This project is an extension of a fidget spinner modeling and printing lesson that I did with my class and is described at:
I got the idea for this fidget spinner-based experiment after remembering the gyroscopic precession demonstrations in college using a custom bicycle wheel as shown in this video:
Though the video is labeled Conservation of Angular Momentum, that is not directly evident from the video. I thought it might be possible to show conservation by showing that as the person/rig supporting the spinner spun faster and faster (by increasing the angle of the spinner axle) the spinner itself would spin for a shorter length of time. I also had a lot of fun designing the rig to mount the spinner and provide an additional rotational element (which had to get its momentum from the spinner).
The included video shows how the rig is constructed and how the experiment is performed. I've also attached a data sheet and presentation that I used with my students. The key to good data is consistency in the force of the spin, not introducing additional forces on the rotor, when the rotor is released and when the stopwatch is started.
As I say in the presentation, the rig is not unbreakable. In particular, the support arms can be broken more easily than the other components simply because of their orientation on the build plate. So students should refrain from "smacking" the spinner to get it started. Be gentle!
Students use a stopwatch to time the length of spin of the spinner with different post length configurations. The greater the difference in the height of the posts the shorter the faster the rotor should spin and the shorter the spinner should spin - I hope!
Theoretically, any spinner with a radius of less than 40 mm should work though in order to leverage the support arm design you would need to utilize a design for the caps like the one included in:
Clear Flex Seal Liquid is a great product for applying to the base of any PLA-based object (and maybe other filaments as well) to keep the object from sliding on smooth surfaces. I applied it to the bottom of the chess pieces that I printed and it works great to reduce slipperiness and the click of a piece as it moves from square to square.
I've had poor luck with superglue and now prefer to use epoxy to attach the arms to the caps.
The components were designed in Fusion 360 (*.f3d files included). Depending on your printer and filament you may need to adjust component and slot thicknesses/widths.
Overview and Background
The lesson starts with a discussion of Conservation of Energy and Conservation of Mass and then focuses specifically on Conservation of Angular Momentum and a practical method for validating the concept using a modified fidget spinner and a angular momentum isolation rig.
Lesson Plan and Activity
See the attached presentation on Conservation of "X" and data collection sheet.
a stop watch
- conservation of
- angular momentum
- plotting data