Bearing

“ If a bearing be bored to very nearly its finished size and first released altogether from the pressure of the holding chuck, or other device, and then re-chucked, it is probable that the finished bore would be practically quite round and true, but such re-chucking is not the usual practice. ”

“ In ball bearings the load is concentrated at a few points, the points where the balls touch the race, and in the roller bearing at a few lines, the lines of contact between the rollers and the surfaces of the journal and bearing ”

“ Half-round bearing dies are usually made to cast two bearings at a time, for the reason that it is just as easy to cast two pieces of such a shape as it is to cast one, and, in addition, the die is balanced in a better manner. ”

“ Also, the bevelling of any piece of timber or plank to any required angle: as the bearding of dead wood, clamps, &c.
BEARDING-LINE. In ship-building, is a curved line made by bearding the dead-wood to the shape of the ship's body. [91]
BEARERS. Pieces of plank placed on the bolts which are driven through the standards or posts for the carpenters' stages to rest upon.
BEARING. An arc of the horizon intercepted between the nearest meridian and any distant object, either discovered by the eye and referred to a point on the compass, or resulting from finical proportion. ”

“ The first bearing having been laid down, the line is drawn and made the scale length of the chain line; the blade of the square is then pushed to the station thus found, and the next bearing set off. This operation is repeated until all the lines have been laid down. If the work closes properly, the plotting of the secondary lines may be proceeded with. ”

“ The bearing is made self-aligning by providing the bearing proper with an enlarged central portion of spherical shape, held in a spherical seat formed in the pedestal by turning, milling, or by casting Babbitt or other fusible metal around it, thus allowing the bearing to adjust itself to the exact direction of the shaft. ”

“ The angular distance between a reference direction and the rhumb line through two terrestrial points is called rhumb or Mercator bearing. A bearing differing by 180°, or one measured in the opposite direction, from a given bearing is called a reciprocal bearing. The maximum or minimum bearing of a point for safe passage of an off-lying danger is called a danger bearing. ”

“ Ever stop to count up how many bearings there are about your car? If you haven’t, you are likely to lose your bearings while you hunt for the several hundred bearing points of the modern automobile.
A bearing is a support for a moving member, so designed as to minimize friction and receive wear, and to permit of fine adjustment. ”

“ A bearing surface may be scraped ever so carefully, yet the lack of sufficient weight in the casting, or of ample proportions of the bearing surface itself, will quickly result in the alignments becoming inaccurate. ”

“ Trunnion bearing, for oscillating cylinders, &c. The steam is conveyed through the bearing, which has a stuffing box and gland to prevent leakage.
830 & 832. Swinging support for a shaft, having a sliding bevil gear or other motion upon it which has to pass the swinging support; used for lathe sliding gear, overhead travellers, &c.
831. Ball and socket centre for car bogies, &c.
833. Pedestal with side adjustment for the brasses by taper keys and screw adjustments.
Bearings running under water are generally lined with strips of lignum vitæ and require no lubricant. ”

“ Thence I went on cautiously, taking my bearings from one great tree on the ridge that lifted its bulk against the sky; slower and slower, till, just this side a great windfall, a twig cracked sharply under my foot. It was answered instantly by a grunt and a jump beyond the windfall—and then the crashing rush of a bear up [29] the hill, carrying something that caught and swished loudly on the bushes as it passed, till the sounds vanished in a faint rustle far away, and the woods were still again. ”

“ They waded waist-deep in the grass, in a compact body, bearing an improvised stretcher in their midst. Instantly, in the emptiness of the landscape, a cry arose whose shrillness pierced the still air like a sharp arrow flying straight to the very heart of the land; and, as if by enchantment, streams of human beings—of naked human beings—with spears in their hands, with bows, with shields, with wild glances and savage movements, were poured into the clearing by the dark-faced and pensive forest. ”

“ In Fig. 620, a represents the bearing of the feed screw of the lathe, and b b a sleeve, a sliding fit upon a, prevented from revolving by the pin h, while still having liberty to move endways. c represents a casing affording journal bearing to b b, having a fixed gear-wheel at its end c′, and an external thread upon a hub at that end. d is the flange of c to fasten the device to the shears of the latter, being held by screws. ”

“ The finest workmanship is required therefore to make good roller or good ball bearings.
Bearings for High Speeds and Forced Lubrication.—When the shaft turns the metallic surfaces of the brass and the journal are prevented from actual contact by a film of oil which is formed and maintained by the motion of the shaft and which sustains the pressure between the journal and the brass provided the surfaces are accurately formed and the supply of oil is unlimited. ”

“ Fig. 493 represents a cross-sectional view of the shears beneath the headstock; a a are the shears or bed having the raised Vs marked v′ and v on which the headstock and tailstock rest, and v′′ and v′′′ on which the carriage slides. a and a′ are the shears [I-134] connected at intervals by cross girts or webs b to stiffen them. c c are the bolts to secure the headstock to the shears. d is a bracket bolted to a′ and affording at e journal bearing for the spindle that operates the independent feed spindle. ”

“ The bolts, set-screws, pulleys, bearings, shafting and clutches of a plant, although among the foremost factors in its efficiency, are very often neglected until they reach the stage where their condition absolutely compels attention. ”

“ Flat bearings are scraped to conform to master surface plates and straight edges, and the boxes of important cylindrical bearings are scraped to fit the revolving piece, which is ground. This work necessarily calls for much skill on the part of the workman, and the care with which scraping is performed largely influences the accuracy of the resultant bearings. ”

“ Wheel of wood, 88"·5 in circumference, on the same axle as a cast iron barrel of 14"·9 circumference; axle is of wrought iron, 0"·75 in diameter, mounted in oiled brass bearings; power is applied to the circumference of the wheel, load raised by rope round barrel; velocity ratio, 5·94; mechanical efficiency, 5·54 ”

“ Even trained woodsmen sometimes get “turned around” but they usually find their bearings soon because of the general knowledge of the country and the main landmarks, shapes and heights of mountains, the trend of the ridges, the prevailing winds, the general direction and ultimate outlet of the streams, etc. The danger of getting lost is further offset by a proper knowledge of taking one’s bearings, by range finding, by the knack of traveling by direction and by correct compass reading. ”

“ Our bearings are very easy to adjust, and their special form prevents oil from getting to the inside of the machine. All high speed Shafts, viz., Fan, Side and Beater Shafts, have ring oiling bearings. ”

“ When the bore is intended to penetrate but a few fathoms, the whole work may be performed directly by the hands; but when the bore is to be of considerable depth, a lofty triangle of wood is set above the bore-hole, with a pulley depending at its summit angle, for conducting the rope to the barrel of a windlass or wheel and axle, secured to the ground with heavy stones. The loose end of the rope is connected to the rods by an oval iron ring, called a runner; and by this mechanism they may be raised and let fall in the boring ”

“ Stock and bow drills may be easily made, as in Fig. 1. The arm of a tree will afford a socket above, and the wood or iron to be bored must be firmly fixed below; a good sized disc of heavy wood, the sheave say of an old block, or a piece sawed off a hard tree, acts as a fly wheel. For smaller work a cotton reel (Fig. 2) does well for the bow strings to work on ”

“ As I worked with my axe and hammer, I heard a light wagon come rattling up the road. Across the valley a man had begun to chop a tree. I could see the axe steel flash brilliantly in the sunshine before I heard the sound of the blow. ”

“ And he shall lie naked on the ground without litter, bedding, or cloth, and without anything over him; and he shall lie on his back with his head to the west, and his feet to the east, and one arm shall be drawn to one quarter of the room by a rope, and the other arm in like manner to the other quarter, and in the same way shall his legs be extended, and upon his body shall be placed iron and stone, as much as he can bear ”

“ The people who lived so simply had better tools and more numerous implements than we suppose. Most countrymen possessed a ladder, a hand-mill, an axe, a crowbar, nails, a gimlet, hedge-clippers, a branding iron, a wheelbarrow, and often a light cart, a plough, harness, reaping-hooks, scythes, a hoe, spade, rake, flail, sieve, bushel, knife, hammer, a long ferruled staff, a bow ”

“ The load, placed pannier fashion, is not tied on. Its weight keeps it in position. But the four-footed bearer will take into his head to ease the task by walking close against a tree in a way that throws the entire load to the ground. ”

“ Find something that will do for the spindle of a drill.
Show how to drill a hole by twirling the spindle or awl on the thigh.
[50]
Show how one person can twirl an upright spindle.
Show how two persons can twirl an upright spindle with their hands.
Show how they can do it with a strap. Can you think why stones are sometimes bound to the shaft of a drill?
Look at the picture of the bow drill and see if you can make one.
Draw a picture of the Cave-men working upon their trophies.
IX THINGS TO THINK ABOUT
Think of as many tools and weapons as you can that the Cave-men found ready to use. ”

“ When the farmer encounters a stone which is the great impediment of his operations, he drives the blade under it, and bringing the knee or angle to the ground, has in the long handle a very forcible lever. ”

“ Now, if you or I have occasion to turn over a stone, the chances are we'll stoop over it, take hold of it by its farther edge, and pull it over toward us, and of course, unless we straddle it or watch it pretty close, we're likely to drop it on our toes; but a bear always turns a stone over not toward himself, but to one side. ”

“ A stretched rope is in a state of stress, because at any cross section the part on each side is pulling the part on the other side with a force in the direction of the rope's length. A plate of metal that is being cut in a shearing machine is in a state of stress, because at the place where it is about to give way the portion of metal on either side of the plane of shear is tending to drag the portion on the other side with a force in that plane. ”

“ If there is no corner to help, we must lean the whole weight of our body upon the rope where it runs out to us round the belay on our axe; so crushing the racing rope into the snow and reducing the final tug upon the driven axe shaft. ”

“ In the East the grain is threshed by the trampling of beasts, or sometimes, as in this picture, by a rude kind of threshing wheel. The wheels are carried in the framework on which the man is sitting. Sometimes a sledge with iron or stone teeth driven into the bottom is used. ”

“ Here the workmen first made room to fix their instruments, and then, by strength, and the help of those two mechanic powers, the screw and the lever, they raised out of their ancient beds those massive bodies, and then filling up the cavities with gravel, set them up, mostly end-ways, along the sides of the road, as directions in time of deep snows, being some of them, as they now stand, eight or nine feet high. ”

“ These are held to their backs by a broad strap going over the forehead, and the hair is left thick, and made to grow thicker over the eyes, in order to make a matting for this strap. I have seen stones and bricks so carried that weighed, I was told, four hundred pounds. Their heads bow to the burden, and they trot along under their huge loads as fast as a horse can walk. ”

“ If they do, they carry a lighter load, not, however, on their heads, but on the bent back or shoulders, protected by a sack. I have observed a woman carrying a stone on her head which it took four of them to lift. ”

“ Farther, such weights draw the rope up again with considerable force, while it is wound backwards and forwards over the cylinder.—As this machinery may be fixed in a garret, or other spare-room at the top of a house, the rope may be conduced through the ceiling into a lower chamber; so that sedentary persons, or invalids, may take sufficient exercise, without quitting their habitation, or exposing themselves to the vicissitudes of the weather. ”

“ I anticipated every moment that my bearers would have complained of the road, which was badly paved, and very steep the greatest part of the way; but they were fine, hardy, muscular men, and quite indifferent to a toil with which habit had rendered them familiar. Each bearer carries a long stick in his hand, which assists to support and steady him, over the uneven ground. ”

“ The friction of a rope bent, or wound round an immovable cylinder, is sufficient, with a very small power, to sustain very great weights. Divers methods have been contrived for bending timber, in order to supply crooked planks and pieces for building ships ”