Flywheel Power

1. Read the Article, ``Reinventing the Wheel'' by Will Hively in Discover, vol. 17, no.8. This article is on reserve in the library and is also available online. Go to their website and search for articles written by Hively.
2. What is radius of the disks discussed in the fourth paragraph of Hively's article? (Calculate the radius using the revs per minute and the speed on the edge of the disk given in the article.)
3. Calculate how much energy can be stored by this 50 pound disk. State your answer in both Joules and kilowatt-hours.
4. How much would it cost in Maine to spin up this flywheel? Assume that electricity can be converted to flywheel energy at 96% efficiency.
5. Estimate how far a car powered by 16 such flywheels could go between recharges. (Hint: See problem C11R.2.)
6. Estimate how much energy is stored by the flywheels in use in the pottery studio. (If you have questions about their specification, ask Ernie---he made them.) Your write-up should state how you arrived at this estimate.

Bonus Question/Other Stuff to Think About

• Take a look at the technical report by Trinity Flywheel Power on reserve in the library. In the first equation, what are the dimensions of sigma_k the hoop stress? Do these units make sense? How do you think hoop stress is defined?
• Find some more recent information on flywheels. Has Bitterly successfully tested his car?

The following web sites may prove useful:

1. http://www.trinityflywheel.com/index.htm.
2. http://godzilla.lerc.nasa.gov/ppo/flywheel/program.html.
3. http://www.windbreak.com/.
4. http://weirdrichard.com/FLYWHEELS.HTM.

Web page maintained by dave@hornacek.coa.edu.