search

moorepants / resonance

Learning Mechanical Vibration Engineering Through Computation
https://moorepants.github.io/resonance
MIT License
47 stars 12 forks source link

3. Measuring a Bicycle Wheel's Inertia Feedback #168

Open MicheleShi opened 6 years ago

MicheleShi commented 6 years ago

Attached are my comments for notebook 3. This notebook had a nice balance between the new coding tools and the vibrations concepts. My major concern was that in the beginning of the notebook there was a lack of motivation for using the data. We jumped right into simulating without knowing why we needed the data. Also, I wasn't sure why the center of percussion was important.

3_Measuring_a_Bicycle_Wheels_Inertia_MS.docx

MicheleShi commented 6 years ago

Questions:

  1. Why initially assume the wheel as an infinitely thin hoop mass if it was so much easier to just curve fit the data for a more accurate model?
  2. How do we differentiate between the two moment of inertias of the wheel (moment of inertia about the radial axis and the spin moment of inertia about the axle)?
  3. Why is it important to locate the center of percussion?

Concerns:

  1. We start with data but then go into working with a resonance system and we’re not given any motivation as to why the data is important. It’s shown later that the data is useful for making the mathematical model more accurate through cure-fitting, but initially we don’t know the usefulness of the data.
  2. We use the TorsionalPendulumSystem, the CompoundPendulumSystem, and the SimplePendulumSystem. The differences between these three systems is not clearly addressed. I think in lecture we spent time differentiating the three with drawings.
  3. Period of oscillation is defined in this notebook, but in the previous notebook it is assumed the students know what period of oscillation is for a vibrating system.
  4. Loops are introduced in this notebook, but in the previous notebook loops are necessary to do the exercises.
  5. Stiffness is introduced as one of the three fundamental characteristics that govern vibrations (Objective 6), but then stiffness is not addressed in detail. It is calculated in one exercise, but then lumped into the proportionality coefficient for the relationship between period and inertia.

Suggestions:

  1. It’d be useful to visualize the different axes of the system in order to understand the multiple mass moment of inertias.
  2. Dynamics, ENG 102, is required for this course. I know I was confused at first between area moment of inertia and mass moment of inertia, so clearly define mass moment of inertia and relate it back to what was taught about rigid bodies versus particles (i.e. must account for rotation).
  3. Make use of boldface text to draw attention to important definitions that are introduced.
  4. To emphasize the importance of experiments to validate a mathematical model, introduce the experimental data after calculating the free response through the resonance systems.