1000000031

rope draws up ¡tonds in' the fame woy .s lhe rope

claes in the abovc-mentioned crane, lhe gib-work here

being fuppofed tO be of lhe

f.me

fon. But lhefe

cr.oe.

are vcry

dangerous

to the meo in lhe

wheel ;

{"r,

any

,;>f

the men fhould chance tO fall, .he burden will

m.ke

the whecl run

b.ck

and lhrow lhemall about wilhin it;

which oflen breaks .heir limbs, and fometimes kiUs lhem.

The late ingenious Mr

Padmori

of Brillol, whofe contri ·

vanee lhe

Forementioned enne

is,

obferving

(his dangerous

conllruélioo, cootrived. method fo r remedying i., by pu.–

tiog cog••11 around .he oUlfide of .he ,vhecl, and

~pplyiog

trundle E

mrn

it ;

.which ¡ncrcaCcs

lhe

powcr as much

as lhe numberof cogs in the whed

greater

than lhe num–

ber of llaves in .he trundle: aod by pUlling a ra,che,–

wheel F on

lhe.

axis o( [he trundJe,

(;\5

in lhe above-men–

tioned crane, with a

C3teh

to (aH into it, lhe great

wheel

í.

llop. from runoiog back by the force of the weigh" e·

"en if aU the men in it Olould leave off walkiog_ And

one man working¡lllllt lhe winch

or two meo

lhe

oppofi.e winebes wheo needful, the 'lnen in ,he wheel are

much affified, and much greater weigl\u are raired, than

(ould be by meo only wi,hin .he wh«1. M r_

Par/more

pUl alfo a grip,e.wheel G upon .he axis of .he trundle,

whieh

being~ehed

in lhe fame manoer

d(cribed in

\he former craoe, heavy burdens may be le' down wi.h–

out the lean daoger.

And

before this

contrivance;

the

Jowerio~

of goods was al\Vays attended wi,h .he ulmoll

Q.anger

the men in the wheel; as every ene mull be

fenfible of,. who has feen fueh eogioes a' \Vork.

And i, is furprifing ,hat lhe matlers of wharfs and

cr·.nes mould be fo regardlef. of .he limbs, or even lives

of their workmen, that, excepting the late Sir

Ja.mu

CrudofGr<en\Vieh,

and fome gentlemen at Brillol, lhere

ís

fearce

iDllaoce of any \Vho has uled .his fafe eoo–

trivanee.

TH'

llru~ure

o( wheel-carriages is generally fo weU

known, .ha< it would be needlefs tO defcribe lhem. Aod

tberefore, we {hall ooly point

OUt

fome

inconvenicncie9

a.:ending lhe eommon melhod of plaeing ,he wheels, and

loading ,he waggons.

lo eoaches, .nd all other fo.r-wheeled earriages, the

fore wheel1 are made of a lefs fize than .he hind ones,

both on

aceDunt

turDing

{horr, and to avoid cuuing

rhe braces :

olherwife

the carriage would go much earie:r

if lhe fore-wheels were a. high as .he hind ooes; ,"d ,he

Jligher the betler, beeaufe ,heir mOlioo would be fo mueh

.he /lower on lhcir axles, and

confe~uently

lhe friélioo

proporrionably takcn off. Uut·

carrien

and coachmen

give .nolher reafon for making ,he fore-wheels mueh

'0"'''

.han 'he hind·wheeb; namdy, .hat when lhey

are fo, the hind-wheels help

pum on ,he fore oncs :

lvhieh i. ioo unphilofophical and . bfurd to deferye • re–

(utalion; and ye, for lheir f.lis(.élion, we

0,,11

mew by

~xperiment

char

has no

cxilltnce

bUl iD

their

O'NO

¡ml–

gin:uion~.

pl.in,

lha. ,he fmaU \Vhcel. mufl 'uro os mueh

(ter.cr

rounrt

lhilO

[he

g re3t

ones, :as lheir circurnfcren–

c~s

:are

I,·r".

And th: reforc, when Ihe

carri~ge

is load–

equ.Uy

heavy on bOlh .xles, lhe fore-axlc mull en–

dur: .s much more friélion, and confoqueotl

\Vear out

as mueh fooner, than lhe

hin.l.axle,

as th:: fore-whcds

are le(s th:tn tht: hind ones. Bu!

lhe

great

mi5fortune

i,.

tha, all ,he carriers 'o a man do obftinalely perfin,

gaintl lhe

clearen

reafon and demonllration, in putting.

Ihe heayier pa" of lhe load upon the fore-axle of lhe

waggon; which not ooly makes the

(riaion

greatdt

where

ough.

be lealt, bu, alfo prdfe,h lhe fore-\Vheel.

dceper ioto lhe ground lhan the hínd

wheels,

nOlwith–

/landing .he fore-whee!s, beiog lefs ,h.o rhe hin4 one.-,

are wilh fo much lhe greater

difficulty

drawn oue of a

hole or over an oblt.c1e, eyen foppofing the weigh"

. heir axles were equa/. For ,he difficullY, Wilh e'lual

\Veigh.., will be as lhe depth of ,he hole or heigh, of the

obllacle is

.he femid ia,"e'er of ,he \Vhcel. Thus, if

\Ve

fuppofe ,he (,nall wheel

(fig

4')

of lhe waggon

AB 'o faU inlo a hole of ,he dep'b

Er,

whieh is equal

to [he (emidiameter of lhe whcel, and lhe w:tggon

drawn horizontaJlyalong;

is cviq,ent, that the painl E

of ,he fmaU whcel wiU be d rawn direllly againfl the top

of ,he hole; and ,herdore, aU the power of horfes aod

men

will

nOl

be able to draw

out, unlefs the grouDd

gives \Vay before i._ Where.s, 'if lhe hiod \Vheel

faU.

into fueh a hole, it finks not near fo deep in proportioo

to its femidiametcr; and therefore, the paint G of the

large wheel \Vi U no. be drawn direélly, bu, obliquely, a–

gainll .he .op of lhe hole; aod (o wiU be eafily gOl out

of il . Add.o ,his, lhal fince a fmaU \Vheel wiU of,en

fiok to .he bOllom of a hole, in whieh o grea. wheel will

go bu, a

very

lillle \Vay, the fm. U wheels ough, in all

reafon

loaded with leCs

weight than tbe great ones;

.nd .heo lhe heavier pan of ,he load would be lefs jolted

up\Vard and down\Vard, and .he horfes tired fo mueh ,he

Jefs as .heir draugh, raifed ,he load 'o lefs heights.

It is [rue, that whcn the

waggon

road is much up hill,.

.here may be danger io looding ,he hiod p.r, mueh heavier

.han ,he fore pa,,; for ,hen lhe weigh. would overhang

.he hiod axle, efpecially if .he load be high, .nd endan–

ger .ilting up the fore-wheels (rom lhe ground. In .hi.

e. fe , lhe fafell w.y would be 'o load i, equally beavy

both axles; and

then,

O1uch

more of the weight

would be .hrown upoo rhe hind-.xle lhao upon .he fore

one, as the ground

rifes froOl

level

below the

carri3ge.

Bu, as .his feldom happens, and wheo i. does, a fmall

.emporary weigh. laid upon lhe pole between the horfes

\Vould overbalance lhe d.nger ; and ,his \V.igh, might be

thrown

into

(he

\V3ggon

when

comes to level gronnd ;

i, is (lrangc ,ha, an .d.,otage fo plain and fo obvious as

would arife (rom loading

tl1<

hind-wheels heavien, mould

no, be laid hold of, by eomplying \vith ,his method. .

To eoofirm thefe reafonings by experiment, le. a fman

model

of a

\Vaggon

made,

Wilh

irs Jore

Y(heels

in–

ches in diamcter, and its

hind·wheeJs

4.}; the

whole

model weighing about 20 ounees.

Lec

thls liHle c,lrriage

be loaded any

ho\V

Wilh weights, and have a fmaU cord

tit.:o

cach of

its

cnds,

equally

high from .he ground

re(ls upon; and Jet

be drawn aloDg a horizonr;tl board.

r"n

by a weighl in • fcale hung

lhe cord a' the fore

pa,,; lhe cord going over a pulley a' the eod of ,he

board tOo(acilitate

lhe

draught, and the wc:ight jult fuf–

licient to

draw

it aloo,::. Thcn, turo rhe carriagc, and

hang .he fcale 30d weigh ' tO lhe hind eord, aod

will