New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1899-06-18
CERTAIN cRossTowN sTREETcARs.

other uses. and II has done certain kinds OF
work satisfactorily. II runs small engines. Op-
crates drills for blasting purposes. has an ex-
tensiye popularity in mines, furnishes the high
pressures needed in caissons FOR submarine
work is employed in airbrakes and railway
signalling propels mail and merchandise through
pneumatic tubes and drives a great variety OF
other machinery. 1t has also been used 70 hurl
dynamite shells from cannon whore ordinary
gunpowder was likely to do harm TO both pro
jecte and gun.
The attempt to utilize compressed air in OPP
Grating streetcars dates back ten or fifteen
years but until two three years ago ths
venture was not attended with reasonable sue
cess Certain difficulties peculiar to that class
Of work were overcome only after prolonged
experiment. that this particular development
IL distinctly modern one.
II IL only after recognizing these facts that
one is in 4 position to appreciate the beauties
Of the big air compressor that has Just been
installed at West Twenty -fourth-st. and the
North River. romnally for the American Air
Power Company but really for the Metropolitan
/ Traction Company. which is about to run
/ or its crosstown cars with air.
/ When power is stored for future use by com
pressing air it is usual 70 put the latter into
storage tanks at a higher pressure than that
| al WUltn II - USED ne nlHueT tue pressure
the work is obtanable from a given vol
ume. Accordingly. when any Wholesale Job. like
running heavy streetcar for several miles Is
about to be performed It Is desirable TO employ
: much greater pressures. at least for storage
purposes. than in any Of the other common ap-
plicatons Of compressed air. The gas enters
. the cylinder of the motor at a pressure OF 80
pounds to the inch. perhaps, having first passed
through reducing valve"
But the huge TASKS or bottles that are placed
under the to carry the compressed afr are
charged at the station at a pressure OF 1000
pounds TO the inch or more. The compressor
that charges these TASKS and the stationary
storage tanks at the power house then. must
ne capable Of squeezing the air down TO about
200 or 800 pounds to the inch.
The plant just installed In West Twenty
fourth-st. is exceptional In being the first COM
binaton made OF engine Of 1000 horse
power with a compressor that develops 900
pounds 10 the inch. The engine. built by the
Ais people, Of Milwaukee. il OF the vertical
. cross compound type. The compressor made
by the InGersoll- Sergeant company divides It's
work into four stages. AT the first 1t brings the
pressure up TO ~ pounds, at the second to 1S0
al the third to SO and at the last TO 300 The
height OF the double machine Ia sixty feet
steam engine In the latter. vapor. already
under high pressure pushes piston along ard
develops power thereby In a compressor power
from another source pushes the piston, and thus
squeezes Up air from a low 10 a high pressure
Just as the expansion Of the steam Is often IL
vided into three or four stages. so the COM
preston Of air is usually effected by degrees
instead Of all at once. This compressor has four
cylinders The biggest has a diameter Of 10
, inches and carries on the Arst part OF the work.
p The next has diameter Of "a inches. the third
one is II inches across and the fourth only q,
But the pistons in them all have strokes Of the
, same length-GO inches.
Here is another point Of comparison between
the engine and the compressor. Expansion chls
any yapor and compression heats it, The steam
r that enters the cylinders Of an engine grows
cooler and cooler It drives the piston before
IT, The air in a compressor gets hotter and
hotter as the piston drives il into a corner II
a single-stage compressor is used 70 carry the
Z pre- ssure up to 100 pounds TO the inch ordinary
! atmospheric air would be heated to 40 or per-
haps 80 degrees Fahrenheit This would 30
bad for machinery 1t is customary. therefore.
% divide the work into two or more stages. and
send the hot air into apparatus fOr cooling II
d after each compression. BY going up 70 only
80 pounds at the outset the temperature is kept
- down to the vicinity Of 300 or 80 degrees The
four-stage compressor is provided with four
coolers one for each cylinder. that the air
3. enters the storage tanks at something like ordi-
nary temperatures
- The steel bottles in which the air is stored are
% intended to sustain a pressure Of only 300 or
= 800 pounds ordinarily but 70 insure safety
they are tested up to 1000 pounds to the inch
before being put into service. In the power sta
ton about six hundred ~ these bottles are 20