The goal of this post is to evolve the pinch valve I built (discussed in this post).  I’ll start with the results.


Below is an image I took as we tested the new pinch valve.  The other image is a close up of the enclosure when the arm is in the closed position:

NewImage              NewImage

Frustrated FAIL! Water still flowed through the tube.

Venturi Effect

ChallengesBringOpportunites And then there is science…

While I failed with this attempt, I did become familiar with the Venturi effect…something we all probably learned about at some point in school…I don’t remember.  

Here is a Kahn Academy video that helped me get a clue what the Venturi effect is all about:

The exciting thing I learned was using “the Venturi” method instead of an air stone/air pump to add oxygen into a tank of nutrients.

Here is Rob Bob’s video:

Here is mediamaker2000’s riff on Rob’s:

Ooh!!! Science over $$$!!  Take THAT to those that insist on the Dakota Access Pipeline…#NoDAPL 

Take 2 Build

This go around I’m starting with:


  • a Fusion 360 model of this servo motor I am using that I got on from the Fusion 360 Gallery.  The easiest way to make an enclosure is to fit it around the part to be enclosed.  While a .stl file works fine, I like starting with a F360 file so that I can more easily modify dimensions when the designer created a parametric model.  


  • Trying out the Servo motor with the test I used last time (GitHub location).  This lets me know which way to orient the model.  Doing so makes shaping the enclosure easier than last time.  Easy peasy since the wiring is the same as it was for take 1.


After evolving the enclosure and arm (about two days worth of design/prototype/fit), I was able to test….

On To Take 3

While I got closer, I failed.  For take 3 I’m going to design a new way to pinch.  One that is more like what is shown in the image from this document: