When making my "O" rolls I used this method to figure out the paper
speed at any given point in the roll.  There is approximately 250 feet
of paper, maximum, on an "O" roll.

I used a rotary measuring-wheel counter (it displays in feet or inches)
and measured the distance and time from start to finish at Tempo 70.

A graph was drawn, with Vertical = paper speed (feet/minute) and
Horizontal = distance (feet).  You would figure that the graph should
be a straight line, but it isn't.  The drive in my case is an electric
motor; a vacuum air-motor would show different characteristics.
For example, from my graph:

   distance  speed

    0 feet    70   (7.0 feet/min.)
   75 feet    78.5
  150 feet    82

However, no matter what kind of drive, you can get the basic
conditions.

Steve Bentley,
North Vancouver