See also:

• DYNAMOMETER (Gr. Suva u , strength, and OTpov, a measure)

DYNAMOMETER (Gr. Suva u , strength, and OTpov, a measure)  , an See also:

• INSTRUMENT (Lat. instrumentum, from insincere, to build up, furnish, arrange, prepare)

instrument for measuring force exerted by men, animals and See also:

• MACHINES

machines . The name has been applied generally to all kinds of See also:

• INSTRUMENTS

instruments used in the measurement of a force, as for example electric dynamometers, but the See also:

• TERM

term specially denotes apparatus used in connexion with the measurement of See also:

• WORK

work, or in the measurement of the See also:

• HORSE (a word common to Teutonic languages in such forms as hors, hros, ros; cf. the Ger. ross)

horse-See also:

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

power of engines and See also:

• MOTORS, ELECTRIC

motors . If P represent the See also:

• AVERAGE

average value of the component of a force in the direction of the displacement, s, of its point of application, the product Ps See also:

• MEASURES

measures the work done during the displacement . When the force acts on a See also:

• BODY

body See also:

• FREE

free to turn about a fixed See also:

• AXIS (Lat. for " axle ")

axis only, it is convenient to See also:

• EXPRESS (through the French from the past participle of the Lat. exprimere, to press out, by transference used of representing objects in painting or sculpture, or of thoughts, &c. in words)

express the work done by the trans-formed product TO, where T is the average turning moment or See also:

• TORQUE, or TORO (Lat. torquis, torques, a twisted collar, torquere, to twist)

torque acting to produce the displacement 0 radians . The apparatus used to measure P or T is the See also:

• DYNAMOMETER (Gr. Suva u , strength, and OTpov, a measure)

dynamometer . The factors s or B are observed independently . Apparatus is added to some dynamometers by means of which a See also:

• CURVE (Lat. curvus, bent)

curve showing the See also:

• VARIATIONS
• VARIATIONS, CALCULUS
• VARIATIONS, CALCULUS OF

variations of P on a distance See also:

• BASE

base is See also:

• DRAWN

drawn automatically, the See also:

• AREA

area of the See also:

• DIAGRAM

diagram representing the work done; with others, integrating apparatus is combined, from which the work done during a given See also:

• INTERVAL

interval may be read off directly . It is convenient .to distinguish between absorption and transmission dynamometers . In the first See also:

• KIND (O. E. ge-cynde, from the same root as is seen in " kin," supra)

kind the work done is converted into 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.)

heat; in the second it is transmitted, after measurement, for use . Absorption Dynamometers.—See also:

• BARON
• BARON (1835-1895)
• BARON, MICHEL (1653—1729)

Baron See also:

• PRONY, GASPARD CLAIR FRANCOIS MARIE RICHE DE (1755-1839)

Prony's dynamometer (See also:

• ANN

Ann . Chim . Phys .

1821, vol . 19), which has been modified in various ways, consists in its See also:

• ORIGINAL

original See also:

• FORM (Lat. forma)

form of two symmetrically shaped See also:

• TIMBER

timber beams clamped to the See also:

• ENGINE
• ENGINE (Lat. ingenium)

engine-See also:

• SHAFT
• SHAFT (O. Eng., sceaft, from scafan, to shave; the word is common to Teutonic languages)

shaft . When these are held from turning, their frictional resistance may be adjusted by means of nuts on. the screwed bolts which hold them together until the shaft revolves at a given See also:

• SPEED, JOHN (1552–1629)

speed . To promote smoothness of See also:

• ACTION

action, the rubbing surfaces are lubricated . A See also:

• WEIGHT

weight is moved along the See also:

• ARM (a common Teutonic word; the Indo-European root is ar, to join or fit; cf. the Lat. armus, shoulder, and the plural word arma, weapons, Gr. apphs, joint, and the reduplicated apapilKSV, to join)

arm of one of the beams until it just keeps the See also:

• BRAKE

brake steady midway between the stops which must be provided to hold it when the weight fails. to do so . The See also:

• GENERAL
• GENERAL (Lat. generalis, of or relating to a genus, kind or class)

general theory of this kind of brake is as follos:—Let F be the whole frictional resistance, r the See also:

• COMMON

common See also:

• RADIUS

radius of the rubbing surfaces, W the force which holds the brake from turning and whose See also:

• LINE

line of action is at a perpendicular distance R from the axis of the shaft, N the revolutions of the shaft per See also:

• MINUTE
• MINUTE (Lat. minutes, small; minuere, to make less)

minute, w its angular velocity in radians per second; then, assuming that the adjustments are made so that the engine runs steadily at a See also:

• UNIFORM

uniform speed, and that the brake is held still, clear of the stops and without oscillation, by W, the torque T exerted by the engine is equal to the frictional torque Fr acting at the brake surfaces, and this is measured by the statical moment of the weight W about the axis of revolution; that is T=Fr=WR .. Hence WR measures the torque T . If more than one force be applied to hold the brake from turning, Fr. and therefore T, are measured by the algebraical sum of their individual moments with respect to the axis . If the brake is not balanced, its moment about the axis must be included . Therefore, quite generally, The torque T at any instant of steady See also:

• RUNNING

running is therefore {WR =WIRi1 . See also:

• LORD
• LORD (O. Eng. hldford, i.e. hldfweard, the warder or keeper of bread, hlIf, loaf; the word is not represented in any other Teutonic language)
• LORD, JOHN (1810-1894)

Lord See also:

• KELVIN, WILLIAM THOMSON, BARON (1824-1907)

Kelvin patented a brake in 1858 (fig . 2) consisting of a rope or See also:

• CORD (derived through the Fr. corde, from the Lat. chorda, Gr. xop(5rt, the string of a musical instrument)

cord wrapped See also:

• ROUND (O. Fr. rond, Lat. rotundus, the Fr. is the source also of Du. rond; Ger., Swed., Dan. and Nor. rond)

round the circumference of a rotating See also:

• WHEEL (0. Eng. hweol, hweohl, &c., cognate with Icel. hjol, Dan. hiul, the Indo-European root is seen in Sanskrit chakra, Gr. r in Aos, circle, whence " cycle ")
• WHEEL, BREAKING ON THE

wheel, to one end of which is applied a regulated force, the other end being fixed to a See also:

• SPRING (from " to spring," " to leap or jump up," " burst out," O. Eng., springau, a common Teut. word, cf. Ger. springer, possibly allied to Gr. QnrFpxecOac, to move rapidly)

spring See also:

• BALANCE (derived through the Fr. from the Late Lat. bilantia, an apparatus for weighing, from bi, two, and lanx, a dish or scale)

balance .

The See also:

• ROPES, JOHN CODMAN (1836–1899)

ropes are spaced laterally by the blocks B, B, B, B, which also serve to prevent them from slip-ping sideways . When the wheel is turning in the direction indicated, the forces holding the See also:

• BAND

band still are W, and p, the observed pull on the spring balance . Both these forces usually See also:

• ACT (Lat. actus, actum)

act at the same radius R, the distance from the axis to the centre line of the rope, in which See also:

• CASE
• CASE, JOHN (d. 1600)

case the torque T is w (W–p)R, and consequently the brake horse-power is (W–p)RX2erN . When 33,000 FIG . 1 . changes the weight W rises or falls against the action of the spring balance until a See also:

• STABLE

stable See also:

• CONDITION (Lat. condicio, from condicere, to agree upon, arrange; not connected with conditio, from condere, conditum, to put together)

condition of running is obtained . The ratio p is given by e°, where e =2.718; p is the coefficient of See also:

• FRICTION (from Lat. fricare, to rub)

friction and 0 the See also:

• ANGLE (from the Lat. angulus, a corner, a diminutive, of which the primitive form, angus, does not occur in Latin; cognate are the Lat. angere, to compress into a bend or to strangle, and the Gr. ayKOS, a bend; both connected with the Aryan root ank-, to

angle, measured in radians, subtended by the arc of contact between the rope and the wheel . In fig . 2 B=2ir . The ratio W/p increases very rapidly as 0 is increased, and therefore, by making 6 sufficiently large, p may conveniently be made a small fraction of W, thereby rendering errors of observation of the spring balance negligible . Thus this kind of brake, though cheap to make, is, when 0 is large enough, an exceedingly accurate measuring instrument, readily applied and easily controlled . It has come into very general use in See also:

• RECENT

recent years, and has practically superseded the older forms of See also:

• BLOCK
• BLOCK (from the Fr. bloc, and possibly connected with an Old Ger. Block, obstruction, cf. " baulk ")
• BLOCK, MAURICE (1816–19or)

block brakes .

It is sometimes necessary to use See also:

• WATER

water to keep the brake wheel cool . Engines specially designed for testing are usually provided with a brake wheel having a trough-shaped rim . Water trickles continuously into the trough, and the centrifugal action holds it as an inside lining against the rim, where it slowly evaporates . Fig . 3 shows a band-brake invented by See also:

• PROFESSOR (the Latin noun formed from the verb profiteri, to declare publicly, to acknowledge, profess)

Professor 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)

James See also:

• THOMSON, JAMES (1822-1892)
• THOMSON, JAMES (1834-1882)
• THOMSON, JAMES (r700-1748)
• THOMSON, JOHN (1778-184o)
• THOMSON, JOSEPH (1858-1895)
• THOMSON, SIR CHARLES WYVILLE (1830-1882)
• THOMSON, THOMAS (1773-1852)
• THOMSON, WILLIAM (1819-189o)

Thomson, suitable for testing motors exerting a See also:

• CONSTANT, BENJAMIN (1845-1902)

constant torque (see See also:

• ENGINEERING

Engineering, 2znd See also:

• OCTOBER

October 1880) . To maintain eµ° constant, See also:

• COMPENSATION (from Lat. compensare, to weigh one thing against another)

compensation for variation of p is made by inversely varying B . A and B are fast and loose pulleys, and the brake band is placed partly over the one and partly over the other . Weights W and w are adjusted to the torque . The band turns with the fast See also:

• PULLEY

pulley if µ increase, thereby slightly turning the loose pulley, otherwise at See also:

• REST (O. Eng. rest, reste, bed, cognate with other Teutonic forms, e.g. Ger. Rast, Riiste, rest, and probably Gothic Rasta, league, i.e. resting or stopping place)

rest, until 6 is adjusted to the new value of A . This form of brake was also invented independently by J . A . M .

L . Carpentier, and the principle has been used in the Raffard brake . A self-compensating brake of another kind, by See also:

• MARCEL, ETIENNE (d: 1358)

Marcel Deprez, was described with Carpentier's in 188o (Bulletin de la societe d'encouragement, See also:

• PARIS
• PARIS (also called ALEXANDROS)
• PARIS, ALEXIS PAULIN (1800-x881)
• PARIS, BRUNO PAULIN GASTON (1839-1903)
• PARIS, FRANCOIS DE (169o-1727)
• PARIS, LOUIS PHILIPPE ALBERT
• PARIS, TREATIES OF (1814-1815)

Paris) . W . E . See also:

• AYRTON, WILLIAM EDWARD (1847-1908)

Ayrton and J . See also:

• PERRY
• PERRY (from Fr. Moire, from poire, a pear)
• PERRY, MATTHEW CALBRAITH (1794–1858)
• PERRY, OLIVER HAZARD (1785-1819)

Perry used a band or rope brake in which compensation is effected by the pulley See also:

• DRAWING

drawing in or letting out a See also:

• PART

part of the band or rope which has been roughened or in which a See also:

• KNOT
• KNOT (O.E. cnotta, from a Teutonic stem knutt; cf. " knit," and Ger. knoten)

knot has been tied . In an effective water-brake invented by W . See also:

• FROUDE, JAMES ANTHONY (1818-1894)

Froude (see Proc . Inst . M . E .

1877), two similar castings, A and B, each consisting . (I) T=MR (2) The See also:

• FACTOR (from Lat. facere, to make or do)

factor 0 of the product TO is found by means of a revolution See also:

• COUNTER

counter . The power of a motor is measured by the See also:

• RATE

rate at which it See also:

• WORKS

works, and this is expressed by TT6oN in See also:

• FOOT

foot-pounds per second . 33 000 or in horse-power See also:

• UNITS, DIMENSIONS OF
• UNITS, PHYSICAL

units . The latter is commonly referred to as the " brake horse-power." The See also:

• MAINTENANCE (Fr. maintenance, from maintenir, to maintain, support, Lat. manu tenere, to hold in the hand)

maintenance of the conditions of steadiness implied in See also:

• EQUATION (from Lat. aequatio, aequare, to equalize)

equation (1) depends upon the constancy of F, and therefore of the coefficient of frictionµ between the rubbing surfaces . The See also:

• HEATING

heating at the surfaces, the variations in their smoothness, and the variations of the See also:

• LUBRICATION

lubrication make i continuously variable, and necessitate frequent See also:

• ADJUSTMENT (from late Lat. ad juxtare, derived from juxta, near, but early confounded with a supposed derivation from justus, right)

adjustment of W or of the nuts . J . V . See also:

• PONCELET, JEAN VICTOR (1788-1867)

Poncelet (1788–1867) invented a form of Prony brake which automatically adjusted its grip asµ changed, thereby maintaining F constant . The principle of the compensating brake devised by J . G . Appold (1800–1865) is shown in fig .

1 . A flexible See also:

• STEEL, FLORA ANNIE (1847– )

steel band, lined with See also:

• WOOD, ANTHONY A2 (1632-1695)
• WOOD, JOHN GEORGE (1827—1889)
• WOOD, MRS HENRY [ELLEN] (1814—1887)
• WOOD, SEARLES VALENTINE (1798—188o)

wood blocks, is gripped on the motor See also:

• FLY (formed on the root of the supposed original Tent. fleugan, to fly)

fly-wheel or pulley by a See also:

• SCREW (O.E. scrue, from O. Fr. escroue, mod. ecrou; ultimate origin uncertain; the word, or a similar one, appears in Teutonic languages, cf. Ger. Schraube, Dan. skrue, but Skeat, following Diaz, finds the origin in Lat. scrobs, a ditch, hole, particularl

screw A, which, together with W, is adjusted to hold the brake steady . Compensation is effected by the See also:

• LEVER (through O. Fr. leveour, levere, mod. levier, from Lat. levare, to lift, raise)
• LEVER, CHARLES JAMES (1806-1872)

lever L inserted at B . This has a slotted end, engaged by a See also:

• PIN (a doublet with " pen " from Lat. pinna, feather, pinnacle, which is said to contain the same root as irirvs, pine tree, and properly to mean a sharp point or end)

pin P fixed to the framing, and it will be seen that its action is to slacken the band if the load tends to rise and to tighten it in the contrary case . The See also:

• EXTERNAL

external forces holding the brake from turning are W, distant R from the axis, and the re-action, WI say, of the lever against the fixed pin P, distant RI from the axis . The moment of WI may be See also:

• POSITIVE (or PORTABLE) ORGAN

positive or negative . of a See also:

• BOSS

boss and circumferential See also:

• ANNULAR, ANNULATE

annular channel, are placed See also:

• FACE (from Lat. fades, derived either from facere, to make, or from a root fa-, meaning " appear "; cf. Gr. cbatvstv)

face to face on a shaft, to which B is keyed, A being free (fig . 4) . A See also:

• RING (O.E. hring; a word common to Teutonic languages; and probably cognate with the Lat. circus, Gr. KtpKOS or KpLKOS, Skt'. chakra, wheel, circle, cf. also " harangue "); in art, a band of circular shape of varying sizes, made of any material and used f

ring See also:

• TUBE (Lat. tuba)

tube of elliptical See also:

• SECTION
• SECTION (Lat. sectio, cutting, secare, to cut)

section is thus formed . Each channel is divided into a See also:

• SERIES (a Latin word from serere, to join)

series of pockets by equally spaced vanes inclined at 45° . When A is held still, and B rotated, centrifugal action sets up vortex currents in the water in the pockets; thus a continuous circulation is caused between B and A, and the consequent changes of momentum give rise to oblique reactions . The moments of the components of these actions and reactions in a See also:

• PLANE

plane to which the axis of rotation is at right angles are the two aspects of the torque acting, and therefore the torque acting on B through the shaft is measured by the torque required to hold A still .

Froude constructed a brake to take up 2000 H.P. at 90 revs. per See also:

• MIN

min. by duplicating this apparatus . This replaced the propeller of the See also:

• SHIP

ship whose engines were to be tested, and the See also:

• OUTER

outer casing was held from turning by a suitable arrangement of levers carried to weighing apparatus conveniently disposed on the See also:

• WHARF

wharf . The torque corresponding to 2000 H.P. at 90 revs. per min. is 116,772 foot-pounds, and a brake 5 ft. in See also:

• DIAMETER (from the Cr. &a, through, µErpov, measure)

diameter gave this resistance . Thin See also:

• METAL
• METAL (through Fr. from Lat. metallum, mine, quarry, adapted from Gr. µATaXAov, in the same sense, probably connected with ,ueraAAdv, to search after, explore, µeTa, after, aAAos, other)

metal sluices were arranged to slide between the wheel and casing, and by their means the range of action could be varied from 300 H.P. at 12o revs. per min. to the maximum . Professor See also:

• OSBORNE

Osborne See also:

• REYNOLDS, JOHN FULTON (182o-1863)
• REYNOLDS, SIR JOSHUA (1723-1792)
• REYNOLDS, WALTER (d. 1327)

Reynolds in 1887 patented a water-brake (see Proc . Inst . C.E . 99, p . 167), using Froude's See also:

• TURBINE (Lat. turbo, a whirlwind, a whirling motion ,or object, a top)

turbine to obtain the highly resisting See also:

• SPIRAL

spiral vortices, and arranging passages in the casing for the entry of water at the hub of the wheel and its exit at the circumference . Water enters at E (fig . 5), and finds its way into the interior of the wheel, A, See also:

• DRIVING (from " to drive," i.e. generally to propel, force along or in, a word common in various forms to the Teutonic languages)

driving the See also:

• AIR (from an Indo-European root meaning " breathe," " blow ")
• AIR, or ASBEN

air in front of it through the air-passages K, K . Theta following into the pocketed See also:

• CHAMBERS (the Fr. chambre, from Lat. camera, a room)
• CHAMBERS, EPHRAIM (d. 1740)
• CHAMBERS, GEORGE (1803-1840)
• CHAMBERS, ROBERT (18oz-1871)
• CHAMBERS, SIR WILLIAM (1726-1796)

chambers Vi, V2, it is caught into the vortex, and finally escapes at the circumference, flowing away at F .

The air-ways k, k, in the fixed vanes establish communication between the cores of the vortices and the See also:

• ATMOSPHERE (Gr. fir µ6r, vapour; orkaipa, a sphere)

atmosphere . From k to 30 H.P. may be measured at See also:

• LOO (formerly called " Lanterloo," Fr. lanturlu, the refrain of a popular 17th-century song)

loo revs. per min. by a brake-wheel of this kind 18 in. in diameter . For other speeds the power varies as the See also:

• CUBE (Gr. K46os, a cube)

cube of the speed . The casing is held from turning by weights See also:

• HANGING

hanging on an attached arm . The cocks regu- lating the water are connected to the casing, so that any tilting automatically regulates the flow, and therefore the thickness of the film in the vortex . In this way the brake may be arranged to maintain a constant torque, notwithstanding variation of the speed . In G . I . Alden's brake (see Trans . Amer . See also:

• SOC

Soc . Eng. vol. xi.) the resistance is obtained by turning a 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)

cast See also:

• IRON [symbol Fe, atomic weight 55.85 (0=16)]

iron disk against the frictional resistance of two thin See also:

• COPPER (symbol Cu, atomic weight 63.1, H=1, or 63.6, O = 16)

copper plates, which are held in a casing free to turn upon the shaft, and are so arranged that the pressure between the rubbing surfaces is controlled, and the heat See also:

• DEVELOPED

developed by friction carried away, by the regulated flow of water through the casing .

The torque required to hold the casing still against the action of the disk measures the torque exerted by the shaft to which the disk is keyed . Transmission Dynamometers.—The essential part of many trans-See also:

• MISSION

mission dynamometers is a spring whose deformation indirectly measures the magnitude of the force transmitted through it . For many kinds of spring the See also:

• CHANGE (derived through the Fr. from the Late Lat. cambium, cambiare, to barter; the ultimate derivation is probably from the root which appears in the Gr. «a urmu', to bend)

change of form is practically proportional to the force, but the relation should always be determined experimentally . General A . J . See also:

• MORIN, JEAN (latinized JOANNES MORINUS) (1591-1659)

Morin (see See also:

• NOTICE

Notice sur See also:

• DIVERS

divers appareils dynamometriques, Paris, 1841), in his classical experiments on See also:

• TRACTION (Lat. trahere, to draw)

traction, arranged his appar- atus so that the change in form of the spring was continuously recorded on a See also:

• SHEET

sheet of See also:

• PAPER
• PAPER (Fr. papier, from Lat. papyrus)

paper drawn under a See also:

• STYLE
• STYLE (from Gr. a-6'1ms, a column; a different word from that used in literature, see below)

style . For longer experiments he used a " Compteur " or See also:

• MECHANICAL

mechanical integrator, suggested by J . V . Poncelet; from which the work done during a given displacement could be read off directly . This See also:

• DEVICE

device consists of a See also:

• ROLLER

roller of radius r, pressed into contact with a disk . The two are carried on a common See also:

• FRAME

frame, so arranged that a change in form of the spring causes a relative displacement of the disk and roller, the point of contact moving radially from or towards the centre of the disk . The radial distance x is at any instant proportional to the force acting through the spring .

The angular displacement, 0, of the disk is made proportional to the displacement, s, of the point of application of the force by suitable driving See also:

• GEAR (connected with " garb," properly elegance, fashion, especially of dress, and with " gar," to cause to do, only found in Scottish and northern dialects; the root of the word is seen in the Old Tent. garwjan, to make ready)

gear . If d4 is the angular displacement of the roller corresponding to displacements, do of the disk, and ds of the point of application of P, a, and C constants, then d~=xr=QPds=C.Pds, and therefore =C fg12Pds; that is, the ri) angular displacement of the roller measures the work done during the displacement from s, to s2 . The shaft carrying the roller is connected to a counter so that may be observed . The angular velocity of the shaft is proportional to the rate of working . Morin's dynamometer is shown in fig . 6 . The transmitting spring is made up of two See also:

• FLAT (a modification of O. Eng. flet, an obsolete word of Teutonic origin, meaning the ground beneath the feet)

flat bars linked at their ends . Their centres sl, s2, are held respectively by the pieces A, B, which together form a sliding pair . The block A carries the disk D, B carries the roller R and counting gear . The pulley E is driven from an See also:

• AXLE (in Mid. Eng. axel-tre, from O. Norweg. oxull-tre, cognate with the O. Eng. exe or eaxe, and connected with Sansk. dksha, Gr. a wv, and Lat. axis)

axle of the See also:

• CARRIAGE

carriage . In a dynamometer used by F . W .

See also:

• WEBB, MATTHEW (1848-1883)
• WEBB, SIDNEY (1859– )

Webb to measure the tractive resistance of trains on the See also:

• LONDON

London & See also:

• NORTH
• NORTH, BARONS
• NORTH, MARIANNE (1830—1890)
• NORTH, ROGER (1653-1734)
• NORTH, SIR THOMAS (1535?-16o1?)

North-Western railway, a tractive pull or push compresses two spiral springs by a definite amount, which is recorded to See also:

• SCALE
• SCALE (1) A

scale by a See also:

• PENCIL (Lat. penicillus, brush, literally little tail)

pencil on a sheet of paper, drawn continuously from a storage See also:

• DRUM (early forms drome or dromme, a word common to many Teut. languages, cf. Dan. tromme, Ger. Trommel: the word is ultimately the same as " trumpet," and is probably onomatopoeic in origin; it appears late in Eng. about the middle of the 16th century)

drum at the rate of 3 in. per mile, by a roller driven from one of the carriage axles . Thus the diagram shows the tractive force at any instant . A second pencil electrically connected to a See also:

• CLOCK

clock traces a 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

time line on the diagram with a kick at every See also:

• THIRTY

thirty seconds . A third pencil traces an observation line in which a kick can be made at will by pressing any one of the See also:

• ELECTRICAL
• ELECTRICAL (or ELECTROSTATIC) MACHINE

electrical pushes placed about the See also:

• CAR (Late Lat. carra)

car, and a See also:

• FOURTH

fourth draws a datum line . The spring of the dynamometer car used by W . See also:

• DEAN (Lat. decanus, derived from the Gr. 8eaa, ten)
• DEAN, FOREST OF

Dean on the See also:

• GREAT

Great Western railway is made up of thirty flat plates, 7 ft . 6 in. See also:

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

long, 5 in . X fin. at the centre, spaced by distance pieces nibbed into the plates at the centre and by rollers at the ends . The draw-See also:

• BAR
• BAR (0. Fr. barre, Late Lat. barra, origin unknown)
• BAR, CONFEDERATION OF
• BAR, FRANCOIS DE (1538-1606)
• BAR, THE

bar is connected to the See also:

• BUCKLE, HENRY THOMAS (1821–1862)

buckle, which is carried on rollers, the ends of the spring resting on plates fixed to the under-frame . The gear operating the paper See also:

• ROLL (O. Fr. rolle, roulle, mod. role, Lat. rotulus, dim. of rota, wheel)
• ROLL, ALFRED PHILIPPE (1846– )

roll is driven from the axle of an See also:

• INDEPENDENT

independent wheel which is let down into contact with the, See also:

• RAIL

rail when required . This wheel serves also to measure the distance travelled . A Morin disk and, roller integrator is connected with the apparatus, so that the work done during a See also:

• JOURNEY (through O. Fr. jornee or journee, mod. Fr. journee, from med. Lat. diurnata, Lat. diurnus, of or belonging to dies, day)

journey may be read off .

Five lines are traced on the diagram . In spring dynamometers designed to measure a transmitted torque, the mechanical problem of ascertaining the change of form of the spring is complicated by the fact that the spring and the whole apparatus are rotating together . In the Ayrton and Perry transmission dynamometer or spring coupling of this type, the relative angular displacement is proportional to the radius of the circle described by the end of a See also:

• LIGHT

light lever operated by mechanism between the spring-connected parts . By a device used by W . E . Dalby (Prot . Inst.C.E . 1897–1898, p . 132) the change in form of the spring is shown on a fixed See also:

• INDICATOR (from Lat. indicare, to point out)

indicator, which may be placed in any convenient position . Two equal sprocket wheels Qi,Q2, are fastened, the one to the spring pulley, the other to the shaft . An endless band is placed over them to form two loops, which during rotation remain at the same distance apart, unless relative angular displacement occurs between Qi and Q2 (fig . 7) due to a change in form of the spring .

The change in the distance d is proportional to the change in the torque transmitted from the shaft to the pulley . To measure this, See also:

• GUIDE (in Mid. Eng. gyde, from the Fr. guide; the earlier French form was guie, English " guy," the d was due to the Italian form guida; the ultimate origin is probably Teutonic, the word being connected with the base seen in O. Eng. witan, to know)

guide pulleys are placed in the loops guided by a geometric slide, the one pulley carrying a scale, and the other an See also:

• INDEX

index . A recording drum or integrating apparatus may be arranged on the pulley frames . A See also:

• QUICK

quick variation, or a periodic variation of the magnitude of the force or torque transmitted through the springs, tends to set up oscillations, and this tendency increases the nearer the periodic time of the force variation approaches a periodic time of the spring . Such vibrations may be damped out to a considerable extent by the use of a• dash-pot, or may be practically prevented by using a relatively stiff spring . Every part of a See also:

• MACHINE
• MACHINE (through Fr. from Lat. form machina of Gr. µnxavil)

machine transmitting force suffers elastic deformation, and the force may be measured indirectly by measuring the deformation . The relation between the two should in all cases be found experimentally . G . A . Hirn (see See also:

• LES

Les Pandynamometres, Paris, 1876) employed this principle to measure the torque transmitted by a shaft . Signor Rosio used a telephonic method to effect the same end, and mechanical, See also:

• OPTICAL

optical and telephonic devices have been utilized by the Rev . F .

J . Jervis-See also:

• SMITH
• SMITH, ADAM (1723–1790)
• SMITH, ALEXANDER (183o-1867)
• SMITH, ANDREW JACKSON (1815-1897)
• SMITH, CHARLES EMORY (1842–1908)
• SMITH, CHARLES FERGUSON (1807–1862)
• SMITH, CHARLOTTE (1749-1806)
• SMITH, COLVIN (1795—1875)
• SMITH, EDMUND KIRBY (1824-1893)
• SMITH, G
• SMITH, GEORGE (1789-1846)
• SMITH, GEORGE (184o-1876)
• SMITH, GEORGE ADAM (1856- )
• SMITH, GERRIT (1797–1874)
• SMITH, GOLDWIN (1823-191o)
• SMITH, HENRY BOYNTON (1815-1877)
• SMITH, HENRY JOHN STEPHEN (1826-1883)
• SMITH, HENRY PRESERVED (1847– )
• SMITH, JAMES (1775–1839)
• SMITH, JOHN (1579-1631)
• SMITH, JOHN RAPHAEL (1752–1812)
• SMITH, JOSEPH, JR
• SMITH, MORGAN LEWIS (1822–1874)
• SMITH, RICHARD BAIRD (1818-1861)
• SMITH, ROBERT (1689-1768)
• SMITH, SIR HENRY GEORGE WAKELYN
• SMITH, SIR THOMAS (1513-1577)
• SMITH, SIR WILLIAM (1813-1893)
• SMITH, SIR WILLIAM SIDNEY (1764-1840)
• SMITH, SYDNEY (1771-1845)
• SMITH, THOMAS SOUTHWOOD (1788-1861)
• SMITH, WILLIAM (1769-1839)
• SMITH, WILLIAM (c. 1730-1819)
• SMITH, WILLIAM (fl. 1596)
• SMITH, WILLIAM FARRAR (1824—1903)
• SMITH, WILLIAM HENRY (1808—1872)
• SMITH, WILLIAM HENRY (1825—1891)
• SMITH, WILLIAM ROBERTSON (1846-'894)

Smith . (See Phil . Mag . See also:

• FEBRUARY

February 1898.) H . Frahm,' during an important investigation on the torsional vibration of propeller shafts, measured the relative angular displacement of two flanges on a propeller shaft, selected as far apart as possible, by means of an electrical device (Engineering, 6th of February 1903) . These measurements were utilized in See also:

• COMBINATION (Lat. combinare, to combine)

combination with appropriate elastic coefficients of the material to find the horse-power transmitted from the engines along the shaft to the propeller . In this way the effective horse-power and also the mechanical efficiency of a number of large marine engines, each of several thousand horse-power, have been determined . When a See also:

• BELT (a word common to Teutonic languages, the Old Ger. form being bale, from which the Lat. balteus probably derived)
• BELT, THOMAS (1832-1878)

belt, in which the maximum and minimum tensions are respectively P and p lb, drives a pulley, the torque exerted is (P–p)r lb ft., r being the radius-of the-pulley plus See also:

• HALF

half the thickness of the belt . 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 . In W . Froude's belt dynamometer (see Proc .

Inst.M.E., 1858) (fig . 8) the guide pulleys GI, G2 are carried upon an arm free to turn about the axis O . H is a pulley to guide the approaching and receding parts of the belt to and from the See also:

• BEAM
• BEAM (from the O. Eng. beam, cf. Ger. Baum, a tree, to which sense may be referred the use of " beam " as meaning the rood or crucifix, and the survival in certain names of trees, as horn-beam)

beam in parallel directions . Neglecting friction, the ' H . Frahm, " Neue Untersuchungen fiber See also:

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

die dynamischen Vorgange in den Wellenleitungen von Schiffsmaschinen mit besonderer Berucksichtigung der Resonanzschwingungen," Zeitschrift See also:

• DES

des Vereins deutscher Ingenieure, 31st May 1902 . See also:

• DYSART

DYSART unbalanced torque acting on the beam is r { P– p } lb ft . If a force Q acting at R maintains See also:

• EQUILIBRIUM (from the Lat. aequus, equal, and libra, a balance)

equilibrium, QR/4=(P—p)r=T . Q is supplied by a spring, the extensions of which are recorded on a drum driven proportionally to the angular displacement of the driving pulley; thus a work diagram is obtained . In the Farcot form the guide pulleys are attached to See also:

• SEPARATE

separate weighing levers placed horizontally below the apparatus . In a belt dynamometer built for the See also:

• FRANKLIN
• FRANKLIN, BENJAMIN (1706-1790)
• FRANKLIN, SIR JOHN (1786-1847)
• FRANKLIN, WILLIAM BUEL (1823-1903)

Franklin See also:

• INSTITUTE (from Lat. instituere, to establish or set up)

Institute from the designs of Tatham, the weighing levers are separate and arranged horizontally at the See also:

• TOP (cf. Dan. top, Ger. Topf, also meaning pot)

top of the apparatus . The weighing beam in the Hefner-Alteneck dynamometer is placed transversely to the belt (see Electrotechnischen Zeitschrift, 1881, 7) . The force Q, usually measured by a spring, required to maintain the beam in its central position is proportional to (P—p) .

If the angle 61=B2 = I2o°, Q = (P — p) neglecting friction . When a shaft is driven by means of gearing the driving torque is measured by the product of the resultant pressure P acting between the wheel See also:

• TEETH (O.E. Eel); plural of tooth, O.E. top)

teeth and the radius of the See also:

• PITCH
• PITCH, MUSICAL

pitch circle of the wheel fixed to the shaft . Fig . 9, which has been reproduced from J . See also:

• WHITE
• WHITE, ANDREW DICKSON (1832– )
• WHITE, GILBERT (1720–1793)
• WHITE, HENRY KIRKE (1785-1806)
• WHITE, HUGH LAWSON (1773-1840)
• WHITE, JOSEPH BLANCO (1775-1841)
• WHITE, RICHARD GRANT (1822-1885)
• WHITE, ROBERT (1645-1704)
• WHITE, SIR GEORGE STUART (1835– )
• WHITE, SIR THOMAS (1492-1567)
• WHITE, SIR WILLIAM ARTHUR (1824--1891)
• WHITE, SIR WILLIAM HENRY (1845– )
• WHITE, THOMAS (1628-1698)
• WHITE, THOMAS (c. 1550-1624)

White's A New See also:

• CENTURY (from Lat. centuria, a division of a hundred men)

Century of Inventions (See also:

• MANCHESTER
• MANCHESTER (popularly Manchester-by-the-Sea)
• MANCHESTER, EARLS AND DUKES OF

Manchester, 1822), illustrates possibly the earliest application of this principle to dynamometry . The wheel D, keyed to the shaft overcoming the resistance to be measured, is driven from wheel N by two See also:

• BEVEL (from an O. Fr. word, cf. mod. biveau, a joiner's instrument)

bevel wheels L, L, carried in a loose pulley K . The two shafts, though in a line, are independent . A torque applied to the shaft A can be transmitted to D, neglecting friction, without change only if the central pulley K is held from turning; the torque required to do this is twice the torque transmitted . The torque acting on the See also:

• ARMATURE (from Lat. armatura, armour)

armature of an electric motor is necessarily accompanied by an equal and opposite torque acting on the frame . If, therefore, the motor is mounted on a See also:

• CRADLE (of uncertain etymology, possibly connected with " crate " and " creel," i.e. basket; the derivation from a Celtic word, with a sense of rocking, is scouted by the New English Dictionary)

cradle free to turn -about See also:

• KNIFE (0. E. cuff, a word appearing in different forms in many Teutonic languages, cf. Du. knijf, Ger. Kneif, a shoe-maker's knife, Swed. knif; the ultimate origin is unknown; Skeat finds the origin in the root of " nip," formerly " knip "; Fr. canif is a

knife-edges, the reacting torque is the only torque tending to turn the cradle when it is in a See also:

• VERTICAL (from Lat. vertex, highest point)

vertical position, and may therefore be measured by adjusting weights to hold the cradle in a vertical position . The rate at which the motor is transmitting work is then T2,rn H.P., where n is the revolutions per second of the armature . 550 See James Dredge, Electric See also:

• ILLUMINATION

Illumination, vol. ii .

(London, 1885) ; W . W . See also:

• BEAUMONT
• BEAUMONT, BELMONT, or BELLOMONT
• BEAUMONT, CHRISTOPHE DE (1703-1781)
• BEAUMONT, SIR JOHN (1583–1627)

Beaumont, " Dynamometers and Friction Brakes," Proc . Inst.C.E. vol. xcv . (London, 1889); E . Brauer, " Ober Bremsdynamometer and verwandte Kraftmesser," Zeitschrift des Vereins deutscher Ingenieure (See also:

• BERLIN
• BERLIN, CONGRESS AND TREATY OF
• BERLIN, ISAIAH (1725–1799)

Berlin, 1888); J . J . Flather, Dynamometers and the Measurement of Power (New See also:

• YORK
• YORK (HOUSE OF)
• YORK, EDMUND OF LANGLEY, DUKE OF (1341-1402)
• YORK, EDWARD
• YORK, FREDERICK AUGUSTUS, DUKE OF (1763-1827)
• YORK, RICHARD, DUKE

York, 1893) . (W . E .