To measure RPM’s you will need a low flare ball (spare ball is good), a  piece of tape (4 to 6 inches long), and a video camera. Place the piece  of tape running from the bowler’s PAP to above the fingers. Film from  behind, with a close up of the hand at the release point. As the ball is  being released, stop the tape. Assign the tape a position on a clock  (i.e. the piece of tape points to 10:00). In slow motion, click off 10  frames and freeze. Count the amount that the tape rotates as hours, as  if it was the hour hand on a clock. Multiply the amount of hours by 15.  (For example, the ball started at 10:00. After 10 slow motion frames the  tape ended at 5:00, passing 10:00 once). One complete rotation around  (10:00 to 10:00) counts as 12 hours. 10:00 to 5:00 (the ending position)  equals 5 hours. This is a total of 17 hours of rotation. Multiply the  amount of hours (17) by 15. This equals 255 Rpm’s. The other way to  measure revolutions is called hand revs. You will also need the piece of  tape and a video camera for this. Repeat the steps for measuring RPM’s,  however let the ball travel 15 feet down the lane. This is the distance  of the fourth arrow. Note the starting position of the tape and count  the amount of times the ball has rotated using fractions, not hours.  Take the total amount of rotations and multiply by 4. This equals hand  revs. For example, the ball started at 9:00 and ended at 3:00, passing  past 9:00 three times. This would result in 3 1/2 rotations. 3 1/2 X 4 =  14 hand revs. Why do we not count the total amount of revs the ball  rotates all the way down the lane until it hits the pins? Because  friction will slow down the ball speed and create additional  revolutions. By using the first 15 feet, we are counting the rotations  in the presence of lane oil, a very low friction environment. In our  Surface Friction Selection Chart, we use hand revs rather than RPM’s.