Pulleys Sentence Examples
Pulleys and drums for communi cating a constant velocity ratio are circular.
Wrapping ConnectorsBelts, Cords and Chains Flat belts of leather or of gutta percha, round cords of catgut, hemp or other material, and metal chains are used as wrapping connectors to transmit rotatory motion between pairs of pulleys and drums.
One train of mechanism may diverge into two or moreas when a single shaft, driven by a prime mover, carries several pulleys, each of which drives a different machine.
The angular velocities of a pair of connected circular pulleys or drums are inversely as the effective radii.
The length L of an endless belt connecting a pair of pulleys whose effective radii are r,, r,, with parallel axes whose distance apart is c, is given by the following formulae, in each of which the first term, containing the radical, expresses the length of the straight parts of the belt, and the remainder of the formula the length of the curved parts.Advertisement
F = T1 Ti = T1 (I ef9) Ta(ef 1)j When a belt connecting a pair of pulleys has the tensions of its two sides originally equal, the pulleys being at rest, and when the pulleys are next set in motion, so that one of them drives the other by means of the belt, it is found that the advancing side of the belt is exactly as much tightened as the returning side is slackened, so that the mean tension remains unchanged.
The pulleys, which are made as large as possible up to zo ft.
But a floor, however heavy, suspended by three wire ropes and properly balanced over large, well-mounted pulleys, requires an amount of energy to work it which does not exceed that required to operate a platform of moderate dimensions, and there is a freedom, a safety and a facility of working with a complete floor which no partial platform can give.
The Torque Was Measured By Weights 0 And P Suspended By Silk Ribbons Passing Over The Pulleys N And Round The Disk Kl.
Cords require either cylindrical drums with ledges or grooved pulleys.Advertisement
When the a,ces of a pair of pulleys are not parallel, the pulleys should be so placed that the part of the belt which is approaching each pulley shall be in the plane of the pulley.
This form is extended to include the cases of several pulleys on the same sifaft.
Such persons may sometimes get a good deal of exercise in a short time by the use of dumb-bells, of elastic cords, or of cords running over pulleys and weighted at one end.
These wheels receive motions from bands and pulleys from a steam or other engine contained in the car.
Benjamin (American Machinist, 1898) on castiron pulleys loaded by a belt to imitate the conditions in practice led him to the conclusion that the rim is usually not sufficiently rigid to load the arms equally, and that the ends of the arms are subjected to bending movements of opposite sign, that at the nave being almost invariably the greater.Advertisement
Pulleys are also built up of wrought iron and steel, and can then be constructed entirely free from internal stress; they are thus much lighter and stronger, and are not liable to fly to pieces like cast iron if they break.
Wooden pulleys are preferably made of maple, the rim being formed of small sections morticed, pinned and glued together, with the grain set in such directions that any warping of the material will leave the cylindrical form practically unaltered.
Wooden pulleys are generally made in two halves, bolted together at the rim and nave, and are provided with wooden spokes dovetailed into the rim and secured by keys.
The rims of pulleys, round which flat bands are wrapped, may be truly cylindrical, in which case the belt will run indifferently at any part of the pulley, or the rim may be swelled towards the centre, when the central line of the band will tend to run in the diametral plane of the pulley.
Parallel shafts may be driven by flexible bands or connectors passing over pulleys, the central planes of which coincide, without any guiding arrangements for the belting.Advertisement
A common arrangement for driving a lathe spindle, in either direction at several definite speeds, is to provide a countershaft on which are mounted two fixed pulleys and two loose pulleys to accommodate two driving belts from the main shaft, one of which is open and the other crossed.
The belts are moved laterally by the forks of a striking gear pressing on the advancing sides of the belts, and the pulleys are arranged so that the belts either wrap round the loose pulleys, or can be shifted so that one wraps round a fixed pulley, while the other still remains on its loose pulley.
The dimensions of the pulleys are generally so arranged that the return motion of the lathe spindle is faster than the forward motion.
An alternative arrangement consists in providing two loose pulleys on the counter-shaft, driven by open and crossed belts respectively, and arranging two clutches on the shaft, so that by the movement of a sliding block, controlled by hand, one or other of the clutches can be put in gear.
The proportions of cone pulleys for open or crossed belts may be determined by considering the expression for the half length (1) of a belt wrapping round pulleys of radius r 1 and r 2 respectively, and with centres distant c apart.Advertisement
When pulleys are mounted on shafts which are parallel to one another, the band will retain its position, provided that its central line advances towards each pulley in the diametral plane of this latter.
Guide pulleys are set with their diametral planes in the planes containing corresponding pairs of tangents, and a continuous belt wrapped round these pulleys in due order can then be run in either direction.
Frames or blocks containing pulleys or sheaves are used in combination for lifting heavy weights.
Belts (the most frequently used of all wrapping connectors) require nearly cylindrical pulleys.
Pulleys are usually cast in one piece, and the proportions of the various parts are designed to resist the unknown stresses due to contraction of the casting in cooling, in addition to the stresses to which pulleys are subjected in use.
In determining the dimensions of corresponding drums of cone pulleys it is evident that for a crossed belt the sum of the radii of each pair remains a constant, since the angle a is constant, while for an open belt a is variable and the values of the radii are then obtained by solving the equations r 1 = l/ir - c(a sin a + cos a) + 2c sin a, r 2 = l/7r - c(a sin a +cos_a) - lc sin a.
If the motion is reversed the condition is no longer satisfied and the belt will leave the pulleys.
In the most general case two points may be chosen on the line of intersection of the diametral planes, and tangents drawn to the pitch circles of the pulleys.
A usual value of for hemp ropes on cast-iron pulleys is 0.3, and the exponential log ratio is therefore 0 3ur cosec 20 when 9 =7r.
An endless chain B, passing through guides C and D, encircles these pulleys and the single loose pulley E of the lower block, as indicated.
Having attached the pulleys, the cables were threaded through from the rails on the prompt side wall.
Activities from Inventor's Workshop link directly to the teaching of wheels and axles, gears, pulleys and cams.
The main drive pulley was 4.25 " in diameter and the rear idler pulleys, running on ball bearings, 3.5 " .
This wire is passed over any number of small idler pulleys to the surface being cut.
The main drive pulley was 4.25 " in diameter and the rear idler pulleys, running on ball bearings, 3.5 ".
The largest of the 4-step spindle pulleys was 6.5 inches in diameter and took a 1 3/8 -wide belt.
There are lots of different methods depending on the manufacturer involved, but systems can use simple brackets, ropes, pulleys or cables.
Add additional braces, pulleys or cables (depending on the stair system you are installing).
If the window is an older sash-weight model, remove the parting stop as well as the balance cord pulleys.
Traction-The process of placing a bone, limb, or group of muscles under tension by applying weights and pulleys.
Soon afterward the company added wheels, gears, and pulleys which allowed children to create vehicles of all kinds as well as items with gears.
The piercer uses hooks to pierce through specific parts of the body; these hooks are attached to pulleys or another mechanism and used to lift the piercee off of the ground for a period of time.
The Greeks used an intricate design of pulleys and wheels so that a float would rise and fall with the water, automating the "machinery," and through a gear system maintain time on a disk on the front of the clock.
Each machine guides the user through a specific movement while controlling the motion with a series of pulleys.
This simple machine doesn't contain weight plates or pulleys; instead it uses your own weight as resistance to tone your hams and glutes.
FreeMotion is the only line of commercial products that has a full-line of selectorized equipment that uses pulleys and tension allowing you to move in all planes of motion.
Some of the best options have dual adjustable pulleys that allow you to manipulate the angle of resistance for a wide variety of exercise options.
The position of the reversing link is altered by means of a cord, passing over two pulleys, fixed respectively in the engine-house and on the derrick.
The substitution of machinery for hand labour in cutting coal has long been a favourite problem with inventors, the earliest plan being that of Michael Meinzies, in 1761, who proposed to work a heavy pick underground by power transmitted from an engine at the surface, through the agencies of spear-rods and chains passing over pulleys; but none of the methods suggested proved to be practically successful until the general introduction of compressed air into mines furnished a convenient motive power, susceptible of being carried to considerable distances without any great loss of pressure.
This system presents the greatest advantages in point of economy of driving power, especially where the gradients are variable, but is expensive in first cost, and is not well suited for curves, and branch roads cannot be worked continuously, as a fresh set of pulleys worked by bevel gearing is required for each branch.
The surface arrangements of a modern deep colliery are of considerable extent and complexity, the central feature being the head gear or pit frame carrying the guide pulleys Surface which lead the winding roes from the axis of the it arrange= g P P to the drum.
To prevent accidents from the breaking of the rope while the cage is travelling in the shaft, or from over-winding when in consequence of the engine not being stopped in time the cage may be drawn up to the head-gear pulleys (both of which are unhappily not uncommon), various forms of safety catches and disconnecting hooks have been adopted.
A and B are fast and loose pulleys, and the brake band is placed partly over the one and partly over the other.
In the Farcot form the guide pulleys are attached to separate weighing levers placed horizontally below the apparatus.
The other six are connected to each other and to the lowest one by wire cables and pulleys in such a way that when the cable which connects the two lowest tubes is wound in by means of a winch, each of the tubes except the fixed one will rise within the next one through the same distance.
A belt tends to move towards that part of a pulley whose radius is greatest; pulleys for belts, therefore, are slightly swelled in the middle, in order that the belt may remain on the pulley, unless forcibly shifted.
Chains require pulleys or drums, grooved, notched and toothed, so as to fit the links of the chain.
Wrapping connectors for communicating reciprocating motion have usually their ends made fast to the pulleys or drums which they connect, and which in this case may be sectors.
The speed-cones are either continuous cones or conoids, as A, B, whose velocity ratio can be varied gradually while they are in motion by shifting the belt, or sets of pulleys whose radii vary by steps, as C, D, in which case the velocity ratio can be changed by shifting the belt from one pair of pulleys to another.
Thus these two small pulleys are always running, but in opposite directions.
Driving pulleys are usually constructed of cast iron, and are of circular form, having a central nave by which they are secured to the shaft by keys or other fastenings, and straight or curved arms connecting the nave to the rim, which latter is of a form adapted to the connector.
Pulleys are also made of paper, wood and other materials.
In English practice there are as many separate endless ropes as there are pairs of grooves in the two pulleys to be connected, but in cases of American practice the rope is continuously wound round the two pulleys, and the free end passes over a pulley mounted on a movable weighted carriage to adjust the tension.
Pulleys may be detachably connected to a shaft by friction clutches, so that they may be thrown in and out of engagement at will.
Just as in a clock, the result of the complicated motion of innumerable wheels and pulleys is merely a slow and regular movement of the hands which show the time, so the result of all the complicated human activities of 160,000 Russians and French--all their passions, desires, remorse, humiliations, sufferings, outbursts of pride, fear, and enthusiasm--was only the loss of the battle of Austerlitz, the so-called battle of the three Emperors--that is to say, a slow movement of the hand on the dial of human history.
Among the manufactures of Oneida are wagons, cigars, furniture, caskets, silver-plated ware, engines and machinery, steel and wooden pulleys and chucks, steel grave vaults, hosiery, and milk bottle caps.
P and p may be measured directly by leading the belt round two freely hanging guide pulleys, one in the tight, the other in the slack part of the belt, and adjusting loads on them until a stable condition of running is obtained.
As the line of connection of those pulleys is the same as that of the I proposed teeth, they will rotate -
When the poise is at the zero end, and there is no load on the platform, the end of the steelyard is down, and has locked the ratchet wheel by means of the pawl; the shaft being thus locked, the sprocket wheels are stopped, the drum-shaft runs free by the friction clutch, and the two pulleys which are connected by the crossed band are running idle.
In this last form an endless band of hard iron wires passes slowly round two wooden pulleys driven by clockwork.
This is an upright frame, usually made in wrought iron or steel strutted by diagonal thrust beams against the engine-house wall or other solid abutments, the height to the bearings of the guide pulleys being from 80 to 1 00 ft.
The poise having arrived at the end of its run and unable to go further, the mitre wheels and the sprocket gearing are stopped, and the two pulleys and the cross belt run idle till the.
Wheels creak on their axles as the cogs engage one another and the revolving pulleys whirr with the rapidity of their movement, but a neighboring wheel is as quiet and motionless as though it were prepared to remain so for a hundred years; but the moment comes when the lever catches it and obeying the impulse that wheel begins to creak and joins in the common motion the result and aim of which are beyond its ken.
A pulley carried on a rotating shaft and connected to another pulley on a second shaft by an endless band consisting of a flat belt, rope, chain or similar connector serves for the transmission of power from the one shaft to the other and is known as a driving pulley; while combinations of pulleys or "sheaves," mounted in fixed or movable frames or "blocks," constitute mechanisms used to facilitate the raising of heavy weights.
The combination of these stresses generally limits the rim velocity of cast-iron pulleys to 80 or loo ft.