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THE MUSIC TRADE REVIEW
11
The Elimination of Frictional Resistance in the Mechanism of the Player-
Piano Is a Problem Which Is Holding the Close Attention of Pneumatic
Engineers—The Cause of Friction in the Player; How It Can Be Overcome
Those who have followed carefully the prog-
ress of the player-piano since the first days of
fifty-eight-note cabinets, are aware that an un-
ceasing search for improvement has gone on,
in the mechanical no less than in the purely
musical aspects thereof. The mechanical de-
tails are more or less, by the layman, taken
for granted. The purchaser enjoys the results
without thinking of the labor that has been
expended since the first days of the "piano
players." The same thing is largely true of
the trade itself. Only the actual experimenters
in the factories know what they wish to accom-
plish, and even they scarcely ever take time to
analyze their results. Yet it is very important
for the future of the industry that they should.
To put in a nutshell the thought in mind
one might say that the aim and object of all
mechanical work is to eliminate friction. The
term friction, really, means simply "rubbing."
When two mechanical surfaces come together
in mutual motion, the rubbing that ensues
transforms part of the energy of motion into
heat, which may raise the temperature of the
surfaces sufficiently to cause distortion of them
and dislocation of the mechanism. Friction,
then, raises the temperature, wastes energy by
transforming it into heat that is not needed,
and lowers efficiency. The elimination of fric-
tion is the aim of every engineer and mechanic.
Now, theoretically, we may suppose, every
man engaged in the various engineering prob-
lems that have to do with pneumatic mechanism
is aware of these facts. And the progress of
the player mechanism from early days to the
present time, shows that to an admirable extent,
the recognition has been put into practice. But
candor compels the statement that pneumatic en-
gineers, in the course of their earnest, sincere
and generally successful work of improvement,
have been perhaps less successful in the gen-
eral reduction of frictional resistance than in
any other branch of their work.
The statement is made advisedly, although it
would be easy to bring up a host of objections
to it. A few considerations of practical im-
port, however, will serve to show what is meant
by the charge.
Mechanical Friction in Contacts
In the first place, we remarked at the be-
ginning of this article that the layman accepts
improvements as a matter of course, not wast-
ing time in finding out whether they have been
easily made or not. By the same token, how-
ever, it may be asserted with equal confidence
that the layman unerringly puts his finger on
defects; even though he may not know their
causes or the difficulties attending their re-
moval. Thus, the failure of repetition or the
binding of parts due to lack of oil on moving
transmission gears, are patent to the layman;
and condemnation of the player oft follows
as a matter of course.
Now we have here points of the utmost im-
portance.
Let us consider them.
It is, of
course, true that the piano action, by itself, is,
if anything, not so fast in repeating power
as the pneumatic action.
In other words,
the pneumatic can certainly collapse and re-
cover ten times per second, while the piano
action, at least that of the upright, cannot do
this. Allowing for the fact that ten trills per
second on the same note are beyond practical
needs in playing, it remains that the player
action is faster. Still, we constantly find that
the repetition of the player-piano when pneu-
matic and piano actions are in conjunction, is
slower than the normal speed of the piano ac-
tion when tested alone. Allowing, once more,
for possible cases where a mechanism is not
in good condition, and confining our attention
to new instruments in perfect order, we find
that the repetition is frequently not as fast
or as certain as it should be, or as can be had
by operating the piano action alone through
any simple mechanical means.
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The answer to the problem thus raised, is,
fortunately, not far to seek. If we suppose,
for the moment, that the dimensions of the
valves, their relations to the pneumatics, and
the arrangements of the channels, etc., are
properly calculated and carried out, so that no
impediment from such sources is to be looked
for, it follows that the trouble must be found
in the contact between piano and player ac-
tions. Such contact is nearly always by one
of the three following means:
We have a direct contact between pneumatic
and abstract through a lug or spur on each, or
we have a set of plungers running from the
pneumatics to the wippens, to make contact
therewith either immediately or through a split
hinged finger or lever; or else we have the
pneumatics contact a set of auxiliary rocking
levers, which in turn contact through their
further arms, the wippens or the abstracts of
the piano action.
In the first case it would seem that friction
is reduced to a minimum. So it is, but for one
fact.
The contact surfaces are usually faced
with felt. Felt against felt is almost as bad
as steel axle grinding against brass bearing with-
out grease.
Friction develops certainly and
immediately.
It is not bad enough to bring
the motion to a stop, but quite enough to re-
strain it. A better scheme would be to use a
buckskin of fine texture with the smooth side
out, well graphited and burnished, against a
graphited wooden lug.
In the second case, the plungers are either
of wood or of wire. When they are wooden,
friction develops in the bearings of any guide
rail that may be necessary to hold them steady.
If they are passed through a guide rail bushed
with felt or even fine bushing cloth, friction
results, and if the contact be close it is almost
certain that wooden rods will at some time
swell up and stick. The remedy would be to
build the plunger rods like the abstracts of a
piano action, making them turn on bushed brass
flanges, fitted with center pins.
In the third case, the conditions spoken of
above may all exist, with the additional friction
caused by additional bearing surfaces. Such
elaborate arrangements do not, in reality, con-
vey any improvement in touch and they do dis-
sipate energy.
They are prolific sources of
unsteady and slow repetition, and it would be
much better to eliminate them altogether.
On very light pumping at high speed, espe-
cially with the hammers thrown up towards the
strings, friction between pneumatics and piano
action shows most noticeably, and it would be
much better to eliminate felted surfaces and
wooden rods entirely wherever possible.
Mechanical Friction in Valves
The elimination of friction in valve systems
did not begin to receive special attention until
comparatively recently, because the develop-
ment of the player business on its engineering
side had not proceeded far enough. But it is
now beginning to be seen that the motion of
valves constitutes one of the most profitable
fields of study for the player-pneumatic-engi-
neer.
The horizontally moving valve is now giv-
ing place to one vertically positioned. The
guide pin is being examined and the conclusion
is being reached that it constitutes a source of
unnecessary frictional resistance. There is no
doubt that the conclusion is justified by the
facts,
Yet it is evident also that if we are
(Continued on page 12)