The St. Charles herald. [volume] (Hahnville, La.) 1873-1993, 1917-11-17
UNIQUE TEST FOR LIBERTY ENGINE

To approve or condemn the perform
ancc of these untried types.
So they set to work to build Il con
crete. tomb-like structure, about j.
feet long by s feet wide and 612 1eet
high This concrete chamber was ;"
constructed that it could be made
vacuum if necessary. The walls are
l. inches thick and tarrel on the out
side. They needed thick walls be-
cause at 10000 feet altitude the air
pressure is about seven pounds to the
square inch-about half the pressure
at sea level That meant that When
the scientists got 10 duplicating AR
pressure AT 10000 feet the walls hau
10 support an outside pressure of air
equal to eight pounds To ia" square
inch. II the wallis Wer" not built thick
they would crush in like paper.
Either Hot or Cold.
Then a complete heating and re-
frigerating plant WAS Installed ;" that
when the four or six big fans winch
ore to vhirl the air over the engine III
10 miles All hour start their gale IL
will be down to the temperature that
one finds thousands Of feet up.
Into this air chamber they expect
to put the engine type that IS TO BE
tested. mounted 50 that it can tilt for
ward. backward or SidewiSe, just as it
would behave in the air.
As soon us everything is ready the
doors are locked and made alright,
and the engine is started. When it
starts. the air on the inside of the
chamber is the same density rs the
outside air, bat when the engine be-
Gins 10 suck in air To make explosions
the inside atmosphere rapidly becomes
exhausted. The chamber is provided
with an intake valve which will admit
the air that is needed.
The chamber is also provided with
glass windows, through which the eX-
pprts may watch instruments which
register the air pressure and the tenn
perature of the chamber. BY data Sc
cured in actual flights the bureau eX-
perts know the exact density of the
air at each of the various hundred
] =
rOmeter would give this data only np-
proxinately. When the engine starts
and begins consuming air on the in
side of the chamber the inside pres
sure begins to drop from Il pounds to
the square inch TO IA pounds. to Is
pounds and 50 on, until it has reached
rarity that corresponds 10 Il great
| height.
As soon az 1t reaches this rarity the
| intake valve is opened slightly. and
| only enough air is admitted TO take the
/ place of the inside air that the engine
| is consuming. This, of course. keeps
the pressure inside at the desired rar-
/ ity, and to ell intentS and purposes
/ the engine is now flying at an altitude
! of 10000 feet.
General Mobilization.
AS soon as the engine starts, other
| parts of the chambers machinery start
| too. For instance, the exhaust begins
| to work. 1t would be utterly imprac-
| ticable to discharge the gases from
! the engine into the outside air through
| the ordinary exhaust pipe. With the
| air inside at seven pounds pressure
and the outside air at Il pounds the
! force of the outside pressure would
| jam great quantity of atmosphere
back up the exhaust pipe, fill the
| chamber with fumes and smoke and
reduce the inside pressure to normal.
| To overcome this the experts de-
h i,I,, II
/ suck the gases and fumes from the en-
I zine with a force sufficient to prevent
the outside air from rushing in. Also,
+ the fumes and gases will pass through
! pipes which spray these gases with
! cold water, thus keeping down the
temperature in the chamber.
The actual horsepower performance
Of the engine can be determined with
ont trouble. Every ounce OF pull it
generates is transmitted To Il big cleo
trio generator on the outside, and the
amount of electricity generated by the
engines power makes it perfectly sim
! pie for the scientists to determine
/ when the engine is falterng
/ Through the glass doors of this con
/ crete chamber, the scientists will OBJ
/ serve the engine itself or the inStru-
! mcntS attached, which will register
/ every performance of that piece of
! mechanism. If 1t won't work in an
! air-pressure Of seven pounds to the
! inch, that engine will never do for high
| observation work.
Tests Pre-compresson Also.
| Broadly speaking. this is the chief
/ use 10 which that concrete chamber
will be put. 1t has another use, how
! ever. That is The testing of pre-com-
| preston devices. 1t has been found
| advisable To equip all airplaneS that
| are expected to attain great height
! with a pre-compreSsion attachment.
| This is designed TO gather and CON
/ centrate n quantity of air and ut the
/ moment of each discharge Of the CYL
! inderS, inject it into the cylinders to
! supplement the deficient supply that
rlA engine can take through its intake