The Cape Girardeau Democrat. (Cape Girardeau, Mo.) 1876-1909, 1897-12-25
FARM AND GARDEN.
c FORCE TESTS.
Resistance of Road Surfaces Meas
ured hY the TracfoUrnnh.

ured by the Tractograph.
Traction may be defined as the re-
distance which a stationary body Of
fers to motion, or the force required TO
move a given weight on a given surface.
II is found that the resistance offered
by different surfaces varies consider
ably, and consequently the force re-
CURED to impart motion TO bodies on
them varies likewise. Experiments to
determine the force Of traction on diff
ferent surfaces have been made from
time TO time. during the last 60 years,
the latest being those conducted by the
road inquiry Office Of the department OF
agriculture.
In order to secure n continuous rec.
ord as we'll as n measure of the tractiye
force. m apparatus called a tracto.
graph. arranged to make q graphic
record. was attached to q loaded
wagon which vas driven over different
surfaces and gradients. These tests
gave the following results:
The force OF traction Is not constant,
but varies with the character OF the
road at any given instant. being most
uniform on the Smootbest surfaces.
md constantly increasing the varia-
lions as the roughncsS Of the road IN.
crehses until Il becomes merely q
quick succession Of violent pulls. A
team Is thus subjected TO a continuous
Jerking motion, which greatly In
creases the fatigue caused by the elm.
pie pull necessary TO move q load. On
asphalt the variation Of traction Is very
small; on smooth macadam IL is some.
what more. and on an ordinary dirt
road IL is seven or eight times as great
as on macadam. II the dirt road be
actually bad the result Is practically
n series of heavy blows transmitted to
the team through the collars. and these
blows are estimated TO be doubly as
fatiguing as a steady pull, even at the
maximum traction of the road. On q
smooth road the traction itself is less,
and is comparatively constant. so that
the pounding effect on the team dis
appears. thus enabling them to use
their whole strength in hauling much
heavier loads with less power.
The effect of tie variation Of trac.
ton, due to irregularity of road surface
is analogous to the effect of vibration on
a bicycle rider. Every wheelman
knows how vibration increases as roads
become rough; but. owing to pneumat-
ic tires, the comparison is moi entirely
fair. Ride a pneumatic-tired wheel
over a piece of poor %macadam; then
ride n with cushion tires and finally
one with solid tires, and the enormous
increase in vibration and greater diff
Guilty Of propulsion will illustrate the
changes in tractive force on teams go
ing from good to poor roads.
During the tests small mules cas-
lily drew over 5000 pounds up a
ten per cent. grade of smooth
macadam, but were unable to pull
the same lad down a six per
cent. grade of sand. though the indi.
Gator showed that nearly double power
was applied, and three-quarters of the
load was removed before it could be
started. A loaded wagon, with two
inch tires, drawn over a dirt road cut
it into deep ruts, while the same load
with four-inch tires only smoothed the
surface, and it was found that the
traction on the road where the narrow
tires had been used was double what il
was on the section where the wide tires
were used.
The tractive force for different road
surfaces, expressed in terms of the
number of pounds required to move one
ton, as found in these tests, is as fol-
lows:
Tractive