Bracing strut

“ It may be hardly necessary to insist that bracing intended to stiffen a structure against wind, local crippling, or vibration, should be made complete, not stopping short at some point, because it cannot conveniently be carried further, as is sometimes done, unless the strength of those parts of the structure through which the forces from the bracing must be communicated to the abutments is sufficiently great, considered with reference to other stresses in those parts which have also to be endured. ”

“ It is unnecessary to vary the size of these braces, except in very long spans, when they should increase from the centre to the ends. For short spans, (less than one hundred feet,) a brace 5 × 5 is large enough. For larger spans 7 × 7 is sufficient.
198. Diagonal bracing, when it can be introduced, is a very desirable part of a bridge. When the road is on the lower chord this cannot have place in full, but may be applied as in fig. 74.
176
Fig. ”

“ In a steel structure, a can very easily be made a tension member by anchoring its lower end to a heavy [Pg 35] foundation. This resists the tendency to overturn and makes a very stable structure. In practice, braces can generally be located parallel to the line of resultant strain, Fig. 29, or outside this line, as shown in Fig. 30, so that the strain due to the pull of the rope will come mainly on the inclined brace and not on the upright. ”

“ Old structures are very frequently deficient in bracing, which may, in such cases, be advantageously introduced; or girders individually weak may be rendered collectively efficient by suitable bracing. ”

“ Bracing, whether to strengthen a structure against wind, to insure the relative positions of its parts, or for any other purpose, cannot be arranged with too great care and regard to its possible effects. Forces may be induced which the connections will not stand, with loose rivets as a consequence, and inefficiency of the bracing itself ”

“ Braces and trusses are something like rafters and when the run is known, there should be no difficulty in getting the lengths and proper bevels.
In the first place it is always best to make a pattern and then mark out the timber work from the pattern. Suppose we want braces having a “four-foot run”—that is, the brace is to form a diagonal from points four feet from the post and four feet from the girt. Take a piece of stuff already prepared, six feet long, four 109 inches wide and half-inch thick, gauge it three-eighths from jointed edge. ”

“ A piece of the webbing having been previously stitched on to the sides of the material, it should now be braced with twine by means of a packing needle, passing the string over the stretchers between each stitch taken in the webbing, and, finally, drawing up the bracing until the material is strained evenly and tightly in the frame. If the fabric is one which stretches easily, the bracings should not be drawn too tightly. ”

“ For such structures the bracing should consist of a few good members, with a solid form of attachment, rather than of a multiplicity of lighter adjustable members, which will commonly give great trouble in maintenance; being very possibly also, in the case of sea-pier work, in unskilled hands. ”

“ Where the sheeting and bracing are of sufficient size, are tightly keyed up, and extend to the bottom of the trench, or where the bank is supported by a retaining wall, the earth near the bottom cannot break out, and the equation is not valid.
However, if, from any cause, such as insufficient sheeting, the break has taken place over even a part of , the mass, , above will tend to tip over at the top, giving the greatest pressure on the top braces. ”

“ For a simple structure the necessary bracing may be obtained by "letting into" the studding 3 × 1 inch strips, as shown in drawing. To do this [464] hold the brace in the position it is to occupy, and make a pencil mark on both sides of it on each timber, sawing on the inside of these lines to a depth equal to thickness of brace. Remove the wood between saw cuts with a chisel. Test to see that brace comes flush with outside of studs, and nail securely in position.
When the frame is finished up to the roof the putting on of the siding may begin at any time. ”

“ If we wish to lay out a brace having a three-foot run on both post and beam, the matter is quite simple, for we can take 12 inches on the tongue and 12 inches on the blade and transfer this distance three times on a straight line and we have the extreme length of the brace from point to point, and by marking along the blade at one end of this length and along the tongue at the other end we also get the bevels. ”

“ A housed brace joint is a joint in which the brace is housed into the rectangular members except that the outer end of the mortise is cut at right angles and the inner end diagonally to receive the brace which is cut to correspond. ”

“ The struts, spars, etc., must be properly bedded into their sockets or fittings. To begin with, they must be of good pushing or gentle tapping fit. They must never be driven in with a heavy hammer. Then again, a strut must bed well down all over its cross-sectional area as illustrated above; otherwise the stress of compression will not be evenly disposed about the centre of strength, and that may produce a bending stress. ”

“ Even with that precaution, the string very often bruises the arm, and ladies sometimes have the bracer wadded, or lined with India rubber to make it more elastic, and thus to diminish the force of the rebound. ”

“ In cutting braces always allow in length from a sixteenth to an eighth of an inch more than the exact measurement calls for.
Directly under the half-inch marks on the outer edge of the back of the tongue will be noticed two figures, one above the other. These represent the run of the brace, or the length of two sides of a right-angled triangle; the 62 figures immediately to the right represent the length of the brace or the hypothenuse. For instance, the figures 36-36 59-91 show that the run on the post and beam is 36 inches, and the length of the brace is 50.91 inches. ”

“ Fig. 13.—Outside Braces. In the village of Naruge, in Yamato, I noticed in an old inn a diagonal brace which made a pleasing ornamental feature to a solid frame-work, upon which rested a ponderous supplementary roof, heavily tiled. As the horizontal beams were supported by uprights beyond the ends of the brackets, no additional strength was gained by these braces in question, except as they might prevent fore and aft displacement. ”

“ Now, these proportions will give ample strength for both flexure and compression, for if we block the two sticks composing the end brace together, and firmly connect them by bolts, we shall have a built beam of 24" x 10"—whence = 165925 lbs., and as 134400 lbs. was all that the conditions demand, we really have an excess of strength. The next set of braces supports the weight of the rectangle included between the upper ends of the braces and the two chords, and the dimensions of the sticks are calculated in the same manner. ”

“ Although the worker may produce various forms of strip-metal work, the bracket is, as a rule, the most profitable to handle. The plain bracket is shown in Fig. 3, and is made by bending the strip at the proper angle on form A, after which the brace is adjusted by means of rivets. A rivet hole boring tool will be needed. A small metal turning or drilling lathe can be purchased for a few dollars and operated by hand for the boring, or a common hand drill can be used. ”

“ BORING TOOLS
"Boring tools are very interesting," said Ralph. The brace and bit for soft woods have practically taken the place of the old fashioned augers, gimlets, etc. The reason is not hard to find. An auger or gimlet could bore but one size of hole, while with a brace and set of bits almost any diameter can be secured. A little later on, I'll tell you about a Yankee invention along this line.
"The brace is a sort of universal tool holder, and any tool designed to fit into it is known as a bit, as for example a countersink bit, or a screw driver bit, and several varieties of drills. ”

“ But the limb they carry is heavy, so they rapidly become overstretched and it is difficult to keep them properly adjusted.
b. The stretching is naturally diminished if the upper part of the brace is not elastic but an elastic section is inserted in its lower third, in front and behind.
c. But the patients almost always say that better command of the limb is obtained with inelastic braces. If the strap is wide on the shoulder, the pressure is well borne, and the lower attachment may be made narrower, consisting of a leather thong (Fig. 64) . ”

“ Another difficulty in fitting a short forearm stump arises from the fact that the antero-posterior diameter of the forearm immediately below the elbow increases considerably when the joint is flexed, because of the contraction of the muscles arising from the condyles. If the forearm socket is made to fit closely when the elbow is extended it will be too small when the joint is flexed and will prevent full flexion. If it was made to fit with the elbow flexed, there is risk of the stump slipping out of the socket when the joint is extended. ”

“ Old braces were braces, these are mere sources of weakness, they do not brace; when weight is applied to the seat the tendency is to drive the legs apart, then out falls the brace. No mortice holds it, it has no function to fulfil. In the old chair how firm all the joints are made! Stout oak pegs are driven through every mortice, and every precaution is taken to prevent gaping at the joints, to resist strain put on them. ”

“ The tighter the lace is drawn the more powerful will be the extending force.
Instead of attaching the extension brace to the leg piece it may be made to pass under a pulley in the interior of the knee. What actually happens is that the thigh piece drops, owing to its weight, when the limb is swung free; this throws a strain on the brace which is transmitted to the leg piece by the following mechanism. ”

“ The theory of the invention is that, as the collar at the bottom of the standard is raised, the braces will force the ribs to expand to the circumference limited by the tape or elastic affixed to the lower extremities of the ribs. Should the collar be pushed above the mean center of expansion, which is attained when the braces are at right angles with the standard, the tendency to expand would cease, and contraction would begin. ”

“ When the tubes are good and of ample dimensions these frames are good, but harm may so easily be done to the steel tubes by injudicious brazing that it is well to watch the frames carefully at all joints and connections, so that any flaw or any loosened lug may be discovered. When spring hangers or brackets are attached to these frames so that they splay outward or out of the direct line of pressure from bracket to frame, they put a torsional stress on the frame which aggravates the tendency to fracture or loosening. ”

“ Brazing and Welding.
It is somewhat amazing that brazing as an essential operation in the making of a joint should still be employed, as it is difficult to imagine anything less suited to the conditions under which aircraft operate. The advantages of a uniform high-grade steel possessing a high ultimate tensile strength are dissipated by the intense heat necessary for the action of brazing, resulting in the strength of the finished joint becoming an extremely problematic quantity, indeed this is rendered the more so by the individuality of the workmen. ”

“ But most braces, you may not be aware, slip down unpleasantly on the shoulder-blade, and so lead to an awkward habit of hitching them up by the sleeve-hole of the waistcoat at frequent intervals. Such a habit must be felt to be ungraceful. ”

“ BRACE. The braces are ropes belonging to all the yards of a ship; two to each yard, rove through blocks that are stropped to the yards, or fastened to pendants, seized to the yard-arms. Their use is either to square or traverse the yards horizontally; hence, to brace the yard, is to bring it to either side by means of the braces. In ship-building, braces are plates of iron, copper, or mixed metal, which are used to bind efficiently a weakness in a vessel; as also to receive the pintles by which the rudder is hung. ”

“ He was caught in a reclining posture, his back firmly supported by a solid beam. Another lay across his breast, but he had been able to shrink a little away from it so that it no longer oppressed him, though it was immovable. A brace joining it at an angle had wedged him against a pile of boards on his left, fastening the arm on that side. His legs, slightly parted and straight along the ground, were covered upward to the knees with a mass of debris which towered above his narrow horizon. His head was as rigidly fixed as in a vise; he could move his eyes, his chin—no more. ”

“ In a shoulder brace, a back support comprising a plurality of non-elastic back stays symmetrically spaced on either side of the medial line thereof flaring upwardly and separating at the top to embrace the shoul- der blades, with straps secured across the upper end of said stays to brace and hold the same in position, and straps secured to the upper corners of the back support and adapted to pass from the rear forwardly over the shoulders and thence rearwardly under the armpits and thence to the front of the waist, with a loose sliding attachment for the passing under blades the straps. ”

“ One wooden brace and two iron braces are to be put in, as shown upon the plan hereto annexed. The wooden brace is to be of one piece, or of two pieces well bolted together, of selected lumber, free from knots and other imperfections, squared, and measuring 6 by 8 inches in 337 cross section. The iron braces are to be of 1 inch diameter, best quality wrought-iron rods. The bearing plates, four to each rod, are to be not less than 10 inches in diameter, of sufficient strength, and securely and permanently fastened to the braces. ”