The Clarksburg telegram. [volume] (Clarksburg, W. Va.) 1874-1926, 1912-07-25

An onED MAcApAM ROAD WITH MACHINE
TRAVELLING SIXTY MIhRS PER RouR-Nc
DUST.
chimes owned in the United States, and
the number is increasing at a marvel.
Gus rate.
The fact that must give us concern
is 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.
&c and that we are in the midst of q
transition period which must eventual.
ly reVolutionize the science and art OF
the road builder. The highway en-.
gineer OF today is called upon to ascer.
tain In what way the automobile In.
Jures the road, what is the exact cause
Of the injury, and finally to devise an
adequate remedy,
When Tresaguet. the great French
engineer, made his report to the coun,
ell of bridges and roads In lTT5 he sci
forth the principles Of construction
which. as modified and added to by
John L. Macadam in the early part OF
the nineteenth century, have proved
adequate until the twentieth century,
These great road builders and their
successors sought to secure road ca.
pable OF withstandlng the wear Of iron
tired horse drawn vehicles, for the mo.
tor driven vehicles had no place In
their philosophy. They worked upon
the theory that the dust nbraded from
the crushed stone would fill the yoids
between tile angular fragments aud
when wet serve as cement, thereby
making the road surface practically a
monOlith The iron shod horses and
the iron tired wheels passing over the
road from time to time were depended
upon to wear OF a sufficient amount OF
rock dust to replace that carried away
by wind and water. and this under the
action of moisture reeemented, thereby
automatically renewing the bond of the
road surface.
The rubber tired wheels. moving at
excessive speed, fail to produce amy
new dust from the rock. but the ire
me1dpns shearing effect Of the driving
wheels loosens this dust, aud us the
body of the machine displaces large
volume of; dir the detected currents
carry ne rock dust OF the rond, there
by efeetihg a permanent loss of the all
essential binder. 1t follows that the
road 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
driving wheels. leaving the road badly
rareIed or disintegrated. Ii Is. Of
course. apparent that the effects de-
scrihed are greatly intensified on
curves, where skiddIns is most fire.
quent.
Highway md mechanical engineers
have given much study TO the action Of
the automobile ON the road surface.
and many Ingenious theories have been
advanced While 1t Is true that the
clipping OF the tire, skidding. shape Of
the eur body, suction of the pneumatic
tires. all contribute TO produce the ef-
feet, the most conclusive experiments
seem to wnrrpnt the assertion that the
great tractive force or shear exerted
by the driving wheels of motorcars Is
the main factor Of injury.
A series Of tests conducted by the
United Staies Office OF public roads in
1908 produced some interesting results
along this line Cars Of various weights
and types were run over a measured
course at different rates of speed and
right angle photographs taken of each
run. A sixty horsepower car stripped
for racing. weighing with its driver
and mecbanician about $500 pounds,
was driven over this stretch Of road at
rates OF speed varying from five to six.
ty miles per hour. the speed being in.
creased Eve miles per hour for each
trip over the road. Up to fifteen miles
an hour little or no effect was produced
On the road. but from twenty miles an
hour the effect was striking with each
Increase in speed. These dcmonstra-
lions proved that little or no effect is