Year: 1869

The use of the word ''hOrse pOwer'' is
very common, vet few, except good me-
chanics and engineers, attach a definite
meaning to it, but regard itas Indicating
loosely about the power one horse would
exert, it is however, when used in the
sense under consideration, as definite as
possible, and means the power required
to lift thirty-three thousand pounds av-
OiTdupOis one foot high in one minute.
A horse hitched to the end of a rope,
over a pUlly one foot in diameter, placed
over deep well, travelling at the rate Of
about two and a half miles per hour, or
twO-hundTed and twenty feet per min
ute, will draw up one hundred and fifty
pounds the same distance he travels.
The force thus eXerted Is called in me-
Chanics, "hOTse-pOwer," +" it being an ap-
Proclamation to the average amount of
continuous power it is fair to demand of
n strong horse. IF we multiply the
weight raised Onnhuudred and fifty by
the number Offpet twas moved permin-
ute, two hundred and twenty the pro-
duct will be the number OfpOUndS which
the same power would raise only one foot
high in the same lenTth OF time, thirty
three thousand pOUnds.l The dynamo
meter IS an instrument made for meas
uring power, particularly that used in
drawing. Those used in testing the draft
O agricultural implements are simply,
very strong spring balances, or spring
Steely0rds graduated to indicate the pow
er required to raise any weight, within
any reasonable limits, ut the rate of two
and a half miles per hour When we
apply the dynamOmeter in ascertaining
the draft Of machines, if the index indi-
Gates one hundred and fifty pounds, it 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 pully one foot IN
diameter, at the rate of two and half
miles per hour, and for other weights.
The velocity at which a team moves is
to be considered, as we'll as the weight to
be raised, or the load to be drawn. If a
horse travels faster than two and a half
miles an hour, while raising one hun
dred and fifty pounds out of a well,
he eXerts more than one horse power. If
he walks slower than this, he does not
exert a force equal to one horse power.
In asCertaining the dTaught of plOw or
reaper mower, by driving faster than
two and half miles per hour, the dyna-
mOmeter will indicate more than the
correct draUght; and by driving
slower, the draUght would appear to
be less than it really is. In testing the
dTaught of machines a team should al
ways move at the rate of two and half
miles an hour, OrtwO hundred and twen-
ty feet per minute, which is the univer-
sally accepted rate with reference to
which dynamOmetersa are graduated and
an easy one to which an approximate in
driving with almost any kind of rate.
Many persons have supposed that three
hundred pOUnds-twO7 7horse power-rep-
resented the same force that team
would exert when dragging three hun
dred pounds along the ground. A horse
canbaUl six hUndredpOunds OH the hard
ground, with ease; buthe could not draw
hard enough on the dynamOmeter to
mark more than two hundred and fifty
or three hundred pounds except for few
minutes. The power of a man is esti-
mated at One-fifth that of horse pow
eT.