Hopkinsville Kentuckian. [volume] (Hopkinsville, Ky.) 1889-1918, 1900-04-06


+ this does bot depend . anyuisc 5
{ The roadway
While ascending The horses mus
exert the pulls called for by boil
{ roadway and grade. Thus. san,
roadway calls for 400 pounds pe
ton, while steel calls for TO- A 2
per cent grade calls for 392 pounds
Hence the pull needed to draw on
ton up such grade is 702 pounds
on sand, but 4O2 on steel liz tn,
same way it may be seen that pulls
Of 400 and 20 pounds, respectively
are needed in ascending a 3 pei
cent grade on sand and steel.
Now notice what these figure.
mean. On level horse can draw
40 times as much on steel as or
sand; on 3 per cent. grade, less
than Z times as much; on 9 per
cent. grade, about times; while
on a 20 per cent. grade, barely 2
times as much. five compare steel
with nacadam we shall see that on
a level, a horse can draw 6 times
as much on steel as on macadam;
on a 3 per cent grade, 1874 times
as much; while on a 9 per cent.
grade, only ia as much. Thus. a
road of high class has little adj
vantage over one Of lower class if
the grades are heavy.
AS already pointed out the pull
of the team, ascending, is divided
into two distinct parts. The part
spent in overcoming the resistances
OF the roadway is entirely lost. But
the part that overcomes the down
ward pull of the grade is not lost,
but is simply spentin accommodating
work for future use. The amount
OF this last. per ton of load, is a de-
Unite quantity for any given verti-
cal ascent, and cannot be increased
or diminished in any way whatever.
Every bit of it is recovered on the
descent, as we shall see. If not re-
covered too fast it all goes to re-
lieving the team But, if recovered
toe fast, the excess is wasted by
the brake, or the team has to undo
it by the additional work of holding
back.
In the descent the grade pulls |
forward and the roadway holds |
back with the amounts, per ton of
load, already pointed out. SO long
as the pull of the grade does not
exceed the resistance of the road
way there is no waste. The team
pulls with a force equal to the diff
ference and gets more or less of re-
lief at every step. But when the
grade pulls harder than just
enough to overcome the resistance
Of the roadway the brake must be
used, or the team must hold back,
and waste results. This shows
that there should be a definite
init, different for each kind oil
.oadway to the steepness of grade.
Thus for sand, which offers a re-
sistance Of 400 pounds per ton, %
per cent grade, which pulls with
992 pounds, is somewhat below the
init. But such grade on steel, |
which openly opposes 10 pounds,
would give an excess Of ISL pounds
% be wasted by the brake.
One half OF one percent, is the
INIT for the grade on steel FIX
ending the examination to the
other roadways we see that, to
avoid waste on the descent grade
should be sleeper than 20 (about) /
,, 3 or 4 per cent, respectively, on
a sand, dirt, macadam, or steel
roadway. 1t now remains to see
whether conditions connected with
the ascent demand the lowering Of
these limits. In the first inquiry
we had for guidance well-known
facts from mechanics, and figures
from the dynamometer But in
this second inquiry we must be
guided also by human judgment
But this is based on much expert
ence and is singular in its unanim-
ity. It is the unanimous opinion of
men who have had to do with !
horses, so far as the writer can |
learn, that two horses may, without
harm, haul as great load for
little while as four horses should !
for several hours, but no greater