Music Trade Review -- © mbsi.org, arcade-museum.com -- digitized with support from namm.org
THE MUSIC TRADE REVIEW
The Function of the Equalizer in Player Mechanisms Is Often Misunderstood
—It Is Not a Reservoir, Though Often Described as Such, but It Is the Means
Whereby Constant Power Is Maintained in the Reciprocating System
In some remarks in the department of pneu-
matics of this Player Section delivered a few
months ago we had occasion to speak at length
on power systems for supplying the place of
the ordinary foot-driven bellows of the player-
piano. It is evident that some part at least of
what was then said contrived to miss its mark,
for a correspondent in a recent communication
asks us whether we meant to imply that with a
power vacuum system we should be able to do
away with, or contemplated doing away with
the "reservoir," as he called it, or the equalizer,
as we prefer to have it named. The asking of
this question implies a misunderstanding of the
functions and real usefulness of the so-called .
"reservoir" or equalizer; a misunderstanding
common enough, one has reason to believe, to
justify one in trying to set it right here.
Owing to the unhappy confusion in which the
technical terminology of pneumatic musical in-
strument making has from the first been
plunged, many delusions are commonly received
as truth which could never for a moment en-
joy consideration if a more definite and accur-
ate nomenclature were in universal usage. It
has been customary, ever since the player busi-
ness began to be a business, to speak of the
equalizing bellows of the bellows system as a
"reservoir." In consequence of this inaccurate
use, the idea has persisted that the duty of this
device is in some way or other to "store up
power." A further and incidental, but at the
same time consequent delusion has been that
the size of the equalizer, or the number of equal-
izers or the spring pressure used in expanding
them, have in some mysterious way the prop-
erty of influencing the efficiency of the bellows
system. The idea had been carried into the
entire realm of player experiment and thought,
so that even when it is proposed to use a power
system, the tendency of common notions is at
once to find place for an equalizing bellows and
to insist on the necessity for it.
The Function of the Equalizing Bellows
Let us examine the facts impartially. The
ordinary foot or motor driven bellows system
consists of two, three or more bellows, which
operate back and forth in reciprocating motion.
In each double oscillation of each bellows unit
one movement is devoted to producing the re-
quired expansion of the interior air, which is
collected in the opened bellows. The reverse
movement is devoted to the exhaustion of this
collected air into the atmosphere. One half of
the bellows' movements therefore are non-
power strokes. In fact, we have a two-cycle
machine or single-acting engine. If enough of
such reciprocating units are mounted on a shaft
it would be theoretically possible, of course, to
arrange them so that the power production will
be virtually continuous; but to do this requires
a multiplicity of units and a burden on the driv-
ing motor which places the scheme beyond
practicality. Still, it may be admitted that with,
say, four units mounted on one shaft, something
not far from continuous power production is
achieved. The reason why only an approxi-
mation is reached lies in the fact that the power
stroke is not efficient from beginning to end.
Of course, with the two units of the foot-
driven system, we have a very distinct and defi-
nite hiatus in power production at the end of
each stroke, when one foot is all the way down
and the other all the way up.
Now, in either case, the only function of an
equalizer is to close up the gaps and so pro-
duce the effect of constant power in the recip-
rocating system. The equalizer operates to
bridge over the moments of non-power produc-
tion.
The Case of Foot-Driven Bellows
In the case of the foot-driven bellows, it is
plain that a system of equalizers is absolutely
necessary. In the first place, be it remembered
that the bellow systems have to supply power
simultaneously to two pneumatic-power con-
suming systems in the player, systems different
in their functions and requiring two different
kinds of pneumatic power. The first is the sys-
tem of speaking pneumatics of which the main
requirement is for extreme flexibility with power
to rise and fall whenever required, instantly and
within a wide range. The second is the system
of non-speaking pneumatics, as for the hammer-
rail, for the damper pedal, for the automatic
tracking device, if any is used; and above all
for the pneumatic motor, which last alone is
responsible for the consumption of about one-
half of the power input. Thus we need at one
and the same time a power flexible for the
speaking pneumatics and rigid for the non-
speaking system. Plainly the first step in ob-
taining this double requirement is a system of
equalizers which shall tend to maintain con-
tinuous power input, while through systems of
auxiliary governors, which are equalizers in min-
iature, certain minima of power levels can be
maintained under all conditions for the non-
speaking system. Hence, in all foot-driven sys-
tems, or in power-driven systems where the
number of units is not sufficient to produce con-
stant power input—that is to say, in almost all
the possible cases where the reciprocating bel-
lows units are used—some form of equalizer is
necessary. The necessity is not to increase
power, nor to 'store up power' nor to do any-
thing at all save come into action at moments
when the power-input periodically pauses. As
soon as we get into the habit of using the rela-
tively accurate term 'equalizer' instead of the
quite inaccurate term 'reservoir' we find it much
easier to understand the described function.
The Problem of Constant Power
From what has been said above it becomes
plain that if we can get a constant stream of
power without gaps or pauses, we automatically
eliminate the necessity for anything like an
equalizer. If it be a question of distributing
the power after its production to two or more
varying systems contained in the complete in-
strument, each needing its own individual level
of tension, it is equally plain that the equalizer
is not any more needed even there, for power
may be distributed from the continuous pro-
ducer and at each of the varying systems may
be made to pass through a reducing valve until
the power is brought down to the level required.
This, of course, is based on the assumption that
power is produced at a maximum constant
level and that any alterations in level will be in
the nature of reductions. Such a system, of
course, is the only correct one and in all power-
driven instruments is the one used. The only
trouble is that the maximum is usually held too
low. In actual fact, it is not only a good idea
but the only right method, to have all the non-
speaking pneumatics operate on maximum ten-
sion, so that they may be made as small as
possible and at the same time operate with that
instantaneous action necessary to efficiency.
Complete Dynamic Control
For the speaking pneumatic system, it is plain
that if we have a power system operating on a
maximum and this maximum be high enough—
as by hypothesis it will be—to give the utmost
power on any note in playing that could be
asked for, the control of the speaking system
will be merely vested in one or more governing
bellows which may operate over the whole bank
of pneumatics or over sections of them accord-
ing to the preferred method. Anyhow, whether
a divided pneumatic system be used or not, it
is plain that the controlling apparatus can easily
be made to work normally on a very slight
amount of power by the simple process of re-
ducing through automatic cut-offs controlled by
the springs of a governing bellows. If, further-
more, this control be made to operate through
finger levers or through the feet on pedals—
which would be much better—then that com-
plete dynamic control will be possible, toward
which we all yearn and of which we all dream.
Selection of individual notes is something dif-
ferent and need not be considered here, although
one may say that there is no difficulty about
incorporating any such system with the arrange-
ments here suggested.
It is, of course, plain from all the above that
any system of power production which elimin-
ates the reciprocating motion and substitutes
rotary motion with continuous input of power
may do away with the equalizer, simply because
the latter is merely a stop-gap and is not needed
when the gap has been abolished. Moreover,
it is easy to see that such a constant level con-
tinuous power system is controllable without
the use of any equalizing system, merely by
the ordinary expression and motor governors,
perhaps with slight modifications. It is likewise
plain that the equalizer in itself is not an engine
of positive production, but merely a balance
wheel.
WRIGHT METAL PLAYER ACTION
ADDRESS
ALL
CORRESPONDENCE
TO
George H. Beverly
Sole Distributor
Easily 100% in advance of any action ever offered. Simple—Responsive—Durable
—Beautiful. Contains the Wright "Ideal" bellows.
Being made of metal (the logical material for player actions) it cannot be affected
by dampness or any climatic conditions. Its exclusive features save many dollars
in repair work and make many sales in competition.
Factories
KNABE BUILDING
M. S. WRIGHT CO.
437 FIFTH AVENUE, NEW YORK
WORCESTER,
MASS.