The sun., 1919-09-07

pulsion for ships was discussed
az soon as electric motors be-
gan to be used as a motive force in
driving automobiles and other vehicles
OF land transportation, but actual
serious consideration Of It's application
awaited the development OF the steam
:, ,turbine. When turbine development
had reached the stage where It COM
bined high speed with light weight
and reasonable economy In fuel con-
sumption engineers were ready to
adopt electricity as the means Of
transmitting the power Of the turbines
TO the propellers.
The steam turbine, as every one
knows, is like many other modern In
yentions-merely the extension and
adaptation Of a principle which has
been well known to humanity for
many thousand years. Essentially, 1t
is nothing more than the water wheel
familiar to every boy and girl, except
that instead of water the stream
which passes across the blades fixed
to revolving shaft Is a stream of
steam at high pressure and the entire
shaft with its hundreds Of blades is
enclosed in steam tight covering.
The change Of elements from the
water Of the mill race to high pres
sure steam, however, has an impor-
tant effect. If the greatest efficiency
IL to be obtained, that Is, IL the great
est power is to be generated in pro-
portion to the water and coal or other
fuel consumed in making steam, the
turbine must be run at very high
speed.
The fact that the machine has no
reciprocating parts of course results
in q very great reduction in the
amount of vibration as compared
with the old fashioned type Of marine
or stationary engine, and this fact
combined with the greater economy
and simplicity OF the mechanism.
served to commend its adoption to de-
signers of marine engines nearly a
quarter Of a century ago. But there
is a distinct limit to the speed at
which the screw Of a steamship may
be driven to produce the maximum
propelling force, and this limit Is far
below the economical speed Of the tur-
bine engine. An increase In propeller
speeds above certain well established
limits not only gives no increase in
the sheep Of the ship but even results
In a decrease, due to the churnine
effect of the screw.
stern Driving Troublous.
The first effort of the designers
therefore, was to combine these two
Hlechanisms. the high speed turbine
and the low speed screw propeller by
means OF reduction gearing, just q,
the high speed gasolene engine is
geared down to the drive shaft Of ar
automobile. In this they were sue
cessful to such degree that for sew,
eral years practically all the fast,
est types Of steamships, both CONNER
cial liners and vessels Of war. hav,
been driven by steam turbines with
suitable reducing gears. There still
remained. however. several disadVan
tages. the chief Of which was the ne
cessity Of mounting separate turbines
for driving the vessel astern.
The electric generator, like the tur
bine. reaches its greatest efficiency a
high speeds and the combination Of
turbines and generator on the sam
shaft and theferore revolving at tn
same speed Is now the usual, In fact
the pnly type Of power station on land
The success attained in the perform
anoss Of tthe U. s. s. New Mexico
recently commissioned and assigne,
as flagship of the Pacific feet, indi
Gates that floating power stations O
this type. Transmitting their power t
the ships propellers through electri
Kaotors. will become the twentieth
century method Of propulsion afioat
tust as the electric street car. sub
way and locomotive have become tn
Ast word In locomotion on land.
- So successful has this ship prove
that the United States navy has bee
won over to the principle OF tn
electric drive and has determined I
equip all future capital ships wit
electrical machinery, while the theor
already Is making strides in the meI
camille marine field. Thus electricit
comes again to the forefront OF scien
the achievement and the electrical