Musical Brakes


 To build a wheeled device that will coast down a ramp and brake to a stop in a prescribed area.

Permitted Materials
  1. Wheels made from standard music or computer CDs.
  2. No restrictions on the materials used for the frame or other parts of the device.
Other Constraints
  1. The device must have at least three wheels which are attached to one or more axles. The wheels must rotate but the framework cannot rotate. The axles may or may not rotate. The device must fit completely in a box 30 cm. x 30 cm. x 30 cm.
  2. The wheels must be made from CDs but may be cut, drilled, glued together, etc. Only the wheels (CD material) may touch the ramp and floor. The device must be completely self contained – no remote controls of any type.
  3. No energy sources (batteries, pre-wound springs, etc.) other than gravity are allowed.
  4. No lubricants are allowed.
Testing Procedure
  1. The device will be placed on the ramp, by one of the participants, and released (somewhere along the 4′ length). A score will be determined by measuring the distance the device (rear end) rolls past the beginning of the stopping zone, which is located four feet beyond the bottom of the ramp. The shortest distance into the stopping zone wins. If any part of the device crosses out of the two foot wide by three foot long stopping zone, it results in a scratch.
  2. Contestants will have three attempts. The best of the three will be used as the final score. The three attempts will be scheduled consecutively; however, contestants may opt to delay the third attempt to make minor repairs or adjustments. I n the event of a tie, the second best of the three attempts will be the tie breaker.
  3. Practice runs in the testing area, prior to the actual competition, will not be allowed.
    The ramp is constructed from a two-by-four foot sheet of hardboard (smooth side up) and is elevated fourteen inches on one end. The transition to the floor is provided by a duct tape junction.
College of Saint Benedict
Saint John’s University

Jim Crumley
Chair, Physics Department
SJU PEngl 107
Physics Department