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TECHNICAL^SUPPLY DEPARTMENT
William Braid White, Technical Editor
The Scale Drawing, the Fundamental
Basis of the Construction of the Piano
The Third of a Series of Articles on the Construction of the Piano—Drawing the String Lines—
The String Spread—Placing the Forked Bars—Reasons for the Bass String Scheme—
Problem of String Dimensions—Why Ratios Are Changed
KFORE going on with the discussion
which was adjourned on August 7, I
should like to say a word of cordial com-
mendation. J. E. Jennings, factory manager
and technical expert of the Chase-Hackley Piano
Co., Muskegon, Mich., delivered an address be-
fore the National Association of Piano Tuners
during the convention of this body which was
held last week in Chicago, on "Scale Drafting."
He made, as might have been expected, a rapid
survey of his subject and was obliged to hurry
more over scientific or technical details than if
he had been talking to colleagues instead of to
tuners and outside service men; but all that he
said was in every way admirable. I was glad
too to find him in so general an agreement,
with myself on matters of essential importance.
String Lines Continued '
When one begins to draw in the: treble string
lines, one will, of course, make each of these
long enough to take in the speaking lengths, the
hitch-pins ends and the tuning pin ends. When
once all these lines have been drawn in accord-
ing to the sweep and the spread already laid
down, the whole of the string plan, with the
exception of the bass, may be said to be in
sight, and it will then be possible to obtain some
idea of the appearance of the completed scale.
Should one thereupon draw in also the bass
string lengths? I can see no good reason for
not doing so. Lengths, weights and other di-
mensions are not yet determined, but this mat-
ters not since what we now wish to do is to
have the space on our paper laid out in such
a manner as to show, at the earliest possible
moment, what demands must be made in the
way of sound board area and shape of case. Of
course it is already agreed that the outer peri-
meter of the case shall have been furnished
before we draw in any string lines, so that, to
such extent, we are limited in available area and
curves. What was said in the last article about
the inside rim line and the space needed be-
tween, inner rim and edge of plate to allow for
errors in casting, etc., will also have to be kept
in mind.
Wheri then we come to consider how to lay
out a bass string section in lines on paper we
first have to be sure that we know how many
treble strings we can manage and how many
must be overstrung. Without going for the
moment into acoustical details, I may say that
in a grand pianoforte of five feet two inches
overall one must have at least twenty-six and
more likely twenty-eight bass strings. In fact
it is almost certain in the present case that we
must have twenty-eight bass strings and so we
shall spread out our treble strings according
to the rules suggested in the last article until
we have come to the line representing unison
No. 29. This shall be the last of the treble
unisons. From unison number 1 to unison num-
ber 28 will be overstrung. In due course we
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shall see the reason for this and shall discuss it
in a manner calculated to enable the reader to
discover in any given case what he should do
whenever such a decision has to be made by
him.
String Spread
I have already said that in laying out the
spread of the treble strings I do not care to
spoil the damper line, and of course the same
principle applies to the angle which the bass
strings make with the hammer-line. One way
of getting at the right procedure is to begin
by considering the bars which must span the
space where under and overstrung strings are
crossing. The object of these bars is simple.
One of them must run parallel with the longest
understrung and one parallel with the first over-
strung string. That being so it is obvious that
both must start from the same point on the
tuning pin plate and branch out fork-wise at
some determined point. It is the decision as to
just where this point shall be that decides also
the question of the damper line. There is not
the slightest mechanical reason for beginning
the forking just where the last treble and first
bass damper .stand side by side. Yet most
small grands arc built with the forking point
placed precisely where it will interfere .'with the
line of the dampers and compel the regulator to
bend the wires so that the felts and moldings
are anywhere from half an inch to an inch and
one half nearer the tuning pins than they should
be. This is not necessary. Moreover it is not
only negatively but positively bad, because it
spoils the damping and likewise makes the
scale look very clumsy and badly finished. I am
aware that the sin in this case is shared by
some of the finest makes of pianoforte, but that
does not affect the facts.
Placing Forked Bars
Suppose then that we take a damper molding
of the right size and place it so that the felt of
the end nearer to the tuning pins would, if it
were in place, have its outer half precisely over
the middle of the hammer-line. Let us then
draw a pencil line at a distance of one-half inch
from this damper molding towards the bass, and
parallel with the string. This should be the
treble-ward edge of one of the bars, namely, the
William Braid White
Associate, American Society of Mechanical
Engineers; Chairman, Wood Industries
Division, A. S. M. E.; Member, American
Physical Society; Member, National Piano
Technicians' Association.
Consulting Engineer to
the Piano, Industry
Tonally and Mechanically Correct Scales
Tonal and Technical Surveys of Product
Tonal Betterment Work In Factories
References
to manufacturers of unquestioned
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For particulars,
address
209 South State Street, CHICAGO
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bar which is to take up the compression strain
of the strings between unisons number 29 and
number 58. Let us then draw another line on
the bass side of this first one at a distance of
one inch from it. Let both be carried from the
front to the rear edges of the drawing.
Let us now go to the extreme bass edge of
the drawing and measure a space of one and
one-half inches inwards from that and two
inches from the front edge of the plate. Mak-
ing a dot, here we note that this should repre-
sent where the inside edge of the extreme bass
bar will pass. Inwards from this we may come
another inch, and a dot here should show us
where we can safely place the first tuning pin
of single unison number 1. Let us then draw
a line from this tuning pin point to the ham-
mer line so that it makes with the hammer line
an angle of about five degrees only, in fact is
very nearly parallel with the edge of the case.
Make a dot there on the hammer line and then
other dots at intervals of seventeen-thirty-
seconds of an inch along the line until the neces-
sary twenty-eight hammer striking dots have
been set in.
Then we look at the dot representing the
place of union number 28. Take a damper
molding corresponding and place it on the ham-
mer line as described before. Then we see
how near we can come to drawing a bar line,
just as before, parallel to the molding at a dis-
tance of half an inch from it, which, of course,
will bring us across the two lines representing
the other bar on the treble side. We draw in
the second line too and then have four lines,
two crossing two, which will represent the
points at which the two bars will cross each
other and their general directions on either side
of the hammer line.
We now observe that these lines cannot be
left like this, because evidently if they were
the bars made from their pattern would inter-
fere with the strings of number 28 and number
29. We have to bring them together at the
crossing point and on the side of this place
remote from the tuning pins and from there
to the plate carry them back in a single bar,
like a handle to the fork. This will give us the
necessary clearance for strings.
Having these bar lines thus drawn in we can
draw the bass string lines parallel to the bass
side of the fork and run them across the draw-
ing as before.
Reasons for Bass String Scheme
Now it may be said that this is all rather
radical. But I beg the reader to bear with me
for a moment until he has examined the plan
carefully. In the first place we are laying out
directions, and not lengths—as yet. In the
second place there is very little advantage in-
deed to be obtained by swinging around the
long treble and the bass strings at a very wide
angle; very little advantage indeed and what
there is of that is mainly in a slight increase of
length, which, however, is more than paid for
by poor damping and crowded tuning pins. In
my opinion the cross-over should be at as acute
an angle as will give us strings of fair length
considering their pitch. It must be remem-
bered that the lengths have to be shortened
anyhow, and we shall soon discuss a rule for
them which will give us a way of compen-
Tuners
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