Measure Rev Rate

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Revision as of 15:55, 20 April 2011 by Trackbowler (talk | contribs)
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Calculating Rev Rate requires a video.

Place Tape from PAP to above fingers.

  • Make sure the tape is contrasting in color to the ball. This will allow you to easily see the rotations.

Film a few throws

TAKE NOTE of the Frames Per Second you're recording in. Most video cameras are either NTSC-30FPS or PAL-25FPS, but other rates do exist.

On a frame-by-frame player (Quicktime) count the number of times the tape revolves over 10 frames. Be as exact as possible with this calculation.

  • 1/4 rotation over 10 frames is equivalent to 45 RPM, so a minor mistake in reading the video can be large
  • To minimize error, throw more than one shot, and average your results.
  • The higher the video quality, and the higher the frame rate, the more exact results you can obtain.

A short duration such as 10 frames is best, as this allows you to remove many effects of the lane such as friction.

You will end up with X Revolutions / 10 Frames

At this point, it's simply conversion factors from high school science class:

  • I am using 30FPS, as most video cameras in the US will use this *

(x Revs / 10 frames} x (30 Frames / Second) = (revs / Second) (Revs / Second) (60 Seconds / 1 Minute)

Multiply X Revs by 3, (or multiply by 30 and divide by 10) The Multiply your result by 60. It's pretty simple!

For example: If the ball Completes 2 FULL rotations only over 10 frames

2/10 * 30/1 * 60/1 = 360RPM


Video Courtesy of JustinWi