1000000031

70 / 868

M E e H A
1 .nd a"is G; and ro ,he ¡:ib "'Jul" be pull<d vioJ.ntly
tO thAr fide, ~nd cilhcr bl! l)foJ~f!n lO piec~s . or bl'Cdk
eVt'ry (hire that came: in ttS \\ay. Thelc rl.lllc:rs Olull be
placcd fo, lh;u lhe lides ü( lheln, round which lhe rope
b,nd" m,y kecp ,he mi"Jle of ,he bond"d pu, tlireélly
ev~n Wilh rhe centre of ,ile hoJe in which tht. uppcr gud·
gcon of lhe gib rorr.s in Ihe bClm f. T he truer [beCe
rollcrs are placed, lhe caticr lhe glb;s managed , and lhe
Id$: apuo fwing tither w"y by the force of lhe;: weight K.
A ratchc[- wheel QJs lixl upon lhe axis D, ocar lhe
trumBe E; and unto this whccl {,dls the CdlCh oc cJick
R. This hintlcrs lhe IllJchine (rom running back by lhe
weigh t of lhe burden K, ir lhe m.m \Vho T<lir~s il lhould
happeo la be carelcfs, and fa leave off worklOg al the
~ inch A fo(,.ner than he ought to do .
' Vhen rhe burden K is raired tO iu proper height from
the fhip, and brought o\·er the quay by turning lhe gib
about. it is let down gcndy upon lhe quay, or into a
cart ClanJiog thereoo, io (he fullowiog manoer : A nlan
..kes hold of the rope 11 (whieh gOts O\'er ,he pulley v ,
aDd is tied tO a hook a' S in ,he ea,eh R) .ntl fo Jifen·
glges the catch from lhe ra:chet whcel QJ. aod lheo, the
maD at the winch A turos it backward, and lers down
lhe weigh, K . Bu, if ,he weigh, pulls too h..d againrl
Ihis man, ano,hor lays hold of lhe h.ndle V, and by
pulling i, downward, draws lhe gripe U c10re 'o lhe wheel
Y, which, by rubbiog bard ag.inn ,he gripe, hinders lhe
too quick defceot of Ihe weigh t; and nOl anlyfo. but e\'en
Clops it at any time, ir required. By this mcans, heavy
gaods may be eirher raifed or let downat pleafure, \Vith a
out any daoger of huning the meo \Vho \York lhe cngine.
When part of ,he goods are eraned up, aód ,he rope
is In be le! down for more, !he eareh R is firn difenga–
ged from ,he ra,ebe'·wheel Q, by pulliog ,he eord 1;
lhen the handle '1 is ,urned h.frround baekward, whieh,
by ,he crank nn in ,he pieee D, pulls down the h
betweeo the guides 11J aod rn (io which it lliues in a
groove) . nd ro direngages ,he 'ruodle B from the wheel
e : .od ,hen, the heavy hook .l a, the end of ,he rope
H defeeods by its Own weigh!, and 'uros ,he great
wheel F wi,h its "undle E, and ,he wheel e ; and ,his
l.n wheel aéls like • /ly agaion ,he wheel E and hook {3,
and fo binders it froln going down too quiek ; whiln ,he
",eigh, X keeps up ,he gripe U (rom rub"iog againrl ,he
wheel Y, by means o( a cord goíog from the , over
!he pulley w to ,he hook W in ,he gripe; fo ,hat ,he
gripe never touehe, the wheel, unleCs i, be pulled down
by !he handle V.
. Wheo the crane is to be fet at work again, for drawa
iog up aoo,her burden, ,he handle '1 is ,urncd half round
{orfwards: which, by the crank nn, raifes up the frame
h, aod eaures ,he trundle B 10 lay holtl of ,he whecl C ;
and ,heo, by turning ,he wineh 11, ,he "ur¿en of good.
K is drawn up as before.
The crank nn turos pretty fiiff in the mortife near o,
and flaps againll the fanher end of it wlll~n it has gOt
jun. linle beyond !he perpendieul.. ; ro !hat it can never
come back of ítrelf: and lhcrefore lhe trnndlc B có\nnt.:ver
come away from the wheel e, until the hu.ndle r¡ be toro·
ed r(lUod.
The gre.. rope runs upon rolle" in ,he lever L M,
V OL . llI. N°. 71.
N 1 e s.
",hieh keep i, from "ending be!'Veen ,he axle at G and
the pulley 1. This lever ruros upon lhe axis N by means
of tht wdght O, which is jufi rufficienl to keer its end
L up (O (he rop:; lo thar, ;\$ the great axlc lurns,
nod {he rope coils round ¡t, lhe lever n fes wi :h rhe rope ,
and prevenls lhe coilings fronl guing over one another.
T hc power oC thís crane m.1 y be eHin1:'.tc:d thus: Sup.
pafe lhe trundle B lO have 13 fiaves or rou nds, and the
whed e 'o h. ve 78 rpur eogs; ,he truodle E 'o have 14
, and ,he wh"e1 F 56 eog': ócn. by mul,iply–
ing {he ll:ilves af the lrundles, 13,and 14. inro 00: ano·
ther, ,heir produél will be 18. ; and by multiplyiog ,he
cogs oC lhe wheds, 78 and 56. into one anolher, thei r
produél will be 4368; .od dividiog 43 68 "y 18., ,he
quodent \ViII be 24 i which fhe ws lhal lhe winch A makes
24 turns for oue luro of lhe wheel F and ilS axle G on
\Vhieh ,he great rope or ehain HIH winds . So ,hat, if
lhe lenglh or radius af the winch A were only equal to
h.llf ,he diame,er of !he grea, axle G , aclded 'o half ,he
,hiekners of ,he rope [-1, ,he power of ,he eraoe would
be as 24 'o 1: bu, ,he radius of the ",vineh beiog dou1>le
the above Icngth, it doubles the faid power, and fo Olakes
it as 48 to 1 : io which cafe aman may raife 48 dmes as
mueh \Veigh, by thi, eogine as he eould do by his na–
tural (lrenglh without it, making proper allowance for
the [r¡aionof the working pans. - T ....o men may work at
once ... by having another winch on the oppofite end of rhe
axis of the trundle under B; .nd fo make ,he pOlVer rlill
double.
If this po'Ver be ,hought gre.'er ,han wha! may be
generally wan,ed, ,he wheels m.y be made wi,h fewer
cog,. in proponion to lhe llaves in [he trundles: and fo
!he pow,r may be of wh.,ever degree is judged to be re–
quifi,e. But if ,he weigh' be ·ro great as \ViII require
yet more power ' o raire i, (ruppore a double qu.n!i,y)
,hen !he rope H may be pu, under • moveable pulley,
as 1', . nd ,he end of it tied 'o a hook in the gib at,;
\Vbieh will give a double power tO the maehioe, and fo
raife a double weigh' hooked 'o ,he block of ,he move–
able pulley.
''lhen only rmall burdens are to be raired, ,his may
be quiekly done by men pufhiog !he axle G round by the
haod-fpokes y,y )',y; h. viog fi,n difengaged !he trundle B
from ,he wheel e: and then, ,his wheel will only aél a•
• fly upon the \Vheel F; and !he ea,eh R will prevent
its ruooing back, if the meo fhould inadvertently leave
off puO,ing before ,be "urden be uohooked from (3.
L anly, \Vhen very heavy burdeos are tO be raired,
whieh migh, end.nger ,he breaking of the eogs in ,he
wheel F; lhrir force againfi lhere cogs may be much a–
ba,ed by men puO,ing round ,he hand-fpokesy,y,y.)", whilr!:
the man at A turns the winch.
W e have only fhcwn the working parts of this crane,
without the whoJe of the bcams which fupport them;
knowiog ,hat ,here are eafily f"ppored, and ,ha, if ,hey
h. d " cen dr>wn, ,hey would hal'e hid a grea! de.1 of
,he \Vorking parts from fight, .nd .Ifo eonfu(ed ,he firrure .
Another \'ery gcod CrtlJJ: is O1a,le in lhe following
mann«. AA (r.g. 3.) is a gre., wheel ,urned by men
w,lkiog wi,hi o it a, H. On ,he plr' C, of its axle BC,
thc rope D is wouod as th<! wherJ turos j and Ihis
O t rol'o