THE MECHANICAL ARM

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP83-00423R001200070002-9
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 22
• Document Creation Date: November 9, 2016
• Document Release Date: November 16, 1998
• Sequence Number: 2
• Content Type: REPORT

Approved For Release 1999/09/10 : CIA-RDP83-00423R001200070002-9
CPYRGHT
General Mills, Inc.
Q 1ECHANICAL DIVISION
rpp
THE MECHANICAL ARM
A remotely controlled manipulator for performing a handling job in nuclear labora-
tories, in powder plants, and in other activities where exposure of an operator is
undesirable. This general purpose manipulator is power driven electrically. Unit
provides for shoulder, elbow, wrist, and hand motions. Hand and special tools
replacement remotely interchangeable. Crane bridge carriage and vertical telescop-
ing column available for extensive space coverage if desired. Variations of unit
specified obtainable for specific applications. Typical specifications, accessories, and
special features indicated on reverse side of this sheet.
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 CPYRGHT
TYPICAL SPECIFICAT ONS*
(Specifica ?ions below based o Model C)
ARM MEMBER
SHOULDER ROTATION -
SHOULDER SWING - -
ELBOW SWING - - -
WRIST ROTATION - -
HAND CLOSING; - - -
HAND FORCE - - -
WRIST TORQUE - - -
ARM SWING TORQUES -
SHOULDER ROTATION TORQUE
VERTICAL LIFT (With all members
of arm vertical) - -
CONTROL POWER SOURCE -
CONTROL WEIGHT -
ACCESSORIES AND SPECIAL FEATURES -
21/2 R FM Max. Speed, 1400? range
2/3 R FM Max. Speed, 1.80? range
2/3 R M Max. Speed, 110 range
6 R M Max. Speed, Continuous range
15 I r. P.M. Max. Speed, 5-inch range
1501 s.
30 Ft. Lbs.
120 F . Lbs.
40F.Lbs.
110 lolt 60 Cycle Single Phstse 1KW
Normal Max.
200 L s.
135 L s. (without crane or column)
Determined by environmental conditions
Teles ping columns for vertical motion,
bridge carriages, under-water operation
featu s, grip and load indicators, cable
reel take-up units for crane bridge applica-
tions, use of special materials, special
power source requirements,' and load re-
quirements are all items which can be sup-
plied and/or adapted to special installa-
tions.
*Custom manipulators of all sizes and capacity can be esigned and constructed to meet specific
application requirements. Specifications of other models obt inable upon request.
For further information
Write to ...
EQUIPMENT SALES DEPARTMENT
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GP 'A
.,oo~fA A'i
 Approved For Release 1221/09/10 : CIA-RDP83-00423R001200070002-9
CPYRGHT
General Mills, Inc.
1.
QVIECHANICAL DIVISION
THE MECHANICAL ARM
A remotely controlled manipulator for performing a handling job in nuclear labora-
tories, in powder plants, and in other activities where exposure of an operator is
undesirable. This general purpose manipulator is power driven electrically. Unit
provides for shoulder, elbow, wrist, and hand motions. Hand and special tools
replacement remotely interchangeable. Crane bridge carriage and vertical telescop-
ing column available for extensive space coverage if desired. Variations of unit
specified obtainable for specific applications. Typical specifications, accessories, and
special features indicated on reverse side of this sheet.
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 CPYR9Troved For Release 1999/09/10: CIA-RDP83?00423R001200070002-9
TYPICAL SPECIFICATIONS*
(Specificat!ons below based on
Model C)
RM MEMBER
A
SHOULDER ROTATION - - - - - - 2'/s RP
Max. Speed, 1400? irange
SHOULDER SWING
- - - - - - - - 2/3 RP
Max. Speed, 180 range
ELBOW SWING "-
- - - - - - - 2/3 RP
Max. Speed, 110*! range
WRIST ROTATION
- - - - - - 6 R
Max. Speed, Continuous range
HAND CLOSING! - - - - - - - - - 15 In
P.M. Max. Speed, 5-inch range!
HAND FORCE - - - - - - - r - 150 L
s.
WRIST TORQUE - - - - - - - - - 30 Ft
Lbs.
ARM SWING TORQUES - - - - -
- 120 F
Lbs.
SHOULDER ROTATION TORQUE - -
VERTICAL LIFT (with all members
- 40 Ft
Lbs.
of arm vertical) - - - - - - - 750 L s.
CONTROL POWER SOURCE - - - - 110 V~ It 60 Cycle Single Phase -KW
II Normal Max.
CONTROL WEIGHT - - - - - - - 200 L s.
ARM WEIGHT - - - - - - - 135 L s. (without crane or column)
MATERIALS - - - - - - - - Deter ined by environmental conditions
ACCESSORIES AND SPECIAL FEATURES - - Telescoping columns for vertical motion,
bridge carriages, under-water operation
featur s, grip and load indicators, cable
reel t ke-up units for crane bridge applica-
tions, use of special materials, special
powe source requirements,! and load re-
quire ents are all items which can be sup-
plied nd/or adapted to special installa-
tions.
*Custom manipulators of all sizes and capacity can be signed and constructed to meet specific
application requirements. Specifications of other models obt inable upon request.
For further information
Write to ...
EQUIPMENT SALES DEPARTMENT ZOp3f yfyv `$ rjljc~?~
PHONE R 8811
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 53-8-4proved For Release 1999/09/10 : CIA-RDP83-00423R001200070002-9
CPYRGHT
PLEASE NOTE:
Reprint of paper to be delivered at the Con-
ference of the Instrument Society of America
September 21 - 25, 1953, Morrison Hotel, Chi-
cago, Illinois.
CPYRGHT
This paper or any part thereof must not be
reproduced in any form without the written per-
mission of the Instrument Society of America,
1319 Allegheny Avenue, Pittsburgh 33, Penn-
sylvania.
Price to members, 25c; to non-members, 50c.
A REMOTE CONTROLLED MECHANICAL ARM
By
E. R. VAN KREVELEN, Project Engineer
General Mills Mechanical Division
Engineering Research and Development Department
Minneapolis, Minnesota
ABSTRACT:
This paper describes an electrically powered
mechanical arm and a unique remote control
system. This equipment has been developed to
fill a need in certain industries, such as Atomic
Energy, Munitions and Chemical, for a manipu-
lator with the versatility and flexibility of a
human arm to be used in areas unsafe for per-
sonnel. The design considerations, features, and
applications of the equipment are presented.
A REMOTE CONTROLLED
MECHANICAL ARM
INTRODUCTION
The advent of atomic energy and increased
expansion in the fields of high explosives and
chemistry has brought about increased de-
mands for the safeguarding of operating per-
sonnel. The handling of radioactive materials
with their penetrating and harmful radiations
requires remotely controlled manipulators. Op-
erations in this field are many and varied, and
impose difficult requirements for versatility and
dependability. Such requirements preclude the
design of special devices of limited use in favor
of more universal units having a variety of
functions.
A good compromise in remote handling
equipment is the Model E Mechanical Arm de-
scribed in this paper. This manipulator is a gen-
eral purpose, heavy duty instrument capable
of many independent and precisely controlled
motions. Since the human arm is one of the
most versatile handling devices known, the
Model E Mechanical Arm has been designed to
incorporate many of its features. Added to
these features are tireless operation and the
ability to assume any working position for in-
definite lengths of time. A wide range of sensi-
tivity permits the handling of fragile glassware
or heavy equipment weighing up to 750
pounds. The use of electric drive motors and
control circuits places no limitation on the dis-
tance between the operator and the Arm.
Fig. 1.-Model E Mechanical Arm and Control
- Console.
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The Mechanical Arm with its associated
crane is positioned by eight basic: motions.
These motions are non-interacting and are all
controlled by two pistol grip type control han-
dles on a single control console. The left hand
controls the crane bridge, cross carriage and
hoist while the right hand controls the shoulder
rotation, shoulder joint, elbow joint, wrist rota-
tion and grip member. Each motion has a con-
trol range of six speeds in each direction. The
control handle mechanism is designed in such
a way that movements of the operators arm,
as he grasps each handle, corresponds to simi-
lar movements of the Mechanical Arm. The con-
trol handle motions and the resulting arm and
crane motions are tabulated in Figure 2.
may be assembled or repaired remotely. "Feel"
has been purposely omitted from the hand in
favor of visual indication of the direct measure-
ment of gripping force ;and wrist torque. These
m ters have high and low sensitivity ranges, so
th it the operator can: control applied forces
raging from a few ounces to several hundred
unds. An audible system for force indication
h Js also been developed. Audio tone pulses
e anate from a loud speaker in the console.
A force increases the pulse rate increases pro-
rtionately making it unnecessary for the op-
erator to take his eyes away from the work.
This system is used in conjunction with the me-
ters so that either audio or visual indication
may be selected at the, throw of a switch.
CRANE DESIGN
ARM
CONTROLLING
CONTROL
'
ACTION
HANDLE
HANDLE ROTATION
CONTROL HANDLE
LDRM MOTION
CRANE
BRIDGE
LEFT
LEFT B RIGHT
SWING
+r
CROSS
CARRIAGE
LEFT
IN B OUT
TRANSLATIONAL
,
VERTICAL
HOIST
LEFT
UP 8 DOWN
SWING
/
y
GRIP
RIGHT
SQUEEZE
HANDLE
WRIST
RIGHT
LEFT a RIGHT
N
ROTATION
HANDLE ROTATIO
ELBOW
UP B DOWN
l
JOINT
RIGHT
SWING
SHOULDER
JOINT
RIGHT
IN a OUT
TRANSLATIONAL
I
l/
m
SHOULDER
ROTATION
RIGHT
LEFT B RIGHT
SWING
Fig. 2.-Table of Control Actions arid Corres-
ponding Arm Movements.
Two types of remotely interchangeable grip
members or hands permit a variety of objects
to be handled. One hand is a pair of spring
loaded parallel jaws and is used for general
purpose work. The other hand has a hook and
anvil arrangement for heavy lifting and for the
handling of round objects. Many special tools
as well as screw drivers and socket wrenches
may be grasped by these hands so that motors,
gear reducers and other mechanical equipment
he crane mount is made in two units. One
unit is a movable crane bridge which complete-
ly pans the work area..A cross carriage or trol-
le rides the crane bridge and provides transla-
tional freedom at right angles to the bridge
tr vel. The Mechanical Arm proper is suspend-
ed below the carriage: by a telescoping tube
ho st.
Fig[ 3.-Cross Carriage Assembly showing Ver-
cal Hoists and Transverse Drive Motors.
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Fig. 7.-Schematic Diagram of Crane Bridge
Control. This is typical of all of the Motor
Control Circuits.
One of the eight motor control circuits is
shown schematically in Figure 7. Each motor
has a bank of seven relays associated with it.
The two relays K, and K2 reverse the polarity
of the DC voltage from the rectifier which in
turn reverses motor rotation. The other five re-
lays K3 through K, are for tap switching. It can
be readily seen that these relays are in a fail-
safe circuit. If a relay should fail to close, only
the voltage tap picked up by that relay will be
lost. The rest of the circuit will remain undis-
turbed. If a relay should freeze in the closed
position, this voltage will automatically excite
the motor when the reversing relay closes. The
highest speed relay closed at any time always
takes precedence, so any combination of relays
may be closed without danger of short circuits
or other detrimental effects.
The relays are energized by rotary switches
of special design. These switches are mounted
on the control mechanism and are actuated by
movement of the control handle. The relays op-
erate from 24 volts AC which is supplied by a
separate transformer. Each relay coil is shunted
with a capacitor to reduce transients across the
switch contacts when the circuit is opened on
an AC peak.
All other voltage supplies are taken from the
main power transformer. There are three sec-
Fig. 8.-Basic Five Motion Control Mechanism
showing Rotary Switch Construction.
ondary windings on this transformer. The first
winding is rated at 260 volts and is tapped at
16, 24, 32, 48, 64, 82, 128, 156, 200, and 260
volts. These taps are wired in multiple to eight
rows of 10 jacks located on the relay mounting
panel. Immediately below each row of jacks is
a row of 6 cords and plugs. These cords termi-
nate at the normally open contacts of the speed
relays. With this arrangement any combination
of six speeds may be independently set up for
each motor. The motor field rectifier is excited
by the second winding which is also rated at
260 volts. The third winding supplies 18 volts
to the wrist torque and grip force indicator re-
sistance bridges. All AC voltages are about 20
per cent higher than the desired DC voltage.
These higher voltages are necessary to offset
the IR drop in the selenium rectifiers.
Figure 9 is a simplified diagram of one of
the force measuring bridges. DC excitation is
supplied to the bridge by a full wave selenium
rectifier. The resistance element is in the fore-
arm gearbox and is connected in potentiome-
ter fashion making it possible to sense both an
opening and a closing grip force. This also
doubles the system sensitivity since the bridge
has two active arms. The potentiometer wiper
is mechanically linked to a non-linear spring
which deflects with grip reaction force. The non-
linear characteristic provides increased sensi-
tivity for small gripping forces. The meter has
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 Approved For Release 1999/09/10 : CIA-RDP83 00423R001200070002-9
CPYRGHT
shoulder joint and elbow joint and their respec-
tive gear trains are enclosed in the upper hous-
ing. The wrist rotation and grip motors are ex-
ternally mounted on either side of he elbow.
These two motors are coupled by flexible shafts
to the forearm gearbox. The leads to all motors
pass through a slip; ring assembly inside the
main housing. A multiconductor coiled cable,
enclosed by the telescoping tubes, terminates in
a brush assembly fixed to the wall of the main
housing. A pancake slip ring is mounted above
the internal gear trains allowing the whole
mechanism from the. shoulder down to continu-
ously rotate within the housing. A speed range
from a few degrees per minute to 8 RPM is pro-
vided for this shoulder rotation motion.
The upper arm has a vertical swing of 180
degrees about the shoulder joint at a maximum
speed of 2/3 RPM and a torque of 75 foot pounds.
The forearm has 200 degrees of vertical swing
at approximately the same speed and torque.
A pantograph chain drive between tFe forearm
and upper arm keeps the forearm in the some
angular position in space as the upper arm is
swung forward and! back. This feature is par-
ticularly valuable 'When open containers of
liquid are to be handled without spilling.
The wrist may LLe rotated continuously in
either direction at a maximum speed of 6 RPM
and will exert torques up to 30 foot pounds.
The hand will open or close at a maximum rate
of 15 inches per minute with a maximum force
of 150 pounds for the parallel jaws and 600
pounds for the hook and anvil.
CONTROL SYSTEM
All crane and arm motors, with the exception
of the grip, are shunt wound and separately
excited. The shunt motor was expressly selected
because of its very wide speed range and con-
stant torque characteristics. The use of shunt
motors permits dynamic braking and allows
changes in position of only a few thousandths
of an inch at a time for all motions including
the crane. A split field, series wound motor was
selected for the grip because of its variable
torque characteristics.
Fit. 6.-Control Console showing Tilted Control
Handle Construction for Ease of Operation.
Early models of the Mechanical Arm utilized
th ratrons and magnetic amplifiers for motor
co trot. These controls provided a continuously
a justable speed range but sacrificed low cost,
re iability and valuable space. Field use of
these early arms showed, that at most, a six
speed control was ample for even the most
exacting work. With the six speed requirement
d finitely established, ci simple Ward Leonard
control system was designed.
The basic element of the present control sys-
te is a power transformer with a tapped sec-
o dory which provides a stiff source of variable
voltage. Relays, actuated by the control han-
dl s, select desired voltages from the trans-
former and feed them to selenium rectifier
bridges which in turn excite the motor arma-
tures.
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CPYRGHT
The crane bridge assembly is supported on
two stainless steel tubes 33/8 inches in diameter.
This tubing size allows a maximum span of 15
feet with minimum deflection under full load-
ing. A '/a horsepower, 220 volt DC motor is
vertically mounted at one end of the bridge. A
drive shaft through one of the tubes is geared
to the motor. Pinion gears on either end of the
shaft engage racks on the bridge tracks. Maxi-
mum bridge speed is 15 feet per minute.
The carriage is driven by a 1/6 horsepower,
220 volt DC, gear head motor. A pinion gear on
the gear head output shaft engages a single
rack traveling the length of one of the bridge
tubes.
The hoist is powered by a'/s horsepower, 220
volt DC motor. A drum which is geared to the
motor shaft drives the hoisting cable which
travels down the inside of the telescoping tubes.
An electrically released brake, integral with the
motor, will hold the hoist in any position. A
vertical travel of 87 inches can be provided by
only three telescoping tubes. Additional tubes
may be added for increased vertical travel.
Over-travel in all motions of the crane is
limited by cam operated micro-switches. The up
and down hoist limit switches are actuated by
a traveling nut riding on a threaded member
directly coupled to the cable supply drum. The
carriage and bridge have roller actuated
switches that are tripped by stationary cams.
Further protection is received from four spring
loaded switches mounted below the four cor-
ners of the cross carriage. These switches are
ensitive to a slight amount of carriage tilt and
interrupt the appropriate motion should the
rm or telescoping tube strike a fixed object.
When the Mechanical Arm is to be exposed
to corrosive atmospheres, all exposed metal
arts are either painted with Amercoat or are
abricated of stainless steel. By totally enclosing
he electric motors and using polyethylene in-
ulated wire, maximum protection is afforded
he electrical system.
ARM DESIGN
Fig. 4.-Mechanical Arm with Parallel Jaw
Grip.
The arm is powered by five 1/50 horsepow- Fig. 5.-Mechanical Arm with Hook and Anvil
r, 115 volt DC motors. The shoulder rotation, Grip.
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CPYRGHT
Fig. 9.-Schematic Diagram of Typical Circuit
for Measurement of Grip Force.
a zero center scale, and range changing is ac-
complished by varying the shunt resistance
across the meter terminals.
Each motor circuit is fused separately and all
fuses are located in the right hand leci compart-
ment of the control console. The output terminal
strips are also located in this section. The central
compartment contains the transformers, crane
rectifiers and relays; The arm motor rectifiers
are housed in the left leg. Front, rear, top and
side panels are removable for service and
maintenance.
Fig 10.-View of Control Console showing Ac-
cessibility of Components for Maintenance.
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 Approved For Release 1999/09/10 : CIA-RDP83-00423R001200070002-9
General Mills, Inc.
a
ECHANICAL DIVISION
LWO
CPYRGHT
THE GENERAL MILLS RYAN FLIGHT RECORDER
Model A
SOME IMPORTANT FEATURES AND ADVANTAGES
? Records air speed, altitude, vertical acceleration, time and heading
(optional).
? Continuous 300-hour recording.
? Operation for 10 minutes following power source failure.
? Recorded data will not be destroyed by 1/2 hour exposure to 2000?F
open fire.
? No electronic circuitry - maximum reliability, minimum maintenance.
? Self-contained - no remote pickups; connections to standard equip-
ment only.
? Direct recording - no magnetic playback, photographic reproduction,
or other process required.
? Weighs 16 pounds with fireproof case; 12 pounds with non-fireproof
case.
? Repeatability - no sensitivity or zero shifts.
 CPYRGHT
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SPECIFICATION FOR
THE GENERAL MILLS RYAN FLIGHT RECORDER
RANGE OF FUNCTIONS MEASURED*
ACCURACY OF RECORDING - -
Indicated air-speed: 0 to 500 miles per hr.
Altitude (standard pressure conditions):
1000 feet to + 40,000 feet.
erticat acceleration: -- 3G to + 12G`s.
ime: 1 minute, 15 minute, 30 minute and
0 minute marks.
eading (optional): 0-360?.
2% of full scale altitude pressure and
indicated air speed, -?= 0.2G on vertical
cceleration, and ? 3?: on heading.
Vertical accelerometer flat to two cycles
er second for optimum measurement of
ust and shock characteristics.
alibration charts provided with recorder.
OPERATING AMBIENT TEMPERATURES -
430?C to + 50?C.
METHOD OF RECORDING - - - - - - tyli embossing on aluminum foill 21/4 inches
ide and 1 mil thick.
SPEED OF RECORDING CHART - - - - - - 1/2 to 5'/2 inches per hour (constant rota-
ional speed on take-up spool). Time marks
oordinate trace events.,
LENGTH OF RECORDING - - - - - - - ontinuous, 300 hours; maximum.
METHOD OF DRIVE - - - - - - - - - 8-volt motor with power spring to escape-
ent mechanism which controls speed of
hart take-up drive.
PRESSURE SOURCE - - - - - - - - - - perates from standard pitot-static tube
nstalled on aircraft. 1/4 inch flared tubing
:onnection for pitot tube, 3/s inch flared
tubing connection for static pressure.
POWER SOURCE - - - - - - - - - - 22 to 32 volts D.C. No change in chart
speed results from voltage variation.
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 C P ~ MRT For Release 1999/09/10 : CIA-RDP83-00423R001200070002-9
THE GENERAL MILLS RYAN FLIGHT RECORDER
A record of a flight with various maneuvers.
Test record of flight at a series of altitudes for different indicated ai'r-speeds.
2.0 G LETTERS "A" SHOW RELATIVE
A INSTANTANEOUS POSITIONS
For further information
Write to ...
MECHANICAL DIVISION
 CP,M1w For Release 1999/09/10: CIA-RDP83.00423R001200070002-9
TIME OF OPERATION WITHOUT POWER
Approximately 10 mint. (except heading).
16.5 lbs. total with fireproof case; 12 lbs.
with non-fireproof case.
EXTERNAL DIMENSIONS - - - - - - - -
INSTRUMENT MATERIALS -
RESISTANCE TO FIRE**
RESISTANCE TO SHOCK -
RESISTANCE TO SEA WATER AND HUMIDITY -
METHOD OF ANALYSIS OF RECORD
INSTALLATION*** -
* Heading funciJion optional; availability subject to type
** Fireproof case optional.
With fireproof case inclluding supports, ap-
proximately 13'/s inches x 16 inches x 15
inches high.
With non-fireproof ease, approximately
111/2 inches x 14 inches x 13 inches.
Frame, aluminum; spherical fireproofing
case is double walled; outside wall zinc
plated mild steel; inside wall aluminum;
insulation between we Hs Perlite.
Record is preserved under 2000?F tempera-
ture for one-half hour': resulting from open
fire when fireproof case is used.
Designed such that record will not be dam-
aged under 100G acceleration or shock.
Record will withstand; 36 hours immersion
in sea water. Instrument designed to with-
stand salt spray and normal humidity tests.
Use of transparent overlay for rapid scan-
ning: For precision analysis, tool maker's
microscope or photographic enlargement.
Recommended for installation in tail of air-
craft to further increase resistance to fire.
Mounting lugs at essentially C.G. of in-
strument provided.
of compass instruments installed on aircraft.
*** All functions self-contained. No remote pickups require
compass instruments already installed in the aircraft).
that acceleration response of commercial aircraft to g
any part of the aircraft as it is at the C.G.
(except for connection to existing pitot-static and
is believed sufficient evidence exists to conclude
usts and landing shock is essentially the same in
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 CPYRGHT
PreprAppFgl1 do FtprbReL d19WQ%i t~C4ArR12P , A4&380 1200070002-9
Instrument Society of America, September 21-25, 1953, Hotel Morrison, Chicago, Ill.
Discussion sent to the ISA will be considered if received by October 1, 1953.
This paper or any part thereof must not be reproduced In any form without the
written permission of the Instrument Society of America, 1319 Allegheny Avenue,
Pittsburgh 33, Pa.
Price to members 25 cents, to non-members 50 cents.
Please Note: Statements and opinions advanced in this paper are to be under-
stood as individual expressions of the author(s) and not those of the Society.
The V.G.A. Flight Recorder
CPYRGHT
Abstract. The V.G.A. Flight Recorder is a
permanently installed instrument for con-
tinuously recording, on aluminum foil, the
indicated air speed, static pressure-altitude,
compass heading, and vertical acceleration
of aircraft for long operating periods. The
instrument records information sufficient for
determining the three dimensional flight
path of the aircraft. Abnormal atmos-
pheric disturbances, aircraft operational
variations, and other flight conditions are
recorded.
The instrument, mounted in the tail of
the aircraft, is light in weight, small in
size, predominantly mechanical, extremely
rugged, fire resistant, designed for mini-
mum maintenance, and will operate for a
period of time without electrical power.
IN 1948, the Civil Aeronautics Admin-
istration outlined suggested specifi-
cations for a flight recorder which was
proposed for installation in all com-
mercial aircraft. The purpose of the
recorder at that time was to aid the
government in accumulating data which
could be employed in arriving at recom-
mended operating procedures designed
to reduce air mishaps.
A survey revealed that there was a
need for development of a recorder
which would require a minimum of at-
tention with maximum reliability, pro-
vide for long recording, and offer re-
sistance to destruction by fire, water
and shock. Since that time, a number
f recorders have been developed. One
r more of the following disadvantages
as been found to prevail: weight was
oo great; occupied considerable space;
recording time was low; no resistance
o water, fire and shock was nil; elec-
ronic circuitry generally increased
aintenance, made reliability uncertain,
nd offered questionable repeatability
haracteristics. Initial, operating, and
naintenance costs were high.
Recognizing the limitations of elec-
ronic type recorders, Professor James
Ryan of the University of Minnesota,
eveloped a recorder which would pre-
lude these difficulties and disadvan-
ages. The principles developed by him
[ages. since been embodied in the General
ills Ryan Flight Recorder.
?L Manager of Market Development, Me-
chanical Division, General Mills, Inc., Min-
neapolis 13, Minn.
*2 Technical Specialist, Engineering Re-
search and Development Department, Uni-
versity- of Minnesota.
This recorder is unique in that it is
small; light in weight; preserves the
record under conditions of high tem-
perature, shock, and exposure to water;
is self-contained; and provides for long
recording. Elimination of electronics on
all functions, with the possible exception
of one, provides a high degree of reli-
ability, low maintenance, and repeat-
ability. Operation for a short time
following a power failure is another
advantageous feature.
Fig, 1. Upper Half of Housing Being Re-
moved
DESCRIPTION
The Flight Recorder shown in Fig. 1
measures vertical acceleration, indicated
air speed, standard pressure-altitude,
and time. Direction recording, with the
requirement of remote sensing, is avail-
able as an optional feature. These func-
tions, and the direction element, are
mounted in a spherical case, 111/2-in. x
14-in. x 13-in. high, including the exter-
nal instrument supports. An insulated
fireproof case, also available, slightly
increased the external dimensions to
131/2-in. x 16-in. x 15-in. high.
Fireproof Case
The fireproof case, made in two hemi-
spheres as illustrated in Fig. 1, consists
of an outer stainless steel shell and an
inner aluminum shell. Between these
shells is a one-inch layer of granulated
Perlite, an excellent temperature in-
sulator. At the separation diameter of
each half of the case, a solid retainer
is made from Marinite, also a high tem-
perature fire resistant material. The
fireproof case prevented destruction of
the record when the instrument was
exposed to a 2,000 F. flame for a period
of 30 minutes.
General Assembly of
Recording Mechanisms
Fig. 2 illustrates an exploded view
of the recorder elements.
Fig. 3 shows the recorder with the
upper and lower housings removed. A
portion of the instrument is mounted
on the upper side of a support plate and
the remainder on the lower side. The
upper assembly contains the recording
mechanism and the air speed sensing
component; the lower assembly contains
the altimeter sensing unit, the electric
chart drive motor, and the accelerometer
element. Pipelines leading to the pres-
sure sensing components are connected
at the side of the case. An electrical
receptacle for connection to the 28-volt
motor on the chart drive mechanism and
the conductors for the direction function
are at the same location.
The total weight of the instrument
is 16.5 lbs in the fireproof housing and
12 lbs. with a non-fireproof case. The
instrument assembly without a case
weighs 8 lbs.
Air Speed and Altimeter Elements
The air speed element is a pressure
diaphragm having static and dynamic
chambers. The air speed unit provides
a total displacement at the chart of
about s/.%-in. for an indicated speed of
500 miles per hour at sea level. The
altimeter unit is an aneroid bellows and
provides, at the chart, approximately
two inches of displacement for altitude
indications up to 40,000 feet. In each of
these elements, the diaphragms act upon
simple lever mechanisms providing a
magnification of approximately five at
the recording styli.
Vertical Accelerometer
The accelerometer element consists of
a block of metal supported by cantilever
springs. It is so designed that the move-
ment of the weight and, therefore the
stylus, is in a straight line. The accel-
erometer measures between the limits of
minus 3G and plus 12G for a total dis-
placement of about two inches on the
recording chart. The natural frequency
of the accelerometer is approximately
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Apprnvpd
430 cycles per minute. It is, by design,
damped for flat response pp to approxi-
mately two cycles per second. This value
was selected after careful consideration
of the nature of aircraft movement due
to air disturbances and landing shocks.
Therefore, in order to maintain this
natural frequency in the most active
range, a secondary spring is introduced
in the assembly which increases the
over-all spring rate when shock loads
are between 4.5 and 12G.
The styli of all the elements are
slightly displaced in the direction of
chart movement to preve t interference. with successively larger m ica ions ea
An additional stylus p ovides a base fifteen minutes, 30 minutes and 60 min-
line for all the primary unctions. The utes of time. These markings correlate
styli emboss impressions o a line width all recorded events with time.
of approximately 0.001 nches, as the
cha: t passes over a back ng plate. Record Analysis
Recording Medium and rive
The recording medium is full-hard
aluminum foil, 21/4-in. wide and 0.001-in.
thick. The recorder will accommodate
a chart strip up to 100 feet in length.
This length of record pro ides recording
for approximately 300 h rs flight time.
The recording strip is r Iled on a spool
which is driven at the rate of one turn
TIME MARK
Fig. S. Recorder Witj.iout Housing
per hour by means of a small 28-volt
d-c motor operating at revolutions per
hoar. At this drive seed, the chart
mcvement varies from .5 to 5.5-in. per
hour, depending upon he diameter of
the roll, or an averag of 41/2-in. per
hoar. The speed of the c art drive motor
is governed by a clock ork mechanism.
A spring drive betwee the motor and
the escapement mechan sm permits the
chart drive to run a proximately 10
minutes after the pow r to the chart
drive motor is turned o , or if the power
in the aircraft fails.
Time-Marker
A cam-operated styl s, activated by
a gear, indicates 1-minu a time intervals
For a quick analysis of the record to
provide a general indication of the mag-
nitude of recorded data, a transparent
template, which shows the calibration
of each function, is placed over the
record for reading at any instant of
time. The template, illustrated in Fig.
4, is marked in miles per hour, the alti-
tude in feet, the acceleration in G's, and
the direction in degrees. The template
and foil may be magnified by means of
a film reader for continuous scanning.
For a more accurate analysis, the record
may be' analyzed under a toolmaker's
microscope or other magnifying device;
or it may be photographed with edge
lighting and enlarged to any size de-
sired.
Operating Conditions
The instrument is highly resistant to
extreme humidity effects, and will with-
stand the vibration and impact condi-
tions experienced by normal aircraft
operation. The recorder is so designed
that the record will not be damaged
under a 10OG acceleration.
The record will not be destroyed when
exposed to a 2,000 F temperature, re-
sulting from an open fire, for a period
of up to 30 minutes and will be pre-
served for over 36 hours when immersed
in sea water.
Operating ambient temperatures are
in the range between minus 30 C and
plus 50 C.
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53-9-1
 CPYRGHT
The dr a eo
vary from 22 to 32 volts d-c without
affecting the operation of the chart
Accuracy
The accuracy of recording is com-
mensurate with the pilot's instrument
indications, since standard aircraft sens-
ing elements are employed. Simplicity
of design, ruggedness, reliability and
repeatability of results led to an instru-
ment with the following performance
tolerances:
1. Pressure-altitude at standard con-
ditions: Plus or minus 2 per cent of full
scale and plus or minus 200 feet at low
altitudes.
2. Vertical acceleration: Plus or
minus 0.2G over the full range.
3. Air speed: Plus or minus 3 per
cent of full scale and plus or minus 6
miles per hour at low speeds.
4. Direction: Plus or minus 3?.
Figs. 5, 6 and 7 illustrate typical cali-
bration curves for acceleration, air
speed, and altitude, respectively. Fig. 8
is an altitude correction chart taking
into consideration the existing baromet-
ric pressure at the time of recording.
As an instrument to provide data for
Fig. 5. Typical Calibration Curve for Verti-
cal Accelerometer
00
a
2.00 1
a00
00
30 0O
200
10000
SEA L.E VEL
E
INDI~
FUNCTIONS
INCLUDE
COM PR E SSIBILI
\1
loo 010 .30 AO .7o .9 t 1.10
INCHES DISPLACEMENT FROM REFERENCE
0
Fig. 6. Typical Calibration Curve for Air
Speed Element
1 r to altitude in feet.
.6 .B 40
Fig. 7. Typical Calibration
sure-Altitude (Standard
Curve for Pres-
Atmosphere)
29-0 29.5 30.0 30.5 31.0
Fig. S. Altitude Correction Curve
00-
00
00
00
'U
N
-
ff
00
00 -
5 0
0 2
0 3
0
0 5
o,
ALTITUDE IN THOUSANDS OF FEET
Fig. 9. Conversion Curve, Pressure in Milli-
bars to Altitude In Feet
analyzing air mishaps, it is desirable
to have a repeatable record based on
standard atmospheric conditions which
may be later corrected to the existing
barometric pressure for the area at the
time corresponding to the recorded
event. Such information is available
from meteorological records throughout
the country.
Fig. 9 is a chart converting pressure
Figs. 10 and 11 are typical flight rec-
ords illustrating recorded impressions
for various aircraft maneuvers.
INSTALLATION
For most applications, recommenda-
tion is made that the recorder be in-
stalled in the tail of the aircraft to aid
in its recovery in the event of an acci-
dent. There is sufficient evidence to
indicate that the movement of most air-
craft responding to gusts or landing
shock is essentially the same in the nose
and the tail as it is at the center of
gravity. Installation in the tail, there-
fore is quite feasible and desirable.
there are no special remote pickups
required; all connections being made
directly to existing aircraft signals in
parallel with instrumentation in the
cockpit of the aircraft.
The air speed and altimeter elements
are connected to the aircraft pitot-static
lines. Similarly, appropriate signals
from the fluxgate/gyrosyn instruments
in the cockpit are received by the re-
corder for use in the servo unit of the
direction element. In the event such
navigation instruments are not avail-
able or do not lend themselves to con-
nection in this way, a separate signal-
producing compass may be employed.
APPLICATION
CONSIDERATIONS
It is believed that a recorder of the
design described should have wide ap-
plication by commercial airlines, execu-
tive aircraft operators, the transport
service of the military, fighter and
bomber wings, and aeronautical re-
search and development activities.
The Airlines and Executive
Aircraft Use
Some uses, mentioned below, have
been suggested as a means of increasing
efficiency and reducing operating and
maintenance costs. There are very likely
many more uses of benefit to the airlines
not mentioned here.
1. Minimize inspection time required
through a knowledge of gust, landing
shock, and other overstressing loads. An
inspection procedure could be estab-
lished such that the degree of inspection
is a function of the degree of accelera-
tion measurement which the aircraft
has experienced. For instance, a small
recorded shock may suggest limited in-
spection, a larger record of acceleration
would mean slightly more inspection;
and a large record of shock may mean
complete inspection. The problem of how
much inspection need no longer be left
to guesswork.
2. Minimize consumption of fuel by
statistical determination of optimum
altitude, air speed, and take-off condi-
tions, for specific aircraft and various
payloads.
3. Comparison of performance of like
and different aircraft to aid in evalu-
ating future fleet purchases.
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 CPYRGHT
4. Statistical determination of elapsed
time of flight between established
points; assisting in the preparation of
time tables and providing statistical
information for establishing engine
checkup and overhaul periods.
5. Statistical determination of the
practicability of following flight plans
in altitude and direction for given fore-
casted weather and traffic conditions.
6. Based on the statistical determina-
tions of best flight conditions for maxi-
mum efficiency, pilots can! be advised as
to how best to fly the airgraft to obtain
flight efficiency and to reduce wear and
tear on equipment.
7. Determination of the degree of
flight roughness experienced for re-
ported atmospheric conditions; provid-
ing data for determining' the limiting
passenger comfort conditions and the
limiting conditions for precluding over-
stressing the aircraft.
8. Determination of fatigue condi-
tions through a knowledge of frequency
and intensity of stress conditions, per-
mitting studies on the life expectancy
of aircraft.
The executive aircraft! owner gains
the same kind of benefit: from the use
of such a recorder.
Development and Design; Use
The use of a recorder #vhich will re-
produce true acceleration! phenomena is
vital in aircraft structural design. The
concept of a true recording at low fre-
quency conditions is very important,
since the majority of overstressing con-
ditions resulting from air disturbances
and landing shocks are believed to occur
at frequencies below two cycles per
second.
The V.G.A. Flight ;Recorder, of
course, is not a laboratory instrument;
but it is a simple and rugged instru-
ment for field use and will yield results,
the validity of which, within the error
tolerances specified, is certain because
of the direct linkage recording mecha-
nism.
Its direct recording feature is desir-
able in flight test work where immediate
analysis is necessary to permit continu-
ation of the next phase of the test pro-
gram.
The Military Use
The Armed Services can rightfully
claim to be the largest operating airline
in the world. While the, military can
gain through reduction of operating and
maintenance costs of this' vast fleet, the
matter of safety in this particular oper-
ation is an aspect where! an immediate
gain can be realized. Analysis of air
accidents is extremely vital not only to
the saving of lives, but also in minimiz-
ing the number of aircraft losses.
To emphasize the unusual need for
reducing air accidents in the military,
one has only to review :statistics pre-
sented recently by the past president of
the Aero Medical Association, Major
General Harry G. Armstrong, in a talk
expressing the need for "An Aero Medi-
cal Center for the Unified States Air
Fig. 10. Typical Flight Becc'rd of Hard Turns, Drives, Pull-outs, and a Stall, Showing the
Variation n Normal Acceledr'ation, Altitude Air Speed, and Time During Maneuvers for a
Fig. 11. Test Record of Flight at a Series of Altitudes or Different Indicated Air Speeds
"During the first two y
months of World War
States Air Force lost
while, it lost approxi ately 11,000
through flying accidents in the United
Air Force, within the co
of this country, suffere
aircraft accidents resultin
of 15,613 crew members;
billion or more dollars
destroyed aircraft, and
airplanes' represents oft
test for the effort and
in the training of the
fabrication of the airpl
These figures are p
in studying flight recor
"'Crash-Worthiness of Air
Injury Prevention", by E
J. J. Ryan, The Journal o
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55,821 major
in the death
major injury
era; the total
the damaged
part of the
me consumed
ews, and the
raft and Crash
J. Baldes and
Aviation Medi-
promotion of safety; that is, in reduc-
tion of aircraft losses, in training of
pilots, etc.
There is another area of benefit to
be derived by the military service from
the use of recorders. Installation of
flight records aboard combat aircraft
may provide statistical data relating to
the manes in which pilots fly aircraft
under combat conditions. This data
would seem important to operational re-
search units of the military to aid in
determining statistically, if possible,
how the Ace pilot differs from other
pilots in terms of methods of handling
combat aircraft.
In sumimary, instrumentation, as in
the V.G.A. Recorder, has application in
the promotion of safety, in research and
development, and in reducing aircraft
operating and maintenance costs. It is
hoped that the acceptance of recorders
will be as wide as possible so that every
aircraft will carry a permanent record
of the unusual conditions which it has
encountered.
00423R001200070002-9
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PLEASE NOTE
Reprint of paper to be delivered at the
National Instrument Conference and Exhibit
of The Instrument Society of America, Septem-
ber 8 - 12, 1952, Public Auditorium, Cleveland,
Ohio.
CPYRGHT
This paper or any part thereof must not b
reproduced in any form without the writte
permission of the Instrument Society of Amer
ica, 1319 Allegheny Avenue, Pittsburgh 33,
Pennsylvania.
Price to members, 25c; to non-members, 50c
A NEW TYPE OF PACKAGE HYGROMETER
By
KENNETH C. COON*
INTRODUCTION
The predominant factors affecting the pres-
ervation state of materials in storage are the
existing temperature and moisture conditions.
In determining the pertinent moisture condition
for non-hygroscopic materials, it is obvious that
a relative humidity measurement is sufficient.
For moisture determination of hygroscopic ma-
terials in equilibrium with the surrounding at-
mosphere either absolute moisture content or
relative humidity may be measured. A number
of instrument types, such as the sling psychro-
mater, hair hygrometer, dew point indicator,
and electric hygrometer are and have been
available for determining relative humidity in
physically large enclosures. The Package Hy-
grometer was primarily developed as an in-
strument to be used in determining moisture
conditions existing within small low-cost pack-
ages or enclosures where conventional instru-
mentation techniques are impractical. Two
types of Package Hygrometer, differing pri-
marily in the type of sensing system, have been
developed and tested. A description of each
type and its relative merits will be presented
and discussed.
GENERAL DESCRIPTION
Though not limited to use in small spaces,
the Package Hygrometer's greatest usefulness
is expected to be in the field of packaged per-
ishables. A small, dual passage probe is used
to pierce the container or package and project
into the enclosed air space. A continuously
flowing air sample is withdrawn from the pack-
age by a small centrifugal blower. The air sam-
ple passes from the probe passage into the
*-Associate Engineer, General Mills, Inc., Engineering
Research and Development Department.
,
ing and is returned to the package through a
second probe passage. The sensing elements
are mounted in the measuring chamber.
The determination of relative humidity in-
volves the measurement of two variables: tem-
perature, and quantity of water vapor present
per unit volume. The package hygrometer util-
izes a thermistor for obtaining the temperature
measurement, while commercially available
Dunmore type humidity sensing elements are
used for obtaining the humidity measurement.
Each Dunmore type element consists of a bifilar
coil wound on a polystyrene form. The form
provides a base for a lithium chloride coating,
which serves as a variable resistance conductor
between the two halves of the bifilar winding.
The resistance of the conductive lithium chloride
coating is a function of the quantity of water
vapor present in the surrounding air, and de-
creases as the quantity of water vapor per unit
volume increases. The sensing elements are
mounted in the probe unit as shown in Figure 1.
The power supply and indicating equipment
are included in a separate, portable case. The
indicating equipment is used to measure the
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conductance of the humidity sensing elements,
and, by proper switch positioning, of the ther-
mistor. A current magnitude in microamperes,
when referred to the proper calibration curve,
is a measure of the humidity or temperature.
The indicating equipment may be operated
from the AC line, or from self-contained storage
batteries. For battery operation a 24-volt vibra-
tor supply is incorporated. The meter, sockets,
and all controls are mounted on the instrument
panel. The indicating equipment and probe
unit are illustrated in Figure 2.
MULTIPLE HUMIDITY ELEMENT SENSING
SYSTEM
Since each humidity sensing element is sen-
sitive over only a narrow range of relative hu-
midities, a total of eight elements are necessary
to cover the entire humidity range. The eight
elements are paralleled through a suitable re-
sistance network, so that only a single conduct-
ance measurement is necessary.
Operating procedure for the instrument is
straightforward. The cables are connected to
their respective sockets and the instrument
armed up and standardized. The package
hose humidity is to be measured is pierced
with the. probe. The blower motor is'then ener-
g zed and allowed to run until the humidity
meter indication stabilizes. If the measured
relative humidity is only moderately different
( 0% - 30%) from the relative humidity of the
a r trapped within the enclosed probe passages
fr m previous measurements, stabilization will
h ve occurred within two and one-half minutes.
T e temperature is obtained by switching the
indicating circuit to temperature and referring
the microammeter scale reading to the ther-
mistor calibration curve. After the measure=
ments have been completed and the probe
withdrawn from the package, the small hole
must be carefully sealed to maintain the pack-
a e integrity. The stabilized humidity reading
is referred to the humidity calibration curve for
the particular temperature. Interpolation be-
tween humidity element temperature curves
may be necessary. The relative humidity in
percent is obtained directly from the humidity
el ment calibration curves. The thermistor and
h midity calibration curves are illustrated in
Fi ures 3 and 4.
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With careful operation, the accuracy of the
instrument is plus or minus 3% relative humid-
ity. It has been calibrated for use over the tem-
perature range of 40 - 100 degrees F. How-
ever, increased error will be introduced if the
package free air space is less than 500 cc.
SINGLE HUMIDITY ELEMENT SENSING
SYSTEM
A probe unit using a single Dunmore type
element was designed and tested. The humidity
element which was selected is sensitive to low
relative humidities only. An electric heater was
introduced in the air inlet passage to the meas-
uring chamber. When relative humidities above
the normal range of the single humidity ele-
ment are encountered, the heater is energized,
which raises the air stream temperature. Since
the absolute quantity of water vapor contained
in the air stream is constant, raising the temper-
ature effectively decreases the relative humid-
ity. The air stream temperature is gradually
increased until the relative humidity lies within
he sensitivity range of the single humidity ele-
ment.
This type of construction reduced the volume
f air passages enclosed within the probe unit,
enabling accurate measurements to be made in
.enclosures as small as 250 cc. However, the
humidity elements are temperature sensitive
as well as humidity sensitive; and the humidity
elements introduced excessive thermal lag into
the system. Also, a high humidity measure-
ment could not be immediately followed by a
low humidity measurement, since sufficient
heat remained in the probe unit to reduce the
relative humidity below the sensitivity range
of the single humidity element. The unit was
satisfactory as a laboratory instrument, but was
limited to semi-continuous use.
CALIBRATION
To calibrate both instruments it was neces-
sary to provide a wide range of constant rela-
tive humidities. The relative humidities above
enclosed saturated salt solutions were accepted
as standard. Published data is available *, **
on the equilibrium relative humidities over var-
ious salt solutions. The use of supersaturated
solutions must be avoided, and extreme care
exercised to maintain constant temperature.
The Package Hygrometer was calibrated direct-
ly using the salt solutions as absolute standard.
MAINTENANCE
Routine maintenance should include no more
than storage battery servicing. The sensing ele-
ments should maintain their calibration for at
least one year. However, excessive dust has a
detrimental effect on the elements; generally
slowing the response time and/or shifting the
calibration slightly. To maintain extreme ac-
curacy, the unit should be re-calibrated period-
ically.
. SUMMARY
The Package Hygrometer is a portable instru-
ment, primarily useful in determining moisture
donditions existing within low cost cartons or
packages. The multiple sensing element type is
recommended for ease of operation and maxi-
mum reliability. The accuracy of 3% relative
humidity is maintained without difficulty. The
instrument is calibrated for a wide range of
temperature and relative humidity, covering
most commonly encountered storage conditions.
The instrument is a useful aid in packaging de-
velopment and research.
*-American Paper and Pulp Assoc., Report No. 40
(1945).
**-International Critical Tables, Vol. 1, pp. 67, Mc.
Graw-Hill, (1926).
Acknowledgement: The support of Wright Air Development Center, United States
Air Force, in sponsoring this project is gratefully acknowledged.
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25X1A2g
Inquiries for Info. on Flight
Recorders, Mechanical Arms,
Package Hygrometer and Plastic
Balloons.
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