The herald. [volume] (New Orleans, La.) 1905-1953, 1917-11-08
UNIQUE TEST FOR LIBERTY ENGINE

ance Of these untried types.
So they set to work to build con
crete, tOmb-like structure, about -
feet long by 6 feet wide and 6lz feet
high. This concrete chamber was so
instructed that il could be made Il
vacuum II necessary. The walls are
- inches thick and tarred on the out
side. They needed thick walls be
! Cause AT 2O,ecO feet altitude the air
pressure is about seven pounds to the
! square inch--about half the pressure
at sea level. That meant that when
| Tho scientists got 10 duplicating air
! pressure at 2O.uGO feet the walls had
! 20 support an outside pressure If air
equal to eight pounds to thu square
inch. Ii the walls were not built thick
they would crush in like paper.
Either Hct or Cold.
Then complete heating and re-
. frig"rIting plant was Installed 50 that
when the four or six big fans which
are to whirl The air over the engine AZ
~ miles an hour start their gale II
will be down 10 the temperature that
one finds thousands OF feet Up.
Into this air chamber they expect
to put the engine type that Is 10 be
/ tested mounted SO that 1t can tilt for
ward backward or sidewise, tust Us II
would behave In the air.
As SON as 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 as the
/ outside air, but when the engine be-
gins To 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-
I perts may watch instruments which
register the air pressure and the tenn
perature of the chamber. BY data So
cured in actual flights the bureau eX-
pertS know the exact density Of the
air at each of the various hundred
foot levels. An ordinary aneroid ba-
rometps would give this data only ap-
pruXimatc!y. When the engine starts
and begins consuming air on the in
side Of the chamber the inside pres
sure begins to drop from l. pounds To
the square inch 10 II pounds. To Is
! pounds and 50 on, until it has reached
rarity that CORRESPONDS To great
| height
As soon as II 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 NJ the desired rar-
| Try, and 10 all intents and purposes
/ the engine IS now flying al an altitude
| OF 10000 feet.
General Mobilization.
As soon rs the engine starts. Other
parts OF the chambers machinery start
too. For instance. the exhaust begins
10 work. II would be utterly imprac-
ticabie 10 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 a great quantity OF atmosphere
! back up the exhaust pipe, Ill the
chamber with fumes and smoke and
reduce the inside pressure TO normal.
To overcome this the experts de-
signed blower attachment which will
suck the gases and fumes from the e.
CINE with n force sufficient 10 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
out trouble. Every ounce OF pull It
generates Is transmitted to big cleo
tric generator on the outside, and the
amount Of electricity generated by the
engines power makes ii perfectly SIM
pie for the scientists to determine
when the engine Is faltering
Through the glass doors Of this con-
crete chamber. the scientists Will OBJ
serve the engine itself or the instru-
ments attached, which Will register
every performance OF that piece OF
mechanism. II II won't work IN an
air-pressure OF seven pounds to the
inch, that engine will never do for high
observation work.
Tests Pre-compression Also.
Broadly speaking. this is the chief
use TO which that concrete chamber
will be put. 1t has another use. how
ever. That Is the testing OF pre-com-
preston devices. Il has been found
advisable to equip oil airplanes that
are expected 10 attain great height
with a pre-compression attachment.
This is designed TO gather and con-
centrate q quantity OF air and at the
moment OF each discharge OF the CYL
inders, inject II into the cylinders 10
supplement the deficient supply that
the engine can take through its intake
valves.
There are many Of these pre-com-
preston devices being offered TO the
government. which at this time cannot
be proven except under actual battle
conditions. but with the use Of the