Tube (mechanics)

“ In order to reduce the strength of the current a piece of brass tubing, F, is pushed into the space, C, surrounding the core, or if no brass tubing of the required size is on hand, roll a paper tube, cover with 4 or 5 thicknesses of tinfoil and then wrap with more paper, using glue to hold the tinfoil in place and to keep the tube from unwinding. When the tube is pushed all the way in, the current produced will be almost unnoticeable, but when it is withdrawn the current will be so strong that a person cannot let go the handles until the coil is shut off. ”

“ The lower end of the tube is firmly supported on rollers that are capable of being moved forwards or backwards by a double rack, connected with a set of wheels and pinions. By an adjustment at the lower extremity of the tube, the speculum is turned to a small inclination, so that the line of collimation may not be coincident with the longitudinal axis of the tube, but may cross the tube diagonally, and meet the eye in the air at about two inches from the edge of the tube, which is the peculiarity of the construction, that supersedes the necessity of applying a second reflector. ”

“ Therefore we have, that in resistance to flexure the tube should be as large in diameter as practicable, which means that it must be as thin as possible. This result is only modified in practice by the necessity of guarding against dinging and also against imperfections in the steel. A surface crack will ruin a very thin tube which otherwise may be harmless in a thicker, but it is safe to say that it is best to use reasonably large thin tubes. ”

“ In operating large tubes, that is to say, tubes six or eight inches in diameter, there is an advantage in using compressed, rather than exhausted air, in the construction of the sending and receiving apparatus, especially when the tubes are very long. With an ample supply of compressed air always at hand, the air-cushions can be made shorter and more effective in bringing the carriers quickly to rest.140 With exhausted air the cushions are ineffective, and consequently must be made very long in order to stop the carrier before it strikes the closed end of the tube. ”

“ Seamless tubes, which are stronger than those just described, are made by drawing a bloom of the metal perforated by an axial hole or provided with a core of some refractory material, or, in certain cases, by forcing the plastic metal by hydraulic pressure through an appropriate die. The seamless steel tube industry is now of great dimensions owing to the development of steam engineering. Another type of seamless tube is the cast-iron tube, usually of large diameter and employed for gas and water mains ”

“ Take a tube which is very regular, and about one-eighth or one-twelfth of an inch diameter in the bore; solder a reservoir at each end, one of them much larger than the other; make a bend near the large reservoir, and then fill the instrument with alcohol to A. Above that, place the first index, which consists of a very small piece of tube closed at one end and cut off square at the other. In the interior of this tube the two ends of a hair are fixed, by means of a little rod of iron, which is pushed into the tube. ”

“ The hands must be held steady, and the tube must be under good control at all times, so that both ends may be rotated at the same angular velocity, even though they may be of different diameters, and the tube be neither drawn apart nor pushed together unless such a motion is expressly desired, as it sometimes is. ”

“ In this way it is possible to get a tight, smooth tube. Immediately withdraw the core, twisting it slightly in a reverse direction if it tends to stick. Before using the core again, make sure it is free from glue and regrease it. When a sufficient number of tubes have been made and hardened, neatly trim the ends off squarely, and then form an equal number of short tubes, about 2 in. long, by winding a strip of glued paper on a large wire nail until a diameter is reached that will fit snugly into the pipes already made. ”

“ These must make so good a fit that when slightly lubricated they shall prevent the passage of air between them and yet set up very little friction. If you cannot find a piece of steel rod and brass tubing which fit close enough naturally, the only alternative is to rub down a rod, slightly too big to start with, until it will just move freely in the tube. This is a somewhat tedious business, but emery cloth will do it. The rod should be 3-3/8 inches, the tube 2-1/8 inches, long. I used rod 3/16 inch in diameter; but a smaller rod would do equally well. ”

“ An iron rod, screwed into a stand or base, and conical at the top, passes up through the tube and supports the whole upon its point. To stiffen the arrangement, three bent strips of tin are fastened to the top of the tube and to the inner rim, as shown in the woodcut, where the middle strip conceals the central tube. There is room inside the circle of test-bottles to place the other bits of apparatus when not in use. ”

“ The tube is thus slowly drawn through the hole in the die. As these dies are of very hard material, either hard cast iron or hardened steel with hole a little smaller than outside of the tube, they compress the tube upon the mandrel inside and the thickness of wall is thus regulated, the excess metal being squeezed out so that the tube is very materially lengthened. Tallow or grease with the lime-coat lubricate the tube, a little being continually drawn into and through the somewhat funnel-shaped die. ”

“ The transverse section of this tube is an elongated ellipse. The principle of action is this: interior pressure tends to straighten the tube, external pressure causes it to coil more. Hence as the atmospheric pressure decreases, the ends of the tube become more apart.
This movement is augmented and transferred by a mechanical arrangement of small metallic levers to a radius bar, which carries a rack formed on the arc of its circle. This moves a pinion, upon the arbour of which a light pointer, or “hand,” is poised, which indicates the pressure upon a dial. ”

“ You will also need some brass rod which will just slide into the tube tightly. Cut off two pieces of the brass rod each one and three-quarters inches long and slip these through the upper holes in the binding-posts and into the glass tube as shown in Figure 234. Before putting the second rod in place, however, you must put some nickel and silver filings in the tube, so that when the rods are pushed almost together, with only a distance of about one-sixteenth of an inch between them, the filings will about half fill the space. ”

“ Upon the shaft or axis of the propeller wheel, or upon a shaft geared therewith, there is a hermetically closed tube or receptacle, D, which is placed at right angles with the shaft, and preferably so that its longitudinal axis shall intersect the axis of said shaft. In this tube or receptacle is placed a weight, such as a ball, which is free to roll or slide back and forth in the tube. ”

“ Two immense tubes, lying side by side, each ten feet in diameter, made of a substance more durable than steel, form the road bed of this lightning system of travel. The cigar-shaped cars have hard rubber-wheels and fit over raised bars all around on the inside of the immense Tube. ”

“ If a tumbler, electrified in this way, be inverted over pith balls, instead of brass-filings, the balls will leap with surprising velocity up the sides of it.
The luminous Discharging-rod. Provide a glass tube in the shape of a common discharging-rod, about ten inches in length, and let the bore of the tube be nearly the eighth of an inch in diameter; upon one end fasten with cement, or otherwise, a brass knob, so as to be perfectly air tight. Now expel the air from the tube, by heat or the air pump, and then fix another knob upon the open end, in a way similar to the former. ”

“ The tubes are riveted together into continuous hollow [Pg 49] beams; they are of the uniform width of 14 feet 8 inches throughout; they are constructed entirely of iron, and weigh about 12,000 tons, each tube containing 5000 tons of wrought iron, and about 1000 tons of cast iron. The tubes were constructed each in four sections; the sections extending from the abutments to their corresponding piers, each 250 feet long, were built in situ, on immense scaffolding, made of heavy timbers for the purpose, even with the railway ”

“ The tubes of the Paris system are of wrought iron, in lengths of from fifteen to twenty feet, the joints being made with flanges and bolts. The interior diameter is 2.559 inches with a maximum variation to 2.519 inches. The bends are made with a radius of from six to one hundred and fifty feet. Water frequently gives trouble by accumulating in the tubes. Traps are placed at low points to drain it off. ”

“ It is practically a huge spinning with hot metal. After this single rolling process, the new formed tube is subjected to two drawings in a mandrel, in practically the same fashion that American tubing is treated, until it is reduced to the required diameter and gauge. ”

“ The construction of the vertical inner-tube system is simple, and consists of the required number of manifold sections, suitably arranged to conform to the circular space occupied, the flat inner end of each upper manifold being rigidly bolted to a heavy transverse beam, which in turn is supported in suitable pockets secured to the upper part of the shell. ”

“ It is very natural to ask the question, why are tubes sometimes operated by compressing the air and at other times by exhausting it? We answer by saying that it is usually a question of simplicity and convenience that determines which system shall be used. ”

“ The outer extremity of the two tubes supports the platinum spiral, which is fixed to them very simply by the aid of two small brass needles of conical form, which pinch the wire in the tube and hold it in place. There is nothing easier to do than replace the wire. ”

“ Experience shows that, where great exactness of manipulation cannot be obtained, it is necessary to allow only one train in each section of a tube, whether worked by vacuum or pressure. But where there is no intermediate station, and where the tube can be carefully worked, carriers may be allowed to follow one another at short intervals in a tube worked by vacuum, although it is not perfectly safe to do so in one worked by pressure. ”

“ It is, however, necessary for one who would succeed in making it, to exercise himself in the art of well bending a tube. After a few attempts, you may finish by producing a pretty-regular spiral. The tube chosen for this instrument should be six or seven feet long, and about one-third of an inch in diameter. You commence by making a bend, nearly at a right angle, about four inches from one of its extremities. ”

“ To remedy this evil, I have given the principle a rotatory form in fig. 1; where A B C is a spiral tube, duly fastened to the bottom of a shallow tub D E. At B is seen a conical roller, having the middle of the bottom of the tub for its summit and centre of gyration. The tube A B C, occupies rather more than one circumference; so that the cone presses during a small part of it’s revolution on both spires at once: by which means the Machine would act without even one valve ”

“ The spiral tube may be led round any corners, but the frictional resistance of the cable inside the spiral tube increases with the total angle of curvature of the guide tube; the laws of friction of a rope passing over a drum apply. ”

“ The inner tube need not possess high tensile strength, provided that it is easily distensible, for the reason that, during use, it is protected by the casing of the tyre proper, which confines and supports it against the air-pressure applied. Inner tubes are therefore cured to give a long life without developing the maximal physical properties. ”

“ Very small and fine glass tubes, such as are used in experiments to demonstrate capillary attraction, water or other liquid rising in them when they are plunged into it, are made by heating as long a section of tubing as can be handled in the flame—2 in. will be found enough—and, when very hot, giving the ends a sudden vigorous pull apart. The tube pulls out and gets smaller and smaller as it does so, until at last it breaks. But the fine thread of glass so made is really a tube, and not a rod, as might be supposed. ”

“ But we are dealing with air, which is an elastic fluid, and, as we stated before, it expands as132 the pressure is reduced and becomes larger in volume. It is this expansion that increases its velocity as it flows along the tube. It must go faster and faster to make room to expand. Since the same actual quantity of air in pounds must come out of the tube each minute as enters the tube at the other end in the same time, to prevent an accumulation of air in the tube, and since it increases in volume as it flows through the tube, it follows that its velocity must increase. ”

“ The most extensive use of small pneumatic tubes in this country has been in our large retail department stores for despatching cash to and from a centrally located cashier’s desk. Seamless brass tubes are usually used, and, since the tubes are short, the air is either compressed or exhausted by means of positive rotary blowers. At the outlying stations the tubes are usually open to the atmosphere, while at the central station simple forms of valves are used for sending and receiving. An outgoing and a return tube are always used, and the air is kept in constant circulation. ”

“ The tube is a mere hair-like hollow filament of glass, and the ink, which would not itself flow from a tube of so fine a bore, is squirted out by electrical repulsion when the insulated reservoir in which it is contained is electrified at the receiving station by an ordinary machine. ”