FRICTION. . 
but. fit fyftem i is ever Ganging with alterhate inverfion. 
In this-a&, the ‘incumbent w makes inceffant, yet un- 
ed; andt 
of | on. 
gree of friétion muft evideritly depend on the 
angles of the natural protuberances, and which are deter- 
mined by the e a or the — eect os 
nc 
* Ph 1e 
oap, or ae by readily ac- 
cee itfelf to fie ae on of conta&, mutt tend 
to- — it, and therefore mutt leflen the ae or foften 
the of the fuc cceffively em ag: prominences, and 
ee diminith likewife the eke w ae thence refults 
In order'to diminifh the refi which friGtion occafions 
im machines, that {pecies of ee which arifes from one 
‘body being dragged over SS has been naar into 
that which is occafioned by one body ro life upon another. 
‘This may be eafily effected | in a manner alréady eae 
in the beginning a: this article, by applying wheels or rollers 
to the fockets or bufhes 
large wheels, an ae axles Of wheel-carriages. This a 
-ratus a pe have been: 7. recommended by Cafatus (Me. 
oli 1.) ; and it was afterwards mentioned by 
pie (Mitcell Berol. A i. p. 306.) and Wolfius (Op. 
Mathem. tom. ii.. p. 680.) ; ae it was not ufed in praétice till 
Sully awa it to clocks in t r 1716, and ahentas - 
cranes In 172 owever, eee rel were no tm 
will permit. Th e ae thould eft cic two Rasa as 
‘large as circumftances will allow, having th 
each otHer as poffible, but no. thicker than sa te is pnely 
neceffary to fuftain the fuperincumbent weight. When thefe 
. precautions are properly attende 
arifes from the friction of the gudgeon 
tremely trifling. The effects of sition e kewitein foine 
a’ 
mm reafure f the im pelling 
cava and by pr opor rtioni me the fize of the EiGio-whees 
the preiiure which they fev raily fuftain. If we fuppofe, 
for oe that the weight of a wheel, eee iron gu ud- 
ns move in bufhes ? brats, is 100. "pounds 3 then the 
fition ling from both it its ea will be. pine . 
Tf we fu uppole: alfo that _a force equal’ to 
coe is, fs capleyed to es the Aer and a€ts in’ the & 
e cafe of overthet wheels, the 
wil thes’ be 
. pounds, and the fri@tion only 1g p 
indeed to gr the moving force aia dined ‘ eae to 
: tie gravity 0 e 
8 often impracticable for the: engineer to apply th 
‘power but in a: given way ; ma there are ee éafés in. 
vhich fuitain the gudgeons - wi 
to, - aang = 
cimpelling { 
“ungtiénts will: Heffen “their fiGion: alittle, ‘but it ‘will: be 
‘greatl 
which the miovirig ‘force'may be fo exerted, as at leaft not to 
ig ae fri€tion which‘arifes from the wheel's weight. 
e moving force is nét exerted in a perpendicular 
obliquely, as in underfhot wheels, ‘the dgeon 
orce on one part of the ee than 
on any other part. This point will evidently be on the fide 
of the buth oppotite to Pe Ww - ie power is applied, and 
its diftance from weft poi the focket, which is fup- 
poled eens penile with the gudgeon, being called: 
direct oes ia 
will prefs with, greater 
x, we fhall have tang. » = -—, that is, the tangent of 
V 
the a d between the point of greateft preffure and 
the- ince co of the buf, is equal to the fum of -all the 
horizontal forces, divided by the fum of all “the vertical 
forces and the weight of fied ‘whee H oe rag the for- 
mer, and V the latter quantities. ee 
preflure being thus de aes the e fup- 
ported at that part by the la reeft once in ie to 
age the ear upon their axles 
the two following cafes as alain = been 
fuceefsfully arplapes Mr. Gottlieb on 
roller ‘about four or fix inches long, Sones turns within a 
groove cut in the are part of the: When wheel-car- 
es are at refi, ottlieb ha given mi per Be ban 
i proper pofition ; fe it is eviden of great- 
eft preffure will change when rae are a a eee ae 
vi : riage. is poi 
ever, W with the weight of the load; but it is 
ciently obvious that the friGtion-roller fhould be at. a little 
diftance from the loweft point of the axle-tree. 
amett of Briftol has applied friction=rollers’in adif- 
fere ent | comer which does ae ; 
w eakein the axle-trée: 
ite he axes of thefe \allere are Hee ina creulae 
ring - each end of tlie nave, and thefe rin ngs, and confe- 
sara the rollers,.are kept fepa ate ‘and parallel‘ by means 
of bolts ied between the rollers from’ one fide of 
the nave to.the 
e ingenious mechan 
ay eafily re ve by a 
les 
ayo application of the eee principles 
As it appears from the experiments of Fei ergufon and 
Coulomb, that tHe leatt ‘friGtion is generated when polifhéd 
iron moves upon brafs, the gudgeons and. pivots of wheels, 
and io axles of fridion-rollers,, - all be made of folithed 
iron ufhes.in w udgeons ‘move, arid the 
fs. “M. de 
the 
fr jGtion- wheels, ffiould be formed: of polithe éd bra 
li Hire recommends the fockets or bufhes:to‘be made’ fquate 
and not concave... 
When every nccaaee contrivance has been adopted for-~ 
Lidia the obftruGtion which arifes ‘fem the attrition 
of the communivating: — it pay a ge ibaa removed” 
by thte judicious application of: ‘ungue The ‘proper 
for this purpofe a fe ane § greafe atid ibe re the fur-.. 
faces are made : of wood, afid oil.when they are: of metal. 
When the foree se which the . urfaces are cS factor 
will ‘dir: he friction tha 
Whe en. the ae firfaces: ‘are pesaiy vA all, 
