Juniata sentinel and Republican. [volume] (Mifflintown, Juniata County, Pa.) 1873-1955, 1879-05-07
SCIENTIFIC.

Inlprored Steam EHy.hc.-'n m mlkin
Steam motors of all Kinds, the tendency
has been of late to construct engines
with high piston speed. By high in
itiaI speed in the motor much of the gear
ing need to obtained speed in the ma
chinery thai it moves Is dispensed with.
The steam is more thoroughly employ
ed, and the size and weight of the en-
gine for a given power are duced.
The most important Improvement in
this direction has sprung from radical
change i'm the construction of the steam
cylinder and its moving parts. The
cylinder is increased in length and re
duced in diameter, and in place of one,
there are two pistons, designed to move
in opposite directions. The first piston
has rod passing through the center OF
the second, and the second piston has
two rods, one on each side of the CEN
trail rod. Each piston has Its piston
TO connected with crank on three
throw crank-shait. These cranks are
placed opposite each other, the single
rod of one piston balancing the two of
the other. 1t will be observed that. by
this change in the construction of the
posite directions, each making to-
and fro excursion over half the length
of the cylinder. For instance: If the
two pistons are each at one end of the
cylinder, the steam may be admitted
behind them both, and thus drive them
together When they meet at the CEN
ter, the steam enters at central port
and drives them apart till they reach
their original positions, when the ex-
cursion is finished and one revolution
of the crank is accomplished. The eff
feet of this disposition of the moving
parts is 10 create perfect balance IN
the reciprocating action of the engine.
The pull of one piston balances the
thrust of the other. Itis no longer a
series of pulls and thrusts, as in the or
linary engine, but resulting motion
of the combined pull and thrust of the
two plstons. The advantages obtained
by this balancing of the pistons are
found in the reduced length and weight
of the connecting-rods and the bed
plate of the engine, steadiness OF mo
ton, as there is no pull or thrust on the
shaft and its bearings, higher speed
and greatly increased power As there
is 10 straining between the cylinders
and the shaft. the engine rests securely
on its bed. As the two pistons travel
over only one-half of the length of the
cylinder in the same time, aud as the
area of the piston surface is double
that of a single-piston engine, the pow
er is more than doubled for given
speed. The strain caused by the ex-
pansion of the steam between the pis-
ton and the end of the cylinder, as in
the ordinary engine in the balanced
engine is spent on the two ends of the
cylinder in One-half of the stroke. and
between the two pistons in the other
half. In either case tie strains are ex-
actly balanced. Thus the engine may
run at high speed without producing
a troublesome jarring or shaking OF the
motor. In marine work il is thought
the balanced engine will prove of ad-
vantage, as il may be driven at high
speed without shaking the ship, and by
giving the engine higher speed, a
screw of more effective pitch may be
employed. The only disadvantages
found in this form of motor lie in the
multiplication of the connecting-rod DDS
and stufiing boxes, but these defects are
more than balanced by the steadiness
and increased speed and power OF the
engine.