The Bossier banner. [volume] (Bellevue, Bossier Parish, La.) 1859-1952, 1912-08-22

AN OILED MACADAM ROAD WITH MACHINE
TRAVELLING SIXTY MILES PER- HOuk-No
DUST.
chimes owned in the United States. and
the number is increasing at 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
fic and that we are in the midst of a
transition period which must eventual!
ly revolutionize the science and art of
the road builder The highway ell
gineer of today is called upon to ascer
tain in what way the automobile i'll
jures the road. what is the exact cause
of the injury, and finally to devise Az
adequate remedy.
When Tresaguet. the great French
engineer, made his report to the colln
ell of bridges and roads in l775 he set
forth the principles of construstio,
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 ana 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 fill the voids
between the angular fragments and
| when wet serve as cement. thereb.
| making the road surface practically IL
monolith The iron shod horses at.d
| the iron tired wheels passing over tn,
road from time to time were derelidtd q
upon to wear off Il sufficient amount I'll
rock dust to replace that carried away
| by wind and water. and this under tht
action of moisture recemented. tllercb.
automatically renewing the bond of thu
road surface.
| The rubber tired wheels. moving al
excessive speed. fail to produce an,
new dust from the rock, but the tire
mendous shearing effect of the drivin;
wheels loosens this dust. and rs tlt
| BODY of the machine dispiaccss il hrs,'
volume of air the DETECTED current!
carry the rock dust off the road tlure
BY effecting a permanent loss of the al
essential binder 1t follows that tls'
road is soon stripped of its inc bind
ing material. exposing the upper o
| wearing course of the stone. Thes
stones robbed of the binding materia
are soon loosened by the shear Of TIL
driving wheels. leaving the road badl.
| raveed or disintegrated II Is.
course, apparent that the effects de
scribed are greatly intensified o.
curves. where skidding is most fri
Quent.
i Highway and mechanical engineer
have given much study to tine action
the automobile Oh the road surface
and many ingenious theories have bee
advanced While it is TRUE that III
slipping of the tire. skiddins. shape "
the car body. suction Of the rheunsitl
tires. all contribute to produce the el
feet. the most conclusive experiment
seem to warrant the assertion that IN
great tractive force or shear eScfte
by the driving wheels Of notoreafs
the main factor Of injury,
A series of tests conducted by u
United States office OF pubic roads
1908 produced some interesting result
along this line. Cars Of various weight
and types were run over n measure
course at different rates OF speed in
: right angle photographs taken OF ea'
run. A sixty horsepower car Stripe
for racing. weighing with its drive
and mechanician about 2.s00 pound
+ was driven over this stretch of road
rates of speed varying from five to 81!
ty miles per hour. the speed being Il
: creased five miles per hour for eae
3 trip over the road Up 10 fifteen mslt
: an hour little or no effect was isrns1,' =
e on the road, but from twenty miles i
+ hour the effect was striking will, ra'
8 increase In speed. These demnnsfr
9 tions proved that little or no effect