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MMD > Archives > November 1998 > 1998.11.07 > 06Prev  Next


Roll Compensation for Tempo
By Craig Brougher

Tim Baxter was wondering about how much compensation was ideal to keep
tempo even. I started looking over my claim on the Cryin' For the
Carolines roll and realized I somehow got a decimal pt. off on my
measurement. So what it looks like to me now in that roll (alone) is
only 1% in 30 ft. But I really wouldn't go by that.

Since I don't have many of the later pop numbers on Ampico and play
mostly the earlier Ampico rolls, I realized that few of my pop rolls
have compensation at all, just like Robbie said (Still, their tempo
is just fine, to me). I would like to hear from someone like Don Rand
or Richard Tonnesen on the roll acceleration question, too. I know they
have to figure it, but don't know exactly how closely.

The tempo number on the roll is the paper speed the roll begins with.
From there, it speeds up relative to the change of the ratio between
the empty take-up spool and  growing take-up spool diameters. Pi is
constant, so the increase is linear with respect to circumference, but
not linear with respect to overall paper length because the greater the
number of turns of paper on the spool, the less and less percentage
each additional turn makes to the increasing speed.

That would seem to me then that while one might roughly plot a straight
line from the initial and ending tempo points, he would have to
understand the buildup better by plotting other points between if he
were to make more than just one compensation.

I have a very large roll that plays about 25 minutes, but don't have a
metronome or a rolling counter, so it is difficult for me to check out
some of these roll tempo questions. I would just say, call Mr. take-up
spool "a", and call the overall finished diameter with all the paper on
it "b", and so "b"-"a" / "a" would be the diameter increase, hence the
ratio that you would add 1 to, and then multiply by the initial tempo
to find the finished tempo of the roll. Then tempo times .02 gives you
the inches/sec of the paper.  From this, then, you are able to calculate
any particular paper speed at a certain overall diameter, but not the
rate of paper speed change.

From my perspective on this question, it seems as though the first few
feet of a roll increases tempo a greater percentage than the last few
feet of the same roll. The longer the roll therefore, the less and less
increase in tempo there will be, given no changes in motor speed. (A
vertically declining curve with respect to paper speed, total paper, or
overall time).

Craig Brougher


(Message sent Sat 7 Nov 1998, 16:22:57 GMT, from time zone GMT-0600.)

Key Words in Subject:  Compensation, Roll, Tempo

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