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The Pythagorean cup is a drinking vessel designed to drain its contents via siphon action if it is overfilled. If the cup is partially filled, it holds liquid which can be drunk in the usual fashion. If it is overfilled it drains the entire contents of the cup into the drinker's lap. This object was classically used as a warning of the dangers of gluttony and over-consumption.
Unfortunately, Pythagorean cups feature a distinctive central stem to house the siphon tube which drains the cup - see for instance https://www.printables.com/model/669646-classic-pythagorean-greedy-syphon-cup. This gives away the surprise and spoils some of the fun! Fortunately, modern 3D printing allows us to build a more devious cup, with a hidden siphon.
This object is a Pythagorean cup with the siphon tube concealed in the drinking vessel walls. The siphon tube traverses more than 300 degrees of the circumference of the rim, so a moderately filled cup will not drain when it is tilted. This object has been printed and tested, and is 100% functional! It makes a great brainteaser or science demonstration for students.
One good way to help understand the object is through this educational video.
Instructions
This object was originally printed on a Makerbot Replicator 2:
Material: Makerbot True Yellow PLA (Or your own favorite choice)
Layer Thickness: 0.2 mm
Shells: 3
Temp: 240 C (Can be simply 200 C)
Infill Type: Hex
Infill Density: 20%
Raft: None
Supports: None
For other printers and materials, the chief concern is producing a watertight or nearly watertight surface on the inside of the cup and siphon tube. If you have trouble achieving this, decrease the layer thickness to 0.1mm and bump up the number of shells. If this does not do the trick, tune your extruder for fatter extrusions.
The STL file produces a ~8 cm tall cup at native scale. The STL mesh is dense enough that it should scale up or down very nicely.
Thanks to jstuben on Thingiverse for the original design!
The Fake Devious Pythagorous Cup doesn't slop the water from the bottom, instead, it acts as a normal, drinkable cup. While your victim sits across from you, you can demonstrate using your (fake) cup that nothing odd happens to the cup (even though there's a hole in the top and bottom), taking down their guard and making the prank more ridiculous.
The author remixed this model.
I am including a non-working Pythagorous cup for those “pranking” those across the table and lowering suspicion, alog with an extra large model that often increase affectiveness.