Evening star. [volume] (Washington, D.C.) 1854-1972, 1929-05-26
V WILBUR WRIGHT FIELD.
~ Dayton, Ohio, May 25.-
w Army engineers here are
h q occinnn thu 1nnnCf


M Dayton, Ohio, May 25.-
Wv Army engineers here are
v Harvesting the most
terrific centrifugal forces ever
produced by man to learn secrets
which will spell greater safety
to those who ride the air.
The greatest propeller test stand
in the world, on which a propeller
40 feet long may be whirled to
destruction by electric motors
totaling 5000 horsepower, now is
to be constructed here as part OF
a unit of three similar stands.
The first of these stands, equipped
with 5000 horsepower motors, now
is almost ready for operation.
The stands will be used to test
every type of propeller used by
the Army to determine whether
they are safe to use. Experts in
charge of the stand characterize
aviation propellerS as the worst
potential source of bad crashes
known today, especially in the
case of the multi-motored plane
where the props" are swung
alongside the fuselage.
On the 3,000-horsepower stand
now virtually completed here, any
type of aviation propeller now in
use may be run to destruction.
Speeds of as great as 1890 revolu-
tionS per minute may be obtained.
Army officers say it is almost i'm
possible to appreciate what this
means in terms of destructive
force.
Have Tremendous Force.
At this speed, it was pointed out
by M. A. Smith, chief of the pro-
peller test work, the tips Of the
ordinary aviation propeller are
field rifle bullet. When the hub
of a propeller travelling at this
velocity snaps the blades fly off
with as much force as 6-inch
Navy rifle shell of the armor-
piercing type. The striking force
of half a blade whirled off the Jack
shaft at this speed is estimated
at 100000 pounds, MIR. Smith
said.
Naturally, when a blade lets go
at such a speed, an enormous
strain is developed on the motor
and it's mount, especially when
only part of one blade let's go and
the uneven weight continues to
whirl at enormous speed. In order
to handle this strain a huge steel
and concrete anchor" weighing
5000 tons, imbedded to a depth of
more than 25 feet in the earth, is
required, this huge anchor alone
costing $4,000 to $4,000, Mr..
Smith said.
The new stand is being con-
structed in accordance with de-
signs prepared on the basis of ex-
perience with a smaller stand of
the same type at McCook Field,
Dayton, which now is being
abandoned by the Army Materiel
Division in favor of Wright Field.
Cuts Half Through Rail.
On this McCook Field stand,
said Mr.. Smith, who is known
throughout the Air Corps as
IN. A." micarta propeller blade,
which is composed Of nothing but
layers of canvas impregnated
with a chemical compound and
bonded together under enormous
pressure, was turned up until it
snapped. When the fabric blade
broke off the hub one blade
hurtled through six inches of oak
and four inches of pine without
any perceptible lessening of force.
Another similar blade cut half
way through railroad rail
weighing so pounds to the foot,
cut the entire end off a small
building near the stand, took the
top off a high-tenSion post and
then "cartwheeled" a long dis
lance over the ground before ex-
pending its energy.
To safeguard the personnel en-
gagged in the tests bombproof
room has been constructed deep
down in the monster concrete
foundation. The top OF this
bombproof room is composed Of a
layer of 24-inch steel I beams on
edge, pad" of six inches OF oak,
also on edge; two inches Of chan
mel steel, four inches more of oak,
and, finally, on top, two inches of
steel armor plate. Thus a total of
more than three feet of steel and