Bismarck daily tribune. [volume] (Bismarck, Dakota [N.D.]) 1881-1916, 1912-05-03

ANTO1L&O AAOAOAM ROAD WITH MACHINE
T ra;av SIXTY MILES PER HouR-so
chimes owned in the United States, and
the number is increasing at a marvel
Gus rate.
The fact that must give us concern
10 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
" 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 Its he set
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 a road ca
pable Of withstanding 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 abraded from
the crushed stone would ill the voids
between the angular fragments and
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 recemented, thereby
automatically renewing the bond Of the
road surface.
The rubber tired wheels, moving at
excessive speed. fail to produce any
new dust from the rock, but the ire
mendous shearing effect Of the driving
wheels Nloosens this dust, and as the
body Of the machine displaces large
volume of air the detected currents
carry the rock dust OF the road, there
BY e1ecting permanent loss Of the all
essential binder. It 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
IRE soon loosened by the shear Of the
driving wheels. leaving the road badly
raveled or disintegrated. 1t is. Of
course, apparent that the effects de- ,,
Icribed are greatly intensified on
curves, where skidding is most fire.
1uent
Highway and mechanical engineers
have given much study to the action Of
he automobile on the road surface,
md many ingenious theories have been
advanced While it is true that the |
dipping of the tire. skidding. shape Of
he car body. suction Of the pneumatic
Tres, all contribute to produce the ef-
let, the most conclusive experiments
Ieem to warrant the assertion that the
reat tractive force or shear exerted
y the driving wheels Of motorcan II
he main factor Of injury. -, |
A series Of tests conducted BY the
United States Office Of public roads in
0O0 produced some interesting results
long this line. Cars Of various weights
nd types were run over measured
curse at different rates Of speed and
light angle photographs taken Of each
IN. A sixty horsepower car stripped
Or racing. weighing With itS driver
nd mechanician about $500 pounds,
vas driven over this stretch Of road at L
ates Of speed varying from five to six-
: miles per hour. the speed being in
reased five miles per hour for each
ip over the road. Up to fifteen miles
q hour little or no effect was produced
q the road. but from twenty miles an
our the effect was striking with each
lcrease In speed. These demonstra.
ons proved that little or no effect b u