Evening star., 1932-06-05
SCIENCE MEASURES
STRAIN IN D|R|G|BLE
Half Of 0ne-Thousandth of
an Inch Recorded on
New Instrument.
BY the Associated Press.

AKRON, Ohio. June 4-Measuring
the stress, or ache" Of glider in an
ariship has been reduced to terms of
less than half a thouSandth Of an inch
by new instruments developed in the
Goodyear Zeppelin research depart
ment here.
Numerous gauges and instruments are
located at almost every conceivable
point on the U. S. s. Akron structure.
approximately a thousand Of these
gadgets are scattered over the frame
work and wire used to restrain the
giant gas cells to their places.
Some of the instruments are new,
designed by DR.. Wolfgang Klemperer
and associates Of the research depart
ment. Others are improvements on ex-
isting devices.
Measures Minute Strain.
One Of the newest is the micro
paralactic strain gauge, which will
measure contraction or lengthening OF
an aluminium alloy girder amounting
to only a hundredth of a millimeter, or
less than half a thousandth Of an inch.
A change of three -hundredths of a
millimeter in an 11-inch length of
one type of girder used in the Akron,
and her sister ship. the U. S. S. Macon,
now under construction, represents
strain Of 1000 pounds to the square
inch.
The gauge has the appearance of
small range finder, with an eyepiece
in the center A pocket battery furnish
es beam Of light at either end, and
two knobs, operated like those on
radio set, regulate intensity OF the lights
SO there in no overshadoWing OF the
image seen through the eye piece.
Before the girder is even placed in
the ship, two marks exactly II inches
apart are engraved on the surface by
means Of special tool. When experts
a ship in fight, they train the gauge
on these marks
Read Extent of Stress.
If there is no appreciable strain,
system Of prisms brings the two marks
into a single image observed through
the eyepiece. II there is strain. the
effect is seen in separation OF the two
images. the direction of shift indicating
whether there is contraction or expen-
sion. A scale also seen through the
eyepiece permits the observer to read
the extent of the stress
BY marking the girder before 1t even
is placed in the ship, scientists at
Goodyear Zeppelin consider they have
begun at zero in stresses upon the
metal.
Strain Set to Music.
Moreover, as long as the original
marks can be found, observations may
be made at any time during the life
Of the ship, and the total stress deter
mined from before the time the beam
became a part Of the structure.
Another device improved by Good
year-Zeppelin research engineers, the
acoustic strain gauge, makes audible.
in musical notes. the stresses Of the
airship framework.
A wire is clemped over a measured
distance Of the frame. and increased
length Of the girder results in increased
tension OF the wire. An electromagnetic
defects another wire, tension of which
is known. Sound of the DETECTED wire
is picked up, as from violin string,
magnified and a standard tone re-
produced through loud speaker. FIRE.
quency of the two DETECTED wires thus
may be compared. and the tension of
the test section determined.
A number Of such listening posts"
may be located throughout the ship
and "soundings" made at intervals by
an operator through switchboard.