind of thing. They would frown on a chemist using his time to kludge together a piece of improvised equipment. Their safety people would not allow the operation of a device that was not purpose manufactured. But when you work for a small company this is one of the things you have to do, and I enjoy every minute of it.

About gaussling

Gaussling is a senior scientist in the chemical business. He occasionally breaks glassware and has been known to generate new forms of hazmats. Gaussling also digs aerospace, geology, and community theatre. View all posts by gaussling

19 responses to “Hillbilly Engineering- A Homebuilt Kugelrohr

  • Morris

    Back in the day we used to distill styrene in large glassware using a custom mixer. Heavy rubber hose attached to a 1949 Cadillac windshield wiper motor. Inherently XP- the motor ran on vacuum.

    I could go on…

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  • around the corner and down the hall

    Back in the mid 1990’s I was a student at a small college quite similar to the one you have described and had the fortune to learn from a professor who unfortunately had to leave after my first year with him. I must have caught lightning in a bottle because I learned more in that (school) year than in any consecutive 8 months since. I am quite certain that the foundation provided to me in that time launched me in to the academic career I now enjoy at a major University Medical College. Thank God for small miracles…

  • Gaussling's Weird Friend Les

    Congrats! You made the #3 spot on the Google for “Aldrich kugelrohr still”. Do I have to pay you a microcent?


  • gaussling

    12 microcents. Hey! How is your dad doing?

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  • Jason

    I’m interested in making one of these home built kugelrorhs for our lab. I’m a little confused as to your design. Do you have any pictures of the set up? I’m not really sure what to buy from the hardware store. Also how hot can the oven go? 250C ?

  • Charles Clendenin

    Does anyone have a manual for the original “coffee pot” Aldrich Kugelrohr that uses the air wiper? I have one of these and would like to set it up correctly.
    Thank you,

  • gaussling

    Hi Charles,

    Let me see if I can describe the Aldrich Kugelrohr set up.

    1) The coffee pot should be plugged in to a variac for variable temperature control.

    2) The hole in the upper wall of the coffee pot should have a teflon bearing surface, possibly as a piece of teflon sheet with a hole in it.

    3) The original system had an air motor which could be connected to vacuum or air pressure. The air motor will have a tube shaft that goes thru the body of the motor and a pair of tube connections for air inlet and outlet. The connection you make will be reversed depending on your choice of drive power- air pressure or vacuum. The speed of the reciprocal motion is demendent on the air flow. Start slowly.

    You”ll have to experiment with it to see which is the inlet and which is the outlet. Mount the air motor at a height such that it is horizontal with the side hole in the coffee pot.

    4) The air motor should have a tube in the middle of the assembly. This is the tube shaft that reciprocates when the air is connected. It also in part of the internal vacuum line. Connect a piece of rubber tubing from your vacuum pump to one side of the air motor tube. Flexible vacuum line is needed to cope with the rotary motion of the motor.

    5) On the other side of the motor tube shaft is connected another piece of rubber tubing (4-6″) to which is attached a barbed end of a male standard taper joint. The ground glass side is in the direction of the coffee pot.

    6) To the male standard taper joint is connected a receiver bulb tube (sealed with grease or teflon tape). The male end of the bulb tube is inserted into the coffee pot and the distillation flask is carefully connected inside the coffee pot to the bulb tube. Now is a good time to apply a bit of vacuum to hold the assembly together.

    7) Making sure the assembly is horizontal, carefully apply pressure to the air motor. A speed of one full oscillation per 1-3 seconds is fast enough.

    8) Carefully apply full vacuum to the distillation system, watching for foaming or bumping. When the system is stable, apply heat to the coffee pot with the variac.

    9) The bulb tube should be cooled with something. We used to drip dichloromethane from an extraction funnel and let it drop and wet the surface of the receiver tube. The evaproative cooling effect was quite effective.

    But now that everyone is frightened witless of CH2Cl2, try cutting the bottom 3 inches of a plastic bottle that would exceed the diameter of the receiver tube. Cut 2 U-shaped notches on opposie side and prop below the receiver. Fill with dry ice and your favorite fluid, say, acetone.

    10) Put some music on the CD player and have at it.

  • Hugh

    Improvisation is sometimes necessary. I’m a graduate student in chemistry at a smaller research university in the South; therefore, I understand the necessity to kludge together a piece of equipment. I have synthesized a compound that can only be purified via kugelrohr. I am interested in how you modified the Buchi rotovap. My boss has sent me on a mission to get quotes for kugelrohr devices, but I know that he will more than likely pass out when he hears the quotes. Could you please send me some pictures of the modified rotovap? I think I can picture your setup.

  • Ed Marinelli

    Hi: LIked your article . Would you perhaps know the manufacturer name of the window shield motor? From my recollection it looks like some Sprauge windowshield wiper motors I have seen. Any info you could give would be appreciated as I am in process of tryingf to rig up a Kugelrohr myself.

    • gaussling

      Hello Ed, I do not recall a model number, but Sprague comes to mind. The motor was cylindrical and had two ports on opposite ends. One could attach compressed air to one port or vacuum to the other. The reciprocating component was perpendicular to the motor and was comprised of a metal tube to which rubber hose count be attached. I spent a little bit of google time trying to find the part number but came up empty. I think the motors are still available. I’ll try again.

      • Ed Marinelli

        Thanks….the isssue is coming up again for me. Those units ( the Aldrich Coffee can units were excelllent. Many a compound was distilled by me using that unit. NOw the units are incredibly expensive (fancier but really not that much more functional).

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    • gaussling

      I can tell you this is true. A friend and past colleague now deceased named Irwin “Ike” Klundt invented the apparatus. As he related to me, there was a West Bend coffee pot factory in Milwaukee that occasionally produced off spec coffee pots. Ike took these cylindrical vessels to a fellow who fabricated the oven assembly in his garage. For the reciprocating motion of the bulb tube, Ike found that a pneumatic windshield wiper motor had the design features needed to us either vacuum or compressed air to drive the agitation of the motor. Key to the design was the fact that the air motor used a hollow shaft which could be used to connect the vac line to the bulb tube adapter via rubber hose, solving the problem of having a vacuum bearing. I used to have the prototype motor which was wired to a piece perforated Masonite board. Sadly, the motor is long since lost. It was a good robust design. Then, as happens, Aldrich indulged in creeping featurism and shot the price sky high. Sigh.

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