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MMD > Archives > September 1997 > 1997.09.18 > 13Prev  Next

Roll Tracking Mechanisms
By Craig Brougher

Hal Davis' hilarious essay about the automatic roll tearing devices and
the Standard Player action's "four-eyed monster" was about all I could
stand for one morning.  That's some really good stuff.  But it really
gives a person pause to consider disabling his own tracking mechanism,
and I'd seriously suggest going another route.  Here's why.

Adjusting a tracking mechanism is an art as well as a science.  In many
instances, I have added a tracking mechanism to players, because I know
how aggravating it is to be listening to a roll, and pretty soon it
changes key, or starts playing only two or three notes for awhile as it
scoots around across the trackerbar.  Hal is really saying that his
players that have trackers don't play rolls as well as those that don't.
That is not the case, generally, for a well-adjusted machine.

If you have rolls that are feathered on one edge, naturally, no tracker
is going to work, and it will mistrack.  The idea of a tracker is to
prevent rolls from self-destructing, and when well-aligned, just about
all of them will do that.

There are generally two kinds of trackers -- ones that sense the edge of
the paper by air, and others that sense the edge mechanically.  One of
the most insane kinds of trackers was the Schultz tracker that was a
mechanical edge aligner (supposedly), but that's another story.  For the
most part, trackers worked fairly well.  On reproducers, I don't know
what you'd do without them, because a reproducer MUST track a roll
perfectly in order to play the very low intensity notes without skipping.

Now I will agree with Hal on one point: If all I have to play are old,
beat-up rolls that somebody gave their children to gnaw on, then a
tracker device is better disabled because some trackers will cause the
roll to tear on rewind.  The ones that will still do a passable job, even
on those dog-eared, sawtoothed, folded, and torn rolls are the
differentially balanced trackers, like Baldwin and Ampico B.

But Ampico B trackers must be modified, and differently than that which
Robbie was talking about -- in order to track a fragile roll.  Ampico B's,
in their pristine state, are roll shredders with no equal, because they
require 'way too much pressure on the tracking fingers in order to work.
Their flat springs are much too strong to track an old, fragile roll.

When you are adjusting and regulating a finger tracker, the first thing
you must be sure to do is lighten the touch of the finger on the roll to
a feather-touch.  For example, it is wrong to use the smooth side of a
piece of leather on a Duo-Art or Themodist tracker finger pad because it
"sucks down" too hard, and comes off with a "pop." It also makes a
noise -- a hissing -- all the time.

With thick, soft suede, that pad relieves itself more gradually, and the
vacuum causes the leather in the center of the sensing nipple to "cone"
slightly, creating a graduated action that works like a metering valve at
very tiny differences in paper edge pressure.  That is what you want in
that kind of a tracker system.  I use cabretta for that valve, and it is
really special for the purpose.

However, if you do not adjust that kind of tracker with both wide and
narrow rolls, it will still tear some and fail to track others properly.
They can be a real pain, and you just have to keep adjusting, once you
know that everything is secured down with no lost motion and the
pneumatics are airtight.

Craig Brougher

 [ Robbie's comments:
 [ I agree completely with Craig that the (unmodified) Ampico B tracking
 [ mechanism is a first-rate Destructer!  Dr. Hickman said that he
 [ personally wanted to license the 4-hole Standard tracker, but Ampico
 [ management was opposed.
 [ The Hickman design suffers from (a) too much feeler pressure, (b)
 [ inadequate force to translate the supply-shaft brake drum within the
 [ brake band, and (c) inadequate lateral travel of the supply shaft.
 [ In addition, when the feeler-valves are maladjusted (which is
 [ typical), the hysteresis "dead zone" encourages meandering, which
 [ gets worse with every playing.  Sure, it works fine when it's properly
 [ rebuilt and adjusted, but only with pristine-new rolls -- and the few
 [ of *those* in my collection are of terrible music!
 [ Robbie Rhodes

(Message sent Thu 18 Sep 1997, 11:42:37 GMT, from time zone GMT.)

Key Words in Subject:  Mechanisms, Roll, Tracking

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