A rotating arm and maneuvering basin

Lab.

V.

Sc

Technische Höges

N A V Y D E P A R T M E N T

T H E DAVID W. TAYLOR MODEL BASiN

WASHINGTON 7, D.C.

 BOTAUNG AHM AND MÂKEUVEBING BASIS

by

¥. F. Brownell

Prepared f o r l l t h American Towing Tank Conference held at the David T ^ l o r Model Basln^ September,

1956

July 1956

A ROTATING ARM AKD MAHBÜVERING BAOTJ

W. F. Brownell

TABLE OF GCNTMTS

ABSTRACT

Page

1

INTRODUCTION

ROTATING AHK TEST FACILITY ROTATING ARK

GMTER PIVOT BEARING PERIxTORAL TEÎACK CARRIAGE AND TRACKS

MODEL POSITieïïîBÎG APPARATUS WAVE ABSORBER

SLIP BMO SYSTEM S l i p Rings Brushes ARM DRIVE SYSTSM

Mechanical Drive • E l e c t r i c a l Drive DEY DOCK INSTRUMEKTA-TICB Submarine Balances Balance Jjistramentation Model Attitude Measurement Arm Speed Measurement Programmer

MANEUVERING BASIN TEST FACILITY MANEUVERING BRIDΠAND mCKS MANEUVERING BRIDGE TRUCKS

MANEUVERING BRIDCSl ELECTRIC DRIVE MNEUVERING BRIDGE CARRIAGE

. MNEUVERING KRIDCSl CARRIAGE DKLVE SYSTEM Mechanical Drive

E l e c t r i c a l Drive

' MANEUVERING BRIDGE TROLLEY SYSTEM HJSTRUi^IENTATION

MANEUVERING BASIN vaVEHAKERS Wavemakers Wavemakér Operation Wavemaker Models Blowers Baffle Doors Damper Valves Main Valve Drives

Individual Valare Drives Blower Drives

Individual Damper Valve Drivés

2 2 2 3 .3 3 4 5 5 5 5 5

6

7

10

11

11

13

14

16

17

17

17

19

Page MANEUVERING BASIN WAVE ABSCEBERS ^ ' 23

Wave Absorbers ' 23

Barriers 24 MODEL POWER SUPPLY SYSTEMS 24

BUUDING' . 26

HE; .TING AND VENTIUTING SYSTEM 27

OVERHEAD TRAVELING CRANES AND MONORAIL HOISTS 2?

ELECTRICAL 2Ö Primary Service 2Ö 13.8 kv Svdtchgear 23 Outdoor Substation 23 Indoor Substation 23 2,4 lev Switchgear 23 Auxiliaiy Regulated Power Supplies 29

Lighting 29 Communication and Fire A l a m Systems 29

WATER SUPPLY, STEAM & SEl'JER LINES 29 OVERHEAD PUTFORMS AI^D OBSERVATICN R0CÏÏ4S 30

REFERENCES 31 LIST OF ILLUSTRATIONS 32

ABSTRACT

A new Rotating Arm and Maneuvering Basin for the David Taylor Model Basin i s described. Design information conceming the test f a c i l i t i e s , electric drives^ auxiliary equipment, instrumentation, building and basins i s presented*

INTRODUCTION

Ihe functional specifications of a new Rotating Am and Maneuvering Basin for the Taylor Model Basin were completed i n March 1952^. Phase I Advance Planning Design Studies for the building and test f a c i l i t i e s were carried out and completed i n July 1954 "by Mackenzie, Bogert and White, Architects-Engineers and the engineering divisions of the Model Basin. The Phase I design was critically- reviewed and revised by the Model Basin Staff i n order to reduce the t o t a l estimated cost of the project.

A supplementary Phase I Advance Planning Study4 and the f i n a l bidding plans and specifications were prepared by Sverdrup and Parcel, Consulting Engineers, with the exception of the model positioning eqaipneot and the

six component balance for the Rotating Aim which were designed by the Kpdel Basin, Indnstrial Depairtment, Engineering Divisions. Funds f o r the

con-struction of the project were provided in the Department of the Navy Public Works Program f o r 1956. Contract NQy 36453 ^ f o r the construction of the

com.plete f a c i l i t y was awarded i n May 1956 with a completion date of Novem-ber 1958.

The Rotating Am and the Maneuvering Basin are two separate and com-plete test f a c i l i t i e s housed i n a single building. Figures 1, 2 and 3 show plan views and elevations of the tesrfc f a c i l i t i e s ahd the building and Figure 4 i s a view of a 1:120 scale model of the Rotating Am and Maneuvering Basin.

ROTATING ARM TEST FACILITY

Kie Rotating A m F a c i l i t y w i l l be used to provide design information r e l a t -ing to the directxontd s t a b i l i t y , maneuyerabllity and control of high speed

submarines, torpedoes and surface ships. The f a c i l i t y consists of a c i r c u -l a r basin 260 f t . i n diameter having a water depth of 20 f t . A rotating am r a d i a l l y spans the basin and supports test models by a system of tracks, model tow carriage, positioning apparatus, towing struts and balance. Ttie am pivots on a beailng located on the center island and w i l l be driven by a pair of electric motors, d i r e c t l y coupled to two wheels irAiich support the am and run on an outer périmerai r a i l .

It w i l l be possible to test submarine models up to 20 f t . i n length at depths up to 10 f t . at any a m radius betveen 12 f t . 6 Inches and 120 f t . Indicators, recoxders and control instrumentation for measuring the forces and moments acting on the test models, model attitudes and am speed w i l l be located either in"&e operating console or racks, i n the a m inner bay area- Steady state a m speeds of 30 knots at the 120 f t . radius w i l l be attained In less than 1/2 a revolution of the a m and 50 knots at the same radius i n lees than 2-1/2 revolutions. These speeds are the equivalent of about 3 and 5 Icnote respectively at the 12 f t . 6 inches a m radius. For tests of a 2,600 pound, 20 f t . eufamarine model at 10 f t . depth, a 12 knot speed can be attained vdthin 1/2 a turn for any radius between 4Ô and 120

f t . In addition, surface ehip models oan be tested at any radius within the designed a m speed and powering.

ROTATING ARM

'Sae rotatizig a m shown i n Figure 5 has a span of 129 f t . , a width of 20 f t , and a maximuro height of 20 f t . The a m structure i s primarily a tubular alumlixam Parker truss. "Die chord members are 10 inch O.D. by 3/8 Inch wall, the web members 8 inoh O.D. by 3/16 inch wall, the t i e rode are 3-1/2

inch O.D. by 3/16 inch wall and the half span rods are of stainless steel tubing 3-1/2 inch diameter by 3/16 inch wall. The contractor has the option of using either welded or bolted construction for the fabrication of the arm. Aluminum a l l o y fairings are provided for the main members along the outer half of the a m to reduce windage drag and thus the drive power required at high speeds.

The estimated weight of the a m structure i s about 37^500 pounds. The calculated natural frequencies of the a m are; v e r t i c a l 3.3 ops, h o r i -zontal 3-2 ops, and torsional 4»0 ops. These are considered to be ac-ceptable, f o r the conducting of the submerged submarine tests. There w i l l be a walkway along the center of the am, extending from the outer end to the control and operating area which i s located at the inner bay of the am.

CENTER PIVOT BEARINQ

The pivot for the rotating a m includes a Kaydon tapered r o l l e r bearing assembly designed to take the maximum centrifugal force of the a m which i s about 145,000 pounds. The outer race of the bearing w i l l be connected

to and rotate with the am and the inner w i l l be fastened t h r o u ^ a steel structure to the concrete center island. ïhe bearing w i l l have a 61.5 inch bore, 71.125 inch outer diameter and 5 inch width.- Hie radial rating of the bearing at 500 rpm i s 206,000 pounds and the thrust rating at 500 rpm i s 192,000 pounds. îhe maxijmim speed of the am i s about 7 rpm for the 50 knot test speed at the 120 f t . radius. Figure 6 shows the pivot bearing assem-bly. The concrete center island i s 7 f t . i n diameter at the top to a point 6 f t . - 0 inches below the basin water surface where i t starts tapering out to an 18 f t . - 0 inch diameter at the basin f l o o r .

PERIHIERAL TRACK

Figures 7 and 8 show a layout of the r a i l and a typical section through the track vhich. w i l l be located on the top of the basin wall. The construction consists of individual lengths of ma^ined cast steel r a i l chairs bolted to the concrete basin wall. In turn f l a t plate ground r a i l sections w i l l be bolted to the top of the r a i l chair. Scarf Joints are used for the r a i l s and v e r t i c a l bolted butt joints for the chairs- The r a i l material i s of hardened alloy steel (R/C 30-32). The chair and r a i l w i l l be set to the following tolerance: plus or minus 0.p06 inches i n height above the water, plus or minus 0.001 inch waviness per 6 inches of track and plus or minus 0.125 inches i n diameter of track at any point.

CAFJIIAGE AND TRACKS

The model, tow carriage i s remotely positionable by means of a windlass and cable to any radius between 12 f t . 6 inches and 120 f t . frcm the center of rotatipn> as ^own by Figure 9# For testing submerged models a model yaw table adapter and bearing w i l l be attached to the carriage and a moveable assemblage consisting of the model positioning apparatus, towing struts, balance and model w i l l be connected to the yaw bearing. In addition, a detachable towing beam f o r surface model tests may be connected to the carriage.

In general, the carriage structure. Figure 10, i s of aluminum alloy f a b r i -cated beams welded together. • Support r o l l e r s and guide r o l l e r s attached to the carriage support the carriage during positioning and maintain i t s alignment i n the horizontal plane. Hydraulically actuated toggle clamps hold the carriage firmly i n place during tests.

Aluminum alloy tracks w i l l be fastened to the bottom chords óf the am to support the model carriage. Figure 11 shows a d e t a i l of the track constmc-tion. The support tracks, when installed, w i l l be straight within plus or minus I/64 inches i n any 10 f t . and plus 01* minus 1/32 inch i n the entire length of horizontal finished track and v e r t i c a l reference surface. At any radial position a l i n e normal to the radius across the finished surface of the two tracks w i l l be l e v e l within plus or minus 1/32 inch i n 20 f t . The guide r o l l e r track attached to the bottom t r a i l i n g am chord w i l l have the same tolerance for the guiding surface i n the v e r t i c a l plane,

MODEL POSITIONING APPARATUS

Submerged models w i l l be positioned i n yaw, r o l l and pitch frcaa a remote

3

control station over the center island. Hie functional requirements.are that the angular setting of a submerged test model be maintained within plus or minus one degree during tests and that the model attitude be measured and recorded within plus or minus 0.02 degrees. The am carriage and tracks are designed to meet this requirement. A schematic arrangement of the towing

strut and model positioning apparatus i s shown i n Figure 12, Submerged models w i l l be attached to the twin struts shown. The model struts w i l l be connected at the upper end to a strut beam attached to a rotatable, yaw table, pitch and r o l l assemblage. ïhe yaw table i s bolted to the yaw bear-ing contained i n the towbear-ing carriage. Individual electric drive systems w i l l be used to position the model at any attitude. For pitch and yaw the modél can be rotated without changing the test location of the submerged model. However, for r o l l both the model and struts are pivoted about a point i n tbe overhead r o l l positioning unit and thus are displaced. Lo-cating a remotely controlled r o l l positioning apparatus inside the model was considered, but discarded, because of probl^is connected with closure of ihe required strut slot i n the model h u l l f o r r o l l i n g .

This equipment w i l l permit testing through the following range of model attitudes:

yaw - plus or minus 30 degrees;

r o l l - 10 degrees outboard, 40 degrees inboard; pitch - plus or minus 15 degrees.

The struts can be oriented into the flow as desired since they are rotat-able. Also, strut spacings of 3 f t , 6 inches to 10 f t . can be obtained thus providing towing f l e x i b i l i t y for various length models.

The towing struts w i l l be stainless steel with machined outside surface and of the streamlined EPH type section. At the model their cross'section i s 3 by 0.857 inches for an adjustable length of 20 inches. At this point the s t m t connects to a section which tapers from 7 by 2 inches cross sec-tion to 24 by 6 inches i n a length of 31 inches. The remaining upper 6 f t . 3 inches length of strut i s 24 by 6 inches i n cross section.

WAVE ABSORBER

Around the periphery of the basin a 15 degree slope wave absorber w i l l be inatalled. The absorber w i l l be made of two layers of pemeable bar type concrete beach units resting on an impemeable concrete shelf. Figure 13

shows dimensions of the beach unit. An impemeable beach unit of 15 de-gree slope w i l l be i n s t a l l e d around the periphery of the center island as shown by Figure 14. Hie primary purpose of these absorbers i s to reduce the time required f o r the water surface to become quiet after a test run. These units were selected as a result of a series of tests at the St. Anthony F a l l s Hydraulic Laboratory6 and short length absorbers with slopes

of 5, 10, 15 and 20 degrees of both the pemeable and Impemeable type were tested. Since the space for the beach i s limited due to the require-ment of model tests at extreme r a d i i of the am, i t i s not possible to use

the most e f f i c i e n t absorber i n "Wie Rotating Am Basin, However, i t i s estimated that the absorber selected w i l l reduce the settling time of the basin from 1/3 tö 1/4 of that required i f no absorber were used.

SLIP RING SYSTEH

A s l i p ring system w i l l be used f o r the transfer of power, control and i n -strumentation c i r c u i t s from the shore to the rotating am. In t h i s appli-cation the brushes rotate about stationary s l i p idngs. Hie s l i p ring sys-tem i s supported by a stationary steel shaft r i s i n g from the center pylon structure of the am. Figures 5, 15 and 16 ^ow the location of the s l i p ring assemblage, an elevation of the s l i p ring structure arid a section through the s l i p rings. The s l i p rings w i l l be mounted on a stationary, v e r t i c a l hollow steel shaft of 14 inches outside diameter. The shaft i s divided into tour bolted v e r t i c a l sections for power, instriimentation and control c i r c u i t s . Power c i r c u i t s above 600 volts and below 600 volts w i l l be on separate sections of the shaft. The base of the s l i p ring shaft rests on the support shaft and also supports the brush structure by means of a support and alignment bearing at the bottom and an alignment bearing at the top. Hie s l i p rings w i l l be connected to the shore by means of cables running along the overhead building structure. Hie overhead cables run to junction boxes located on top of the stationary part of the s l i p ring structure. Hie brushes connect to the rotating am equipment by cable 8.

Slip Rings

Slip rings used f o r the power compartments w i l l be of a higJi conductivity copper a l l o y . There 'wi.H be nine s l i p rings i n the above 600 volt compart^ mentjeach capable of carrying 250 amperes. There w i l l be ten s l i p rings i n the below 600 volt power compartment of \ ^ i c h three w i l l be spares, each capable of carrying 200 amperes. The s l i p rings i n the instirumentation and control coarpartments w ü l be of fine s i l v e r . The instrumentation and con-t r o l comparcon-tmencon-ts w i l l each have 59 s l i p rings available.

Brushes

The power brushes w i l l be of copper graphite composition 3/4 inch wide,

1-3Ä inch thick and about 2 inches long, capable of canying 150 amperes per square inch of cross section area. The brush holders w i l l be of copper-alloy. There w i l l be two brushes per brush holder and two brush holders per s l i p ring located 180 degrees apart.

The instrumentation and control brushes w i l l be 1/8 inch wide, 1/4 inch thick and about 1/4 Inch long and w i l l be of silver^graphite material. Two brushes per holder w i l l be used and two holders per riiig, mounted at

180 degrees spacing and suitable for 600 volt operation. ARM DRIVE SYSTEM

Mechanical Drive

The driving force for the rotating am w i l l be provided by two 30 inch diameter ground steel t i r e d traction \dieels v*iich are preloaded against the track surface by means of steel t i r e d keeper \Äieels mounted on pivoted shafts and loaded by nested compression spiings. FigU2*e 1?

shows the drive assCTibly and i t s location. Each drive unit includes one main traction ^ e e l directly coupled t h r o u ^ a 12 f t , shaft to an electric motor, two keeper wheels, and two sets of double nested springs adjusted to provide a total nOraal force of 61,000 pounds per drive \dieel. Hie two drive units w i l l be mounted i n the outer bay of the rotating a m and w i l l be symmetrical about i t s centerline. Fleaible disk typp couplings are pro-vided to provide f l e x i b i l i t y between the motor .and traction wheel.

E l e c t r i c Drive

The electric drive i s an, adjustable voltage d-c system with ^.utomatic feed-back control. A block diagram of the systaa i s shown by Figure 18. The actual motor ratings for the drive motors were not specified, i n order to obtain maximum competition from the manufacturers. Instead operational requirements, weight limitations (drive motors, holding brakes, blowers and supporting r a i l s not to exceed 28,000 pounds) and limitations on torque "and; current were specified. A safety factor of 25 percent i s available i n

Sie t o t a l power. I t i s anticipated that one p o s s i b i l i t y for the drive w i l l be two 250 hp d-c m i l l motors capable of delivering 300 percent of rated torque during acceleration of the am. Control f o r ihe am drive w i l l be from a console located at the inner a m bay near the center island.

Capabilities: Hie drive system w i l l be capable of accelerating the a m to an angular velocity of 0.425 radians per second (30 knots) within 90 de-grees and stabilizing at t h i s speed within plus 'or minus 0.1 percent within the next 90 degrees of a m angular displacement. I t w i l l also be possible to accelerate the a m to a steady state speed of 0.71 radians per second i n less than 2.5 revolutions. Continaous operation at a m speed of 0,425 radians per second and operation for at least 20 minutes at a speed of 0.71 radians per second w i l l be possible. The estimated a m speed constancy i s within fdus or minus 0.tX)0425 radians per second f o r a m speeds up to 0=425 radians per second and plus or minus 0.1 percent of the speed between 0.42? to 0.71 radians per second.

Am speeds w i l l be preset by means of a selector switch and precision po-tentiometers located at the control console. Preset accuracy of speed i s estimated to be within plus or minus 0.00106 radians per second below 0.425 radians per second, and within plus or minus 0.25 percent of speed between 0,425 to 0,71 radians per second.

An inching control i s provided to exactly position the am. Inching speed w i l l be adjustable from zero to aboUt 0,10 radians per second by means of an inching potentiometer at the console.

Drive; The drive system w i l l consist of two d-c series connected 420 rpm shunt wound motors capable of constant torque application to 700 rpm. Hie drive motor w i l l be capable of reverse operation up to 210 rpm (15 knot a m speed). Hie power supply w i l l consist of a motor generator set >àiich includes optionally one or two 900 rpm shunt wound d-c g^erators capable of supplying not less than 700 kw to the drive motors and ha.ving a voltage rating compatible with the drive motors, and a synchronous motor with a rating of not less than 1000 hp, 2300 volt, 3 jfliase, 60 cycle, 0.8 p.f. and

900 rpm, for reduced voltage line reactor start. The synchronous motor w i l l be supplied from a 2400 v o l t switchgear

unit-The Tn-îTTîTn»Tn toroue reqiiired for the drive miotors i s estimated to be 13,534 pound-ft. The maximum that can be provided i s 22,900 poimd-ft. which corre-sponds to the maximum tractive effort which can be developed between the drive wheels and the tracks. The maxiniam drive motor current w i l l not ex-ceed

3000

The excitation for the shunt f i e l d s of the main drive motor w i l l be from a separate source of 250 volts d-c supplied by a package type motor generator set consisting of an a-c motor and a d-c generator, A d-c rotating ampli-f i e r oampli-f approximately 30 kw capacity w i l l ampli-furnish exciting current ampli-f o r the main drive d-c generator and v d l l be driven by a 440 volt, 60 cycle 3 phase induction motor.

Speed Regulation; A high-gain closed-loop electronic speed regulating sys-tem operating from a tachometer feedback signal w i l l contrei the d-c generat-or output voltage and thus the drive m:otgenerat-or speed. Current limit, circuits

Mâiich can be preset "tiy potentiometers at the console are included f o r control of rates of acceleration and deceleration. Two tachometers w i l l be used so that greater accuracy can be obtained i n the low speed range of 0 to 0.212 radians per second. The tachcpeters w i l l be driyen 1:^ an i d l e r vdieel y*iich runs on the peripherial drive track.

Braking: Regenerative braking w i l l be used for stopping and this, together with drag braking, should result i n a deceleration rate not^ exceeding the

peak acceleration rate of 0.12 radians per second per second. For holding the arm i n place, brakes of the spring set shoe type w i l l be mounted on the shaft extension of the drive motor.

Protective Devices; Overvoltage, s l i p detection, zero voltage, loss of f i e l d , ovèrcurréht, overtemperätui^, zero speed, overspeed, ground detec-tion and Undervoltage devices protect the equipment from malfuncdetec-tion or ccônponent f a i l u r e . In addition, a complete system of medianical and elec-t r i c a l inelec-terlocks prevenelec-ts improper am driye operaelec-tion. Malfuncelec-tion of the am control, drive systan, or protective device w i l l be detected by indicating lamps on the console or by a target on the protective device. DRY DOCK

A moveable drydock lAiich can be flooded o r evacuated i s provided so that sub-surface models can be moved from l^e f i t t i n g room area into the ro-tating a m basin to be attached to the roi^ting a m at any desired test radius, Nomally, a submarine model w i l l be f i t t e d with model motors, balance, 'support struts and model positioning apparatus i n the f i t t i n g room. The complete assemblage and instrumentation w i l l then be checked out under water i n the f i t t i n g room test basin.

After checking, the model with support struts and positioning apparatus w i l l be moved to the drydock that w i l l be stored i n the well at the

northwest side of the basin. With the drydock i t w i l l be possible to make adjustanents and repairs to the model^ without removing them frcm the rotat-ing ara.

The drydock i s supporlved by a system of r a i l s on the basin f l o o r and guide •vdieels. Cast iron ballast w i l l be used to prevent f l o t a t i o n of the drydock when i t i s evacuated. The travel and.positioning of the drydock w i l l be by means of a cable drive system having sheaves at the. center island and driven through a high ratio gear reducer by a 7^ hp, 3 Isiase 440 v o l t 60 cycle

I8OO/9OO rpm electric motor equipped with a magnetic holding brake. One end of the drydock; frame i s hinged to act as a door for the entrance and exit of the model, attached to the rotating am. Two 2000 gpm v e r t i c a l pumps driven by 15 hp electric motors are provided f o r pumping out the diydock. Toggle type flood valves w i l l be used f o r f i l l i n g the drydock.

Hie drydock w i l l be of carbon s t e e l painted with red lead and with alumi-num phenolic except f o r under water f i t t i n g s and moving parts \rfiich general-l y w i general-l general-l be .of corrosion-resistant materiageneral-l. The inside dimensions of the drydock are 26 f t . long by I6 f t . wide and 18 f t . deep. This size w i l l per-mit the handling of 20 f t . submarine models with either v e r t i c a l centerline

towing struts or L struts mounted on each side of the model. INSTRUMENTATION

Submarine Balances

Balances are provided to measure the forces'and moments acting on submerged bodies. A forward and a f t assembly. Figures 19 and 20 w i l l be used. The forward assembly consists of 3 individual force balance units and a r o l l moment balance ,unit, Hiis assemblage w i l l be connected to the forward

tow-ing strut and to the test model. The a f t assembly w i l l be attached to the a f t towing strut and the model and w i l l consist of three Individual force balance units joined together and à strut f i t t i n g . Hie balances are of

the linear d i f f e r e n t i a l transforner type which conveirts the force or moment into an e l e c t r i c a l voltage signal. This type transducer consists essenti-a l l y of essenti-an essenti-amessenti-ature which i s posi,tioned freely inside two pessenti-airs of priinessenti-ary and secondary c o i l s . An alternating voltage i s applied to the primaiy

c o i l s which induces a voltage i n the secondary c o i l . When the armature i s centered, there i s no voltage output but when the amature i s displaced by a force there i s an output voltage. The balance i s designed f o r thé f o l -lowinf- forces and moments;

Drag - 1000 pounds R o l l Moment 65O l b f t . L i f t 450 pounds Pitch Moment 1750 l b f t

Side Force 300 pounds Yaw Moment 4900 l b f t

The forces and moments w i l l be obtained from combinations of measurements from the individual force balance units. The r o l l moment w i l l be obtained directly from the r o l l moment balance, A dead weight system i s provided for calibrating the balances.

Balance Instrumentation .

Instrumentation to measure, indicate and record the steady state or slowly varying forces and moments acting on the test model w i l l b.e furnished. Figure 21 shows a block diagram of this measuring, indicating and recording system. The instrumentation w i l l be suitable for operation with either the linear d i f f e r e n t i a l transforner type transducers with 400 cps a-c voltage excitation that are furnished with the balance, or for strain gage type transducers with d-c voltage excitation.

The system consists of a servo-balancing c i r c u i t including a-o and d-c gage control units, amplifiers and demodulating chopper amplifiers, servo motor tachometer generators with associated gear t r a i n and potentiometers, ana-logue to d i g i t a l converters, d i g i t a l recorders of the adding machine type, graphic recorders and d i a l type remote indicators. Hie balancing c i r c u i t detects any unbalance i n the system and supplies a signal to the potenti-ometer drive motor. This activates -Üie balancing potentipotenti-ometer to n u l l the signal and simultaneously rotate the input shaft o f the analogue to d i g i t a l converter to an a^ngular position v ^ c h vdien read out produces a number on the printer corresponding to the measured value. The t o t a l e s t i -mated inaccuracies of measurements at the d i g i t a l recorders are expected not to exceed 0.2 percent of f u l l scale and ^ 0.3 percent o f scale for the graphic recorders. D i g i t a l recording w i l l be i n accordance with a signal from a pregrammer unit. Hie minimiini rate of printing for the dig-i t a l recorders w dig-i l l be one record per second and the scale w dig-i l l be mdig-inus 999 to plus 999, Hie graphic recorders w i l l have a f u l l scale pen travel and balance time of not mpre than 1/4 second and a useable scale width of at least 10 inches.

Model Attitude Measurement

Submerged model r o l l , pitch and yaw angles w i l l be measured, indicated and recorded. The supporting structure w i l l be used as ä reference for these angular measurements. The indióatlons and recoirdings w i l l be i n d i g i t a l f o m and i n degrees and hundredths of a degree. The transducers are ana-logue to d i g i t a l converters which connect d i r e c t l y to the remotely con-t r o l l e d acon-tcon-ticon-tude drive syscon-tems locacon-ted acon-t con-the yaw bearing. Recording \rfill be controlled by signals from, a programmer and continuous readout v d l l bè provided by the d i g i t a l indicator at the console.

Am Speed Measurement

The a m speed pick-up consists of a large gear fastened to the fixed s l i p ring support post. The gear teeth w i l l be meshed to the extemal gear of a pulse generator transducer located on the rotating am stmcture just above the yaw bearing. The transducer includes a housing vàiich i s a stator with i n t e m a l gear teeth and a magnetic pickup c o i l . The rotor includes the transducer external gear and a magnet. As the rotor shaft turns a change i n reluctance occurs between the shaft gear and the hous-ing gear thus induchous-ing a voltage pulse i n the pickup c o i l .

The speed measuring system. Figure 22, includes a dual set of electronic counters with the necessary switching to permit one set to count pulses vAiile the other set i s being- de-coded and the reading recorded on printers. The counting period w i l l be one second with the electronic gate control

supplied by the programmers precision time base. Hie electronic counters count and indicate 9,999 pulses per second. There w i l l be continupus i n d i -cation of am speed at the console by 4-dècade d i g i t a l in-line indicators and' d i g i t a l recordings w i l l be printed at one second intervals and totalized at, the end of a run as directed by the programmer. Am speed measurement and recording w i l l be i n radians per second and the accuracy of the d i g i t a l recorder and the d i g i t a l indicator w i l l be within plus or minus one pulse {£ 0,0001 radian per second).

Two additional speed measuring systems exclusive of the transducers, i d e n t i -cal to the am speed measuring system, are furnished for future connection to ship model propeller shaft revolution per second transducers.

Programmer

A programmer w i l l be used to synchronize the recording of data from several sources to insure that a l l readings are-taken at the same time. Hie program-mer includes a precision time base f o r use i n the synchronizing c i r c u i t and to furnish electronic gate control to electronic counting units. The time base unit vn 11 be crystal controlJLed with a c i y s t a l having a TninimuTn s t a b i l -i t y value of 5 pa-irbs -i n 100,000 and a short t-ime s t a b -i l -i t y of at least one part i n 1,000,000.

Automatic recording of data v o l l be started by the operator using controls furnished i n the instrumentation console. Push buttons on the console pro-vide the operator with a means of inserting record identification informa-tion into the printers and graphic recorders, i n d i g i t a l form. The day of the year, run number and component Identification w i l l be printed with each reading and each t o t a l by the d i g i t a l recorders and at the end of the test run f o r the graphic recorders. The mn number advances automatically at the end of four and ten reading test runs when the d i g i t a l recorders t o t a l -i z e . Aux-il-iary operat-ion pens -i n the grap^-i-ic recorders w -i l l mark the

graphic charts at the time d i g i t a l recordings are made. Also, an indicator i s provided i n thé console to indicate the chart identification infoitnation being printed.

Pushbuttons v d l l be, used to start the record sample data, record four points and t o t a l i z e , record ten points and totalize, and space records cycles. The records sample data cycle causes a l l printers to take one reading, clear and add spaces to the record and cause graphic charts to run, mark records at the instant the printers operated, and add space to the record. The chart identifying printers i n the graphic recorders w i l l not print during the sample data cycle. Operation of the four point and ten point record cycles w i l l be similar to the sample data cycle; however, at the end of the four and t ^ point cycles the piinters w i l l totalize and d e a r , and the i d e n t i -f i c a t i o n printers i n the graphic recorders w i l l operate. At the end o-f these cycles the run number w i l l be increased automatically. Selector

switches w i l l be available to pemit the operator to run the grapdiic and d i g i t a l recorders continuously,

MANEUVERING BASIN TEST FACILITY

The maneuvering basin, equipped vtfith waveraakers, vd.11 be used to conduct model tests concemed with the loss of sea speed, the improvanent of the seakeeping characteristics of surface vessels and the prediction of ship motions i n rough water. Information w i l l also be obtained relating to the maneuverability and control of surface ships and submarines i n smooth and

rough vtfater and the perfomance of submarines mnning near the surface i n waves,

Thè maneuvering basin i s ä rectangular concrete basin 240 f t , by 3^0 f t . with a water depth of 20 f t . except f o r one section 50 f t . by 322 f t . 6 inches that has a depth of 35 f t . The deeper section i s intended foi* free-, running sutmerged model tests.

Pneumatic wavemakers generating waves from 3 f t . to 40 f t . i n length and up to 24 inches i n height w i l l be located on two adjacent walls of the basin. Fixed bar type concrete wave absorbers w i l l be installed along the opposite basin walls, A steel bridge having tracks attached to the underside, along which a controlled model towing carriage riins, spans the length of the basin. Trolley vdres suspended below the bridge provide power f o r model motors, car-riage drive, instruments, l i f t i n g and control. The bridge w i l l be supported on a r a i l system that pemits the bridge to traverse one-^alf the width of the basin and to rotate at angles up to 45 degrees from the longitudinal centerline of the basin.. This rotating feature pemits models to be towed i n head or follovdng seas at any angle from zero to 90 degrees. Figures 1, 2 and 3 show plan and elevation views of the maneuvering basin f a c i l i t y . Ship model tests i n waves w i l l generally bè conducted with 20 f t , or 10 -12 f t , models, Hae top speed of the carriage v d l l be about 15 knots and for 10 knot carriage speed a minimum steacfy state test run of 210 f t . v d l l be available alon^ the Length of the basin.

MANEUVERING BRIDGE AND TRACKS

The maneuvering bridge w i l l be a 376 f t , free span steel bridge weighing about 230 tons. I t i s of the bow-string or t i e d arch typo with' a iniu-span depth of 35 f t . and a constant vddth of 20 f t . Figure 23 shows a plan and elevation of the bridge. The upper chord w i l l be constmcted of 12 inch by 99 pound wide flange beams, the lower chord of two 15 inch by 40 pound channels and the web members mainly of seamless steel tubing of vaiying

sizes up to 7i inches outside diameter by I/4 inch vjall. The main bridge members and bracing w i l l be connected i n the f i e l d by 3/4 inch h i ^ strength

steel bolts or welded i n some instances. Hardened steel tracks w i l l be at-tached to the bridge lower chords to support the maneuvering basin tow car-riage. Also, a centerline hardened steel track attached to the bottom of the bridge w i l l provide a r o l l i n g surface for the carriage drive and guide wheels. The design of the bridge i s such that by means of b u i l t - i n bridge camber and adjustable shimmed tracks, the v e r t i c a l alignment of a fixed point on the tovdjig carriage w i l l maintain i t s elevation within l/B inch vdien the carriage traverses the center 200 f t , of the bridge. Figures 24 and 25 show details of the supporting r a i l , and the drive r a i l ,

An elevated r a i l system. Figure 23, i s provided at each end of the maneuver-ing baain. This allows the bridge to traverse o n e ^ a l f the width of the basin and rotate 45 degrees to the centerline. The redl w i l l be of steel, 80 poun* weight and the track of 4 f t . 3^ inch gage supported on steel t i e s that are embedded i n a concrete box girder. They v d l l be aligned and leveled so that the difference i n elevation of r a i l s at opposite ends of the basin, vdth the bridge i n any orientation, i s wiiihin £ l / l 6 inch.

MANEUVERING BRIDGE TRUCKS

The maneuvering bridge w i l l be supported through pivots by four tmcks, one under each comer of the bridge. One truck at each end of the bridge i s a powered drive tmck and the other an idler, tmck. Each tmck has four single flanged forged steel wheels \*hich w i l l run on the elevated r a i l system.

Be-cause of the width of the bridge there w i l l be considerable end motion of the bridge stmcture relative to the tmcks, v^ien the tmcks enter the curved section of tracks. This end motion i s taken care of by a small four-vrtieeled transverse tmck carrying the bridge support pivot socket. The tmck w i l l be mounted on top of the main tiuck on r a i l s set perpendicular to the main tmck

axis,

MANEUVERING BRIDGE ELECTRIC DRIVE

The bridge drive i s a Ward-Leonard type system. Four 2 horsepower drive motors v d l l be used, tvro a t each end of the bridge, each rated 115 volt d-c

gear type, 84 rpm and capable of constant torque over an 8:1 speed range. The motors w i l l be mounted on the power tmcks and the output shafts f i t t e d for gear connection to the drive shafts of ttie bridge tmcks. Hie d-c power supply w i l l be a motor generator set consisting o f a 250 v o l t d-c shunt vround, separately excited generator and a 440 volt, 3 phase 60 cycle, squirrel cage

m o t o r that drives the d-c generator_and exciter. Control rheostats i n series

with the drive motor f i e l d w i l l be located at the control panel f o r control of each end of the bridge i n combination with the generator f i e l d contrôla A stepless f i e l d control rheostat provides voltage control of the generator output, A rotating type exciter provides excitation f o r the d-c generator and the drive motors. A spring-held, magnetically-release type brake w i l l be motmted on each drive m o t o r shaft extension with a capacity equal to the motor torqUe.

Gontrol of the direction, speed of travel, skew ahd positioning of the bridge w i l l be f r c M a control console located on the east end of the bridge. The Tnav^Tmnn speed of the bridge w i l l be about 30 f t . per minute with the speed variable over the 8Î1 range. A system of mechanical indicators and a skew

indicating and control system permit accurate positioning of the bridge. Hie TnaTTïTiiiini pezmlsslble bridge skew i s 18 Inches, A selsyn system consisting of tvro transmitters driven by" gears on two of the motor shaft extensions, two d i f f e r e n t i a l receivers and two indicators show the skevj. Hie transmit-ters w i l l be directly connected to a drive motor at each end of "Üae bridge. One indicator indicates skevf during rotary motion, the other during trans-latory motion. Hie overall accuracy of the system i s within 5 percent of the maximum permissible skew. Selsyn motmted sv/itches w i l l be i n s t a l l e d at each

receiver to prevent excessive skew, ,v

The bridge operator, through the use of scales and indicators, can accurately position the bridge at one foot intervals on the s t r a i ^ t track and one-half degree intervals on the curved tracks. Scales w i l l be painted on the west and east sides of the basin and pointers mounted on the bridge. A closed c i r c u i t television system i i d l l be used to view the position of the west i n d i -

cator.-MANEUVERING BRIDGE CARRIAC2;

The carriage w i l l be a welded aluminum tubular t m s s stmcture. Aluminum i s used to reduce the power requirements that would otherwise be needed i f steel constmction Were used. The test personnel, carjriage operator, carriage and model controls, test instrumentation and recording equipment w i l l be carried

on the carriage. The basic carriage i s rectangular i n shape. Figure 26, 20 f t . wide by 21 f t . 9 inches loi^'and 6 f t . 8 inches high. The estimated weight i s approximately 20,000 poiinds exclusive of equipment. The tubular members are 3 inch outside diameter with varying waH thickness from 0,125 to

0.500 inches. Â 24 f t , long aluminum alloy detachable towing beam i s provided along the longitudinal centerline of the carriage. This i s not of the floating girder type and w i l l be adjustable i n height. The lower face of the beams can be positioned between 32 and 60 inches above the s t i l l water l e v e l of the basin, The centerline of the lower chord of the carriage t m s s \ri.3J. be 6 f t , 2j Inches above the basin l e v ^ l , Hiese clea-rances have been specified to provide for present and future wave tests on 10 to 30 f t . ship models, A centerline open bay approximately 8 f t . vdde by 10 f t . long i s provided i n the lower horizontal carriage tmss tq^ aid i n conducting special tests,

Hiere w i l l be working platforms on the carriage along each side of the ship models. Provision i s also made f o r outrigger toydng of ship models f o r turning tests. The detacfiable tow beam w i l l be located outboard of the north side of the carriage and the test model, accelerated up to speed by means of stmts at-tached to the tow beam.

E l e c t r i c a l trolleys w i l l be supported from the upper horizontal, plane of the carriage tmssworic. In addition, the carriage drive equipment and the arrest-i r ^ gear strarrest-iker varrest-iharrest-ich engages warrest-ith the arrestarrest-ing gear at each end of the bridge, w i l l be supported on top of the cairiage. A U equipsnent and stmcture are designed to talœ a maximum rate of deceleration of l,3g i n either direc-tion of carriage travel.

The carriage v d l l be supported frcan the bridge by four i d l e r trolleys vrfiich mn on the bridge tracks and are located at the extreme top comers of the carriage. Each support t r o l l e y includes two 10 inch diameter hardened steel wheels and one 4 inch diameter steel keeper vAieel, both contained i n a housing vhich bolts

to a pad on the carriage. The support wheels of each t r o l l e y v d l l ride on the

inner surface of the track flange. The keeper vsheel of the t r o l l e y w i l l be snugged up to ride against the face of the same flange. Also the carriage v d l l be guided along the bridge by foUr 3 inch diamjeter hardened' steel guide wheels, tvro of which are spring loaded. The guicfevÄieels fasten to pads located at the top and the fore and aft ends of the carriage i n the same horizontal plane as the drive wheels. Hie guide vdieels ride against the v e r t i c a l airface of the main traction r a i l of the bridge,

MANEUTOING BRIDC2I CARRIACE DRIVE SYSTEM Mechanical Drive

The driving force for tho carriage w i l l be. provided by two mbber t i r e d trac-tion vrtieels preloaded against the v e r t i c a l faces of the main tractrac-tion r a i l of the bridge. Each vrfieel v d l l be driven by an e l e c t r i c motor t h r o u ^ an 8^ to 1 worn gear reducer. Figure 27 shows the drive.

Hie reducer, motors, and a tubular aluminum truss vfoz^ w i l l be mounted on a steel subbase fastened to the top of the carriage. Each traction vheel w i l l be mounted on a solid shaft vyhich passes t h r o u ^ a preload bearing and w i l l be coupled by a flexible disc type coupling to the hollow output shaft df the re-ducer. The preload bearing housing on each shaft v d l l be supported on both sides by a sliding block arrangement attached to the tmsses. The sliding block arrangement i s the means of transferring the tractive effort o/ the trac-tion vôieels into the tmeses. It also permits adjustment of the reducers due to t i r e wear. Hie traction wheels are pressed on solid industrial t i r e s of 22^ inch diameter on a 16 inch diameter steel wheel. The t i r e base vddth i s 12 inches and v d l l have a grooved tread. The nominal r o l l i n g radius of the vdieels when loaded i s 10,3 inches.

Hie traction wheels v d l l be preloaded to develop tractive effort without s l i p -page by a hydmulic cylinder common to both drives which transmits its. force through the preload bearings to the shafts of the traction wheels. A hand operated pumping unit charges an accumulator to provide the required holding pressure. For may^TmiTn acceleration a preload of about 12,000 pounds i s re-quired at each traction wheel. For lower acceleration the preload can be decreased by raeans of a slow release valve.'

E l e c t r i c a l Drive

Hie primary electric drive i s an adjustable voltage d-c system vdth automatic feedback control. Figure 28 shows a block diagram of the system. As i n the case of the rotating am drive, the motor ratings were not specified so that maximum competition could be obtained from the e l e c t r i c a l manufacturers. In-stead, operational requirements and weight limitations were spelled out. Con-t r o l of Con-the carriage i n eiCon-ther Con-the easCon-tvrard or wesCon-tward direcCon-tion v d l l . be from a control console at cme end of the carriage or an auxiliary control station at the other end of the carriage.

Capabilities; I t i s extremely important that a maYimiiTn steady state test run be available for the- taking of data. This requires that the cairiage acceler-ate to a given speed and stabilize at that speed i n as short a distance ^as

pos-sible and also decelerate i n a short distance. Hie drive system w i l l be cap-able of accelerating the carriage from rest to a speed of ten knots, towing a 1000 pound model, vdthin about 11 f t . (this corresponds to an average acceler-ation rate of 0.4g). The system w i l l stabilize at this speed within plus or minus 0.25 percent i n about three seconds (48 f t . of carriage travel). I t v d l l also be possible to accelerate the carriage to a speed o f 7.5 knots, while towing a 6000 pound model (this corresponds to average acceleration rate of 0.33g within 7 f t . ) and stabilize at, this speed within an additional 38 f t . of carriage travel. In addition, a speed of 15 knots can be obtained

while towing a 200 pound model by accelerating to speed within 50 f t . (about 0,2g). Figures 29, 30, and 31 show the specified operating conditions for the drive system.

The estimated steady-state carriage speed constancy during a test run i s within plus or minus 0.025 knots under 10 knots, and plus or mi nus 0.25 percent of carriage speed hetween. 10 and 15 knot's.

Carriage speed w i l l be preset by a selector svdtch and precision potentiometer calibrated i n increments of 0,01 k3iot. Hie preset accuracy i s estimated to be \dthin plus or minus 0,5 percent of speed between 10 to 15 knots and plus or minus 0.05 knot f o r speeds less than 10 knots.

In addition to the east and west operation of the carriage, an inching control system i s provided so that the carriage may readily be positioned along the am. The inching speed v d l l be adjustable from zero to 0.5 knot.

Drive: The drive system consists of two d-c series-connectejd shunt-vround motors, capable of reverse operation. They w i l l be coupled through 8^25: 1

gears to the mbbêr t i r e d drive wheels and be capable of maching a speed of 2211 rpm which corresponds to a 15 knot carriage speed. The mbber t i r e s of the drive vdieels l i m i t peak tractive effort v^iich can safely develop at the drive r a i l to 17,500 pounds (including current l i m i t overshoot). How-ever, i t i s estimated that a tractive effort of only 13,200 pounds (includ-ing current l i m i t overshoot) i s required at the drive r a i l s .

The maximum drive motor current v d l l not exceed 600 amperes and the maximum motor voltage required i s between 325 to 375 volts per motor. The motors v d l l have a minimum nominal continuous rating of 30 horsepower at 1474 rpm and a 1,15 service factor. The torque requirements w i l l probably require a much larger frame size.

The power supply consists of a motor generator set vhich includes optionally one or two d-c shunt wound generators having a speed of 1200 rpm. Hie supply w i l l be compatible with the peak power and voltage ratings of the drive motors, A synchronous motor rated at 2300 v o l t , 3 phase, 60 cycles, 0.8 p.f-, 1200 rpm supplies power to the d-c gaierator, Povrer f o r the synchronous motor wjJJ. be supplied from the 2400 volt switchgear.

The excitation f o r the shunt f i e l d s of the main drive motors w i l l be from a separate source 250 volt d-c supplied by a package type motor generator set vdth current regulated output. The exciting current for the main drive d-c generator w i l l be provided by a rotating type ampli f i e r of about 15 kw ca-pacity, driven by a low s l i p {3% or less) induction motor.

Speed Regulation: The speed regulating system consists of a high^gain closed-loop electronic regulating system vjhich operates from either a tachometer feedback signal or a loop voltage signal. The regulator w i l l control the d-c generator output voltage and thereby contrbl the drive motor speed.' An open-loop contiol system w i l l also be available i n case of regulator f a i l u r e . In this case the regulator c i r c u i t to the exciter control f i e l d w i l l be replaced by an adjustable voltage suppiy from the drive motor f i e l d source. A l l regu-l a t o r components except the contrbregu-l exciter v d regu-l regu-l be mounted on titie carriage.

Current l i m i t c i r c u i t s are provided for controlling d-c loop current and thus rates of carriage acceleration and deceleration.

The tachometer which supplies the feedback signal v d l l be v e r t i c a l l y mounted on a hinged p l a t f o m and be driven by a spring loaded i d l e r wheel on the drive r a i l .

Braking; An arrester cable and hydraulic arresting gear system of the a i r c r a f t carrier type w i l l be used at each end o f the bridge f o r stopping the carriage when a maximum run i s desired. The arrestors require about 20 f t . to stop the carriage regardless cf speed. The i n e r t i a of the moving parts of the arrestor produces an i n i t i a l instantaneous peak deceleration rate of about 1.3g iiihich drops to a nominal value almost immediately.

If less than a maximum run i s desired regenerative braking can be used. The amount of the normal regenerative braking effort can be established by pre^ setting the deceleration current l i m i t potentiometer located on the control console. The deceleration rate under regenerative • braking vdUL not exceed the maximum acceleration rate of the carriage. Brakes of the spring-set, shoe type mounted on the shaft extension of the carriage drive motors v d l l be used for holding the carriage i n a given position but not to stop'the carriage since they w i l l not have sufficient thermal capacity, ^

Protective Devices: Protective devices similar to those for the rotating a m drive system v d l l be provided to protect the equipment from malfunction or com-ponent f a i l u r e . Also a similar a l a m system and interlocking system i s provided, MANEUVERING BRIDGE TROLLEY SYSTEÎ-Ï

Power, control and instrumentation c i r c u i t connections between the maneuvering biddge and i t s carriage w i l l be by a t r o l l e y system.. The connections to the bridge w i l l be by means of extra f l e x i b l e cable fed from stationary cable r e e l s . The cable reels w i l l be installed on steel angles suspended frbm the building roof stmctural steel approximately- over the midpoint of the l a t e r a l t r a v e l of the center of the maneuvering basin bridge. Hie reels permit two-way pay-out of cables from one side to the other as the center of the fixed mounted reels i s passed during maneuvering bridge travel. The cable reels w i l l connect to

shore by means of cables running along iihe overhead of the building stmcture

to junction boxes at the top and mid-span of the bridge.

The t r o l l e y s selected are of the figure eight, insulated type. The conductors w i l l be r o l l e d copper bars about 3/3 incu oy ± inch finishea naving a contin-uous carrying capacity of 3ÓO amperes. • The insulation around each .conductor w i l l be of the non-bufning type with a minimum wall thickness of 0.075 inches. The insulation, of inverted Ü shape, w i l l allow a gap of about 1/4 inch at the bottom of the conductor where the collector makes contact with ithe t r o l l e y .

Hie connection from the bridge to the t r o l l e y w i l l be by means of slamp-type feeds. The collectors w i l l be insulated,* spring loaded assemblies vdth replaceable shoes made of sintered inetal consisting of 90 percent copper and 10 percent graphite thus being self lubï-lcating and permitting wear on;, the . shoe rather than the conductor. Supporting structure for the collectors w i l l be mounted on the caridage.

Figure 32 shovre the number of trolleys, spares or space provided. There i s provision for 27 tro3Jleys on thé south side of the bridge and 22 on iihe north side.

INSTRUMENTATION

instrumentaliion for the maneuvering basin \ d l l be located on the carriage and consists of six channels of general purpose graf^ic recorders, three speed measuring, d i g i t a l indicating and recording systems, a multi-channel program-ming system and operating consoles from which the carriage and model speeds v d l l be controlled. Hie equipment and instrumentation required for the v a r i -ous test programs to be conducted i n this f a c i l i t y i s either available or w i l l be provided separately.

Hie general purpose recorders include a-c and d-c gage control units .and non-balancing potentiometer type graphic recorders similar to the units for the rotating am. The gage çontrol units w i l l be for operation vdth either d i f -ferential transforner or strain gage type transducers i n dynamometers. The carriage speed transducer w i l l be of the same typé as that used for measuring the rotating a m speed, i t w i l l connect to the shaft of the

tachometer-generator used i n the carriage drive motor speed-.' control system.

Hie carriage, speed measuring system i s i n units of feet and hundredths of a foot p>€r second. The d i g i t a l indicating and recording of speed w i l l be sim-i l a r equsim-ipment to that used for Rotatsim-ing A m speed. D sim-i g sim-i t a l recordsim-ings v d l l be printed at one second intervals and totalized at the end of a ran as d i c -tated by the programmer. The programmer also i s a control system similar to that used for the rotating am. The estimated inaccuracies at the d i g i t a l recorders should not exceed 0,01 f t , per second,

MAIJEUVERING BASIN WAVEMAKERS

Pneumatic type wavemakers v d l l be provided along the west end and the north side of the maneuvering basin as shown by Figure 33. The west bank consists of Ö individual vraveiiiaker units and the north bank of 13 individual units. Wavemakers

The wavemakers w i l l generate waves from 3 to 40 f t . i n length with corre-sponding maximuTTi h e i s t s of about 2,5 inches to 24 inches. Figure 34 shows a t y p i c a l viavemaker assembly. The wave generator dome w i l l be p a r t i a l l y sub-merged i n vfater, of \ inch carbon steel, inverted U-shape, and about 24 f t . 6 inches long. The dome units w i l l be separated fram each other by end plates. The i n t e r i o r of the dome will.be 5 f t , wide and f i t t e d with a grid of v e r t i c a l baffle plates which aid the v e r t i c a l o s c i l l a t i o n of the vfater by damping cross movements of the v^rater. The spacing of the grid plates i s one f t . across the dome width and 2 f t . along the dome length. Two baffle doors f o m part of the grid and these can be used to close off either two ft. or four ft," of the dome width, thus controlling the amount of v/ater i n action. This i n effect makes available three sizes of wavemâkers f o r test operations, namely; a one f t , , "ttiree f t . and five f t . vdde wavemaker.

An adjustable stabilizer consisting of v e r t i c a l plates, open at the bottom and i n the direction of the wave travel, eliminates transverse waves vdiich are sometimes i n i t i a t e d by wavemakers. The submergence, of the front dome l i p , vàiich foms part of the stabilizer, can be adjusted so that .the bottom of the l i p ranges from 9i inches to 22^ inches below the basin water l e v e l , H i i s adjustment provides further f l e x i b i l i t y i n the control of vraves since f o r short waves less submergence of the l i p i s required than for long waves. Wavemaker Operation ; ^ ^ ,

The vraives w i l l be generated by alternately varying yae dome a i r pressure from positive to negative. This i s accomplished by means of blowers located i n the blower equipment room, connected tb the dome by 26''inch inside diameter 10 gage carbon steel ducting and pairs of oscillating valves. The valve system i s ar-ranged 50 that when a i r i s drawn from the atmosphere i t w i l l be forced into the dome and vriien a i r i s drawn from the dome i t v d l l be forced into the atmosphere. The frequency of the oscillating valves determines the frequency and thus the lengths of the deep vmter v^aves i n accoi-dance vdth the formula T = 0.4424 /p< > where ^ i s the wave length i n feet and T i s the period i n seconds. The phase

of each valve pair may either be synchronized vdth each other or hand set to operate at different phases by means of a phase change crank incorporated i n the valve drive system. Wave amplitudes can be varied by adjusting the blower speed and by setting butterfly type damper valves located i n the discharge duct of the blower,

A U the blowers i n each bank v d l l by synchronized e l e c t r i c a l l y so that they always operate at the same speed. In addition, each bank of blowers can be synchronized e l e c t r i c a l l y so that the tvro banks operate at the same speed. The oscillating valves i n each wavemaker bank w i l l be synchronized both i n phase and frequency by torsionally r i g i d shafting and positive povrer takeoffs. Also, both banks! of valves can be synchronized by means of a clutch and miter gear at the comer of the basin where the drive shafts meet. Hie main wave-maker controls w i l l be on a control console located on an elevated p l a t f o m at the mid-length of the north wall of the maneuvering basin biiilding.

A change order to the constmction contract has been requested for programming and individual control of vrave lengths and v*ave amplitudes f o r each of the 8 wavemaker units i n the west bank. This w i l l be acccMplished by 8 additional individual valve drives and 8 additional individual blovrer damper valve drives programmed by a magnetic tape system. Programming, of the valve frequencies of each vmvemaker bank, when each bank operates at synchronized speeds, v d l l also be possible by means of the magnetic tape system.

Wavemaker Modéls

The wavemaker design i s based on the ^ s u l t s of a development p r o g i ^ that culminated i n the installation of a 51 f t . vdde pneumatic vra,v«naker i n the Taylor Model Basin deep vjater basin. The 51 f t , unit i s physically the equiv-alent of tvro of the maneuveidng basin wavemakers. In additixm, a l / l O model of the maneiivering basin was built and tested. The l / l O model vras constructed primarily to check the performance of the wavemakers and the vrave absorbers. The physical dimensions of the vsave absorbers, b asin and vravemakers are to

scale, except for ;he powering and controi syatfems. The results or tne l/lO model test program w i l l be reported on i n a se.parate Model Basin report,

Blowers

The blowers w i l l be single wheel, single i n l e t centrifugal blowers vdth over-hung vheel and shaft. The blower shaft connects directly to the drive motor by means of a gear type coupling. Hie vrtieel and shaft w i l l be balanced sta-t i c a l l y and dynamically for smoosta-th operasta-tion asta-t speeds from 100 sta-to I6OO rpm, Head-cfm characteristic curves for the blower at constant speed w i l l be parallel to those given i n Figure 35 within a tolerance band of plus J inch vräter head.

Baffle Doors

The bottom baffle doors i n each wavemaker dome unit w i l l be operated by an electric motor-driven, vrom-geared valve operator with automatic torque switch cutoff. The unit v d l l be equipped vdth torque switches vjhich detect the torque imposed on the connecting shaft for either direction of rotation and svdtch o f f the motor at a preset torque. The torque switches v d l l be separately adjustable over a range of I50 - 750 inch pounds and w i l l accu-rately monitor the position of the doors and make contact at the end of the opening and closing stroke. The motor w i l l be 440 v o l t , 3 phase 60 cycle vdth maximum outpnit torque of 750 inch-pounds and output speed of about 30 rpm.

Damper Valves

The dampers w i l l be round, single vane, center pivoted, variable position, remote control electric motor-operated valves. These valves w i l l be used to balance the blowers as required by manufacturers tolerances of blowers and motors and also as an auxiliary means of varying the amplitude of waves for' individual wavemakers. The valves v d l l be suitable for 55,000 maximum cfm and a maxi mum pleasure difference of 20 inches of water with the valve closed. The damper valves on the west bank blowers v d l l be automatically controlled and programmed.

Main Valve Drives

There w i l l be two main valve drive systems — one for each bank of vmve-makers. The valve motion and synchronization w i l l be obtained by mechani-cal linkages driven by a 2- 3/I6 inch outside diameter carbon steel line shaft. The line shaft runs the entire length of each v^ayemaker bank. The valve drive systems are WardLeonard type drives, controlled by a h i ^ -gain, closed-loop electmnic speed regulating system iihich operates from a direct-driven tachometer feedback signal. i\ block diagram of the system i s shown by Figure '6.

Capabilities: The valve frequency w i l l be continuously variable from 18 to 30 cycles per minute. One cycle of valve operation corresponds to about 7,5 revolutions of the line shaft so that the maximum l i n e shaft speed w i l l be about 600 rpm. Steady state speed constancy (cyclic average) vdthin plus or minus 1/8 percent of top speed and a preset speed error within plus or minus ^ percent of top speed i s estimated.

Drive; The valve drive motors are 250 volt d-c, 1750 rpm, separately ex-cited shunt types capable of producing f u l l torque at a l l speeds over a speed range of about 4:1. Hae valve drive motor for the west bank of vmve-makers i s rated at 10 horsepower and that for the north bank at 15 horse-povcer, with a 125 percent rating f o r tvro hours. The drive motor connects to the l i n e shaft by means of a right angle gear reducer vdiich has a maxi-mum input of 1750 rpm and a ratio of 2.91:0.

Hie west bank l i n e shaft drive motor may be changed to 20 hp and the north baidc drive motor to 30 hp i n order to accomodate future programming of each

synchronized bank of yalves. I f the drive motors horsepovrer ratings are i n -creased, compatible changes v d l l be made i n the power supply, speed reduc-tion gearing and control equipment.

The variable DC power supply consists of a motor generator set for each valve ^stem. The sets include an induction motor rated at volts, 60 cycles, 1.15 service factor, 1750 rpm, having 25 horsepower for the north wavemaker bank and 15 horsepower for each bank, and a d-c shunt wound generator rated at 15 kw for the north viavemaker bank and 10 kw for the west bank, 1750 rpm and 125 percent for 2 hours.

The power supply for the motor f i e l d s w i l l be either r e c t i f i e r s or rotating equipment at the option of the manufacturer.

Speed Regulation; The control system consists of balancing a tachometer output against a highaccuracy reference voltage and feeding the differences i n -to a precision regula-tor* This controls the f i e l d of the m-rg set genera-tor and thus the speed of the drive motor. Hie d-c tachometer f o r the valve

drive speed control v d l l be directly connected to the valve drive motor shaft. Precision type potentiometers located atthe vjavemaker control console and c a l -ibrated i n increments of one rpm from 435 to 1750 rpm are provided for setting ,valve motor speed. Current limit c i r c u i t s are provided to l i m i t the current

vihich can be safely commutated. , .

Speed Indicators: Two speed-indicating systems v d l l be provided for each valve drive. These consist of a coarse indicator of the d-c voltmeter type and a fine indicator of the high-accuracy transducer and electronic counter type. Both provide visual indication, read continuously and v d l l be c a l i -brated to indicate actual valve period i n milliseconds. Hie d-c voltmeter measures the signal produced by a d-c " permanent magnet tachometer that v d l l be driven from the valve drive motor shaft. The high accuracy valve-period indicator consists of an a-c transducer and an electronic counter vriilch w i l l count cycles of a reference frequency between a given number of impulses from the transducer. The transducer w i l l be direct driven from the shaft extension of the speed-control tachometer. The electronic counter reading i s expected to have ân accuracy wi"hin £ 0.1 percent' of f u l l speed of the drive motor.