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. You can change any of the parameters and make whatever hoops you desire!

EDIT: One thing I have tried recently is attaching them to a motor (speaker) which will oscillate them at a given frequency. It is a great teaching tool for showing students normal modes!

Here is some data recorded with different diameter hoop springs mounted on a force sensor. Each plot is the average of 10 trials with the same hoop, and each trial involved a cart above the hoop on an incline, with the same initial starting height. This is a great way to show the different impulses delivered to the cart, based on changing the diameter of the hoop!

I am also working on collecting data for hoops made with different plastics. In my preliminary trials, there doesn't seem to be much different from PLA and PETG, but a larger difference with ABS.