ers
o te
2
lta ceticee HE oll, *heh cnc
broad that it masked a small record.
for lack of record was not isolated.
retabyss ats5
ae
prerenee nmin
eat
&ewil
ll tani
=
amen
the failure of the timing arrangement allowed the gage to continue
running until a reference line hed »%een scratched on the disc so
yo ao
Noponeanincetat
peerrr
off the turntaple. At lower pressures, a stopped-up orifice might
prevent the formation of a record or, as occurred in one or two cases,
In a few other cases, the reason
In some instances records were obtained but differed from those
produced by the other geges at the same station or presented wilikely
characteristics. Several possible explanations have been offered,
some of these being turbulence created at the front gages causing an
i“erroneous pressure to be méasured by the rear gages, dynamic effects
pf ich cause the responses of the vaiious pressure elements to fluctui ate about their static calibration responses by differing amounts,
\(Wariations in the degree of danping of the capsules, and obstructions
“Whichhave found their way into the orifice.
As yet, a thorough
investigation has not been made of the first three cases, but where
the top of a record was clipped above a certain pressure, it was
found:that some of the permatex which was used to seal the element
gaskets" had,been squeezed into the orifice thus forming a sort of
pressure sensitive valve that was forced closed after the pressure
, reached a dertain value and which did not reopen until the outside
pressure
capsule cduld
“decayed sufficiently that the air trapped inside the
force the "valve" open again.
In another instance of an
erroneous record the orifice was found to be jammed with a very Pine,
hard packed dust. eh
The most :r¢vele¢nt case and, thus, the most disturbing was that
of distorted re
en an attempt is made to compare the gage
inspection data with fe
7
cocrds an unfortunately scattered array of
data presents itself, Ts.
h gage has its own peculiar combination
of turntable wobble, éijiyley, and shaft slippage and very few of the
gages are submitted to“tte s
intensity of shocks caused by
chips on gage surfaces). And,
magnitude of blast pressure or
[flying debris (as indicated by depth of
again, it mey be difficult to separate:
over~shoot in the record fromithe effect of vibrations except where an
indication of the extent of
mping1s given, Even a process of list.
ing the gages in the order of the geverity of a particular fault and
then looking for a trend in the coy
ponding records 1s couplicated
by the interpley of separate faults,
e.g., the same amount of turn~
table wobble in two gages in the same pragsure range may give varying
effects on the record depending on the
e the stylus arm mexes with
the plane of the turntable.
A cursory examination of the recordér)
and its comparison with the
notes on the gages, neglecting as it would
.:: :? the interplay of
gage defects, points to the wobdle in the « : *.:, + ag the chief cause
of the amplitude distortion of the records. Ib;4¢6 difficult to tell
whether the backlash present in the gears of ajl-the drive motors is
alone responsible for the distortion of the ae on
n fe time axis
or whether it is a combination of this and the slip
he coupling
together. This is a valid point of doubt since the meh ble shafts
in some of the gages bound in their bearings thus cr
g a breaking
effect (similar to that of the braking added to some ‘ofthe modified
P, gages) which would tend to prevent backlash.
76