Slashdot Mirror

← Back to Stories (view on slashdot.org)

Investigating Angular Velocity

Posted by michael on from the young's-modulus dept.

mbreitba writes "Sam Barros is at it again, Some may know him for his Railgun research, and some may know him for his homemade cannons. But now he's found a use for all those old CD's you don't need anymore. Personally, I couldn't think of a better use for them."

4 of 271 comments (clear)

  1. why spin the CD at all by Anonymous Coward · · Score: 5, Interesting

    I bet in the future, you'll be able to get "legacy" CD-ROM drives that just take an optical image of the whole disk once, load the content into a buffer, then eject the disk, in about 5 seconds.

    That would be cooler than 12,983x drives.

  2. How do we know how fast it was spinning? by anubi · · Score: 5, Interesting
    He notes using a dremel tool to spin the disk.

    He also notes the disk speed is lowered due to aerodynamic drag.

    Personally, I would have been impressed if he had done something to the disk, maybe going over quarters of it with a black felt pen so an optical pickup could have determined its RPM, instead of guessing.

    At those speeds, gyroscopic effects can really be exaggerated! Gyroscopic effects alone can result in some really bizarre behaviour when the plane of rotation is changed.

    This experiment reminds me the time we got a flywheel spinning off the table-saw motor in high school shop. The flywheel got away from us when unexpected gyro forces wrenched it from our hands. The damage that thing did was talked about from then on to beyond the day I graduated.

    --
    "Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]

    1. Re:How do we know how fast it was spinning? by bm_luethke · · Score: 4, Interesting

      Agreed on the dremel.

      I have a few spare Radio Control car electric motors that have TONS or torque. I bet I can get the CD to spin at nearly thier top speed which is somewhere between 25k-40k depending on the motor. I've broken wooden airplane propellers on them trying to build thing before.

      You can get some of them pretty cheap (25-40 dollars for the motor, 15-25 for a mechanical speed control). Lots of uses for a high torque, high RPM, motor.

      --
      ------- Sorry about the spelling, I suffer from two problems. Dyslexia makes it difficult to spell well, lazy makes it
  3. Other good uses for CDs by dew-genen-ny · · Score: 5, Interesting

    A few years ago, myself and a friend found another, equally interesting use for old CDs:

    You can use a stack of them hooked up together as a big high-voltage capacitor!

    We connected them all up, then passed in ~20K volts, and it really could hold it's charge (I can't remember the numbers - since then, I've lived in amsterdam for 3 years, and a'dam tends to have a negative effect on ones memory....). What was amazing was when you hooked it up to the powersource, all the disks were attracted to each other and clamped up really tight.

    Discharging the thing was amazing, and the 'zap' (for want of a better word) could easily burn through some thick paper...

    Maybe when I've got some time I'll repeat the setup, this time with some photos, then I'll enjoy a good ol' fashioned slashdotting...

    --
    tom-george.comBecause geeks rate higher t