Hoop springs

Print these in PETG, PLA, or whatever! Makes for a great lab where students have to determine the spring constant of the hoop. How does the spring constant change as the diameter of the hoop changes? 

You can also play around with your settings on the seam. Whether they are alined or random. I am not sure currently if this has an effect on the mechanical properties. 

The hole in the loops is designed for a Vernier Force sensor. 

I also have an OpenSCAD file that can generate any set of these if you would like it.