Los Angeles herald., 1910-07-03
COMPARES STEAM
AND CAS- ENGINES
Charles w. Snyder Gives Treatise
on Relative Values of
Power
EoUALIZES BOILER PRESSURE
MiddIeby Car Expert Says Full
Stroke Comes from Throttle
Controlled Cylinder
BY DIR. CHARLES w. SNYDER,
Local Agent Middleby Car

An ordinary gas engine cannot be
started under a load. In a steam en-
gine the pressure in the cylinder is con-
trOlled by the throttle and may be
made to equal the boiler pressure for
practically the fun length of the stroke,
and ii there are two or more cylinders
there is the maximum pressure contin-
uously applied.
The power in gas engine is entirely
different. Each power impulse might
almost be considered as a blow. Take
any single cylinder, for instance, as the
piston begins its power stroke there is
a sudden development of pressure to,
say, 300 pounds per square inch or
more and as the piston passes down.
ward there is at first a marked fall in
this pressure, followed by a gradual de-
crease, so that at one-fourth the stroke
the pressure is not over $50 pounds, at
half the stroke about 70 pounds, and at
about 80 degrees before lower center the
exhaust valve opens and the pressure
ceases.
This gives a. very uneven torque,
there being one-tenth of the stroke de-
veloping no power and about two-thirds
of the stroke where the pressure is
low. In a four-cycle ur-cylinder mo-
tor there is this 80 degrees where no
power is produced between each cylin-
der; in the six-cylinder there is always
quite a portion of the time this pressure
is very low. In a four-cylinder two
cycle the torque is more continuous,
and so far as the turning moment is
concerned the six-cylinder tWo-cycle is
almost ideal. This is due to the fact
that in a two-cycle motor there is an
explosion above each piston on every
revolution.
This irregularity of pressure is taken
care of in a gas engine by the inertia
of the f1yWheel and other moving parts,
and for this reason the single cylinder
motor requires the heaviest flywbeel,
and the weight may be decreased as the
cylinders increase in number.
This inability to start under load
necessitates the use of some mechanism
for connecting the engine with the car
after the engine is in. operation, and
the clutch is the appliance designed for
this purpose.
CLUTCHES FRICTION TYPE
The clutches used in automobiles are
of the friction type, that is, they depend
on the friction developed between two
plane surfaces for the connection be-
tween the engine and the road wheels.
Their action in reality is exactly like
the brakes on your car. You apply the
brakes and the car keps on going, but
finally the pressure has caused these
breaks TO set uOWH anu III tightly
enough to develop sufficient friction to
stop the car. When you let in your
clutch the same thing occurs; as the
clutch goes in the friction increases un-
til your engine is locked and moves as
one unit with your transmission shaft
If you want to demonstrate the SINH
larity between brakes and clutch, lock
your wheels so the car can't start, let
in your clutch and see how soon your
clutch will act as a brake on the en-
gine and stop it.
Friction clutches may be divided into
four types: Constructing, like the brake
on the outside of a hub; expanding,
acting in the same manner as the
brake inside the hub, the cone and
the disk.
The contracting clutch is the sim
plest and is a band of iron, lined with
leather, fibre or some other suita BILE
material, and arranged so that it can
be drawn tightly around a drum. Its
use is limited to planetary gears.
The expanding clutch is in little
use. 1t is arranged inside a drum,
with suitable mechanism for causing
it to expand against the drum.
The most common type of friction
clutches are the cone and multiple disk.
The amount Of friction developed be-
tween two equal surfaces depends on
the pressure between these surfaces,
and in the use of a friction clutch the