Hi All, As with most discussions and experiments, there are qualifying
factors that need to be addressed before you can arrive at a meaningful
As an example, I ran a synthetic pouch material through 2-1/2 million
repetitions to find out if it would fail. It did not fail. Five years
later, in the real world, it was garbage.
One of the major problems with the MMDigest forum is the lack of focus
on very precise issues. Typically, the subjects are far too vast in
scope to be handled without writing a lengthily essay. For example,
this current subject and the previous one about gluing are cases where
the subject is so broad that reaching a meaningful conclusion may never
In regards to this thread, the first thing that's needed is a focus on
a particular type, weight, and thickness of cloth. That's because the
type of testing that should be done on each type of cloth is as different
as how the cloth is used in the player system.
At this moment (lacking the time to do more), I'll explain the test
I do for heavy bellows cloth. I take strips of cloth from two (or
more) manufacturers and soak it in muriatic acid until all the cloth
has dissolved. What's left is the air tight material that's sandwiched
between the two layers of cloth. Then I rinse and dry the material
and examine it under a microscope to see if there are any holes. Then
I take the rubber and put it in direct sunlight for a few days to see
how it reacts to ultraviolet rays. If there are no holes, and the
material stays supple, and it has the required thickness (about 0.035"),
it's good cloth.
In my opinion, the idea of building a bellows and testing it to see how
long the cloth lasts is an inaccurate test because there are so many
other factors which can influence the results of the test. One quick
example is the glue itself. All it takes is one little sharp edge of
glue that is rubbing against the cloth as the bellow opens and closes
to radically change the outcome of the test. And, you may not discover
that sharp edge until after the bellow is disassembled, and that would
depend on how the bellow is taken apart. Then there are the flap
valves, and their associated springs. But I think you get the drift of
what I'm saying here. There are simply too many variables to come to
the conclusion that the cloth is good or bad. The point is, if you
want to test the cloth --Test the cloth!
Also, I have run 'stress tests' on motor cloth after rebuilding the
motor. Here again, I found the results very unreliable because there
are so many other factors which can effect the outcome, i.e., the
sliding valves, the motor timing, glue, etc. However, with the acid,
microscope, micrometer, and sunlight, I can separate the wheat from
the chaff in no time, and know that my results are pretty reliable as
they relate to the air-tight coating, which is, after all, the most
important aspect of bellows cloth.
Most large manufacturers of bellows cloth (and other types of material
goods) have a laboratory where they periodically check the quality of
the products they produce. On the other hand, small companies often
lack the resources for such elaborate facilities. That doesn't mean
to say that small companies are incapable of producing quality goods,
but it does say that the possibility of a poor quality batch getting
through the system is more likely with a small company.
The bottom line to this posting is primarily that I think it would be
to the benefit of all if the authors and editors try to focus on narrow
topics as opposed to broad topics. That way we might be able to come
to some very meaningful conclusions that are indisputable.
John A Tuttle
Brick, New Jersey, USA