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pulleys

pulleys Sentence Examples

  • (2) The hook may be attached to a rope or chain, and the pulling cylinder connected with a system of pulleys around which the rope is led; by these means the lift can be very largely increased.

  • In this last form an endless band of hard iron wires passes slowly round two wooden pulleys driven by clockwork.

  • 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.

  • 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.

  • 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.

  • 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 pulleys, which are made as large as possible up to zo ft.

  • 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.

  • ' To measure this, guide pulleys are placed in the loops guided by a geometric slide, the one pulley carrying a scale, and the other an index.

  • 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.

  • 8) the guide pulleys G1, G2 are carried upon an arm free to turn about the axis 0.

  • 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.

  • (The architect being at that time also the contractor.) The chapters are -- (1) on various machines, such as scaling-ladders, windmills, &c.; (2) on windlasses, axles, pulleys and cranes for moving heavy weights, such as those used by Chersiphron in building the great temple of Diana at Ephesus, and on the discovery by a shepherd of a quarry of marble required to build the same temple; (3) on dynamics; (4) on machines for drawing water; (5) on wheels for irrigation worked by a river; (6) on raising water by a revolving spiral tube; (7) on the machine of Ctesibius for raising water to a height; (8) on a very complicated water engine, the description of which is not intelligible, though Vitruvius remarks that he has tried to make the matter clear; (9) on machines with wheels to register the distance travelled, either by land or water; (10) on the construction of scorpiones for hurling stones; (11) and (12) on balistae and catapults; (13) on battering rams and other machines for the attack of a fortress; (14) on shields (testudines) to enable soldiers to fill up the enemy's ditches; (15) on other kinds of testudines; (16) on machines for defence, and examples of their use in ancient times.

  • 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.

  • Suppose the base-circles to be a pair of circular pulleys connected D~ ill by means of a cord whose course ~f from pulley to pulley is P1IP2.

  • As the line of connection of those pulleys is the same as that of the I proposed teeth, they will rotate -

  • 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.

  • Belts (the most frequently used of all wrapping connectors) require nearly cylindrical pulleys.

  • 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.

  • Cords require either cylindrical drums with ledges or grooved pulleys.

  • 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.

  • Pulleys and drums for communi cating a constant velocity ratio are circular.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • which is useful in determining the original tension required to enable a belt to transmit a given force between two pulleys.

  • Trans., 1894) investigated the question for the cases of loaded and unloaded shafts, and, owing to the complication arising from the application of the general theory to the cases of loaded shafts, devised empirical formulae for the critical speeds of shafts loaded with heavy pulleys, based generally upon the following assumption, which is stated for the case of a shaft carrying one pulley: If Ni, N1 be the separate speeds of whirl of the shaft and pulley on the assumption that the effect of one is neglected when that of the other is under consideration, then the resulting speed of whirl due to both causes combined may be taken to be of the form N1N2~!

  • 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.

  • Thus these two small pulleys are always running, but in opposite directions.

  • 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.

  • 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.

  • 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.

  • 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 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.

  • The combination of these stresses generally limits the rim velocity of cast-iron pulleys to 80 or loo ft.

  • 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.

  • 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.

  • Pulleys are also made of paper, wood and other materials.

  • 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.

  • 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.

  • 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.

  • Repeating this construction for all values of a between o° and 90°, we obtain a curve BPC, which can be used for determining the ratios of corresponding drums of cone pulleys or of conical drums for open belts.

  • 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.

  • 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.

  • 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.

  • The rims of pulleys for hemp or other ropes or cords are grooved, and the sides are usually either inclined at 45° or curved to give a sharper angle at the outside than at the bottom of the groove; in the latter case, as the rope wears it engages in a groove of greater angle and less effective grip. Wire ropes are injured by the lateral crushing of the material, and in this case the grooves are wide enough to allow the rope to rest on the rounded bottom, which is lined with leather or wood to diminish the wear and increase the friction.

  • 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.

  • For leather belts on cast-iron pulleys the value of may be taken as o 4, giving a ratio of the tensions on the tight and slack sides of Ti/T2= 3.514, when the angle of wrapping is 180°.

  • For ropes in the grooves of cast-iron pulleys, where 4, is the inclination of the sides of the grooves, the value of the normal pressure is increased in the ratio of cosec zct) = I.

  • 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.

  • Frames or blocks containing pulleys or sheaves are used in combination for lifting heavy weights.

  • cated cases guide pulleys for inclined pulleys, any FIG.

  • The upper block carries a pair of chain pulleys A (fig.

  • 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.

  • heddle pulleys for weaving suggest cultural links with the Baule and the Senufo.

  • idler pulleys to the surface being cut.

  • 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.

  • spindle pulleys was 6.5 inches in diameter and took a 1 3/8 " -wide belt.

  • (2) The hook may be attached to a rope or chain, and the pulling cylinder connected with a system of pulleys around which the rope is led; by these means the lift can be very largely increased.

  • In this last form an endless band of hard iron wires passes slowly round two wooden pulleys driven by clockwork.

  • 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.

  • 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.

  • 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.

  • 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 pulleys, which are made as large as possible up to zo ft.

  • 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.

  • ' To measure this, guide pulleys are placed in the loops guided by a geometric slide, the one pulley carrying a scale, and the other an index.

  • 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.

  • 8) the guide pulleys G1, G2 are carried upon an arm free to turn about the axis 0.

  • 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.

  • (The architect being at that time also the contractor.) The chapters are -- (1) on various machines, such as scaling-ladders, windmills, &c.; (2) on windlasses, axles, pulleys and cranes for moving heavy weights, such as those used by Chersiphron in building the great temple of Diana at Ephesus, and on the discovery by a shepherd of a quarry of marble required to build the same temple; (3) on dynamics; (4) on machines for drawing water; (5) on wheels for irrigation worked by a river; (6) on raising water by a revolving spiral tube; (7) on the machine of Ctesibius for raising water to a height; (8) on a very complicated water engine, the description of which is not intelligible, though Vitruvius remarks that he has tried to make the matter clear; (9) on machines with wheels to register the distance travelled, either by land or water; (10) on the construction of scorpiones for hurling stones; (11) and (12) on balistae and catapults; (13) on battering rams and other machines for the attack of a fortress; (14) on shields (testudines) to enable soldiers to fill up the enemy's ditches; (15) on other kinds of testudines; (16) on machines for defence, and examples of their use in ancient times.

  • 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.

  • Suppose the base-circles to be a pair of circular pulleys connected D~ ill by means of a cord whose course ~f from pulley to pulley is P1IP2.

  • As the line of connection of those pulleys is the same as that of the I proposed teeth, they will rotate -

  • 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.

  • Belts (the most frequently used of all wrapping connectors) require nearly cylindrical pulleys.

  • 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.

  • Cords require either cylindrical drums with ledges or grooved pulleys.

  • 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.

  • Pulleys and drums for communi cating a constant velocity ratio are circular.

  • 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.

  • 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.

  • 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.

  • 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.

  • (See PULLEYS for practical applications of these principles.)

  • 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.

  • which is useful in determining the original tension required to enable a belt to transmit a given force between two pulleys.

  • Trans., 1894) investigated the question for the cases of loaded and unloaded shafts, and, owing to the complication arising from the application of the general theory to the cases of loaded shafts, devised empirical formulae for the critical speeds of shafts loaded with heavy pulleys, based generally upon the following assumption, which is stated for the case of a shaft carrying one pulley: If Ni, N1 be the separate speeds of whirl of the shaft and pulley on the assumption that the effect of one is neglected when that of the other is under consideration, then the resulting speed of whirl due to both causes combined may be taken to be of the form N1N2~!

  • 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.

  • Thus these two small pulleys are always running, but in opposite directions.

  • 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.

  • 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.

  • 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.

  • 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 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.

  • The combination of these stresses generally limits the rim velocity of cast-iron pulleys to 80 or loo ft.

  • 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.

  • 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.

  • Pulleys are also made of paper, wood and other materials.

  • 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.

  • Means of changing the relative speeds of rotation are furnished by pulleys of continuously varying diameter, or by speed cones (see Mechanics: Applied).

  • 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.

  • 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.

  • Repeating this construction for all values of a between o° and 90°, we obtain a curve BPC, which can be used for determining the ratios of corresponding drums of cone pulleys or of conical drums for open belts.

  • 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.

  • 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.

  • 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.

  • The rims of pulleys for hemp or other ropes or cords are grooved, and the sides are usually either inclined at 45° or curved to give a sharper angle at the outside than at the bottom of the groove; in the latter case, as the rope wears it engages in a groove of greater angle and less effective grip. Wire ropes are injured by the lateral crushing of the material, and in this case the grooves are wide enough to allow the rope to rest on the rounded bottom, which is lined with leather or wood to diminish the wear and increase the friction.

  • 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.

  • For leather belts on cast-iron pulleys the value of may be taken as o 4, giving a ratio of the tensions on the tight and slack sides of Ti/T2= 3.514, when the angle of wrapping is 180°.

  • For ropes in the grooves of cast-iron pulleys, where 4, is the inclination of the sides of the grooves, the value of the normal pressure is increased in the ratio of cosec zct) = I.

  • 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.

  • Frames or blocks containing pulleys or sheaves are used in combination for lifting heavy weights.

  • cated cases guide pulleys for inclined pulleys, any FIG.

  • The upper block carries a pair of chain pulleys A (fig.

  • 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.

  • 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.

  • 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.

  • 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.

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