See also:

• POWER [WILLIAM GRATTAN] TYRONE (1797-1841)

In other cases the energy made available by the prime mover is distributed to a number of See also:

• SEPARATE

I.—MECHANICAL § 1. Methods.—The mechanical transmission of power is effected in general by means of belts or See also:

• ROPES, JOHN CODMAN (1836–1899)

Assuming for the See also:

• SAKE

The term Wv2/g therefore has the numerical value 34.7. Hence equation (2) becomes (t—34.7)/(u—34.7) =1.87, from which, inserting the value 838 for t, n=464.5 lb. Using this value of u in equation (I) H.P. _ (838 — 464.5) X 18.84 X 1.5 550 =19.15. where n is called the efficiency of the transmission. Considering now the general problem of a multiple machine transmission, if Tl, wl, T2, See also:

• W2(P — R1)

When the pulleys are revolving uniformly, A transmitting power to B, one See also:

• SIDE
• SIDE (mod. Eski Adalia)

The See also:

• SOLUTION (from Lat. solvere, to loosen, dissolve)

Then solving equation (4) for u, subtracting t from each side, and changing the signs all through: l—u=(t—Wv2/g) (1—e ee). And the rate of working U, in foot-pounds per second, is U=(t—u)v=(tv—Wv3/g)(1—e 0)• Differentiating U with regard to v, equating to zero, and solving for v, we have v = ~l (tg/3W). Utilizing the data of the previous example to illustrate this matter, 1=838 lb per square inch, W =I.4 lb per foot, and consequently, from the above expression, v=8o ft. per second approximately. A See also:

• LOWER

§ 7. Rope Driving.—About 1856 See also:

• JAMES
• JAMES (Gr. 'IlrKw,l3or, the Heb. Ya`akob or Jacob)
• JAMES (JAMES FRANCIS EDWARD STUART) (1688-1766)
• JAMES, 2ND EARL OF DOUGLAS AND MAR(c. 1358–1388)
• JAMES, DAVID (1839-1893)
• JAMES, EPISTLE OF
• JAMES, GEORGE PAYNE RAINSFOP
• JAMES, HENRY (1843— )
• JAMES, JOHN ANGELL (1785-1859)
• JAMES, THOMAS (c. 1573–1629)
• JAMES, WILLIAM (1842–1910)
• JAMES, WILLIAM (d. 1827)

A rope is less flex- ible than a belt, and therefore care must be taken not to arrange rope drives with pul- See also:

• LEYS, HENDRIK, BARON (1815-1869)

(See also:

• JULY

Again it rarely happens that a shaft sustains a torque only. There is usually a bending moment associated with it. For a discussion of the proper values of f, to suit cases where the stress is variable, and the way a bending moment of known amount may be combined with a known torque, see STRENGTH OF MATERIALS. It is sufficient to state here that if M is the bending moment in inch-pounds, and T the torque in inch-pounds, the magnitude of the greatest direct stress in the shaft due to the effect of the torque and twisting moment acting together is the same as would be produced by the application of a torque of M-~ J (T2+M2) inch-pounds. (II) It will be readily understood that in designing a shaft for the distribution of power to a factory where power is taken off at different places along the shaft, the diameter of the shaft near the engine must be proportioned to transmit the See also:

• TOTAL

Observe that 0 is here measured in radians. The ordinary problems of shaft transmission by solid round shafts subject to a See also:

• UNIFORM

If a pair of wheels is required to transmit a certain maximum horse power, the angular velocity of the shaft being w, the pressure P which the teeth must be designed to sustain at the pitch circle is 550 H.P./wR, where R is the radius of the pitch circle of the wheel, whose angular velocity is w. § io. Velocity Ratio.—In the case of transmission either by belts, ropes, shafts or gearing, the operating principle is that the rate of working is constant, assuming that the efficiency of the transmission is upity, and that the product Tw is therefore constant, whether the shafts are connected by ropes or gearing. Considering therefore two shafts, T1 w1=T2w2; that is w;/w2=T2/T1; i.e. the angular velocity ratio is inversely as the torque ratio. Hence the higher the speed at which a shaft runs, the smaller the torque for the transmission of a given horse power, and the smaller the tension on the belts or ropes for the transmission of a given horse power. § 11. See also:

• LONG, GEORGE (1800-1879)
• LONG, JOHN DAVIS (1838– )

The individual ropes of the series, each transmitting 300 h.p., were each 1.o8 in. diameter and contained Io strands of 9 wires per strand, the wires being each 0.072 in. diameter. Similar installations existed at See also:

• SCHAFFHAUSEN
• SCHAFFHAUSEN (Fr. Schaffhouse)

C. Unwin, Elements of Machine Design; and for telodynamic transmission see F. Reuleaux, See also:

• DIE
• DIE (Fr. de, from Lat. datum, given)

The general features ofhydraulic power transmissions are: (I) a central station where the hydraulic pressure is created, usually by means of steam pumping engines; (2) a system of distribution mains; (3) machines for utilizing the pressure. In cases of public supplies there is the further important matter of See also:

• REGISTRATION

If the accumulator ram descended in one minute the horse power developed during that See also:

• TIME (0. Eng. Lima, cf. Icel. timi, Swed. timme, hour, Dan. time; from the root also seen in " tide," properly the time of between the flow and ebb of the sea, cf. O. Eng. getidan, to happen, " even-tide," &c.; it is not directly related to Lat. tempus)
• TIME, MEASUREMENT OF
• TIME, STANDARD

In any large system where a number of pumping See also:

• UNITS, DIMENSIONS OF
• UNITS, PHYSICAL

In this case the load-factor 2920/8760= .333, or 33.370%. The saving on the whole See also:

• EXPENDITURE

In a comprehensive system of power supply demand arises in a very sudden and erratic manner, and to meet this by forcing the boilers involves greater See also:

• WASTE (O. Fr. wast, guast, gast, gaste; Lat. vastus, vast, desolate)

The details of the London supply given in tablet partly explain this by the relatively high price of fuel, but an equally important factor has been the rise in the local rates, which in the See also:

• PERIOD
• PERIOD (Gr. irepioSos, a going or way round, circuit, aepi, round, and &Sis, way, road)

All the stations and mains are connected together and worked as one system. There are 14 accumulators with a total capacity of 4000 gallons, most of them having rams 20 in. diameter by 23 ft. stroke. The pumping engines are able together to deliver 11,000 gallons per minute. Details of the London supply are given in fig. 3 and in table t. year. Gallons 7 V Eao 0o "-s E O Pumped. ^~ = V L, O a,- e N....-0 e d a o s o o y x se; ., y d 8 3 4.T„5 `--- d. s. d. 1889 163,883,000 0.328 0.524 3'11 10 9 1022 38 1894 400,316,000 0.338 0.553 I.96 10 0 2204 73 f 1898 620,662,000 0.340 0.483 1.98 II 3 3515 109 1903 888,925,000 0.361 0.491 2.7 14 34 5337 146 1909 1,027,147,000 0.354 0.495 2.78 15 I 6504 168 229 The load-factors are calculated on the actual recorded maximum output, and not on the estimated capacity of the plant running or installed. The daily periods of maximum output are shown in fig. 2. The table shows that the load-factors have not been much affected either by the increase of the area of supply or by the in-creased consumption of power.

The coal used has been principally See also:

• DURHAM
• DURHAM, JOHN GEORGE LAMBTON, 1ST EARL OF (1792–1840)

In See also:

• LIVERPOOL
• LIVERPOOL, EARLS
• LIVERPOOL, EARLS OF

The loss in conversion, however, proved to be twice as great as had been anticipated, owing largely to defective apparatus and to under-estimation of the expense of maintaining the converting stations; and the See also:

• NET

6d. per woo gallons =2d. 33,000 X 60 per h.p. hour nearly. This amount is made up approximately of 9d. per See also:

• I000

The use of any particular system of power does not, however, primarily depend upon the cost of running the central station and distributing the power, but mainly upon the mechanical convenience of the system for the purpose to which it is applied. One form of energy is, in practice, found most useful for one purpose, another form for another and no one can command the whole See also:

• FIELD (a word common to many West German languages, cf. Ger. Feld, Dutch veld, possibly cognate with O.E. f olde, the earth, and ultimately with root of the Gr. irAaror, broad)
• FIELD, CYRUS WEST (1819-1892)
• FIELD, DAVID DUDLEY (18o5-1894)
• FIELD, EUGENE (1850-1895)
• FIELD, FREDERICK (18o1—1885)
• FIELD, HENRY MARTYN (1822-1907)
• FIELD, JOHN (1782—1837)
• FIELD, MARSHALL (183 1906)
• FIELD, NATHAN (1587—1633)
• FIELD, STEPHEN JOHNSON (1816-1899)
• FIELD, WILLIAM VENTRIS FIELD, BARON (1813-1907)

The loss of pressure due to the velocity is . v 1 ~\p 6P.0 See also:

• INDEPENDENT

The pipes from 8 in. and below are usually made in See also:

• CAST (from the verb meaning " to throw "; the word is Scand. in origin, cf. Dan. kaste, and Swed. kasta; " cast " in Middle Eng. took the place of the A.S. weor pan, cf. Ger. werf en)

The other pumping stations are situated about 3 M. from Falcon Wharf and about the same distance from each other. The accumulator pressure at the outlying stations is during the busy time of the day maintained at about 800 lb per square inch. Consequently the smaller variations in demand for power throughout the system caused very intermittent running of the plant at Falcon Wharf, and the load-factor there is very low. The pumping plant has now been considerably increased, and part of the plant is constructed to pump into the feeder main at pressures of 800, 900, or Moo lb per square inch according to the demand existing from hour to hour in the Strand district. By this means the output from Falcon Wharf has been doubled with a much improved load-factor. The accumulator in this system is of special construction (fig. 7). The pressure 750 lb per square inch is maintained in the cylinder A from the ordinary hydraulic supply main. The working ram B forms the cylinder for the fixed hollow ram C which is connected to the 6 in. See also:

• BORE

The length of the feeder main in this case is 2000 yds., and at 10 ft. per second there is a loss of pressure of 24o lb per squareinch, but the effect on the coal consumption is almost negligible, as the maximum flow is seldom needed. The engines are specially constructed to take the pressure overload. The feeder main is made of steel. The economical limit of the use of feeder mains is reached when the additional running expenses involved equal the See also:

• ANNUAL

In Manchester See also:

• KENT
• KENT, EARLS AND DUKES OF
• KENT, JAMES (1763-1847)
• KENT, WILLIAM (1685-1748)

Efficiency in this sense is a most uncertain guide. Some of the most useful and successful applications of hydraulic power—as, for instance, hydraulic capstans for hauling wagons in railway goods yards—have a very low efficiency ex-pressed on the ratio of work done to power expended. Hydraulic cranes for coal or See also:

• GRAIN (derived through the French from Lat. granum, seed, from an Aryan root meaning " to wear down," which also appears in the common Teutonic word " corn ")

The development of these applications has been largely due to the very complete machinery invented and perfected by R. H. Tweddell. One of the See also:

• PRINCIPAL

Betts See also:

• BROWN
• BROWN, CHARLES BROCKDEN (1771-181o)
• BROWN, FORD MADOX (1821-1893)
• BROWN, FRANCIS (1849- )
• BROWN, GEORGE (1818-188o)
• BROWN, HENRY KIRKE (1814-1886)
• BROWN, JACOB (1775–1828)
• BROWN, JOHN (1715–1766)
• BROWN, JOHN (1722-1787)
• BROWN, JOHN (1735–1788)
• BROWN, JOHN (1784–1858)
• BROWN, JOHN (1800-1859)
• BROWN, JOHN (1810—1882)
• BROWN, JOHN GEORGE (1831— )
• BROWN, ROBERT (1773-1858)
• BROWN, SAMUEL MORISON (1817—1856)
• BROWN, SIR GEORGE (1790-1865)
• BROWN, SIR JOHN (1816-1896)
• BROWN, SIR WILLIAM, BART
• BROWN, THOMAS (1663-1704)
• BROWN, THOMAS (1778-1820)
• BROWN, THOMAS EDWARD (1830-1897)
• BROWN, WILLIAM LAURENCE (1755–1830)

AurxoxuTIEs.—Armstrong, Proc. Inst. C.E. (185o and 1877), Proc. Inst. Mech. E. (1858 and 1868); See also:

• BLAINE, JAMES GILLESPIE (1830-1893)

Mech. E. (1882 and 1895), Proc. Liverpool Eng. Sic. (1880 and 1885); See also:

• GREATHEAD, JAMES HENRY (1844–1896)

(1896) ; See also:

• ROBINSON, EDWARD (1794–1863)
• ROBINSON, HENRY CRABB (1777–1867)
• ROBINSON, JOHN (1575–1625)
• ROBINSON, JOHN (1650-1723)
• ROBINSON, JOHN THOMAS ROMNEY (1792–1882)
• ROBINSON, MARY [" Perdita "] (1758–1800)
• ROBINSON, SIR JOHN BEVERLEY, BART
• ROBINSON, SIR JOSEPH BENJAMIN (1845– )
• ROBINSON, THEODORE (1852-1896)

The first recorded instance of this being done was by See also:

• DENIS (DIoNysms), SAINT
• DENIS, JOHANN NEPOMUK COSMAS MICHAEL (1729-1800)

Although the air came in contact with the water, it was not cooled, except slightly at the surface of the water and around the walls of the cylinders. The compressors were located near the tunnel, and the compressed air was transmitted through pipes to drilling machines working at the faces in the tunnel. Rotary drills were tried first, but were soon replaced by percussion drills adapted from drawings in the United States Patent See also:

• OFFICE (from Lat. officium, " duty," " service," a shortened form of opifacium, from facere, " to do," and either the stem of opes, " wealth," " aid," or opus, " work ")

See also:

• BROOKS, CHARLES WILLIAM SHIRLEY (1816-1874)
• BROOKS, PHILLIPS (1835-1893)

Many stone quarries have a central plant for compressing air, which is transmitted through pipes extending to all working points, and operates derricks, hoists, drills, stone cutters, &c., by means of motors. Every considerable ironworks, railroad shop or foundry has its pneumatic transmission plant. Also in the erection of the larger steel See also:

• BRIDGES
• BRIDGES, ROBERT (1844– )

Priestly, without knowledge of Pohle's system, built a pipe line down the See also:

• BLUFF (a word of uncertain origin; possibly connected with an obsolete Dutch word, blaf, broad)

In good practice there need not be more than loss through leakage and 1% possibly through friction in the pneumatic transmission of power. Air develops See also:

• HEAT (0. E. haktu, which like " hot," Old Eng. hat, is from the Teutonic type haita, hit, to be hot; cf. Ger. hitze, heiss; Dutch, hitte, heet, &c.)

It also follows that the ideal motor for using compressed air is one which will supply heat to the air as required when it is expanding. Such " isothermal " expansion is often attained, and sometimes exceeded, in practice by supplying heat artificially. Finally, the most inefficient motor for using compressed air is one which supplies no heat to the air during its expansion, or works by adiabatic expansion, which was long very closely approached by most air motors. In practice isothermal compression is approached by compressing the air slightly, then cooling it, compressing it slightly again, and again cooling it until the desired compression is completed. This is called compression in stages or compound compression. Isothermal expansion is approximately accomplished by allowing the air to do part of its work (as expanding slightly in a cylinder) and then warming it, then allowing it to do a little more and then warming it again, and so continuing until expansion is complete. It will be seen that the air is carefully cooled during compression to prevent the heat it develops from working against compression, and even more carefully heated during expansion to prevent loss from cold developed during expansion. More stages of compression of course give a higher efficiency, but the cost of machinery and friction losses have to be considered. The reheating of air is often a disadvantage, especially in See also:

• MINING

(A. DE W. F.) IV.—ELECTRICAL Though the older methods of power transmission, such as wire ropes, compressed air and high-pressure water, are still worked on a comparatively small scale, the See also:

• CHIEF (from Fr. chef, head, Lat. caput)

On the See also:

• CONTINENT (from Lat. continere, "to hold together "; hence " connected," " continuous ")

In the Moutiers-Lyons transmission motor-generators are even designed to give a three-phase constant potential distribution, and in See also:

• REVERSE

The high-voltage constant-current plant lends itself with especial ease to operation, at least in emergency, over a grounded circuit. In some recent plants, e.g. Moutiers-Lyons, See also:

• PROVISION (Lat. provisio)

Inasmuch as transformers can be freely combined vectorially to give resultant electromotive forces having any desired magnitudes and phase relations the passage from two-phase to three-phase, and back again, is made with the utmost ease, and the character of the generating and receiving apparatus thus becomes almost a matter of indifference. As regards such apparatus it is safe to say that honours are about even: some-times one system proves more convenient, sometimes the other. The difficulty of obtaining proper single-phase motors for the varied purposes of general distribution has so far prevented any material use of single-phase transmission systems. Generators for Power Transmission.—The generators are usually large two- or three-phase machines, and in the majority of instances they are driven by water-wheels. Power transmission on a large scale from steam plant has, up to the present, made no substantial progress, save as the networks of large electrical supply stations have in some cases grown to See also:

• COVER (from the Fr. convert, from couvrir, to cover, Lat. cooperire)

Low-voltage machines are usually provided with polyodontal windings, these windings having several separate armature teeth per See also:

• POLE (FAMILY)
• POLE, REGINALD (1500-1558)
• POLE, RICHARD DE LA (d. 1525)
• POLE, WILLIAM (1814—1900)

American practice is based largely upon 6o cycles per second, which is probably as high a frequency as can be advantageously employed. Indeed, even this leads to some embarrassment in securing good motors of moderate rotative speed, and the tendency of the frequency is rather downward than upward. An inferior limit is set by the general desirability of operating incandescent lamps off the trans-mission circuits. For this purpose the frequency should be held above 30 cycles per second ; below this point, flickering of the lamps becomes progressively more serious, especially with lamps having the very slender metallic filaments now commonly employed—so serious, indeed, as practically to prohibit their successful use—and plants installed for such low frequencies are generally confined to motor practice, or to the use of synchronous converters, which are somewhat easier to build in large units at low than at high periodicities. Occasional plants for railway and heavy motor service operate at'as low as 15 –, and more at 25 –. Nearly all the general work of power transmission, however, is carried on between 30 and 6o –. The inferior limit at which it is possible successfully to operate alternating arc lamps is about 40 is ; and if these are to be an important feature in transmission systems the indications are that practice will tend towards a periodicity above 40 –, at which all the See also:

• ACCESSORY

The inferior limit is usually set by the undesirability of too large an investment in copper, and lines are usually laid out from the standpoint of regulation rather than from any other. In ordinary practice it seldom proves advantageous to allow more than 15% loss in the line even under extreme conditions, and the cases are few in which less than 5 % loss is advisable. These few cases comprise those in which the demand for power notably over-runs the supply as limited by the maximum power available at the generating station, and also the few cases in which a loss greater than 5 % would indicate the use of a line wire too small from a mechanical standpoint. It is not advisable to attempt to construct long lines of wire smaller than No. 2 American wire-See also:

• GAUGE, or GAGE (Med. Lat. gauja, jaugia, Fr. jauge, perhaps connected with Fr. jale, a bowl, galon, gallon)

For very long spans, however, See also:

• BRONZE

The poles were little larger than those used in telegraph lines, a favourite size being a 4o-ft. pole about 8 in. in diameter at the top and 15 in. at the butt, set 6 to 7 ft. in the See also:

• EARTH
• EARTH (a word common to Teutonic languages, cf. Ger. Erde, Dutch aarde, Swed. and Dan. jord; outside Teutonic it appears only in the Gr. 'pq'e, on the ground; it has been connected by some etymologists with the Aryan root ar-, to plough, which is seen in
• EARTH, FIGURE OF
• EARTH, FIGURE OF THE

Under ordinary conditions these strains are balanced and come into See also:

• PLAY

At times sleet may accumulate on See also:

• BARE

For line voltages above 60,000 to 70,000 it is apparent that the insulating factor of safety would be seriously reduced, and some recent lines have been equipped with suspension insulators. These are in effect porcelain bells from to in. diameter upward strung together like a See also:

• STRING

It is regarded as the See also:

• STANDARD
• STANDARD, BATTLE OF THE

In point of fact, those who have had the most experience with long distance transmission are the last to worry about the difficulties of using alternating current. Some unusual phenomena turn up in high voltage work, but they are rather interesting than alarming. The lines become self-luminous from " coronal " discharge at a little above 20,000 volts, and at 40,000 or 50,000 volts the phenomenon, which is sometimes aggravated by resonance, becomes of a striking, not to say startling, character. At above" 100,000 volts this coronal discharge must be given serious consideration. Resonance, in substance, is due to synchronism of the periodic electromotive force, or a See also:

• HARMONIC

Since, other things being equal, the rise in electromotive force due to resonance is directly proportional to the magnitude of the harmonics, and the See also:

• CHANCE (through the O. Fr. cheance, from the Late Lat. cadentia, things happening, from cadere, to fall out, happen; cf. " case ")

In point of fact, it is altogether probable that resonance due to the distributed capacity and inductance of the overhead line alone is of rare occurrence and generally of trivial amount, while it is equally probable that resonance due to localized capacity and inductance other than that of the line conductors may, and often does, cause very serious disturbances upon the system. The subject has never been adequately investigated, but the tendency towards formidable sparking and arcing at various points on long-distance transmission systems is generally far greater than can be accounted for by consideration of the nominal voltages alone. The conditions may be still further complicated by the effect of earths or open circuits, which sometimes may produce, temporarily, appalling resonance phenomena, through bringing into action the capacity and inductance of the apparatus and introducing surges. In ordinary working the resonance of the harmonics is not very conspicuous, and the fact that it occurs not systematically, but only in special ways and under special conditions, indicates more strongly than anything else that the vital point is not the time-constant of the line alone, but those of the apparatus connected thereto. A definite and persistent tendency towards resonance may sometimes be effectively checked by the introduction of suitable inductance in the parts of the system most seriously affected, but the best general policy is to avoid as far as possible the presence of the higher harmonics, which are the chief sources of danger. Closely allied to and connected with resonance is the phenomenon known as " surging," which is due to the discharge of the electromagnetic energy stored in a circuit containing inductance and capacity when that circuit is broken. This discharge is an oscillatory one, going on with decreasing amplitude until it is frittered away by resistance and other sources of loss. Its frequency is that of the system affected, and the See also:

• SURGE

Such disturbances when trivial are commonly referred to as " static." Surging, depending as it does on the current ruptured, may, and indeed often does, give particularly formidable effects on circuits of moderate voltage, while on high voltage transmission circuits the usually moderate current and the large margin of safety in the insulation are important ameliorating influences. Maintenance.—Transmission lines are, when practicable, laid out through open See also:

• COUNTRY (from the Mid. Eng. contre or contrie, and O. Fr. cuntree; Late Lat. contrata, showing the derivation from contra, opposite, over against, thus the tract of land which fronts the sight, cf. Ger. Gegend, neighbourhood)

There is no complete See also:

• PROTECTION

The general rule to be followed is that the separate units shall be of such size that one of them may be dispensed with without serious inconvenience. In the case of transformers, the unit in two- or three-phase working is the bank of transformers, which must be used together. In See also:

• CONTINENTAL

In the transmission circuits them-selves the wires are, in practice, never large enough to produce any sensible difference in conductivity for continuous and for alternating currents. In the heavy See also:

• OMNIBUS (Lat. " for all ")

Synchronous rectifiers changing the alternating current into a unidirectional current, suit-able for use with arc See also:

• LIGHTS, CEREMONIAL USE OF

Such a modification of the conditions sometimes takes place much more quickly than would be anticipated at first sight, so that when very long distance trans-See also:

• MISSIONS (Lat. missio, a sending)