Beam (lumber)

“ A light beam, A B, having two square inches of pith, C, at one end, is balanced on a very fine fibre of glass, D D', stretched horizontally in a tube; one end of the fibre being connected with a torsion handle, E, passing through the tube, and indicating angular movements on a graduated circle. The beam is cemented to the torsion fibre, and the whole is inclosed in glass, and connected with the mercury pump by a spiral tube, F, and exhausted as perfectly as possible. G is a spiral spring, to keep the fibre in a uniform state of tension, H is a piece of cocoon silk. ”

“ Every possible exertion was now made to fix the lower ends of the beams to the rock, by connecting them with their respective stanchions, while three strong hoops of malleable iron were employed, for securing the whole in one mass at the top.
The six principal beams of the beacon were thus secured, at least in a temporary manner, in the course of two tides, or in the short space of about eleven hours and a half. The only inconveniency attending this operation, arose from the derrick for raising the first beam being rather too short. ”

“ Paragraph 18 - If the supports, when the beam sits on pegs in the wall, are not one tefach wide and three long, some say that they must be strong enough to support the beam and a half brick and some say that they only need to be strong enough to support the beam. ”

“ A A A, is the frame of the loom, consisting of four upright posts, with caps and cross rails to bind them together. The posts are about six feet high. C C, the cloth-beam, is a wooden cylinder, six inches or thereby in diameter, of sufficient length to traverse the loom, with iron gudgeons in the two ends, which work in bushes in the side frame. On one end of this beam is a ratchet wheel, with a tooth to keep it from turning round backwards by the tension of the web. ”

“ As the beam increased in diameter, one revolution meant a greater length of twist wound on, and the strap had to be moved along the cone drums to diminish the number of revolutions of the beam per minute, and thus keep the speed of the sheet of warp constant.
Numerous presses are used to get a hard beam with a greater number of cuts on it. Although, when extremely hard, the weaving is more difficult, the advantage of fewer gaitings of beams in the shop, doffings at the size frame, and less waste is adequate compensation. ”

“ Up to this beam the lower wall is built of brick set to curve of the timber, from which circumstance it would appear to be a modern insertion. The beam, we may be sure, was straight originally, and the bricks have been fitted to the curve which it subsequently took. Time, no doubt, ate away the lower work of wood, and necessitated the insertion of new materials. The slight curve of the great beam adds, I think, to the interest of the old place, for it is a curve that has grown and was not premeditated; it has grown like the bough of a tree, not from any set human design. ”

“ Other beams ran lengthwise of the body, placed straight, obliquely, diagonally, and in every direction calculated to strengthen and stiffen, and all bound together with rods and bars and bolts. One great beam, reaching from rear part through the body to centre of his forehead, is calculated to sustain fully a ton’s weight, if at any time his great head should need such support. ”

“ All large beams support a uniform dead load consisting of their own weight.
The effect of dead load on a wooden beam may be two or more times that produced by an immediate load of the same weight. Loads greater than the elastic limit are unsafe and will generally result in rupture if continued long enough. A beam may be considered safe under permanent load when the deflections diminish during equal successive periods of time. A continual increase in deflection indicates an unsafe load which is almost certain to rupture the beam eventually. ”

“ The beam trawl may be described as a flattened conical net whose mouth is kept open when in use by a long beam supported at the ends by iron runners, the trawl-heads. Elm is generally preferred for the beam, selected if possible from timber grown just to the proper thickness, that The Beam Trawl.the natural strength of the wood may not be lessened by more trimming or chipping than is absolutely necessary. If the required length and thickness cannot be obtained in one piece, two or even three pieces are scarfed together, and the joints secured by iron bands. ”

“ In the arch, however, this simple scheme is departed from, and the covering elements take on a curved or sloping form. The apparently free float of the span is stimulatingly impressive, especially when executed in a heavy and thoroughly rigid material. The beam is subject to bending stress. Timber makes a good material because of its strength against breakage by bending. Stone is unreliable or outrightly weak against a bending stress, besides adding to the stress by its own weight. There are therefore inherent limitations on the space that can be covered by a horizontal stone beam. ”

“ Mensch states that "it would take up too much time to prove that the counterfort acts really as a beam." The writer proposes to show in a very short time that it is not a beam. A beam is a part of a structure subject to bending strains caused by transverse loading. ”

“ The side of the beam, supposing it square, was found by multiplying the diameter of the cylinder by the length of the stroke, and extracting the cube root of the quotient, which will be the depth or thickness of the beam. This rule allows a beam 16 feet long to bend 1/8th of an inch, and a beam 32 feet long to bend 1/4 of an inch. For cast iron beams the square of the diameter of the cylinder, multiplied by the length between the centres, is equal to the square of the depth, multiplied by the thickness. ”

“ The dull red of the vast beam is obscured by the neutral tint of the ropes which are attached to it; colour generally gives a sense of lightness by defining shape, but this red is worn and weatherbeaten, rubbed and battered, so that its uncertain surface adds to the weight of the boom. ”

“ In Italy, at Milan, Sienna, Ovieto, and several of the larger churches, there is only a beam sustaining the rood, with images of the Blessed Virgin and St. John. Some of them are ornamental in design, but I do not think any of them older than the sixteenth century. There are several examples in France, but all comparatively modern; but in the Domkirche, at Lubeck, there is a most remarkable example of a rood beam, that merits a particular description. The beam itself is composed of a great many pieces of timber, deeply moulded and carved, and enriched with pendent tracery and crocketed braces. ”

“ These carved beams, as Choisy points out, are struts rather than ties. If we take one of the columns standing in an angle in the aisles, an impost of marble connects it with the wall to which it is nearest, and a carved wood beam forms a strut to the other wall. The beam across the central bay of secondary order (Fig. 5) forms a rigid strut to the two wider arches (see Fig. 38, where, however, by oversight the beam has been omitted; it is at the springing of narrow arch high above iron tie) . ”

“ This mode of strengthening a beam by trussing is only adopted in floors, where it is necessary to limit the depth of the truss to that of the beam, to obtain a level surface by means of joists laid across, and supported by, the beam. But it is obvious that much greater strength may be imparted to a [Pg 92] long beam by making it the base of a triangular frame, as is done in roofs, in various manners, when the slanting sides of the triangular frame carry the battens or laths for supporting the tiles or other covering. ”

“ Before each beamer, as the workman is called, is an inclined semi-cylindrical slab of wood covered with zinc. The skin is first spread upon this, and the broad, curved beam of the knife glides across it from end to end, scraping and removing all the loosened hair, the scarf skin, and the small portion of animal matter adhering to the skin. ”

“ Increased moisture content, due to greater humidity of the air, lowers the elastic limit of wood so that what was a safe load for the dry material may become unsafe.
When a dead load not great enough to rupture a beam has been removed, the beam tends gradually to recover its former shape, but the recovery is not always complete. If specimens from such a beam are tested in the ordinary testing machine it will be found that the application of the dead load did not affect the stiffness, ultimate strength, or elastic limit of the material. ”

“ A.--The web of a cast-iron beam or girder serves merely to connect the upper and lower edges or flanges rigidly together, so as to enable the extending and compressing strains to be counteracted in an effectual manner by the metal of those flanges. It is only necessary, therefore, to make the flanges of sufficient strength to resist effectually the crushing and tensile strains to which they are exposed, and to make the web of the beam of sufficient strength to prevent a distortion of its shape from taking place. ”

“ The marking-gage, Fig. 211, consists of a head or block sliding on a beam or bar, to which it is fixed by means of a set-screw. On the face of the head is a brass shoe to keep the face from wearing. Projecting thru the beam is a steel spur or point, which should be filed to a flat, sharp edge, a little rounded and sharpened on the edge toward which the gage is to be moved, Fig. 212. It should project about 1⁄8" from the beam. If the spur be at all out of place, as it is likely to be, the graduations on a beam will be unreliable. ”

“ When the logs are to be converted to whole timbers for use in that size, consideration has to be given as to66 whether the stiffest or the strongest balk is required. The stiffest beam is that which gives most resistance to deflection or bending. The strongest beam is that which resists the greatest breaking strain. ”

“ A pillar supporting a weight is under compression. At c the weight tends to bend the beam. The upper part is under tension, the lower part under compression. This is known as beam action, and depends on whether the beam is supported at one end, as shown, or on both ends. ”

“ To keep the beam truly in its place, which is very necessary, as all the bearings are flat, the recesses for the ends of the studs are formed so as to draw the beam without strain into its true position every time that it is thrown out of gear by the sliding frame. The end knife-edges are adjusted and tightly jammed into exact position by means of wedge pieces and set screws, and the beam is furnished with delicate adjusting weights at its top. ”

“ Thus, if a beam which is one foot broad and one foot deep support a given weight, then a beam of the same depth and two feet broad will support double the weight; but if a beam be one foot broad and two feet deep it will support four times as much as a beam one foot broad and one foot deep. If a beam one foot square support a given weight, then a beam two feet square will support eight times as much. Also a cylinder of two inches in diameter will support eight times as much as a cylinder one inch in diameter. The appended table gives data bearing on the subject. ”

“ It is thus nearly one-third larger in the direction across the line of entrance, which gives to every arch, pointed and round, throughout the roof, a different spring from its neighbours.
The vaulting ribs have the simplest of all profiles—that of a chamfered beam. I call it simpler than even that of a square beam; for in barking a log you cheaply get your chamfer, and nobody cares whether the level is alike on each side: but you must take a larger tree, and use much more work to get a square. ”

“ When the weight reaches 140 lbs. the deflection at first indicated is 2"·37; but gradually the cross lines are seen to descend in the field of the telescope, showing that the beam is yielding and finally it breaks across. This experiment teaches us that a beam is at first deflected by an amount proportional to the weight it supports; but that when two-thirds of the breaking weight is reached, the beam is deflected more rapidly.
366. It is a question of the utmost importance to ascertain the greatest load a beam can sustain without injury to its strength. ”

“ The weakening effect is much more serious where timber is subjected to bending and tension than where under compression. The extent to which knots affect the strength of a beam depends upon their position, size, number, direction of fibre, and condition. A knot on the upper side is compressed, while one on the lower side is subjected to tension. The knot, especially (as is often the case) if there is a season check in it, offers little resistance to this tensile stress. ”

“ The foreman joiner, Mr Francis Watt, was accordingly appointed to attend at the rock to-day, when the necessary levels were taken for the step or seat of each particular beam of the beacon, that they might be cut to their respective lengths, to suit the inequalities of the rock; several of the stanchions were also tried into their places, and other necessary observations made, to prevent mistakes on the application of the apparatus, and to facilitate the operations, when the beams came to be set up, which would require to be done in the course of a single tide. ”