Instrument panel

“ The carillon in the “Parochial-Kirche” at Berlin, which is one of the finest in Germany, contains thirty-seven bells; and is provided with a key-board for the hands and with a pedal, which together place at the disposal of the performer a compass of rather more than three octaves. The keys of the manual are metal rods somewhat above a foot in length, and are pressed down with the palms of the hand. The keys of the pedal are of wood; the instrument requires not only great dexterity, but also a considerable physical power. ”

“ It appears almost impossible that while in the hands of various possessors, so fine an instrument should have been suffered to lie idle in a cabinet, as though it were a picture to be looked at, but not touched. ”

“ Of equal interest is a large semicircumferentor made by an unknown American instrument maker in the second half of the 18th century. The instrument (fig. 34) consists of a plate of hammered brass attached to a quarter circle block of mahogany, with a glass covered trough compass within a silvered opening, and the gradations stamped into the brass. The brass sighting bars are attached to a swivelling bar that can be fixed in place with a set screw underneath the block. The instrument, which is in the collection of the writer, is not signed with a maker's name. ”

“ In the Streeter Collection of Weights and Measures, Yale University.
The most interesting of the three instruments was acquired by the Dartmouth Museum as part of a collection of the late Frank C. Churchill, an inspector in the Indian Service. The instrument (fig. 69) is a quarter circle with a compass in its center and sighting bars mounted on a swinging arm that reads the angle of the brass scale on the arc by means of a vernier. It is mounted on a wooden tripod with the customary ball-and-socket joint, which permits it to be placed on a vertical plane. ”

“ After a few weeks of trial the use of metal blocks or types to [Pg 251] regulate the recording marks was abandoned, and although the construction of the handle, called the manipulator, for regulating the transmission at intervals of sufficient electricity to produce the marks, was a later improvement, he ever afterwards declared that his first rude instrument had the leading features that characterised the more perfect apparatus of later years; or to use his own appropriate words, “It lisped its first accents and automatically recorded them in New York. ”

“ In most instances they show evidence of professional workmanship, and they may have been the work of known craftsmen. One or two examples are obviously homemade by unskilled amateur practitioners. [Pg 71]
Figure 33.—Wooden surveying instrument, maker not known. Compass dial is of metal, painted green, with degrees marked to 90° with metal punches and the letter "N" to designate the north point. The instrument is 12 in. long; diameter is 8 in. In collection of Dartmouth College Museum. ”

“ This instrument is capable of being set to a standard measurement or of giving the actual size of a piece, and is therefore strictly speaking a combined measuring tool and a gauge. The U-shaped body of the instrument is provided with a hub a, which is threaded to receive a screw c, the latter being in one piece with the stem d, which envelops for a certain distance the hub a. The thread of c has a pitch of 40 per inch; hence one revolution of d causes the screw to move endways 1⁄40 of an inch. ”

“ The caps are then rigidly fixed in [203] their different positions by set screws. The focalization to the neutral centre is then established by dampening the steel rods, on the scale at the back, representing the thirds, sixths, and ninths, drawing a piece of small gum tube over them, which establishes harmony to the chord mass of the instrument. Concordance is thus effected between the disintegrator and the ninths of the scale at base of transmitters with telephonic head. ”

“ The various letters referred to in the diagrams will be found marked on the ends of the instrument studs and back of reactance coil box. It is important that the instrument be connected in circuit in the proper manner so that the needle will come to the mark on the upper part of the scale when synchronism is obtained. In case the pointer become moved or a change in its position be necessary, it is advisable to make a check on the indication before relocating the needle. ”

“ To the top of each finger-guide was attached a stout brass wire with regulating screw, which pressing against the outside of the wrist, kept the hand in its proper position with regard to the arm. In addition, there was a board ruled with bass and treble staves, called the gamut board, to be placed on the music-desk, on which each note throughout the entire compass of the instrument was found written precisely above its corresponding key. ”

“ There is practically no mechanism; the system is simple, ingenious, and neither adds to the weight nor to the bulk of the instrument. There are no screws round the head of Potter’s kettledrum; an invisible system of cords in the interior, regulated by screws and rods in the form of a Maltese cross, is worked from the outside by a small handle connected to a dial, on the face of which are twenty-eight numbered notches. ”

“ It seemed to me that in this way a number of distinct telegraph messages might be sent simultaneously from the tuning fork piano to the other end of the [Pg 61] circuit by operators, each manipulating a different key of the instrument. These messages would be read by operators stationed at the distant piano, each receiving operator listening for signals for a certain definite pitch, and ignoring all others. ”

“ Electricity is the means by which the touch on the keys is conveyed to the instrument. A thin rope, composed of the wires that communicate between the key-board and instrument, stretches from each member's seat to the instrument, which is fixed at a considerable elevation. ”

“ When the instrument is not in use, the key is left open, and the needle is held back by its spring. Now, if the California operator should close his key, he would cause his needle to be attracted toward the relay magnets; this movement of his needle exerts a sympathetic influence upon the needle in this instrument. It endeavors to parallel itself to its mate. It moves to the right, overcoming the power of its spring, and, touching the stud, [295] closes the circuit, and the sounder records the fact. ”

“ On the shaft of the little drum p is a pinion, which works into the
teeth of the cog-wheel r. The shaft of r is extended through the dial
of the instrument, and carries an index. The dial is marked off for
volts; g g and h h are standards for carrying the pulleys. ”

“ The trouble is much less than with most of the other methods, and the illumination of the object very slightly interfered with.
To varnish the edges of these covers, make circles of any liquid upon the glass slide, and perform any other “circular” work mentioned hereafter, the little instrument known as “Shadbolt’s turntable” is almost indispensable. It is made as follows:—At one end of a small piece of hard wood is fixed an iron pivot about one-eighth inch thick, projecting half an inch from the wood, which serves as a centre upon which a round brass table three inches in diameter revolves. ”

“ To the top of the inclined boards is connected a small projecting roof to prevent the rain falling on the bulbs of the instrument, which are carried on the face of the vertical board, with their bulbs projecting below it, so that the air plays freely on the bulbs from all sides. ”

“ The part 12 of the instrument may be inclosed, as shown, in a wooden or other shell 12a 12b, of spherical or other form, and which may for convenience be made in sections adapted to be connected together by pins fitting into suitable holes, as shown. A chamber 12c is thus constituted. A hole is provided in the section 12b of this chamber, in which a lens may be placed, as hereinafer described. ”

“ The microscope travels on carefully straightened ways, and is moved by a screw of 1 mm. pitch. The screw head is faced with a silver band and is divided in 1000 parts. The handle for turning the screw is placed on the left side of the instrument so as to have the right hand free for recording readings.
A set of change gears can easily be engaged to give a fast motion to the carriage. The stage will hold plates from 3 to 8 cm. in width and of 60 cm. in length. It can be shifted lengthwise for a distance of 25 cm. and is provided with adjustment for aligning the plates. ”

“ Nor would it be superfluous for a lady to take with her several sets of wires for her piano; they being very scarce. At all events, she ought to qualify herself to tune the instrument; which may be effected in the course of a month, or six weeks, by attention to the instructions of a regular tuner, who would feel himself well satisfied under a moderate compensation. ”

“ If the young experimenter desires to become a proficient telegraph operator, the first thing to do is to purchase a Learner’s telegraph key and sounder.
Connect a dry cell to the binding-posts on the back of the instrument. Screw the set down on a table about eighteen inches from the front edge, so that there is plenty of room for the arm to rest. See that none of the various adjustment screws about the instrument are loose and that the armature of the sounder moves freely up and down through a distance of about one-sixteenth of an inch. ”

“ In this problem the panel board is to be made of 1⁄2-inch stock, flat on the outside, and inset 1⁄4 of an inch. The back of the panel board is flush with the frame and is chamfered off to give the necessary tongue all around to run in the groove. The narrow stock of the framework is not likely to swell or shrink appreciably and, if well constructed, cannot become warped or twisted. The panel, on account of its greater width, may and generally does swell and shrink considerably; but it should be fitted to move easily in the grooves so that its changes may [187] not be noticeable. ”

“ Now the single-needle instrument may be seen at most railway stations and rural post offices in the United Kingdom. In this instrument the needle when moved by a current to the right hand or the left, strikes against a projecting pin placed on each side to arrest its motion; the sender by moving a handle can deflect the needle at will either to the right or the left; one deflection to the left and one to the right represents A ”

“ Most common of these mathematical instruments is the surveying compass, possibly the instrument most needed and produced in America. Recorded in public and private collections are 31 known examples of such compasses made of wood, a rather large number. Furthermore, a substantial number of these were being produced simultaneously by skilled craftsmen who at the same time were making similar instruments in brass. ”

“ A brass rule, called a label, with sight-holes, turning upon a pivot at the centre of the instrument, moved over the marked circumference of the disk. At the zenith part of the instrument there was a small ring by which it could be suspended from the thumb of the person taking an observation. When used the astrolabe was turned to the sun, so that his rays could freely pass through the two sight-holes of the label. In this position the altitude of the sun was indicated on the divided limb of the instrument. ”

“ Owing to the number of motors used, the instrument board is the most formidable appearing piece of apparatus on the bridge, since there is a revolution counter for each power unit in addition to the numerous other instruments required. ”

“ This construction was adopted in the first instruments made, for the purpose of observing the rate of heat transmission through the successive compartments, but these parts are without importance with respect to the practical use of the instrument, and may as well be omitted, as they considerably increase the cost, being nickel-plated and polished on both sides. The top and bottom plates of the cover are of 0.01 inch brass, nickel-plated and polished on both sides, both convex outward, the bottom plate but slightly, the top plate to 4.25 inches radius. ”

“ That this instrument should operate in the best manner, it is essential to have the interior of the brass cylinder polished from end to end, and of uniform diameter. If any irregularity should be perceived in the rate of going, it can be cured completely by taking out the piston, impregnating its leather stuffing with fine rotten stone and oil, and then rubbing it up and down for five minutes in the cylinder, so as to restore the polish. ”

“ It has been the aim of the writer to build a very simple instrument for amateur work which would be adjustable to any latitude, so easily set up ready for work and so portable that it need not be left out of doors from one evening until the next.
The instrument is mounted on a tripod or piece of iron pipe carrying a short vertical rod of 3/8-in. steel. A rectangular wooden frame with suitable bearings rotates about this shaft. The frame has also two horizontal bearings carrying a short shaft to the end of which the frame carrying the hour axis is firmly clamped. ”

“ Jack began carefully sliding a small block connected to the instruments up and down the coiled wire which formed the tuning apparatus, and brought the sending and receiving ends into harmony just as if they had been two musical instruments. ”

“ Panelling.—To avoid the difficulties which would result from the swelling, shrinking, and warping [185] of wide surfaces in furniture it is common practice to make use of the panel. The design of the panel is easily understood. It consists of a framework of ordinary thickness, put together usually with mortise and tenon joints. The inside edges of this framework are grooved, and into the groove is fitted a piece of stock generally thinner than the frame which fills the space between the sides of the frame. The panel board may be in one piece of wide stock or it may be glued up. ”