The Manitowoc pilot. [volume] (Manitowoc, Wis.) 1859-1932, 1916-03-16

tractor pulling two plows at two miles
an hour will do the same amount of
work as one pulling one pillow and trav-
cling at four miles an hour, other con-
ditions being equal, and the horse
power developed at the drawbar is the
same, because the element of time en-
tiers into the determination of horse
power. The slower any given tractor
is geared to move the greater will be
the load which 1t can pull at the draw
bar, as it pulls it less rapidly. The
amount Of work done and the total
amount of power exerted will remain
practically the same.
1t is obvious that in the case men
toned the tractor pulling one plow
and running twice as fast as the one
pulling two plows must move its own
weight over the ground twice as many
times as will the other tractor. If the
weight of the two tractors is the same,
it will be seen that twice as much
power has been expended in moving
the weight of the high-speed tractor
as has been used by the one of low
speed.
A great many farmers find it diff
cult to understand why a tractor of,
say, ten horse power at the drawbar
will not pull as heavy a load as will
ten horses. This is not because a
mechanical horse power is less than
the amount of power developed by a
horse, but is because Of the fact that
a horse has an enormous overload ca
pacity-that is, great deal stronger
pull than he should normally main
tain hour after hour.
A tractor, however, has very little
overload capacity when pulling it's nor
NAL load Thus, if tractor with a
drawbar rating of ten horse power
pulling its normal load of plows I'M
der average condition should strike a
particularly hard spot where the draft
was double for a few minutes it would
STALL while ten horses under similar
conditions could readily increase
their pull sufficient to meet the in
creased draft.
From this it will be seen that in
cases where the draft will vary land
this occurs in practically all kinds of
farm work because of grades, soil va
Ration, etc.) the load which a tractor
will handle satisfactorily is that which
it can pull up the steepest grade or
through the toughest soil in the field
This load may be only half of what it
can pull under more favorable condi.
tons in the same field. 1t will also
be apparent that the working load of
tractor under ordinary farm condi-
lions is considerably less than the
normal load for it's drawbar equivalent
in horses, that is, tractor of ten
horse power on the drawbar will not
pull, except under constantly favor
able conditions, the load which ten.
horse team would normally pull The
difference might be said to be entire
ly in the overload capacity of these
two prime movers. With tractor
it's maximum power is practically its
normal power because it is capable Of
pulling this load continuously but can
not carry anything in excess of this.
On the other hand, the horses nor
NAL load is much less than what he
can do in an emergency.
Until definite authoritative stand
ard of rating tractors has been adopt.
ed, it is recommended that farmers
when comparing different makes of
tractors pay more attention to the
amount of work actually done under
like conditions and with practically
the same fuel consumption than to the
catalogue ratings.