Thanks to John Tuttle for the Craig Brougher references.  The only
problem with the video was that it was only two minutes long!

I followed the discussion on pouches.  The time varying attributes of
vacuum systems creates a reality that is sometimes difficult to grasp.
It is in these dynamics that all the problems of repetition begin.

In Craig's article, the 'static' test of valve sensitivity actually
shows the dynamics of pressure loss of air moving through the 10.5 feet
of tracker tubing.  A vacuum gauge at each end of the tube would show
that a huge pressure loss is occurring due to the combination of pouch
leakage and bleed, consuming air.  It is this air which is removed by
the vacuum pump.

As Craig points out, it is impossible to instrument many of the tests
and measure the parameters.  It is true that the air pressure acting
under the pouch, when the tracker hole is opened, is at atmospheric
pressure and is constant and air fills the pouch through the tracker
hole.  However, when the hole is closed, the air is removed by the
vacuum system through the bleed and the pressure difference changes
slowly.  So the pouch does operate quicker on opening than closing.

That part of Craig's article, where he shows the "Comparison Between
two Pouches" shows the affect of the bleed air flow on the pressure
loss in the 10.5 feet tube.  For the normal Ampico pouch, the bleed is
smaller and the pressure loss is less.

Given a pressure of 2.5" water to operate the pouch, then the white
unsealed pouch lost 32.5" water through the 10.5 feet of tube, whereas
the tan unsealed lost 12.5" through the tube, and the Ampico reference
lost 0.5" through the tube.  The sealed pouches lost 7.5" through the
10.5 feet tube.

If we take the air flow through the 'sealed' pouches as a reference of
100%, then the relative air flows are (approximately)

a. Airflow through tube with sealed pouches 100%

b. Airflow through tube with unsealed pouch (white) 2.1 times greater

c. Airflow through tube with unsealed pouch (tan) 1.3 times greater

d. Airflow through tube with Ampico reference 3.8 times less

Note that the reference air flow of 100% is due to the bleed.

Regardless of what was the end result of the prior discussions, one
cannot rebuild a player without taking notice of the porosity of the
pouch material.  In a production environment, a manufacturer would want
to have pouches with no leakage/porosity, and then use a specific bleed
size to give the required repetition.  For us as re- builders, the
place to start is to use leak-free material or to seal up whatever
material we choose to use.

An aspect which is not often covered, is the difference between lead
tubing and rubber tubing.  With lead tubing, its internal diameter is
less than that of rubber.  From memory, typical rubber tubing has an
ID of around 5.5 mm.  Typical lead tubing has an ID around 3.5 mm.  This
difference in cross section allows a lower pressure loss along a rubber
tube compared to a lead tube and also requires more air to be removed
from a rubber tube compared to a lead tube of the same length.

The cross section of rubber is, say, 38 mm square, but for the lead it
is only 9.6 mm square.  So a lead tube will be more sensitive to pouch
leakage than a rubber tube, but will respond more quickly to being
turned off, if it has the same size bleed.  So maybe, a lead tubed
tracker uses a smaller bleed than a rubber tubed system.  Lead tubing
often gets replaced with rubber.

I would have liked to see more of the valve system in the video.
I got the feeling that the 'opening time' of the pneumatic was the same
for both valves, but I think the slow valve closed the pneumatic more
slowly than the fast valve closed the pneumatic.  Again, I interpreted
the test as showing a comparison of the operation of the Ampico valve
against the normal treated valve and pouch.  If this is correct, then
we are seeing the difference between the Ampico bleed ball valve, and
the normal bleed system so universally used.  Presumably the test used
the 10.5 feet of tubing.  It is interesting to see the innovation used.
Thanks to all for their work.

Paul Rumph