Judith Gap journal. [volume] (Judith Gap, Mont.) 1908-19??, 1912-10-18

TRAVELLING SIXTY MILES PER HOUk-NO
DUST.
chimes owned In the United States. and
che number Is increasing at a marvel
Ous rate.
Tie fact that must give us concern
q that the old methods of construction
which have stood every test for more
than 100 years are inadequate to meet
the conditions Of this new form Of traf
0c and that We are in the midst Of
transition period which must eventual
" revolutionixe the science and art Of
the road builder. The highway en-
xineer Of today is called upon to ascer.
cain in what way the automobile in
lures the road. what is tho exact cause
ef the injury. and finally to devise an
adequate remedy.
When Tresaeuet, the great French
engineer, made his report to the coun-
Gu Of bridges and roads in 1775 he set
forth the principles Of construction
which. az modified and added to by
John l.. Macadam In the carly part of
che nineteenth century, have proved
adequate until the twentieth century.
These great road builders and their
SUCCESSORS sought to secure road Gu
pable Of withsta nding the wear Of iron
t1red horse drawn vehicles. for the mo-
cor driven vehicles had no place In
their philosophy. They worked upon
the theory that the dust abraded from
che crushed stone would I'LL the voids
oetween the angular fragments aud
when wet serve as q cement. thereby
suaking the road surface practically a
Gnonolith. The iron shod horses and
che iron tired wheels passing over the
eoad from time to time were depended
upon to wear OF sufficient amount Of
1gock dust to replace that carried away
by wind and water. and this under the
action Of moisture recemented. thereby
automatically renewing the bond Of the
eoad surface.
excessive speed. fail to produce any
new dust from the rock. but the tire
mendous shearing effect Of the driving
wheels lo0sens this dust and as the
body Of the machine displaces large
volume Of mir the detected currents
carry the rock dust Off the road. there
BY effecting permanent loss Of the all
essential binder. 1t follows that the
voad is soon stripped of its fine bind
ing material. exposing the upper or
wearing course OF the stone. These
stones robbed of the binding material
are soon loosened by the shear Of the
arriving wheels. leaving the road badly
Saveled or dsintegrated. 1t is. Of
course. apparent that the effects de-
ocribed are greatly intensified on
surves. where skidding is most fire.
Onent
Highway and mechanical engineers
have given much study to the action Of
che automobile on the road surface.
end many ingenious theories have been
advanced. While 1t is true that the
shipping of the tire. skidding. shape Of
che car body. suction Of the pneumatic
Nires. all contribute to produce the eff
Feet. the most conclusive experiments
seem to warrant the assertion that the
RTeat tractive force or shear exerted
b the driving wheels OF nlotOrcars Is
the main factor Ut injury.
A series Of tests conducted by the
0lSltcN OulNc VI puO'AN 'o"O' ~
t0OS produced some interesting results
along this line. Cars Of various weights
and types were run over measured
course at different rates Of speed and
sight angle photographs taken Of each
0un. A sixty horsepower car stripped
Dor racing. weighing with its driver
and mechanician about $500 pounds
Vas driven over this stretch Of road a
mates Of speed varying from five to six
u miles per hour, the speed being In
creased 1--WE miles per hour for eacl
Drip over the road. Up to fifteen mile
IN hour little or no effect was produced
On the road. but from twenty miles al
hour the effect was striking with eac
increase In speed These demonstra
lions proved that little or no effect