Hello Co-readers,

Admiring the investigations of our "Master of Precision", Wayne Stahnke,
I want to give also a comment on the subject of roll advance.

Wayne's "experimental" value of 0.856 mm is very close to the "intended"
R60 value of 0.847 mm ( 60 steps in two inches ).

For Ampicos, a roll speed of 80 means a paper speed of ca. 40 mm/sec or
25 ms/mm.

(For an asynchronous advancing device, it's step-size must be counted to
the value of the punch advance.  In case of my roll reader 0.282 = 1.138
mm error total.  The limiting link is still the stepper motor, as I play
the rolls real-time for better audio control.  One day I'll use a faster
one and make the advancing steps smaller).

They say that musicians can hear aberrations in time down to 5
ms. ( I don't believe at all times.  Probably sometimes under laboratory
conditions ;-).  A piano sound takes about 20 ms to arise after the
hammer hits).

Measuring the distances of the timing punches on the QRS test roll,
Amp-1002A,  I found ( with a plastic ruler ) the distances of 152, 149,
150, 153, 149, 150, 150, 152, 149, 151, 150, 150 millimeters.

 [ The non-uniform distances suggest that the original Ampico roll
 [ was poorly copied by QRS. -- Robbie

For the purposes like Wayne described, his acribic [eager *] research
is really needed to "get back to the roots", and from there to rolls of a
quality like the original stencils.

But, for roll-reader constructors who just want to make a MIDI-file or a
roll's copy for their own:  make the advance as small as possible but as
long as needed for your task, and don't be anxious for each 1/254 inch !

Best regards, Horst Mohr

mohr@nemeter.dinoco.DE  H. Mohr Koelnerstr.49 51515 Kuerten 02268/1561

 * [ Editors note:
 [
 [ I wasn't able to confirm nor deny that "acribic" is now an English
 [ word; from the tiny footnotes in my big 1930 (7 kg) dictionary:
 [
 [     acribic:  "acribus initiis, incurio so fine"
 [     [Latin] "With eager beginnings, but with careless ending."
 [     -- Tacitus (Annals, VI.17)
 [
 [ This thought describes the ill-conceived songs which I sometimes
 [ must perform.  I like the word Horst found!
 [
 [ Robbie