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THE
( ), 1 9 1 8
MUSIC THADE
REVIEW
The Leaf Pneumatic, While in Very General Use in Player-Pianos at the
Present Time, Contains Many Imperfections Which Will Necessarily Have
to Be Eliminated Before the Perfect Player-Piano Shall Be Produced
At one time and another \arious suggestions
have been made for .the improvement of the
motor elements in the pneumatic piano playing
mechanisms, meaning by this term to describe
the prime moving parts, such as pneumatics.
Now, after twenty years of pretty continuous
experiment and development, the player design-
ers have come to adopt certain standard meth-
ods and certain standard forms, which therefore
are, supposedly, the best possible. Hut it does
not always follow that because an idea is con-
secrated by use, therefore it is the best; and, on
the other hand, experience teaches us that ac-
cepted notions are frequently superseded by
improvements.
One is led to reflect upon the design of the
prime moving parts of the player mechanism by
the consideration that the leaf-form of pneu-
matic has been completely and blindly accepted
by all designers and so far has never been sub-
jected to any physical and mechanical analysis.
If it has really ever been subjected to this
sort of test in the laboratories of any manufac-
turers the fact has never become public.
Is the leaf or bellows form the best for the
speaking pneumatics of the player action? And
if it is the best, why?
Design
If we consider the bellows or leaf pneumatic
closely we shall see that it essentially consists
of two oblong boards, hinged together at one
of the shorter sides of each, and then clothed
with an air-tight flexible covering which runs
between the extended long sides and over the
short side opposite to the hinge, thus forming
a kind of fan which can be pushed in and out
like an accordeon. This kind of construction
has been used for a long time, in fact, ever since
the earliest days, and is practically universal.
Only two player actions of reputation, so far as
we know (Wilcox & White and Henry F.
Miller), use anything else than this.
Now at first sight it is obvious that the leaf
pneumatic must be hard on the cloth which
covers it, because its shape compels the cloth
to bend over along a straight line between the
two boards every time the pneumatic collapses.
Along this line cracks must sooner or later de-
velop. This may not be so very serious in the
matter of the speaking pneumatics, but it is very
serious in the pneumatics of the pneumatic
motor. These are working constantly at rela-
tively high speed. The cloth naturally cracks
and leaks develop.
Hut in reality the weakness of the type is not
here. It is rather in the uneven distribution of
the power which the peculiar shape of the pneu-
matic involves. it is also in the fact that the
moving board of the pneumatic must move
through the arc of a circle and thereby strike a
glancing blow. This means that the connec-
tion between the pneumatic and the piano action
or key must develop frictional resistance at one
or more points. Then there is no doubt that
the leaf-type of pneumatic is limited in its
power of repetition by the stiffness of the cloth
sides. Y^ery few player actions are capable of
repeating very quickly and certainly on a single
note. The inertia of the leaf pneumatic has not
often been blamed, but is blamable nevertheless.
Friction
As remarked above, these strictures apply
even more clearly to the more rapidly moving
pneumatic motor. A good deal of friction a-id
a good part of the excessive motor drag on ibe
main power plant could be avoided if the cir-
cular movement of the leaf pneumatics couM be
transformed into a straight-line movement.
Very little work has been done, so far as we
are informed, on this subject of the relation of
frictional resistance, circular instead of straight-
line motions, and so on, to the question of
power. The player action is not an economical
machine. It is uneconomical, very largely be-
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cause it is built of materials and is installed in
instruments so peculiar in their make-up that
the sort of lubrication which is possible in ordi-
nary machinery is impossible of use.
The elimination of friction and of other ob-
stacles to the development of power is one of
the most important departments of research for
the future improvement of the player action.
To begin at the beginning, even if the leaf pneu-
matic be retained, its worst defects might per-
haps be got rid of. For instance, the move-
ment of the pneumatic through the arc of a cir-
cle means that the connecting rod must turn
with utmost freedom upon its pivot, if binding
is to be avoided on the guide bearing of the
rod. But when the wooden rod contacts the
piano action through a felt contact cushion fric-
tion develops at once right at this point. If a
different material were used at the point o-f
contact, there would be less friction, better
repetition and less use of power. We had oc-
casion to hear of some research work along
these lines done some time ago, when the pneu-
matics on a certain player were stripped of their
plungers and felt cushions, which were replaced
by other plungers made more perfectly circular,
thoroughly graphited and crowned with cushions
of special smooth buckskin. The result was
shown in a markedly improved repetition.
Diaphragm
We have always had a weakness for the dia-
phragm pneumatic, in spite of the fact that some
of the popular arguments which have been made
on its behalf have been somewhat more ro-
mantic than accurate. In the long run, a pouch
or diaphragm pneumatic will endure better than
the leaf; but for practical purposes the differ-
ence is not so great.
In present conditions
other parts of the player action break down
sooner, although it is probably true to say that
rive years of steady use represent the endur-
ance limit of the leaf pneumatic.
But then,
player actions have not yet been developed to a
point where they will stand five years' solid
pounding without showing distinct evidences of
the wear and tear. Any player as old as that
will show by the effort required to pedal it, by
its slow repetition and the very heavy drag the
motor makes on the main bellows, that it needs
overhauling.
The diaphragm pneumatic, however, has great
difficulties of its own, which really have to
do more with installation than with anything
else. The trouble with them is that they can-
not be so compactly housed, and in a player
action compactness is almost everything. The
weakness lies in the fact that the motion is
of a flexible instead of a rigid wall. If an at-
tempt is made to connect directly between the
rigid piano action and the flexible wall the con-
necting devices must necessarily be complex and
friction producing. The problem is to bring
the diaphragm pneumatic into mechanical con-
tact with its objective without losing all its
effectiveness in extra friction.
Hut the virtues of the type are so many as to
fascinate the experimenter. Only by the use
of a pouch system of design can pneumatics
ever be dimensioned accurately, and the amount
o.t power needed to work them for various dy-
namic effects be correctly calculated. Only by
getting rid of the triangular leaf pneumatic shall
• we ever be able to obtain really scientific data
as to the size and shape of openings, passages,
channels and wind-ways needed to give us \he
best results.