507 Mechanical Movements - Brown Part 2 docx

Byarranging three pulleys,side byside, upon theshaft tobedriven, the middle one fast and the other two loose upon it, and using bothan open and acrossed belt, the directionof thesaid sha

1. Illustratesthe transmission ofpower by

simple pulleys and an open belt. In this

case both of the pulleys rotate inthe same

direction

2. Differs from i in the substitutionofa

crossedbelt for theopenone In thiscase

thedirectionofrotationof the pulleys is

re-versed

Byarranging three pulleys,side byside,

upon theshaft tobedriven, the middle one

fast and the other two loose upon it, and

using bothan open and acrossed belt, the

directionof thesaid shaft isenabled tobe

reversed without stoppingorreversing the

driver One belt will always run on the

fastpulley,andtheotheron oneof the loose

pulleys Theshaftwillbe driveninone

di-rection or the other,according as the open

orcrossedbeltisonthe fastpulley

3. A methodof transmittingmotion from

ashaftat rightangles toanother, bymeans

ofguide-pulleys. There are two of these

pulleys, sidebyside, oneforeachleafofthe

belt.

4. A method of transmittingmotion from

ashaft atright angles toanotherwhoseaxis

is in thesameplane. Thisis shownwitha

crossed belt. An open belt may be used,

but thecrossed one ispreferable, as itgives

moresurface of contact

the band take

upthe slack, the belt transmitsmotionfrom oneof the larger pulleys tothe other; but

whenit is not, the beltis soslack as notto

transmit motion

6. By giving a vibratory motion to the

lever securedto the semi-circular segment,

the beltattachedtothesaidsegmentimparts

a reciprocating rotarymotiontothetwo

pul-leysbelow.

7. A method of engaging, disengaging, andreversing the upright shaft at theleft.

Thebelt isshown on the middleoneof the three pulleyson thelowershafts, a, I/,which pulleyis loose, and consequentlyno

When the beltis traversedontheleft-hand pulley, which is faston the hollow shaft, <,

carrying the bevel-gear, B, motion is com-municated in one direction to the upright

shaft; and on itsbeing traversedontothe right-hand pulley, motion is transmitted through the gear, A,fast on the shaft, a,

whichruns insideof b,andthe direction of the uprightshaftis reversed

8. Speed-pulleysusedforlathesandother mechanical tools,forvarying the speed

ac-cordingto'the workoperated upon.

9. Cone-pulleysfor the samepurpose as

machin-ery, and in all machines which arerequired

torunwith a gradually increasedor dimin-ished speed

10. Isa modification of9, the pulleys

be-11. Anothermethodofeffecting thesame

result as3, without guide-pulleys

12. Simplepulleyusedfor

liftingweights

Inthisthepower must beequaltotheweight

toobtain equilibrium

13. In this the lower pulley is movable

One endof the rope beingfixed, the other

mustmove twice asfast as the weight, and

conse-quentlyeffected

ob-tained bythis contrivance is calculated as

follows: Divide the weight by double the

numberof pulleys in the lower block; the

quotient is the power required to balance

the weight

1 5. Represents whatareknownasWhite's

which caneither be madewith

sep-arate loose pulleys,or a series of

grooves

can be cut in a solid block, the diameters

beingmadeinproportiontothespeedof the rope; thatis, i, 3,and5 forone block, and

2, 4,and 6forthe other Poweras i to7.

Span-ish bartons

1 8. Isacombination oftwofixed pulleys andone movable pulley.

19, 20, 21,and 22. Are different

arrange-mentsofpulley,. Thefollowingrule applies

to these pu'Ieys: In a system of pulleys where eachpulleyis embraced byacord

at-tachedatoneend toafixedpointandatthe othertothecenter of themovablepulley,the

effectof thewhole willbe=the number 2,

multiplied by itselfasmany times as there

26

27

30

/i/i/u\rv

23. Acontrivancefor transmitting rotary

at the bottomof the figure is the movable

one; ifthis pulleywere raised or depressed,

accordingly In order to keep a uniform

tension on thebelt,apulley, A, carried in a

frame sliding between guides (not shown),

guide-pulleys, B,B, and is acted upon by

the balance weight, C, insuchmanneras to

produce thedesiredresult.

24. Spur-gears

25. Bevel-gears Those of equal

diame-tersare termed"miter-gears."

"crown-wheel ;" that gearing with it is a

spur-gear Thesewheelsare notmuchused,

andare only available for lightwork, as the

teethofthe crown-wheel mustnecessarily be

27

"

Multiple gearing" a recent

inven-tion. The smaller triangular wheel drives the larger one bythe movement of its

at-tachedfriction-rollers in the radialgrooves.

28 These are sometimes called "brush-wheels." Therelative speeds can bevaried

by changingthedistance oftheupper wheel fromthecenter of the lower one Theone drivesthe otherbythe frictionor adhesion, andthismaybe increasedbyfacingthelower onewith india-rubber

one shaft at rightangles toanother The spiral thread of the disk-wheel drives the spur-gear, moving it the distance of one toothateveryrevolution

rotarymotionof the driven gearat avarying speed Theywere used onaprinting-press,

thetype ofwhich wereplacedona

rectangu-31 32 33

SO P<0>-SCO

31. Wormor endless screw anda

worm-wheel Thiseffects the same resultas 29;

and as it is more easily constructed, it is

oftener used

32 Friction-wheels The surfaces of

these wheels are made rough, so as to bite

asmuchas possible; oneissometimesfaced

withleather,or,better,with vulcanized

india-rubber

33. Ellipticalspur-gears Theseareused

where a rotarymotionof varying speed is

required,and the variationof speed is

de-termined bythe relationbetweenthelengths

of themajor and minoraxes of theellipses.

34. An internally toothed spur-gear and

pinipn With ordinary spur-gears (such as

representedin 24)thedirectionofrotationis

opposite; but with the internally toothed

gear,the tworotate in the same direction;

and with the same strength of tooth the

gears are capable of transmitting greater

force,becausemoreteeth are engaged

35. Variable rotary motion produced by

spur-pinionworksinaslotcut in the bar, which

turnslooselyuponthe shaftof the elliptical

gear The bearing ofthe pinion-shaft has

applied to it a spring,which keeps it

en-gaged; theslot inthe baristoallowforthe

variation of length of radius ofthe elliptical

gear

so

fromtheir application tomangles converts continuous rotary motionof pinion into

re-ciprocating rotary motion of wheel The

shaftof pinion has a vibratory motion,and

works in a straight slotcut in the upright

!stationary barto allow the piniontoriseand fallandworkinsideandoutsideof the gear-ing ofthe wheel. Theslotcutintheface of

I

themangle-wheel andfollowingitsoutlineis

to receive and guide the pinion-shaft and keepthe pinionin gear

37. Uniform into variable rotary motion. The bevel-wheel or pinion to the left has

teethcut throughthewhole widthofits face Itsteethworkwithaspirallyarrangedseries

ofstudsonaconical wheel

38. A meansof converting rotary motion,

by which the speedis madeuniformduring

apart,andvaried during anotherpart,of the

revolution

spur-gear tothe right,called the planet-gear, is tied tothe center of theother,or sun-gear,

by an armwhich preserves aconstant

dis-tancebetweentheir centers Thiswas used

asasubstitute for the crankin asteam en-gine by James Watt, after the use of the crank had been patented byanother party.

Eachrevolutionof theplanet-gear,whichis

rigidlyattachedtothe connecting-rod, gives twotothe sun-gear, which is keyed tothe

40

40 and41 Rotary converted into rotary of the spring asituncoilsitself. Thechain motion The teeth of these gears, being ison the small diameter of the fuseewhen oblique, give a more continuous bearing the watch is wound up, as the spring has

42 and 43 Different kinds of gears for

transmitting rotary motion from one haft

to anotherarrangedobliquelythereto

44 A kind of gearing used to transmit

greatforceandgive a continuous bearingto

the teeth Each, wheel iscomposedoftwo,

three, or more distinct spur-gears. The

teeth, instead of beinginline,are arranged

in stepstogive a continuousbearing This

system issometimes used fordrivingscrew

propellers, and sometimes, with a rack of

similar character, todrive the bedsof large

iron-planing machines

45 Frictional grooved gearing a

com-paratively recent invention. The diagram

to the right is an enlarged section, which

can bemoreeasilyunderstood

the primemover insome watches,

particu-larly of English make The fusee to the

47 Africtional clutch-box, thrownin and out of gear by the lever at the bottom

iThis is used for connecting and discon-necting heavymachinery The eye of the

disktothe righthas aslotwhichslidesupon

a longkeyorfeather fixedonthe shaft

48 Clutch-box. The pinion at the top gives a continuous rotarymotiontothe gear below, towhich isattached halfthe clutch,

andboth turn looselyon theshaft When

it is desiredtogive motion to the shaft, the

other part ofthe clutch,whichslides upona keyor feather fixed in the shaft,is thrust intogearbythe lever

49 Alternatecircularmotion of the hori-zontal shaft produces a continuous rotary motion of the vertical shaft, by means of the ratchet-wheels secured to the bevel-gears,the ratchet-teeth of the two wheels beingsetopposite ways,and the pawls

act-inginoppositedirections Thebevel-gears

and ratchet-wheels are loose on the shaft,

and the pawls attached to arms firmly se-curedon