Year: 1869

" HIT Is OuesnOTSt rover


The use of the word horsepower
is very common, yet few, except good
mechanics and engineers, attach de-
finite meaning to it, but regard it as
indicating loosely ABOUT the power one
horse would exert. 1t is, however,
when used in the sense under consid-
Grafton, as definite as possible, and
means the power required to lift thir-
ty-three thousand pounds avOirdupois
one foot high in one minute. A horse
hitched to the end of rope, over a
pulley one foot in diameter, placed
over a deep WELL. travelling at the rate
of about twoand a halfmiles per rhour,
or two hundred and twenty feet per
minute, will draw up one hundred and
fifty pounds the same distance he
travels. The force thus exerted is
called in mechanics, a horsepower,
it being an approximation to theaver-
age amount of continuous power it is
fair 10 demand of strong horse. If
we multiply the weight raised Zone
hundred and fifty pOunds) by the
number of feet it was moved per min
ute, two hundred and twenty, the
product will be the number of pounds
which the same power would raise
one foot high in the same length of
time, (thirty-three thousand pounds
The dynamometer is an instrument
made for measuring power, particu-
larIv that eXerted in drawing. Those
used in testing the draft of agricultu-
raj implements are simply very strong
spring balances, or spring steelyaTds,


graduated to indicate the power re-
quired to raise any weight, within any
reasonable limits, at the rate of two
and a half miles per hour. When we
apply the dynamometer in ascertain
ing the draft of machines, if the in
dex indicates one hundred and fifty
pounds, il is shown that the horse is
required to draw just as hard as he


would do if raising one hundred and
fifty pounds out of well with rope
over a pulley one foot in diameter, at
the rate of two and half miles per
hour, and so for other weights. The
velocity at which team moves is to


be considered, as we'll as the weight
| to be raised, or the load TO be drawn.
If horse travels faster than two and


half miles in an hour, while raising
one hundred and fifty pounds out of
q well, he eXerts more than one horse
power. If he walks slower than this


he does not exert force equal to one


horse power. In ascertaining the
draught of plow or reapera and now


er, by driving faster than two and
half miles per hour, the dynamome-
ter will indicate more than the correct


draught; and by driving slower, the


dEaught would appear to be less than
| it really is. In testing the draught of


machines a teams hOuld move at the


rate of two and half miles an hour,


or two hundred and twenty feet per


minute, which is the universally ac-
cepted rate with reference to which
| thermometers are graduated, and an


easy one to which an approximate in
I driving with almost any kind of rate.
Many persons have supposed that
/ three hundred pOunds-two-hOrse
pOwer-represented the same force
/ that team would exert when drag


ging three hundred pounds along on
| the ground. A horse can haul six
| hundred pounds on the hard ground,


with ease but he could not draw hard
| enough on the dynamometer to mark
more than two hundred and fifty or
three hundred pounds except for a few


minutes. The power of a man is esti-


mated at One-fifth that of a horse
power.