Tantalus Cup

by pmoews, published

Tantalus Cup by pmoews Jul 28, 2012
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The Tantalus cup works normally if it is partially filled. If filled to the brim most of the liquid siphons out through the bottom. It is also called a Pythagorean cup.

Thing:17330 by Scooter46290 is a such a cup with a simple but elegant siphon composed of three concentric cones about a central tube. Here is another version where the siphon is concealed in the stem. It has the advantage that the siphon has a greater head and can more completely empty the cup. Open scad and stl files are provided.


There was a leakage problem in early versions. The siphon always worked well. The problem occured when the cup was partially filled. Liquid leaked through the wall of the central stem and slowly trickled out the bottom.

Printing with 100% infill, one shell, and 0.2 mm layer height solved the problem. Playing the gcode files in netfabb Studio was helpful in deciding which parameters to use.

On my Replicator the cup takes a bit under 3 hours to print using 100% infill, one shell, and 0.2 mm layer height. It was printed directly on the build platform.

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Tantalus Cup by pmoews is licensed under the Creative Commons - Attribution license.

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I would be good if you could somehow integrate the siphon into the wall of the cup so you cant really see it.

I just uploaded exactly what you are looking for: http://www.thingiverse.com/thing:27533http://www.thingiverse.com/thi.... It works very well.

Tantalus Cup
by pmoews

If the siphon was in the wall (on the side you drink from) then when
you take a sip the water level always rises above the point on which the
siphon starts working(since you tilt the container, perhaps it's better
to say you lower the point at which the siphon works). If the whole
wall was connected no vacuum would be created but it would still leak.
If the siphons were divided into small sections those would then work
even after you stop taking a sip, which could still be fun but not
really the same...
closer to the real torment of Tantalus though.

only works while you drink because as you tilt the glass the level (of
the liquid) at the center stays about the same or drops a bit...

suppose it would work on a cup with a handle you could put the siphon
in the handle side of the cup wall since that stays about in the center
during drinking... would also allow you to use the handle

well it would be a lot more complicated and well questionable whether it
sill works as well. (both th hiding it and the mechanism itself)

Hmm, for making water-tight objects, would it be possible to use very low (0%?) infill and then flood the inside with resin? (the leaky shell should let out the air, but not the resin)

Very cool design!