All:  I couldn't find this in the archives, so I'm asking (probably
again).

1.  On a big core A-roll (or any other big core roll) what is the
feet/minute tempo difference between the beginning and the end.

2.  If known, what is the approximate difference from tune to tune,
assuming the tunes are each 2-2.5 minutes long.

I have two answers to this so far, but need to know which (if either)
is correct.

   1.  2% increase from tune to tune
   2.  20% increase overall, evenly distributed from tune to tune.

Thanks in advance.  If I figure this out, I'll post a table of the
values.


George Bogatko - gbogatko@intac.com
http://www.intac.com/~gbogatko

 [ I have a re-cut 10-tune A-roll, Capitol A-2077, recently punched by
 [ Carl Lambie.  The outer diameter of the spool is 3.63 inches, and
 [ the overall roll diameter is 4.70 inches.  If the initial speed is
 [ Tempo 70 (= 7.0 feet per minute), the final speed will be 1.3 times,
 [ or Tempo 90.8.  1.3 is the ratio 4.70/3.63.
 [
 [ The speed is constantly increasing.  The Tempo difference, start to
 [ end, is 20.8 ; divide this by 11 to get 1.89.  This is the increment
 [ Tempo difference between the start of each of the 10 tunes (assuming
 [ they are all the same duration).  Expressed as a formula, let
 [
 [   To = initial tempo
 [   OD = outside diameter of roll
 [   CD = outside diam. of core
 [   N =  number of tunes
 [   Delta = tempo difference between each tune
 [
 [ Then
 [
 [   Delta = To*(OD/CD - 1)/(N+1)
 [
 [ -- Robbie