Chapter II as to the controversies that have raged over the question

of priority of invention. It is sufficient to refer the reader back to that portion of the present work where these questions have been treated in a sufficiently copious manner.

We may therefore proceed directly to the task of investigating the nature of the universal metallic framing that has been demonstrated to be so essential in modern constructional systems. Following the plan that we have adopted throughout, we shall first consider the nature and application of this kind of framing to the grand pianoforte.

As to the form, then, of the iron framing, its weight and size. Ever since the first grand pianoforte was produced with an iron plate cast in one piece, designers have been busy with attempts to improve upon the original invention. They have met with but moderate success. There have been multifarious changes in the details of bracing and of fitting the plate to the case, but the general form of the original design remains the same. It may be described in general terms as follows: A plate of iron cast in one piece, which follows the outline of the instrument and is so arranged that it may be secured to the case and to the wooden framing that underlies and knits together the latter and the sound-board. A gap is left in this plate at the point where the hammers strike the strings, and the resultant weakness is overcome by a system of bracing by means of resistance bars, also of iron and cast in the same piece with the main body. At its front end, nearest to the key-board, the plate is extended so as to cover the wrest-plank in which are driven the tuning-pins; and at the end remote from the key-board it is provided with a number of hitch-pins, to which are secured the waste ends of the strings. This plate, further, is so arranged that the sound-board is not covered by it except at the edges, and at the place where the bass bridge is constructed another gap is left in its surface.

The above general description comprehends in bare outline the essential features of the iron framing. There are, of course, many variations of detail, and in seeking for the best methods of designing this important part of the pianoforte we shall have occasion to examine the greater number of these with some care.

Of the various differences of detail that designers have effected in the construction of iron framing, one of the most important is presented in the so-called “cupola” style of construction. In this form the surface of the plate is raised at the edges of the case in such a manner as to give the general outline of a cupola or semi-dome. The result of this method is to increase the resonance of the framing and, at the same time, greatly to enhance the tensile strength of the whole construction. The “cupola” style was the subject of a patent by Steinway & Sons of New York some years ago, but has been extensively copied since that time. The same celebrated house was the originator of another variation upon the classic manner of plate building. Instead of arranging the strings in the usual manner, a fan-like disposition was adopted, with the result of distributing the strain more evenly throughout the entire surface and thus improving the tensile qualities of the whole plate. All these methods of construction, however, have failed to avoid that breaking up of the scale which is made necessary by the interposition, between the string groups, of bars and bracings. It has appeared impossible to obtain the requisite resisting power without the assistance of a number of heavy iron braces cast into the plate and designed to increase the tensile strength, which is weakened by the gap at the striking points of the hammers.

There has, however, appeared an invention which would seem to overcome, in an effective manner, the objections to a multiplication of bracings. The inventor is a member of the celebrated house of Broadwood, and his device is called the “Barless” or “open scale” grand pianoforte. By this invention the barred iron frame is replaced by a plate of mild steel, which is entirely free from bracings, is constructed with a continuous turned-up flange and is bolted in the usual manner into the bottom framing. This flange provides the necessary tensile strength and apparently sustains the tension of the strings in a perfectly satisfactory manner. The advantages presented by a method of construction that avoids the breaking up of the string groups into three or four divisions are obvious and need not be explained in detail.

It may be stated, however, that the principal and conspicuous advantage presented by this method of construction is found in the fact that the absence of the usual barring and bracing tends to subdue the metallic and tinkling quality of tone that is so often found to be induced by the presence of heavy masses of cast iron. At the same time, the material employed is so much more elastic than iron that there is no perceptible loss of resonance, nor is the tensile strength lessened to any appreciable degree. No one who has tested the pianofortes thus constructed has failed to be delighted with the singularly beautiful tone-quality and remarkable evenness that is shown throughout the whole compass. It is indeed a most difficult task to overcome the tendency to production of unduly prominent dissonant partials in those parts of the scale where the bracing is especially heavy, particularly in the lower portions, and consequently we must regard with admiration so successful an attempt to do away with these difficulties by removing their cause.

It may be noted at this point that the eminent firm referred to before as having introduced the “cupola” form of construction, also employ steel in the making of their metal frames, and it seems curious that this example has not been more generally followed.

The two types thus described are the most radical exceptions to the common style of metal framing. It is a matter of regret that manufacturers in general have been content to follow so closely in the footsteps of the pioneers, and have not experimented more energetically with a view to effecting other improvements in the accepted methods. The problem of sustaining the necessary tensions would undoubtedly be simplified by the adoption, at least in part, of the ideas of the eminent firms who have already been mentioned.

In order thoroughly to understand the actual advantages and disadvantages of the various styles of framing that have been described, we must consider how great are the tensions that they are compelled to bear. A concert grand pianoforte of a standard American make is so constructed that it bears a total strain, when tuned at concert pitch, of not less than 30 tons. The requirements of increased tone and the weight and bulk of strings tend constantly to augment rather than to decrease these tremendous strains, and at the same time more and more to induce the production of those dissonant partials that have such a maleficent influence upon tone-quality. Obviously, then, if we are to satisfy the popular demand for greater volume, and at the same time to maintain the highest standards of quality, we must seek for some method that will obviate the employment of yet heavier masses of cast iron and at the same time preserve the necessary strength and rigidity. The methods of construction that have been noticed at some length above seem to present manifold advantages over the older styles. Steel has greater tensile strength than iron, and consequently a smaller bulk of it is required. Again, its elasticity is higher and the vibrations impressed upon it traverse its surface with greater facility and in a shorter period of time. Whether, therefore, we prefer the barless or the cupola style of construction, we must recognize the fact that steel is a better material than iron in any form.

Foremost among the requirements of a successful framing system are that it shall sustain its burden with such rigidity that the strings shall stand in tune and the wooden case of the instrument shall not be twisted out of shape. Even if the material be the best possible, a faulty method of securing the metal frame to the case will not only prevent the consummation of these desires, but will tend to weaken the sound-board and hasten its splitting. It is essential, in fact, that the board should be relieved of strain, and great care must therefore be exercised in fitting the framing. The approved method is as follows: The framing is connected with the system of wooden posts that extend below the sound-board and bind together the sides of the case. The latter connection is made by means of long bolts that extend through the bracings of the frame and are sunk into the posts at convenient places. The sound-board is secured to the sides of the case by means of its ribs, which are continued beyond its edges and pocketed into the sides and the posts, and also by being glued to the bottom surface of the case and to the system of posts. Lastly, the frame is connected both with the board and the posts, by a series of heavy screws that pass through the board and into the posts at regular intervals along its outer edges.

This method of securing the frame and sound-board to the case ensures that the former shall be incorporated within the body of the instrument as rigidly as is possible, and that the latter shall have the fullest protection against those twisting strains that the metal frame alone ought to bear.

With such a method as has been described we can find no great fault. It should be noted, however, that in the barless or open scale construction the bolts that were described as passing through the braces into the posts below are omitted, and the whole frame is supported within the case by a series of bolts driven through the turned-up steel flange at equal intervals in its surface.

Having thus considered the forms of framing that are employed by various makers we may turn our attention to the matter of suspending the strings across the frame and over the sound-board. The upward stroke of the hammer of the grand pianoforte tends to drive the string away from its bridge and thus to lessen the energy with which the vibrations imparted to the string are impressed upon the latter. We may note that all makers are agreed in giving to the strings of a grand pianoforte an upward thrust or “bearing” in order that the blow of the hammer may throw the strings against the upper surface of the bearing-bridge instead of away from it. There are two devices that are generally employed for this purpose. They are known as the “agraffe” and the “capo d’astro bar.”

The first of these was the invention of the celebrated Erard of Paris. It consists of a brass stud screwed into the iron framing (or into the wrest-plank where the plate does not extend over the latter), at the beginning of the speaking length of each string or group of strings. This stud is bored with the required number of holes--one for each string in the group. These holes are bored at such an angle that the ends nearest to the tuning-pins are higher than the other ends, while the pins are placed at a higher elevation than the agraffes. In this manner the string is given an upward thrust as it proceeds toward the tuning-pin, and the blows of the hammer force it against the upper surface of the agraffe, which, being solid, conveys the impressed vibrations through the medium of its own surface to the framing.

The “capo d’astro bar” performs the same functions in a slightly different manner. It is practically a continuous “agraffe,” and consists of a metal bar which is cast into the metal frame at the beginning of the speaking length of the strings. It is fitted, according to the best practice, with an under edge of tool steel, and the strings are caused to pass underneath it on their way toward the tuning-pins, which are higher than the bar, as before. The up-bearing is thus imparted to the strings in a manner similar to that which is followed in the case of the agraffes.

As to the advantages of the two systems, it may be said that the “capo d’astro” undoubtedly overcomes those objections to agraffes which are based upon their tendency to pull out from their places. It provides an absolutely rigid resistance, and is therefore stronger and more reliable.

On the other hand, however, the mass of metal employed is considerably greater than in the “agraffe” method, and the resultant influences upon tone-quality are clearly disadvantageous.

Further, the work of tuning is rendered more difficult by reason of the fact that the strings cannot so readily and correctly be pulled through the space intervening between the bar and the tuning-pin. It is debatable whether the greater rigidity and resonance offered by the “capo d’astro” method are not too dearly bought at the cost of inconvenience in tuning and deterioration of tone-quality. It is noteworthy that most manufacturers confine the “capo d’astro” bar to the high treble register of their instruments, where brilliancy and a somewhat metallic quality of tone are a desideratum.

The iron framing of an upright piano follows the same general lines of construction as have already been noted in the previous discussion of the grand. The functions of the frame are precisely the same and its construction differs outwardly but little. There are, however, certain divergencies from the grand forms that must be noted carefully. For example, it will be remembered that the form of the upright pianoforte is such that the framing has no direct and positive connection with the outside case. It is thus impracticable to consider the sides of the iron plate as homogeneous with the sides of the case, nor is it possible to give to it that consistency of form that, in the grand, results from the shaping of the plate to correspond with the curved outline of the case. This, however, is no reason why the upright iron plate should not be as strong and secure as that of the grand.

Among the various differences of detail that we observe to exist between these two forms of plate is the device adopted to secure the bearing and rigidity of the strings at their upper end deserves notice. The practice is entirely different in this respect as regards the upright, and we are therefore introduced to a new feature: the “pressure bar.” This device has superseded both the old-fashioned pinned bearing bridge and the later agraffe forms. It consists, essentially, of a bar of heavy metal that is screwed into the wrest-plank through the metal plate and is placed so that the strings pass under it on the way to the tuning pins. In fact it occupies the same position as do the agraffes or capo d’astro bar on the grand. Its function is also similar; namely, accurately to delimit the speaking lengths of the strings at the upper end and to assist in the formation of a thrust or bearing whereby the latter may more advantageously be secured.

This form of building the bearing bridge possesses important advantages. It does not require to be cast into the plate, nor is it weakened, as in the agraffe system, by being broken up into a large number of units. Moreover, the bearing for the strings is formed much more smoothly and easily between the pressure bar and its attendant ribs on the plate than is possible when either the agraffes or the capo d’astro bar are used. This is an important point, for such construction tends to make the task of tuning much more rapid and correct.

There are, however, several points to be considered in the designing of pressure bars. As a general thing, it is impracticable to apply this form to the bass strings on account of the fact that the overstringing requires of them a slanting direction. On this account the pressure bar cannot be made properly to maintain the obliquely-running strings in their respective places. It is therefore usual to build the bass bridge after the old pinned type and thus to secure the bass strings by much the same device as is employed in the belly bridges.

As far as the designing of pressure bars is concerned, it will be found that care should be exercised in arranging the space that the bar must occupy and its position with regard to the scale ribs that are placed on each side of it and that support the strings before and after their passage under it. In general it may be said that the pressure bar must be screwed in such a position that its lower curved surface is lower than the upper surfaces of the scale ribs by about one-half of the height of the latter. It must also describe a curve that corresponds to the dip or angle of the scale and must be secured by enough screws (one between each three string-groups is usual), to ensure that the pull of the strings will have no injurious effect upon its rigidity. It is also essential that the curve into which the string is bent during its passage under the pressure-bar and over the scale-ribs be not too deep or sudden. The bearing surface of the bar should be gently rounded until very near its middle point where the string exercises its greatest pulling strain. Here the surface must be curved a little more sharply.

The iron plate of the upright is the chief supporter of the strains imposed upon the structure by the strings. It is necessary, as in the grand, that it should be built so as to have absolute rigidity under these strains, and that it should be always capable of withstanding any others that may by any chance be imposed upon it. Remembering this, what shall we say of the designs that we sometimes see where the iron is cut and shaved away at every possible point in order to save a few pounds of weight? There are pianofortes in existence where the iron framing is so much cut down that the treble can never be depended upon to stay in tune for a reasonable length of time, and where the unevenness of the distribution of metal throughout the body of the frame has caused a warping of the whole instrument out of its proper shape. All this is unnecessary, but it will continue so long as manufacturers are willing to effect small savings at the expense of the future reliability of their product.

It is certainly much better to have the plate of the upright pianoforte so arranged that the total volume of iron, if it is to be decreased, may have this process applied evenly and all through. The most correct design would consider a moderately heavy plate of iron, or better, of steel. This plate would be so arranged that the hitch-pin plate (the portion which carries the hitch-pins) covers the entire surface of the instrument at its bottom end and is bolted into the back with as many and as heavy bolts as are employed at the other end. The upper portion of the proposed plate need not extend over the surface of the wrest-plank, for such a construction can add little to the resisting power of the frame, while it inevitably tends, for reasons that have already been described, to the production of dissonant partials and the consequent emission of a metallic tone. If it is desirable, for any reason, to cut down the weight of a frame, it can better be done at the upper end than at the lower, where diminution of the resisting power of the frame is most severely felt.

We may, then, contemplate a form of iron frame which covers that portion of the back-framing whereon the edges of the sound-board are glued, and that is not continued up and over the wrest-plank. It will be cut away in the centre, as in the grand, and will thus expose a large part of the sound-board to view. It will be provided with a certain number of bracings for the purpose of taking up the strains that are imposed upon the structure at the points of greatest resistance, such as those where the over-stringing begins and ends, and those around the middle registers of the scale. There must not be more of these bracings, however, than is necessary, as it is very important that the scale should be broken up into the least possible number of divisions. The bracings will be so designed that no one of them interferes with the true curve of the belly-bridge. The whole structure will be solidly bolted into the back-framing through the sound-board by a series of long and heavy screws and bolts that will be inserted at frequent intervals along the edges.

We cannot conclude this survey of plate-construction without taking note of a property that is common to all cast-iron structures. We refer to shrinkage. The calculations of the designer, no matter how carefully worked out, must take into consideration the fact that cast-iron shrinks largely in the cooling. It must be noted that the design for the iron plate is the chief portion of the work of scale draughting. As will be explained later on, this work is first done on paper and then transferred to a wooden pattern. From this pattern the casting is made. After the first casting is thus completed it is taken in hand by the designer, who marks and punches it for the boring and pinning and corrects it where necessary. The corrected casting is then used as a model for the future plates that are to be turned out for the same scale. But these also shrink; so that we are compelled to take into account both shrinkages, and allow for each. Fortunately, however, there is no difficulty in arranging this.

The method is as follows: After the string-lengths have been calculated and the size of the iron plate thus determined, a complete drawing is made, showing the exact dimensions, shape, and other features of the proposed plate. This is to be used as the guide for the wooden templet. But this difference exists between the two paper drawings; namely, that the second is multiplied as to every dimension of the plate by a quantity that represents the amount of shrinkage that is known to occur in the two castings.

The average shrinkage of cast-iron in the form of pianoforte plates is estimated at about one per cent. Consequently to account for the double shrinkage it becomes necessary to multiply by the square of 101/100; that is approximately 51/50.

A great deal of trouble will be avoided if the shrinkage is carefully worked out in this manner. Every dimension of the plate is affected, and the greatest care must be taken to ensure that the corrected calculations are accurate. Only thus will it be possible for the ideas of the designer to be brought out in the completed instrument as he expects to see them.