Designed by profhuster@gmail.com
April 2017
This is a dribble cup designed in response to the Make Magazine worst cup challenge. If you hold the handle with your right hand and drink out of the cup, it will dribble until empty. If you use your left hand or face the cup in another direction (not looking at the Drink Safely label) you can drink out of it with out dribbling.
The Physics of the CupThere is a siphon hidden inside the wall of the cup. The inlet to the siphon is at the bottom inside the cup. It is very hard to see, even if you are looking for it. The vertical siphon tubes run up to the lip behind the label Drink Safely. When the fluid level reaches the top of the siphon tube, water fills the tube starting a siphon. Once the siphon starts, it won't stop until the entire cup is drained. The physics is like a traditional toilet bowl; the bowl fills until the siphon is full, then the bowl drains until air is sucked into the siphon ending the process. The drain is concealed in the indented text on the bottom of the cup, so you can't tell that there is a connection to the siphon tube or that anything fishy about the cup. Some of the letters near the edge are connected to the siphon drain, so the fluid dribbles from the letters themselves.
I like the design. The insidious nature of the cup is very well concealed.
Details of ConstructionI built the cup using OpenSCAD. It is an open source (and therefore free) CAD program. It is different than most CAD programs in that it is code based, not GUI based. I use it for all my design needs in a science laboratory.
I set the parameter $fn to the value 96 to make the curves smooth. There are other options in the code. I try to put all of the parameters at the top of the file, so they are easy to change.
Warning: It is a bad idea to send this through a dishwasher. The drying cycle may get hot enough to deform the cup. (I experimented and found this out.)
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