The Farm  School—Mechanics
By Walter S. Smith.
By the term mechanics we mean that
branch of philosophy that relates to machinery. The farm is so machine-ridden,
•jo to speak, in- these wonderful days, that
V. The Wedge.
VI. The Screw.
As the wheel and axle are only adaptations of the pulley, and the wedge and
screw are adaptations of the Inclined plane
the number of simple powers is reduced
to three. Some have made other aud
more extended lists, but a close observance
the whole bar is one arm and the distance
to the weight the other.
By knowing any three of these the
fourth may be found, as hereafter explained. I mean the power, the weight
and the two arms.
There is another lever called third class.
Here  the power is between the fulcrum
long and the fulcrum is placed one foot
from the weight, the six feet will enable
one hundred pounds of power to raise six
hundred pounds of weight. Of the sec-,
oud class, the power arm being seven feet
lung the power is increased by one hundred
pounds; j ml the oue hundred pounds of
power will raise seven hundred pounds of
Group  of   Grey   Percherons,   imported  by Bobert Burgess & Son, Wenona, Illinois.
this branch of philosophy ought to be understood by the farmer. In our ignorance of certain principles we make serious blunders.
I knew a fanner whose mechanical
mind led him to take a place in a machine
shop. Not understanding the nature of
centrifugal force he multiplied the speed
of the grind stone by reducing thc size of
the pulley on the shaft until it made fifteen hundred revolutions in a minute.
This was grinding the plow-shares about
as he desired; but, all at once the stone
exploded, and a fragment mashed in his
forehead.
Inventive men sometimes spend much
time upon implements, and are disappointed because they have not allowed for friction or leverage or strength of material, or
some other simple element of this subject,
as it is taught in the books.
I will give a few lessons, as free as possible from technical terms, and apply them
to the actual experience of the farm. First
let us consider the
— Mechanical  Powers. —
These are six in number; as follows:
I. The Lever.
II. The Inclined Plane.
III. The Pulley.
IV. The Wheel and Axle.
always reduces the list to these six, and
simplifies  them  to the three.
Levers are of different kinds; one having the point of rest, called a fulcrum, between the power and the weight, like the
crow-bar in the act of prying up a heavy
object; and another having the fulcrum at
one end, the power at the other ami the
weight between; like a hand spike, lifting
a log, its further end on the ground.
The lirst is a lever of the first class; the
other a lever of the second class. The
fulcrum may be placed above the lever or
at either side; the principle being thc same
whether the object to be moved is a weight
or an object to slide, roll or push into
the ground.
The wheel-harrow is a double lever with
the weight between the power and the fulcrum;  thnt is, of the second class.
The advantage of these two levers consists in increasing the power. It is not
often that the two arms of the lever are
equal In length. When two men carry
a log, the arms may be equal; and then
each man regarded as a power makes a
fulcrum of the other.
By the word arms Is meant the portion
of the rod between the power and the fulcrum, or between the weight and the fulcrum.      When the fulcrum is at the end,
and the weight.
The fishing pole is an illustration of this
class. And a very good illustration is
the forearm of a man and the wing of a
bird. It is this  form of lever that se
cures speed of movement in flying, hurling weapons, striking with tools, etc; and
there are times when the power cannot be
applied in any other way for a common
mechanical operation.
The lever is used in combination with
each of the other mechanical powers. The
wrench is a lever, aud it is used in combination with the screw to tighten or loosen the taps of bolts; in operating thc jack
scfew for raising heavy objects, such as
buildings, and in the cider press, cotton
press or tobacco press.
It is combined with the wedge and cutter In manipulating the axe, the adz, and
all sorts of shears: and with the pulley in
the wheel and axle. These are operated
clfielly by an extension of the radius called
a crank.
In fact the lever is present in most of
our mechanical operations; and its laws
are important.
Its one chief law is the simple proposition: Power is to weight, as weight-arm
is to power arm.
If a lever of the first class is seven feet
weight.
The third class is not designed to in-i
crease the power, but is a means of applying a power that is greater than the
weight. In that same forearm illustration, the elbow is the fulcrum and the
power arm is the short portion of the bone
that is between the elbow and the insertion of the great muscle of the upper portion of the arm, called the arm proper..
The weight arm is the entire length of the
fore arm from the hinge at the elbow to
the center of the weight to be raised. The
two distances will compare about as one
and three-tenths to 13; or as 1 to 10. If
then the hand supports a weight of 50
pounds, the muscle in raising it must
exert 500 pounds of power. I alluded to
this iu my discussion of the life-force:
while treating the subject of physiology,    i
The legs of the race horse, the wings of
the pigeon, the pedal attachment of the1
bicycle and the arm of the sewing ma-i
chine are all levers of this class-.
There are very difficult problems in'
mechanics, and not one more troublesome
than the calculation of the steelyards.
The weight is movable, and every time!
it changes a notch it sets up a new relationship between the weight arm and the
power arm.      Boys, study it.