Steps of Advance
By Horst Mohr
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
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