Evening star. [volume] (Washington, D.C.) 1854-1972, 1903-07-25
TEST MOTIVE POWER
PROF. LANGLEY'S ASSISTANTS
HAVE BUSY DAY.
Believed That the Machinery Hardly
Came Up to Expectations
of tho Experts.

Special Dispatch to The Evening Star.
Underwater, Va. July 25.-The Smith
sonian Institution experts in the Langley
airship expedition are now giving consid-
cradle attention to perfecting the propellers
for the machine The two-blade apparatus
has finally been selected The principle is
that as the numerous blades advance they
strike atmosphere whose inertia has been
disturbed by the preceding blades. when
there Is not the same amount Of resistance
offered.
It is the expectation Of the inventor to
secure the best results from the propeller
when the machine is running at highest
speed. for he has ascertained from expert
ments that the higher velocity the less the
percentage of what is known as slip and
the greater the efficiency. 1t is also dis
closed that with increased velocity sharp
pitch of the blades gives good results In
fact. Prof. Langley's plans for this portion
Of his machine are being worked out with
regard to the analogy between the best
forms OF aerial and marine propellers.
In the calculations Of the inventor the in
ertia of the air has been an essential con-
sideration 1t is by taking advantage of
this property well that of the elas-
ITCHY of the air that Professor Langley has
persiStently followed the belief in the &C
complishment of rapid aerial navigation.
Associated with the repeated test Of the
propellers the gasoline engine has been test
eu Win regard 10 the amount
of vibration which 1t occasions to the frame
of the aeroplane. Before a flight is at
tempted the jarrng from the engine will be
reduced to a minimum. There is trouble
about developing sufficient gas. The engine
already shows sufficient power to maintain
flight at a high velocity.
Once since he has been on guard Pri-
vate Allison relaxed his stern reserve to
would-be visitors Yesterday a young lady
in boat sailed close to the boat house and
called out. Are you Mr.. Allison?" The
military man gave way and acknowledged
his identity. but even feminine persuasion
availed nothing in the way of extracting
information as to the date OF the first eX-
pertinent.
Yesterday afternoon. through one Of the
end windows sight was gotten Of a
large propeller with two blades which
was being tested. The thing was revolving
rapidly. but it was apparently not com
Ing up to expectations. as the process was
stopped several times at brief intervals
both as a mean of guidance and of forcing
a passage through the air. will be tested re-
peatedly until the Smithsonian experts are
convinced that 1t Is sufficiently perfected to
perform its intended function. The two
wings one fore and one aft on each side,
are expected to give the machine it's soar
ing capacity. just the wings of the buzz
Zard and the ancient pterodactyl sustained
those creatures without fappings. while
they coursed through the air. But it is
Prof. Iangley's idea to depend upon the
propelling force OF the two rapidly revolv-
Ing blades behind to supplement and COM
plete the sustaining power of the wings.
In making his plans he has relied largely
upon the principle of physics which made
1t easier to hold up in the air a body going
at high velocity than 1t Is to sustain one
travelling slowly.