sperry gyrocompass mark 14

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Gyro-compass Mark XIV, Mod. 1, 17-MOOD, 1944, is a service manual for the most widely builtgyro ofWW II. This gyro was used onpretty muchany ship that did not have automated firecontrol.

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GYRO-COMPASSMARK XIV, MOD. I

INSTRUCTIONS 17-1400 D

JUNE 1944

SPERRY GYROSCOPE COMPANY, INC.,MANHATTAN BRIDGEPLAZA, BROOKLYN,NEWYORK

I

SPERRY GYRO-COMPASS

FOREWORD

1. The purpose of this book is to enable the ship's personnelto operate and maintain their Gyro-Compass inasatisfactory and economicalmanner. Ifthe basic principles ofthe Compass are understood and the rules laiddown for operation, care and maintenance are followed carefully, the instrument should give satisfactoryservice for many years. Nonnalreplacements, due to wear, will be necessary fromtime to time. Most ofthesereplacements may be made by the Compass operator, following the instructions contained inthis book. But theoperator should not attempt to make any repairs or adjustments other than those noted inthe text, otherwisehe may seriously affect the adjustments and balances ofthe compass. Itwill be found more economical to havea Gyro-Compass Service Engineer make any major adjustments, overhauls, etc. The Sperry Gyroscope



Company, Inc. maintains a staffofexpert Service Engineers ready to render quick and efficient service inanyport inthe United States. A list of service stations will be found at the end ofthis foreword. Ifit is necessary toengage a Service Engineer, time and money will be saved by stating inyour request for service the nature andcause ofthe trouble.

2. Basically the Compass is much like the very popular Mk. VT and VIII Compasses, ofwhich over 1000have beenplaced inservice on ships representing almost every maritime nation inthe world. Manyimprovements indesign are present inthe new compass but since they are too numerous to detailhere, only afew outstanding changes will be mentioned.

3. The binnacle is designed to support the Compass insuch a manner that the entire unit is shock-proofed. Thedoors are large, permitting free access for oiling and cleaning.

4. Hie mercury ballistic is cast inone piece so as not to be subject to distortion. The mercury tubes are madeofstainless steeL

5. The follow-up systemfor the Compass is the a-c amplifier type. The great advantage ofthe Amplifier Unitover the trolleys and contactors, formerly used, is that it permits much smoother and more accuratetransmission ofthe Master Compass readings to the repeater compasses. Its use also eliminates any rolling orsliding contact betweenthe sensitive and phantomelements. This serves to lessen friction about the vertical axisofthe sensitive element and assists in improving the accuracy ofthe compass. Furthermore, maintenancerequirements are minimized.

6. Inorder to secure constancy ofbalance, allparts are made to have the utmost rigidity, thus balances oncemade are permanent.

7. Special attention has beendevoted to ruggedness, simplicity, and accessibility ofconstruction. This isconsidered specially important for the proper maintenance ofa compass equipment aboard ship.

8. The Mark XIV Gyro-Compass Equipment consists ofthe following groups ofunits:

(a) Master Compass, by which the true northreading is gyroscopically discovered and maintained.

II

(b) Repeater Compasses, which receive and indicate the true heading transmitted electrically fromthe Master Compass.

(c) Course Recorder, which also receives the tme headingelectrically from the Master Compass,and makes a continuous record of the headingon a moving strip ofpaper.

(d) ControlPanel, for governing the electricaloperation ofthe system and for ascertaining therunning conditionby means ofa suitable meter.

(e) Voltage Regulator, to maintainconstant the ship's supply to the motor-generator.(f) AlarmUnit, for indicating failure ofthe ship's supply.

(g) Amplifier Panel, for controlling the follow-up system.(h) Motor-generator, which converts the ship's d-c supply to a-c for energizing the Compass



equipment.

9. Items a and b are treated inthis pamphlet; likewise d, e and fare treated inanother pamphlet. The remainingitems are treated separately. The separate pamphlets are designed to be bound within one cover forconvenience.

MARINE SERVICE STATIONS

East Coast

Baltimore, Md.Boston, Mass.Brooklyn,N.YCharleston, S. C. to

4908 Alson Drive177 State Street55 Johnson Street1645 Belmonte Avenue,

Erik DuffyDaniel O'KeeffeMarine Service Dept.Wm D. VanLoan

Jacksonville, Fla. Area Jacksonville, FloridaNorfolk, Va. to 3504 White ChapelRoad James DuffyWilmington, N. C. Area Norfolk, VirginiaPhiladelphia, Pa. 3830 Brunnswick Avenue John Stone

Gulf Coast

Beaumont, TexasHouston, TexasMobile, AlabamaNew Orleans, La.

1047 Washington Blvd. HE. Camus4037 Coleridge Street E. L. Anderson403 Westwood Avenue C G. Fiske549 Baronne Street J. E. Boelte

St. Petersburg, Florida 3301 Tenth Street NorthC. W. Young, Jr.

West Coast

Los Angeles, Calif 2200 East EmperialHighway W I. SeloverElSegundo, California

III

Portland, Ore. 1744 S. E. Hawthorne Blvd. Glenn MarshSan Diego, Calif 702 Broadway Building L. L. KaiserSan Francisco, Calif 218 Howard Street J F. McConkeySeattle, Wash. 2331 SeventhAvenue H. S. Burtis

Great Lakes

Ashtabula, Ohio 2528 Walnut Boulevard Arnold NelsonBuffalo, N. Y. 29 Charleston Road, Snyder, N. Y. W J. EkenbergChicago, 111. 3006 East 78 Street Charles BlueCleveland, Ohio 620 Frankfort Avenue Frank Phillips



Toledo, Ohio 1852 Wellesley Drive W. L. Weyls

Territories

Honolulu, T. H. 119 Merchant Street E. C. Weyhgandt

CONTENTS

Section PageDescription I 1Operation II 9Maintenance III 13

Cleaning Chart 18Oiling Chart 20

Parts List IV 22FundamentalPrinciples ofGyro-Compass Appendix alIndex Back ofbookControl Panel Carbon Pile Regulator and Alarm Unit Control PanelAmplifier Panel for Gyro-Compass Amplifier PanelMotor Generator Mark XXXVI, Mod 1 Motor Generator

IV

ILLUSTRATIONS

Figure PageGyro-Compass 1 1Sensitive Element 2 2PhantomElement 3 3Mercury Ballistic 4 3

Spider Element 5 4Speed and Latitude Corrector Mechanism 6 5Compass Transmission System: Schematic Diagram 7 7RollDamper 8 16Pitch Damper 9 17Cleaning and Oiling Charts 19.

21APPENDIX

The gyroscope has three axes ofangular freedom la 2aWhen spinning, the gyro exhibits gyroscopic inertia 2a 2aThe original plane ofrotation is maintained no matter how the base is moved about 3a 2aPrecessionabout the vertical axis 4a 3aPrecessionabout the horizontalaxis 5a 3a



Gyro rotor shown insection 6a 4aA gyro with its spinning axis set in the east-west positionat the equator 7a 5aA gyro with its spinning axis set horizontalat the pole 8a 6aA gyro with its spinning axis set horizontalat any point away from the equator 9a 7aTo make the gyro seek the north 10a 7aEffect of the mercury ballistic when applied about the horizontalaxis 11a 8aDiagramshowing the effect ofa mercury-controlied gyro wheel when set with its axle pointing 12a 9aeast or northElements of the gyro-compass 13a 9aAction of the gyro axis when the mercury ballistic is connected to its casing through an eccentric 14a 10apivotGyro-compass damping curve 15a 1laEffect ofunsymmetrical distribution ofweight 16a 12aDiagramillustrating the effect ofship's speed and latitude on the gyro-compass 17a 14a

1

SECTIONI

- DESCRIPTION -

1.NOTE:A discussion ofthe frmdamental principles of the gyroscope is contained inthe Appendix to thistext.

SENSITIVE ELEMENT

2. A gyro must be mounted so that it has 3 degrees offreedom This is accomplished inthe Sperry Gyrocompass as described inthe following paragraphs.3. The gyro wheel is mounted onballbearings ina case so that the wheel is free to turn about its SPINNINGAXIS. See figure 1. Since the axle ofthe gyro aligns itselfwith the meridianwe may speak of the northendand the south end ofthe axle. Carrying this terminology further, we refer to the northand south ends of thegyro rotor case, and the east and west sides ofthe case.

4. The case is providedwith studs aligned horizontally onthe east and west sides. These studs rest inbearingsin the vertical ring. Refer to figure 2. This provides the gyro and ease with freedom about the HORIZONTALAXIS.



soyth v|w figure i mouthMK, XIV GYRO COMPASS

REMOVED FPC-M aiHN4GLEi

I SPEED AND LATITUDE COHRECTGH ID SOT DP GAS.E1. SuSPENtlflK cap II. MEftCUftT 94LLI'3Tio4. FOLLOW-UP TRANSFORMER >?- AZIMUTH MOTOR5,. TRANSMITTER 11, SPItEft TEfiMIMAL flt.QGKi. THUNNlDIl HEADINGS 19. LOST MOTION ADJUST ING KNOB7 VERTICAL FING J1, VEATIC4L RING LOCK6. COMPENSATOR WEIGHT S I SPEED AND LATITUDE CORRECTOR SETTING KNOB$. PHANTOM fllNO SB. AUXILIARY LAtlTUOE CORRECTOR SETTING KNOB

2

5. The vertical ring is provided with ballbearings aligned inthe vertical axis ofthe Compass. This provides thegyro with freedom about the VERTICAL AXIS. The vertical bearings referred to do not actually support thevertical ringand hence they are called the (upper and lower) guide bearings. The actualweight ofvertical ring,case and gyro is home by a group ofwires called a suspension. The reason for this is discussed underPHANTOM ELEMENT.

6. Fromparagraphs 3,4, and 5 it canbe seen that the gyro is mounted with the necessary 3 degrees offreedom The gyro wheel, its case, the vertical ring and the suspension constitute the north-seeking assembly ofthe Compass and are collectively knownas the sensitive element.

7. Because the sensitive element is the north-seekingpart of the Compass, it must be kept as free as possiblefrom disturbing forces. The whole Compass is mounted inits binnacle on a gimbal system so that it may hangundisturbed by the rollingand pitchingmotionofthe ship. Due to any number ofcauses the Compass mightstart swinging on its gimbal supports and thus be subjected to a disturbing force called the "pendulum effect".This effect arises fromthe feet that any weight swinging back and forth as a Pendulumwill turn so as to align itslongest axis inthe plane ofthe swing. Inorder to give the sensitive element the effect ofa sphere so that it hasno "longest axis" and thus not be subjected to the disturbing pendulumeffect, certain weights are added to thevertical ring. These weights are called COMPENSATOR WEIGHTS (see figure 2). They are accuratelypositioned on assembly at the factory and from the above it can be seen that THE SETTING OF THECOMPENSATOR WEIGHTS MUSTNOT BEDISTURBED.

PHANTOM ELEMENT


FIGURE 2SENSITIVE ELEMENT

7 VERTICAL RING9 COMPENSATOR WEIGHT10 ROTOR CASE\4. SUSPENSIONIj compensator

Wi'OHT FRAME17 CASE LEVEL18 ROTOR SEARING

HOUSING PLATE

21. HORIZONTAL CASEBEARING

22 OIL WELL WiAi&OW23 FOLLOW-UP TRANSFORMER

ARMATURE24 armature BRACKET25 UPPER AND LOWER VERTPCAL

RINGQVIDE BEARING STUDS26 $$ AC KjTflO SUPPLT


8. As explained inthe preceding, the sensitive element is thenorth-seekingelement ofthe Compass. For this reason itmust be mounted so as to be free to turn about a verticalaxis inorder that the gyro axle may align itselfwith themeridian. The mountingmust also be arranged so that thesensitive element will not be carried away fromthe meridianas the ship turns beneath it. Any bearing friction, while thesensitive element turns (withrespect to the binnacle) about avertical axis, would cause a disturbance of the Compass. Apractically frictionless method ofmounting the sensitiveelement must be used. The method employed inthe Sperry

| Gyro-Compass is explained inthe following paragraphs.

3


10. Since the phantomelement is kept accurately aligned withthe sensitive element, the former provides a convenient placeto mount the compass card. Reference to figure 3 shows thelocationof the compass card, at the top ofthe phantomstem

11. The phantom element, which consists primarily ofa ringattached to a tubular piece called a stem, is supported by thespider element (figure 5). Ballbearings, called stembearings,keep the 2 elements aligned and permit the former to turnfreely with respect to the latter. The phantomis supportedfromthe hub ofthe spider on a roller thrust bearing.

MERCURYBALLISTIC

12. The mercury ballistic (figure 4) is sometimes referred toas the controlelement.

13. The ballistic is suspended onhorizontal studs fitted intoballbearings inthe phantomring and is attached to a bearingonthe bottomofthe gyro case by means ofan amicalled thelink arm. The bearingreferred to is called the link bearingandis oflset .170" to the east of the vertical axis of the case. SeeAppendix for a discussion ofthe principle involved.

II ~3*

FIGURE 4MERCURY BALLISTIC

ae BAj-fcueims weights tube37, WEHCL>*V nesciyoits 0lJNI


SPIDER ELEMENT

16. The spider element (see figure 5) is mounted on the gimbal systemofthe binnacle on athwartship trunnions.It carries (a) the azimuth motor which drives the phantomelement to follow the sensitive element (seeFOLLOW-UP PANEL), (b) the transmitters for operating the repeater compasses (see TRANSMISSIONSYSTEM), (c) the speed and latitude corrector, and (d) the lubber ring.17. The spider consists ofa main frame, designed to bear the weight of the phantomand sensitive elements.The construction ofthe frame maybe seen infigure 5. A detachable lubber ring is earned on the rimofthespider frame. This ring carries an adjustable lubber line plate which is engraved with a lubber line against whichthe compass card is read. The correctors mentioned are mounted on the spider but are connected to thelubber ring so as to cause the latter to move as required. The con-ections inthe compass indication, as solvedby the corrector mechanisms, are thus introduced into the Compass by shifting the positionof the lubber ring.Hie transmitters for the repeater system, also mounted on the lubber ring, introduce the compass correctioninto the repeater compasses automatically.

18. The speed and latitude corrector (figure 5) isdesigned to compensate boththe MasterCompass and the repeater compass for thespeed and latitude error. The correction forspeed and latitude error could be set into thecompass periodically, except that it varies as thecosine ofthe course and inversely as the cosineofthe latitude. Therefore, some means ofinserting a correction automatically for allchanges incourse must be used. A groove calledthe cosine cam is cut into the bottomoftheazimuth gear on the phantomelement. This camis designed to move the corrector mechanismtheproper amount to correct the compass readingsfor all changes incourse. Changes ofspeed (over 3 knots)

Fb&UKE 5SPIDER ELEMENT

I. 'SPSEP AND LATITUDE 45 LUBflEI* fiintC OH REdQR

5. TRANSMITTER 57 SPEEO ARth LAI CORRECTOR6. TR-UhMlCR BEARING SETTING KNOB

IE A.EIMUTH MOTOR 54 AUXILIARY L AT CORRECTOR45 AilMUTH MOtDR LARGE GEAR 5S7TIRG KNO0*4. SJfM SLIP ftING RfiU5HES 60 COSIHE CAM ARM

5

and latitude (over 3) are set inmanually. The corrector mechanism is shown schematically in figure 6. Roller59 rides inthe cosine camwhich is cut into the lower side ofthe azimuth gear. As the Compass turns inazimuth, the cam causes arm 60 to move. Arm60 constitutes a bellcrank which moves arm62 aboutadjustable pivot 63. This motion is imparted inturn to arm 64 through pivot 65. Arm 64 moves a pivotedblock 66 which is attached to lubber ring45. Thus the lubber ring is caused to move, as the ship changescourse ina given latitude. It can be seen, from a study of figure 6, that for a given movement ofarm60, theamplitude of the resulting movement of the lubber line is determined by the positionofpivot 63. The positionof


FlKECPlVQt


pivot 63 is a function ofship's speed and latitude.This position is determined by means ofa latitudescale which moves across a plate engraved withspeed curves as knob 57 is turned.

19. Itwill be noted that pivot 66, which shifts thelubber ring, is mounted on a block which may betranslated by means ofknob 58. This arrangementpermits the correction for the tangent latitude error tobe superimposed on the speed correction. Anauxiliary latitude scale enables this correction to beset inaccurately.

BINNACLE

when the ship is inheavy weather, dampers areprovided on the gimbal system. See page 16 fordescription and maintenance.

*5 LUBBER BINS 62 ARM

57 SPEED & LATITUDE SETTING 65 ADJUSTABLE RiVOTM A U*. LATITUDE STT|NG KM-Ofi 64 ARM*9 Cosine CAM hqllr 65 FIXED PiVOT60 COSINL CAM ARM (bell CAMK)| 66 ADJUSTABLE BLOCK & PIVOT

20. The binnacle supports and provides a protectivehousing for the Compass. It is provided with a gimbalsystemwithin which the Compass is suspended sothat the Compass may hangvertically regardless ofthe ship's motion, within limits of60 rolland 20pitch.

FlGuftE 21.To prevent violent swinging ofthe Compass SPEED AND LATITUDE CORRECTOR MECHANISM

22. The entire Compass is shock-mounted inthe binnacle to absorb ship vibration. This is done to protect theCompass, movingparts from excessive wear which might result fromundue vibration.

6

23. The sides ofthe binnacle open onhinges to provide convenient access to the Compass. The top may beremoved when necessary.

24. Two lamps, connected inparallel, are provided inthe binnacle for illumination. A switch and terminals areprovided also inthe binnacle to connect the lamps to the lighting systemofthe Compass compartment.

GYRO-DRIVE SYSTEM

25. The gyro-drive system links the ship's supply to the gyro wheel.

26. The Compass gyro wheel is drivenby a 3-phase inductionmotor. The rotor ofthe inductionmotor is apart ofthe gyro wheel, while the stator is attached to the gyro case. This motor is energized by a 3-phase,210-cycle, 50 volt a-c supply. The method ofobtaining this supply is described inseparate pamphlets entitled"ControlPanel" and "Motor-Generator".

27. The supply is lead to the binnacle terminalblock, then to the spider terminalblock, through the slip-ringsmounted on the stemofthe phantomring, across to the vertical ring, downthe east "side" of the vertical ring as



far as the horizontalaxis ofthe case, then across to the case and the gyro-drive motor.

28. This circuit has been lead from the source ofsupply to the gyro motor inthe manner described so that thebalance ofthe Compass will not be disturbed. Where the leads pass from phantomelement to vertical ring, andfrom vertical ring to rotor case, extra flexible conductors are used so as not to exert a torque on the sensitiveelement. THE POSITION OF THESE LEADS SHOULDNOT BE DISTURBED BY THE COMPASSOPERATOR.

TRANSMISSION SYSTEM

29. The transmission system is used to transmit the headingofthe Master Gyro-Compass to all repeatercompasses, and to the Course Recorder should the ship be supplied with this instrument.

30. The system operates on 70-volts d-c and consists ofa transmitter attached to the lubber ringof the Gyrocompass (see figure 5), connected electrically with the repeater motor mounted inthe casing ofeachrepeatercompass.

3 1. The transmitter consists mainly ofa commutator and a roller carnage. The commutator comprises 12segments secured to the lower end ofthe transmitter frame. The roller carriage is secured to a shaft free to turnwithin the transmitter frame and the shaft is geared to the azimuth gear onthe phantomelement. A contact ami,held against the roller carriage by a spring, provides a means to hold the carriage inplace and to connect it tothe 70-volt d-c supply.

32. It has been previously stated that the compass card is attached to the stemofthe phantomelement, andthat attached to the stembelow the compass card is the azimuth gear (see figure 3). The gear on the transmitterroller carriage is meshed with the azimuth gear so that the latter will drive the roller carriage ofthe transmitter asthe phantomelement moves inazimuth.

7



FIGURE 7SCHEMATIC DIAGRAM

SHOWING HOW THE REPEATER COMPASSES ARE OPERATED FROMTHE MASTERCOMPASS

33. The repeater compass consists ofa small d-c step-by-step motor mounted ina casing. The motor drives acompass card which is read against a lubber line secured to the casing.

34. A lamp for illuminating the repeater card is mounted under the repeater motor. The repeater bottomcovermay be removed for access to the lamp. A dimmer switch for controlling the brilliancy of the repeater will befound in the repeater stand.

35. Figure 7 shows the electrical connections betweentransmitter and repeater. The leads marked "SupplyLine" are connected to a 70-volt d-c source: The 70-volt supply is obtained byreducing the ship's 1 1 5-volt d-c supply by means ofa carbonpile regulator or a series resistor (see circuit diagram inControlPanelinstructionbook). Ifthe ship's supply is 220 volts, the 70-volt supply is obtained from a d-c generator which isincorporated inthe compass (220 V.) motor-generator set.

36. Lead 4 (figure 7) carries the positive legofthe circuit to the transmitter when the circuit breaker andrepeater switches are closed on the compass panel. At the transmitter the positive leg is directed to lead 1, 2or 3 depending on the positionofthe roller carriage. The circuit then passes back to the panel, through therepeater switch to the correspondingly numbered coils on the repeater motor. The returnto the panel is madethrough lead 5 which is connected through a fuse and the repeater switch to the commonreturn for the variouscompass circuits.

8

37. Resistors for loadingthe transmitter, and condensers for quenching sparking as the roller carriage passes



from segment to segment, are connected inthe circuit at the compass binnacle tenninal block. See circuitdiagram inthe ControlPanel instruction book.

FOLLOW-UP SYSTEM

38. The Gyro-Compass employs the a-c amplifier type of follow-up control. The amplifier panelused isexternal to the Compass and is described indetail ina separate pamphlet entitled "Amplifier Panel". Forconvenience, the operationwill be described briefly here.

39. A follow-up transformer is mounted onphantomelement (figure 3) so as to be normally aligned with anarmature carried by the sensitive element. The transformer has 3 legs; the center leg is energized from onephase ofthe 210 cycle supply to the gyro motor, while the 2 outer legs are connected to the vacuumtubeamplifier insuch a way that when the transformer and armature are aligned, there is no signal to the amplifier.When the sensitive element moves away from the phantomelement, the signal to the amplifier corresponds indirection and amount to the direction and amount ofsuch movement.

40. The amplifier augments the input signal so as to control2 rectifier tubes, which energize the azimuth motorarmature. Since the field of this motor is continuously excited from the d-c supply, the motor drives thephantomelement so as to bring the transformer again opposite the armature on the sensitive element. Then theinput to the amplifier ceases and the motor stops.

41. Because ofthe sensitivity ofthe follow-up control, inactual operation the phantomelement never becomesmore than slightly displaced fromthe vertical ring, and uponbeing so displaced is instantly brought back intoalignment.

RADIO FILTER

42. An electrical filter, comprising chokes and condensers, is usually providedwithin the binnacle so as tosuppress any interference with the radio equipment onthe Ship.

9

SECTION II

-OPERATION

-

PREPARINGTO START

43. Preparations should be begunpreferably at least 4 hours before the Compass is required for service.

44. Make certain that all supply switches are open.

45. Unlock binnacle top cover, open one door and make sure that vertical ring and rotor case locks areapplied.

46. Take hold ofboth sides ofphantomand vertical rings and turn them slowly until compass card indicatesapproximate heading ofship. The Compass should never be turned inazimuth, with the power olf by pressureon compensator weights or mercury ballistic.

47. Check height ofoil on oilwellwindows. Make sure that oil level is just evenwith center ofdot onwindowand that oil level is the same on both sides ofCompass.



48. Test alarmby throwing switch on alarmunit for a second or so, to make sure relay fijnctions.

49. Adjust speed and latitude and auxiliary latitude correctors to proper setting. (See paragraphs 67 to 69.)STARTING COMPASS

50. Throw control switch on controlpanel to ON.

5 1.Pullout circuit breaker plunger on controlpanelto energize motor generator. Holdplunger out by handuntilmotor-generator speeds up (inabout 5 seconds).

52. When starting alongside a dock, wait until rotor is up to speed (in approximately 10 minutes), then turn onfollow-up switch onamplifier panel. (When starting up at sea, release the rotor case and vertical ring lockinglatches immediately and steady the rotor case by hand untilrotor is up to speed.)53. Wait one minute for rectifier tube filaments to heat up.

54. Release rotor case and vertical ring locking latches.

55. Turn ON azimuth motor switch at amplifier panel.

56. Synchronize all repeaters to the same heading as the Master Compass, and then close all repeaterswitches.

57. Turn switch at alarmunit so as to silence alarm.

10

58. Reset Compass on ship's headingbypressingdown on one or the other ofthe rotor case bearinghousings,and ifnecessary levelthe rotor bypressing against the vertical ringuntil bubble is onnormalsettled position.Check repeaters, and synchronize ifnecessary.

SETTING COMPASS ON MERIDIANWHEN DIRECTION OF NORTHIS KNOWN

59. After Compass is up to speed and operating normally, precess Compass bypressing on top ofeither rotorcase bearinghousinguntilzero on compass card points true north, at which time the card will indicate the trueheadingof the ship. Then level the case by bringingbubble to normal settled positionand allow Compass onehour to settle.

SETTING COMPASS ON MERIDIANWHEN DIRECTION OF NORTHIS UNKNOWN

Within 2 Hours After Rotor Has Come Up to Speed

60. Levelthe case; approximately 21 minutes later level it again; approximately 21 minutes later level it a thirdtime. The Compass then will indicate approximately the true meridian. When the bubble remains at its normaloperating position, the Compass has settled on the true meridian.

Within One HourAfter Rotor Has Come Up to Speed

61.Levelthe case and observe rate oftravelofrotor case levelbubble, inminutes ofarc for any convenientperiod oftime (say 3 minutes). Also note direction ofmovement.



62. Divide number ofminutes ofarc through which bubble traveled by number ofminutes of time allowed forthe test. Multiply this quotient by the constant 5. The product will give approximate number ofdegreesdeflection from meridian.

63. Ifbubble travels to south, Compass should be precessed to east, and ifbubble travels to north, Compassshould be precessed to west. Amount ofprecession should be equal to number ofdegrees obtained inpreceding paragraph. Thus, ifbubble moves to south at rate of6 minutes ofarc in2 minutes of time, whenCompass headingwas 125, then northend ofCompass is pointing approximately 6/2x5= 15west of themeridian and it should be precessed this number ofdegrees to the east, or to 125 - 15 = 110.

64. Levelthe case, again observe bubble movement and make a finer correction ifand when necessary. Whenbubble movement has become less than one minute ofarc in5 minutes of time, Compass should be within onedegree ofthe meridian. The foregoing rule is approximately accurate for deflections up to about 50 inlatitudesbetween0 and 60.

65. Care should be taken that Compass is not started exactly 180 oflfthe meridian, as bubble will travel veryslowly when Compass is heading insuch a direction.

66. The settling positionofthe gyro axle relative to the meridian is reached when the bubble finally occupies itsnormalsettled positioninthe leveL Incase the normalsettled positionofthe bubble is not central, whenCompass is settled on the meridian, its normalsettled position should be recorded and used inmakingtheabove setting.

11

SETTING THE SPEED AND LATITUDE CORRECTOR

67. When Compass is inoperation, the corrector should be set for the approximate speed and latitude of theship. These settings need not be changed for small variations inspeed and latitude, but should be kept within 3knots and 3 respectively.

68. To set corrector, turn knob 57 (figure 1) untilthe scale line corresponding to the ship's latitude on themovable latitude bar intersects the curve representing the ship's speed on the speed plate across which thelatitude bar is movable.

SETTING THE AUXILIARY LATITUDE CORRECTOR

69. To set the auxiliary corrector, turn knob 58 (figure 1) until line engraved on lubber ringcoincides withapproximate local latitude marked on adjustable block ofcorrector.

IFALARM SOUNDS DURINGNORMAL COMPASS OPERATION

70. A momentary failure ofthe supply current will cause buzzer to sound until the supply is restored, and insuch case the accuracy ofthe Compass will not be affected. It is advisable, however, to check repeaters withMaster Compass after any momentary failure ofthe supply.

71. Ifalarmcontinues to sound, the current failure evidently is more than temporary. Turn switch OFF tosilence buzzer. Examine controlpanel immediately. The circuit breaker is adjusted to open approximately 5seconds after ship's supply fails. If on examination, the circuit breaker is found open, repeat instructions forstarting Compass at sea. Check Master Compass and repeaters.



STOPPING COMPASS

72. Openrepeater switches.

73. Turn alarm switch to silence buzzer.

74. Turn OFF azimuth motor switch.

75. Turn OFF follow-up switch.

76. Throw toggle switch on controlpanelto OFF. This de-energizes the circuit breaker coil and causes circuitbreaker to open.

77. Ifstopping Compass at sea, during heavy weather when considerable motionis imparted to the Compass,steady rotor by hand until it stops, then lock it with locking latches. Ifstopping at dock, there is no need ofsupporting rotor by hand; it may be locked immediately.

78. Inspect equipment and clean same ifconvenient. The equipment canbest be cleaned while it is stillwarm

12

NOTES

79. Under normal operation, the rotor case is uncomfortably hot to the bare hand. This should occasion noalarm, as the nonnal operating temperature is approximately 45 C higher than roomtemperature. Keep oillevelevenwith center ofdot inoil-wellwindows at each end ofrotor case.

80. Keep binnacle doors closed and cover locked whenever the Compass is left unattended. Allow nounauthorized personto tamper with it at any time.

81. With ships having 220-volt d-c supply, the operating instructions are somewhat different from thepreceding. Refer to separate instructionpamphlet provided with 220-volt controlpanel.

13

SECTION III

- MAINTENANCE -

82. A summary of inspection, cleaning and oiling instructions is presented herewith. Further details will befound in the Amplifier Panel, ControlPanel, and Motor-Generator pamphlets.

ROUTINEINSPECTION

EACHWATCH

83. Check repeaters with Master Compass to be sure repeater system is functioning properly. Ifsupply failsfor any reasonbe sure to check and, ifnecessary, synchronize repeaters as soon as supply is restored.

84. Check Compass by azimuth observation ifpossible.



85. The speed and latitude corrector and auxiliary latitude corrector should be properly reset wheneverchanges ofspeed and latitude make resetting necessary, as advised inparagraph 67 under OPERATION.

86. Inspect Compass to guard against any abnormal condition ofoperation.

EACHWEEK

87. Check alarmunit by turning switch on alarmunit and noting that buzzer sounds.

88. Check allelectrical connections to make sure they are tight, clean and free from oil.

89. Clean and oil parts as indicated on charts, pages 18-21.

EACHMONTH

90. Polishthe glass over the repeater card. Clean the repeater stand ifit is inan exposed position.

91.Check alignment ofazimuth motor brushes as described onpage 15.

92. Clean and oilparts as indicated on charts, pages 18-21.

CARE OF MERCURYBALLISTIC

93. The mercury ballistic reservoirs are ventilated through smallholes inthe reservoir tops so that the mercurywill not become air bound as it flows from one reservoir to the other. Due to the presence of this air, a certainamount ofoxidationofthe mercury takes place. This takes the form ofa filmon the surface of the fluid andeventually the filmwill retard its free movement. For this reasonthe mercury should be checked about eveiy

14

3 months to make sure that it flows freely. For economy ofup-keep and maintenance, instructions are givenhere so that the ship's personnelmay inspect and, ifnecessary, change the mercury. Itmust be bome inmind,however, that the mercury ballistic is the controlling element of the Compass and that care must be exercised inhandling and adjusting it. The instructions given hereinmust be followed exactly.94. To observe flow ofmercury inballistic, remove tops ofreservoirs, unlock case and tilt ballistic from side toside. This must be done only when gyro is not running. The mercury should flow freely from one reservoir tothe other. The appearance of film on the fluid is not harmful, provided the mercury flows freely. Ifit does notflow freely, proceed as described below. Ifit does, replace reservoir tops, but be very carefulnot tointerchange themwhen replacing.

95. Ifthe mercury needs changing, remove ballistic from Compass as described on page 15. Pour out the oldmercury, keeping that removed from each set ofreservoirs inseparate non-metallic containers.

96. Carefully wipe out reservoirs with a clean clothmoistened with carbon tetrachloride. (Do not use gasoline.)Make sure that all carbon tetrachloride is evaporated from the parts, before replacingthe mercury. Clean outmercury tubes with tube (pipe) cleaners, provided inthe spare parts box. After using cleaners, blow out tubeto remove any lint.

97. Carefully strain mercury removed fromwest reservoirs through fine cheese clothuntil it is clean and bright.Then pour this mercury back into one of the west reservoirs, pouring ina continuous stream so that no airbubbles are trapped inthe tube. Repeat process for fluid removed from east reservoirs. Ifany mercury is



spilled during this process, BOTHsets of reservoirs should be emptied and refilledwith freshmercury found inspare parts box. Eachbottle contains 8 ounces ofmercury. Pour 8 ounces into each set ofreservoirs as described above. After refillingballistic with mercury, replace reservoir tops, making sure not tointerchange them Replace ballistic on Compass as described onpage 15.

ADJUSTMENTS AND REPLACEMENTS

TO REMOVELOST MOTIONINTRANSMITTER

98. Turn lost motionadjusting knob (figure 1) all the way counterclockwise.TO REPLACE TRANSMITTER ON LUBBER RING

99. Positionthe compass card so that it reads to an exact degree. Card may be turned slight amount requiredby turning azimuth motor shaft.

100. Turn lost-motionadjusting knob (figure 1) all the way counterclockwise to take up, as muchas possible,lost motion intransmitter carriage drive.

101. Place roller carriage on contact segment 1.

102. Put transmitter inplace as shown in figure 1 and make sure its gear meshes properly with azimuth gear.Insert mounting screws loosely. With card on an even degree,

15

shift transmitter until roller is again positioned on segment 1, ifit was moved while attaching transmitter. Thentake, up tightly onmounting screws.

103. Start Compass arid repeaters. Check repeater readings and synchronize with Master Compass. If,whencompass card is on an exact degree heading, repeaters do not exactly synchronize, loosentransmitter mountingscrews and tap the transmitter so that it moves slightly on the elongated mounting holes untilrepeater readingsmatchexactly with Compass reading.

TO REMOVEAND REPLACE MERCURYBALLISTIC

104. Remove 2 screws which attach link arm(figure 4) to ballistic frame.105. Carefully lower link arm so that it slides away easily from link bearing onbottomofcase.

106. Back offthe mercury ballistic bearing studs (figure 4) until they are clear oftheir bearings. Lower ballisticframe until it is clear ofCompass and remove from binnacle.

107. When replacingballistic, proceed inreverse order from above. The west bearing stud is pinned to itslocknut and should be screwed inas far as it will go. The east stud should be adjusted so that ballistic hasabout 0.005" side shake when Compass is cool. The locknut then should be taken up so that stud is locked inplace. Ifpossible, use feeler gauge to determine the proper side shake. Ifgauges are not available, the studmay be replaced properly by making a mark onphantomring in line with slot instud before removingballistic.When replacingballistic, take up on stud until it is tight, then back offuntil slot is in line with the mark. Ifthismethod is used, take care not to back off 1/2 turn too much. When replacingballistic, make sure that northside ofballistic frame is onnorth side ofgyro case. A letter N is stenciled onnorth side of frame.



108. When replacing link arm, make sure it engages link bearingproperly before attaching armto ballisticframe.

TO ADJUST AZIMUTH MOTOR GEAR MESH

109. The azimuth motor may be adjusted inor out, with respect to the maingear, by means ofthe set screwand clamp screw on one end of the frame. It should be set so there is no lost motionbetweenthe azimuth gearand the azimuth motor pinion.

110. When makingthis setting the Compass should be slowly turned inazimuthby hand to make sure that it isfree inall positions. There must be no bindingor stalling ofthe azimuth motor inany position about the azimuthgear.

TO ADJUST AZIMUTH MOTOR BRUSHES

111. The azimuth motor brushes are clamped inholders mounted on the azimuth motor frame. The brushesshould be adjusted so that, when they are seated on the commutator, the brushholders are parallel to eachother. To obtain this condition, loosenbrushclamping screws, adjust brushand reclamp. When holders areparallel, the distance fromcommutator to holder is approximately 1/4 inch. When brushes are readjusted, sandthem into fit commutator.

16

TO ADJUST LUBBER LINEPLATE

112. This plate is provided on the Compass to compensate the reading for small permanent errors. Do notattempt to remove such errors by twisting the suspension.

113. The compensation is made as follows: Suppose theCompass reading is 278 and it has beendefinitely established(by sun azimuths, bearings, etc.) that the Compass is 2 low.Simply loosen thumb nuts which clamp lubber line plate tolubber ring and shift lubber line so that reading is 280.Reclamp plate. It is thennecessary to change each repeaterreading so that the repeaters are synchronized with theCompass. NOTE:Ifthe plate is moved only a fraction ofadegree, the repeater headings should be changed byloosening the transmitter on the Compass and shifting it asnecessary to make repeater reading correspond to Compassreading.

ROLLDAMPER

114. A dashpot damper (figure 8) is provided at the aftergimbal bearing to restrict movement ofthe Compass about the fore-and-aft axis. The unit comprises two dash-pots, each containing a piston and a quantity ofoil. Movement of the pistons, due to swinging of the Compassabout the axis mentioned, is opposed because ofthe restricted oil flow.

115. The action ofthe dashpot damper is entirely automatic; no adjustment ofthe unit should be attempted.

FieuRE a

ffOLU DAMPER6ft 1HUPEK DASUPQTS 71. BElltLN? STUPTc. rilffflMt hin ftTuoe 72 caaoan nine



116. The dashpot dampers should be kept filled with compass rotor oil to a point one inchbelow the top ofthe pots. The levelcanbe determined bypushing a smallpiece ofwire through the holes inthe cap. Ifdashpotsare too lull, the oilwill runout when the ship is rollingheavily. Ifthe oil leveldrops below the piston, thedashpots will be useless. The levelshould be checked each monthand new oil added ifnecessaiy.

PITCHDAMPER

117. A fixtion damper (figure 9)is used to restrict swinging of the Compass about the athwartship axis. Thedamper comprises an adjustable friction brushridingon a cam To obtainproper damping action, proceed asfollows:

118. Loosenclamp nuts 67 (figure 9) and raise brush offcam far enough to insert a smallpiece ofpaper underbmsh.

119. Positionadjusting nuts 68, keeping frictionbrushholder horizontal, so that when clamp nuts are taken uptight it is just possible to withdraw the paper without tearing it.

17

PITCH DAMPER67 CLfluf WTS 68. ftDJUSTPNG NtUS

120. Inheavy weather it may be necessary to take up on the damper to prevent the compass case from hittingthe stops on the vertical ring. However, as soon as the weather permits, the dampers should be



readjusted as described above. Ifthis is not done, an error inthe compass indicationmay result.

18

CLEANING CHART

GENERAL

AT MONTHLY INTERVALS - Clean inside ofbinnacle and allmechanicalcompass parts with a soft clothmoistened incarbon tetrachloride. Wipe dry after cleaning. Check allelectrical connections to make sure theyare tight, clean and free from oil.

The crocus paper referred to inthese instructions is an extra fine, highgrade abrasive paper. Do not use anyother kind.

CAUTION: When cleaning or oiling the Master Compass, be carefulnot to disturb the 3 flexible leadsbetween the phantomringand the vertical ring, and betweenthe vertical ringand the rotor case.

MASTER COMPASS

1CORRECTOR COSINE CAM:MONTHLY - Clean out any hard deposit ofgrease and dirt.

2 COLLECTOR RINGS:MONTHLY - Cleanwith a strip ofcloth (about 1/2 inchwide) moistened incarbon tetrachloride, drawing the clothback and forth on each ring surface throughout about halfitscircumference. Then turn compass 180 and repeat. Polishwith a dry strip ofcloth inthe same manner.

3 AZIMUTH MOTOR COMMUTATOR AND BRUSHES:MONTHLY - Wipe offcommutator brushesand brush-aims with a soft clothmoistened incarbon tetrachloride. Polish commutator with a clean, lintlesscloth, holding it against the commutator with the index finger while turning the damping weight back and forthwith the other hand.

4 CORRECTOR:MONTHLY - Wipe excess oil from the outer surfaces ofthe corrector and from thebottomofthe lever arm.

5 TRANSMITTER: MONTHLY - Snap contact arm into the vertical position and remove roller carriage.Clean the contact surface ofthe segments with a smallpiece of folded crocus paper. Insert the edge ofthefolded crocus paper betweenadjacent segments to remove carbon dust. Clean the roller carriage and theinterior of the carriage compartment with a soft clothmoistened incarbon tetrachloride, and wipe out with adry cloth.NOTE: It is not necessary to remove the transmitter from the lubber ring, for cleaning.CAUTION:The Compass must not be turned inazimuth while the contact arm is inthe verticalposition.

6 ROTOR BEARINGHOUSINGAND OIL WINDOW: EVERY 3 MONTHS - Cleanwhen renewinghttp://www.hnsa.org/doc/gyromkl4/ 23/75


rotor bearing oiL After the old oilhas beenpumped out, remove the bearinghousing end plate, shownby theupper arrow. Take out the attaching screws and screw two ofthem into the two threaded holes inthe edges ofthe plate to force the plate and gasket olfthe housing. Clean the oil window with a soft clothmoistened incarbon tetrachloride and held on the end ofa thin hardwood stick. Do not unscrew the oil window from thebearing housing. Ifthe oilwicks are clogged with sediment, remove the assembly by taking out the 4 smallscrews that hold it inplace. Clean the assembly thoroughly incarbon tetrachloride and brushthe wicks offwithstiffbrush. Be sure all carbon tetrachloride has evaporated from the wicks before replacing them. Clean theinterior ofthe housingwith a smallpiece ofcloth saturated with carbon tetrachloride. Use the thin hardwoodstick to force the cloth around the interior of the housing to remove all oil sediment. Dry out interior with aclean cloth to remove all traces ofcarbontetrachloride before replenishingwith oil. (See paragraph 13 underOiling.)

19

7 COMMUTATOR AND BRUSHES:MONTHLY - Wipe olfthe commutator surface and brushes with asoft cloth moistened with carbon tetrachloride. When the motor-generator is stopped, brush the spacebetween the commutator bars axially with a small stiffbrush. Wipe offwith a soft dry cloth. Be sure that noparticles ofdust or dirt remainbetweenthe brushand commutator surface. To insure proper ventilation,brush the screened plates at each end of the motor-generator with a stiff brush.



OILING CHART

GENERAL

WEEKLY OILINGS maybe omitted where such applicationwould disturb the Compass. However, it isrecommended that the intervalbetweensuch oilings be not greater than 2 weeks.

Wherever oil is mentioned inthese instructions, compass rotor oil is implied.

8 CORRECTOR:MONTHLY - Lubricate movingparts with a film ofoil. Add one or two drops ofoil toroller stud incosine cam.

9 TRANSMITTER: WEEKLY - An oilhole at the top center leads to the upper shaft bearing. An arrow athttp://www.hnsa.org/doc/gyromkl4/ 25/75


the bottompoints to the lower shaft bearing. A small arrow above the one just mentioned points to the lost-motiondevice yoke rollers, within the transmitter. Two oil tubes, terminating at the top ofthe transmitter, leadto other bearings requiring lubrication. The top oilhole, the two arrows and the two tubes are painted red andare readily located. Apply two drops ofoil to each lubricationpoint. MONTHLY -Coat gear surfaces with alight film ofoil, using a camel's hair brush. Keep segments and roller carriage free from oil.

10 CORRECTOR COSINE CAM:MONTHLY - After cleaning the cosine camgroove, add a thin coatingof the cup grease supplied inthe spare parts box. Coat azimuth gear surfaces with a light film ofoilapplied witha camel's hair brush. 11BALLISTIC LINK BEARING:WEEKLY - Add 4 drops ofoil to the bearingand itslink (upper arrow). LOWERVERTICAL RINGGUIDEBEARING:This bearing (lower arrow) issubmerged inoil which need be changed only when the Compass is undergoing general overhaul.

12 PHANTOM STEM BEARINGS AND UPPER VERTICAL RINGGUIDE BEARING:WEEKLY -Apply 10 drops ofoil to each ofthe two oilholes underneath the suspension cap. Access is provided to theseoilholes through holes inthe cap.

13 ROTOR BEARINGS:AT WEEKLY INTERVALS inspect oil levelon each side ofrotor case andreplenish ifnecessary to keep the oil surface levelwith center ofdot at center ofglass window. EVERY 3MONTHS renew the oil ineach side ofrotor case as follows: remove oilplug and pump out the oilwith metalsyringe provided inthe spare part box. Remove the bearinghousing end plate as described inparagraph6under Cleaning. Inspect the interior ofthe housingand the oilwicks. Ifwicks are clogged with sediment,remove assembly and clean as described inparagraph6. Before filling oil reservoir clean interior ofhousingand oilwindow as described inparagraph 6. When reinstalling the oilwick assemblies make sure they are putback exactly as they were. The upper ends ofthe 3 wicks should touch the lower edge ofthe ballbearing innerrace. The lower ends ofthe wicks should be coiled inthe lower part ofthe housing so that the oil levelwillcompletely cover them Replace the end plate, tightening the attaching screws evenly allaround, and fill with oilthrough the oilplughole to the center ofdot incenter ofglass window.

14 AZIMUTH MOTOR:WEEKLY - The upper oil tube carries oil to the upper motor shaft bearing, and alsoto the upper and lower intermediate gear shaft bearings. The lower tube leads to the lower motor shaft bearing.Apply 6 drops ofoil to the upper tube, and 2 drops to the lower tube. MONTHLY - Coat gear surfaces witha light film ofcompass rotor oil, using a camel's hair brush.

15 BALLISTIC BEARINGS:WEEKLY - Fillup the cup-type reservoirs on each side ofthe phantomringwith oil (upper arrow). HORIZONTAL ROTOR CASE BEARINGS:WEEKLY - Move vertical ring tomaximum out-of-alignment positionwithphantomring and apply 8 drops ofoil to hole incenter of large nutcontaining the horizontalrotor-case bearings on each side (lower arrow).16 GIMBAL BEARINGS:MONTHLY - The fore-and-aft and athwartship ballbearings are oiled by placinga few drops ofoilon the studs where they enter the bearings. The two azimuth guide pins should be given athin coating ofcup grease.

21

17 MOTOR-GENERATOR:EVERY 3 MONTHS - Turn the grease cups down one full turn.YEARLY - Remove bearings and clean themthoroughly in carbon tetrachloride. After allRace ofcarbontetrachloride has evaporated frombearings, repack themwith cup grease ofthe kind supplied inthe spare partbox, and replace. To repack: coat ballbearings with a thin layer ofgrease. Placejust sufficient grease ineachbearinghousing to cover the lower part ofthe ballbearing.



CAUTION:DO NOT OVER OIL

*

11 13 17

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22

SECTION IV

PARTS LIST

INTRODUCTION

This Parts List contains all replaceable parts for the Sperry Mk. XIV, Mod. 1 Gyro-Compass andAccessories.

The parts are grouped by assemblies and sub-assemblies. A drawing ofthe assembly, and a list ofthe partsgiving the name, part number and quantity required are included for each assembly.

By means ofa symbol each part is identified with the assembly drawing, and the description ofthe part. THESYMBOL IS TO BEUSED ONLY FOR IDENTIFICATION OF THE CORRECT PARTNUMBERAND DESCRIPTION. THE PART NUMBERAND DESCRIPTION MUST ALWAYS BEUSED FORINQUIRIES AND ORDERS.

Letters are used as symbols inplace ofnumerals where a separate drawing for the assembly has beenprepared. Double letters indicate the assembly appears on the same sheet. Single letters indicate the assemblyis shown on a separate sheet.

Standard size screws, nuts, washers, and pins are not assigned part numbers. On inquiries or orders thedimensions in addition to the name must always be given.

ORDERINGINSTRUCTIONS

Quick shipments and prompt replies to inquiries are possible only whencomplete identifying information for parts is given.

Careiulobservance of the following points on inquiries or orders is essentialfor prompt service.



1. Name the part and part number as shown inthe list and statequantity desired.

2. Furnishthe name plate data ofthe apparatus for which parts aredesired.

3. State whether shipment is to be made by express, freight orparcelpost.

DEFINITION OFABBREVIATIONS

Adj. Adjusting Lg- LongAss'y Assembled L.H. Left HandAtt. Attaching, Attachment Mach MachineBg. Bearing Mfd. MicrofaradBkt Bracket Mk. MarkBr. Brass Mod. ModificationBTS Blue Tool Steel Mtg. MountingBz. Bronze Oz OunceCon. Collector PKD Parker KalonDriveCond. Conductor PL PlainPt PointConn. Connecting, Connection Rd. RoundCstg. Casting Res. Resistance, ResistorCu Copper R.H. Right HandDia Diameter R.P.M. Revolutionper minuteEsc Escutcheon Sec. SecondaryFil Fillister S.S. Stainless SteelFP Fishpaper Std. StandardHd. Head Term TerminalHdl. Headless Vam. VarnishedHex Hexagon V. VoltIntemi IntermediateIns. Insulating, Insulation

23

PARTS LIST

LIST OFASSEMBLIES NUMERICAL INDEXAND OF

ORDER OF ARRANGEMENT ASSEMBLIESPart Description ReferenceNumber Page Part Description Reference642128- Compass Ass'y., Master 24-41 Number Page


6/27/2014

H Gyro(Mk. XIV-Mod. 1

642112- Rotor & Case Ass'y. 21, 26L126664- Wick Ass'y., Felt Oil 25. 26J64102- LevelofAss'y., Two 26H Minute94401- LevelAss'y. 26E642113- RingAss'y., Vertical 27F

642 114- PhantomElement Ass'y. 28, 29L642115- Ballistic Ass'y., Mercury 30E642111- Compensator Ass'y. 31D68645- Corrector Ass'y., Speed 3J_C642117- Member Ass'y., Outer 32, 33N150891- Block Ass' y., Coll. Ring 32, 33D Brush643855- Binnacle Ass'y. 34, 35N76377- Damper Ass'y., Cardan 34. 35C642121- Follow-Up Device Ass'y., 36. 37N152076- Electro-Magnetic 36, 37D Transformer Ass'y.642135- Motor Ass'y., Azimuth 38, 39J644235- Transmitter Ass'y., 40, 44L Commutator801041- Carriage Ass'y., 40, 41D Transmitter64024- Compass Ass'y., 42, 43AD Repeater(Mk. XV-092064- Cable Ass'y. 42, 43S8-0195- Movement Ass'y., 42. 43Y Repeater67771- Compass. Ass'y., 42,43

http://vwvw.hnsa.org/doc/gyromk14/

Sperry Gyrocompass Mark 14

6850-L Glass Ass'y., Reading 4960606-J Circle Ass'y., Azimuth (Mk. Ill 4964024- Compass Ass'y., 42, 43AD Repeater(Mk.XV-064102- LevelAss'y., Two Minute 26H64146- Stand Ass'y., Repeater (Bearing 44,45R64147- Stand Ass'y., Repeater(Steering 44,45K64148- MountingAss'y., Repeater 48U Bulkhead

67252- Compass Ass'y., Repeater 42, 43E67771- Compass Ass'y., Repeater 42. 43D (Mk.XV-068645- Corrector Ass'y., Speed 31C70264- Cover Ass'y., Repeater(Bearing 49K71620- BoxAss'y., Radio Connection 49D76377- Damper Ass'y., Cardan 34. 35C80195- Movement Ass'y., Repeater 42. 43Y82622-J Cable Ass'y. 42, 4382926- Cover Ass'y., Repeater(Steering 49E84823- Cable Ass'y. 42, 43D89152- Set ofSpare Parts 51L92064- Cable Ass'y. 42, 43S94401- LevelAss'y. 26E126664- Wick Ass'y., Felt Oil 25, 26J150891- Block Ass'y., Coll. RingBrush 32, 33D152076- Transfomier Ass'y. 36, 37D642111- Compensator Ass'y. 31

30/75

6/27/2014

D Repeater (Mk.XV-082622-J Cable Ass'y. 42, 4380195- Movement Ass'y., 42. 43Y Repeater67252- Compass. Ass'y., 42, 43E Repeater84823- Cable Ass'y. 42, 43D80195- Movement Ass'y., 42. 43Y Repeater642290- Compass. Ass'y., 42, 43C Repeater(Mk.XV-092064- Cable Ass'y. 42, 43S80195- Movement Ass'y., 42. 43Y Repeater642301- Compass Ass'y., Repeater 42, 43D (Mk.XV-082622-J Cable Ass'y. 42, 4380195- Movement Ass'y., 42. 43Y Repeater64146- Stand Ass'y., Repeater 44. 45R (Bearing64147- Stand Ass'y., Repeater 44. 45K (Steering643241- Stand Ass'y., Rep. 46, 47D Column(Bearing643240- Stand Ass'y., Rep. 46, 47B Column (Steering62148- MountingAss'y Repeater 48U Bulkhead6850-L Glass Ass'y.,Reading 4971620- Ass'y., Radio Connection 49D70264- Cover Ass'y., Repeater 49K (Bearing82926- Cover Ass'y., Repeater 49E (Steering

Sperry Gyocompass Mark 14

D642112- Rotor & Case Ass'y. 25, 26L642113- RingAss'y., Vertical 27F642114- PhantomElement Ass'y. 28, 29L642115- Ballistic Ass'y., Mercury 30E642117- Member Ass'y., Outer 32, 33N64212 1- Foliow-Up Device Ass'y.,Electro- 36, 37N Magnetic

642128- Compass Ass'y., Master Gyro, 24-41H (Mk. XIV-Mod. 1642135- Motor Ass'y., Azimuth 38, 39J642282- Cover Ass'y., Repeater (Steering 49C642290- Compass Ass'y., Repeater (Mk. 42, 43C XV-Mod. 0642301- Compass Ass'y., Repeater (Mk. 42, 43D XV-Mod. 0643240- Stand Ass'y., Repeater Column 46, 47B (Steering643241- Stand Ass'y., Repeater Column 46, 47D (Bearing643855- Binnacle Ass'y. 34, 35N644034- Filter Ass'y., Radio 50A644235- Transmitter Ass'y., Commutator 40, 44L801041- Carnage Ass'y., Transmitter 40, 44D

642282- Cover Ass'y., 49C Repeater(Steering60606-J Circle Ass'y., 49

Azimuth(Mk. Ill644034- Filter Ass'y., Radio 50A

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89152- Set ofSpare PartsL

la

APPENDIX

FUNDAMENTAL PRINCIPLES OF THE GYRO-COMPASS

1. The word "gyroscope" is ofFrenchorigin a combination of two Greek words, "gyros", meaning tumorrevolution, and "skopein", meaning to view, the literal translation of the two words being "to view therevolution" ofthe earth. The correct pronunciationofthe word is with the g soft as in "gentleman". Inthe firstsyllable the y is long, as in "sky". Ro is pronounced like the "row" inrowboat, and scope to rhyme with "rope".

2. The reasonthe Frenchhave the distinctionoforiginating the name gyroscope is because the great Frenchscientist LeonFoucault was one ofthe first authorities on the subject ofgyroscopic phenomena, havingsucceeded as early as 1852 inactually producing a gyroscope withwhich he could observe, with the aid ofamicroscope, the ceaseless onward movement ofthe earth's rotation.

3. Ifthe reader will permit one more slight digression, it might be well to remember (before we get down toserious business) that the sphere onwhich we live is in itselfa mammothgyroscope and that there probablywould be no life at all on the earth ifit did not revolve like a top, with the direction of its polar axis fairlyconstant. Otherwise the surface ofthe earthwould be exposed to extremes ofheat and cold with such rapiditythat livingorganisms would not be able to survive.

DEFINITIONAND PRINCIPLES OF THE GYROSCOPE

4. There is nothingmysterious about the gyroscope. Its actions, though they may appear at first to defy thelaws ofphysics, inreality depend entirely upon Sir Isaac Newton's Laws ofMotion.

5. Many of the toys we used to play with were based on gyroscopic principles. A spinning top is an elementaryformofgyroscope, the "diabolo" once a popular object for pastime is another; so also is a hoop, for itwill exhibit the characteristics ofa gyro as long as it has sufficient motion to rollalong the ground.

6. Allof the practicalapplications ofthe gyroscope are based upontwo fundamental characteristics, namely:"Gyroscopic Inertia" and 'Precession".



2a

FIGURE laThe gyroscope has three axes ofangular

freedom

7. Gyroscopic Inertia, or rigidity inspace as it is sometimesknown, is the tendency ofany rotatingbody to preserve itsplane ofrotation. For example, a hoop, when set inmotion,will keep on rolling approximately ina straight line ifundisturbed, instead oftipping over as it would ifnotrevolving.

8. The second characteristic ofthe gyroscope Precession is also exhibited by the rollinghoop. Ifwe wish to changeits direction oftravel, we do not press against the rimat thefront or back, but at the top as though we intended to tipit over about an imaginary horizontalaxis. The hoop resiststhis pressure and turns, instead, about a vertical axis which isat right angles to the axis about which the pressure wasapplied.

9. Ifwe transform the hoop into a wheel, provide anaxle for it, and mount the axle insupporting rings asshown inFigure la, we can obtain a true gyroscope, which is simply a spinning wheel or mass, universallymounted. Only one point the geometrical center of its supporting system is ina fixed position, the wheelbeing free to turn inany direction around this point. The wheel or rotor is free to revolve in its supporting ringabout axis 1. The supporting ring is free to revolve inan outer ringabout axis 2 which is always at right anglesto the axis ofrotationofthe



FIGURE2aWhen spinning, the gyro exhibits

'gyroscopic inertia'

FIGURE 3aThe originalplane ofrotation

is maintained no matter how thebase is moved about.

3a

FIGURE4aPrecessionabout the vertical axis.

FIGURE 5aPrecession about the horizontalaxis.



wheel. The outer ring likewise is free to revolve inpivot bearings ina supporting frame about axis 3 which isalways at right angles to the axis ofrotationofthe inner ring.

10. With this arrangement, the axle canbe pointed inany directionwithout altering the geometrical center ofthe assembly. When such a wheel is spinning, it exhibits exactly the same characteristics as the hoop, but doesso without havingto be rolled along the ground. "Gyroscopic inertia" may be illustrated by spinning the rotorand placing it in the position shown inFigure 2a. Ifthe base of the gyroscope is tilted, as shown inFigure 3a,the rotor, instead oftipping over as it would ifnot revolving, maintains its originalplane ofrotation. Itwillcontinue to do so, no matter how muchthe base ofthe gyro is moved about, as long as it continues to spin withsufficient velocity to overcome the friction between itselfand its supporting bearings.

11. This characteristic is the result of the action of forces affecting the state ofrest and motionofa gyroscopeinthe manner expressed byNewton's First Law ofMotion, which states that every body continues initsstate of rest or of uniform motion ina straight line, unless it is compelled by forces to change thatstate . This law as applied to a rotatingwheel may be expressed by stating that a rotatingwheel tends tomaintainthe directionof its plane ofrotation inspace and the direction of its axis inspace.

12. 'Precession" may be illustrated by applying a force or pressure to the gyro about the horizontalaxis asshown inFigure 4a. Itwill be found that the applied pressure meets with resistance and that the gyro, instead ofturning about its horizontal axis, turns or "precesses" about its vertical axis in the direction indicated by thearrow P. Similarly, ifwe apply a pressure about the vertical axis, the gyro will precess about its horizontalaxisas shown at P inFigure 5a. Ifthere were a complete absence of inertia and friction about the precessionalaxis,the rate ofprecessionwould be such that the resistance of the

4a

gyro would be exactly equal to the applied pressure at any instant, and no movement from this pressure couldensue until the gyro had precessed so that its plane ofrotationcoincided with the plane ofthe applied pressure.Then the precessionwould cease and, with it, all resistance to the applied pressure.

x

13. A convenient way to remember the direction inwhichprecessiontakes place is to regard the pressure as though itacted at a single point on the rimofthe wheel, as indicated bythe black dot inFigure 4a. This point will not move inresponse to the pressure, but a point 90 degrees beyond, inthe direction ofthe wheel's rotation, willmove away instead.

FIGURE 6a 14. There you have the gyroscope ina nutshell, but inasmuchGyro rotor shown insection. For the sake of as the next step will be an explanation ofthe reason for



clarity its mass is considered to be precession, your may wish to ask a question or two at thisconcentrated infour separate particles, A, B, point. You might like to ask, for instance, why it is that ofthe

C, and D. many rotating objects with which you are familiar, somedisplay gyroscopic phenomena and others do not. Why doesa top exhibit gyroscopic characteristics while an engineflywheel, which also spins with high angular velocity, doesnot. Why does a rifle bullet behave like a gyroscope while awindmill merely behaves like a windmill.

15. Gyroscopic properties are inherent inall rotatingmasses, but can best be observed inthose which have thegreatest amount of freedom about two axes inaddition to the spinning axis. The top comes under the lattercategory. The engine flywheel, on the other hand, is limited to one angular axis of freedom its spinning axis.A rifle bullet may be likened to a gyroscope because it is free to revolve about two other axes, inadditionto itsspinning axis; therefore it exhibits gyroscopic inertia, tending to maintaina straighter line of flight than it would ifnot rotating. A windmill has freedom about its spinning axis and also about a vertical axis (as it must be able toturn inany directionunder the controlof its rudder). However, it has no freedom about a horizontalaxis otherthan its spinning axis, and therefore, although precessional forces are impressed uponthe apparatus by shifts ofwind, there are no visible effects. The precessional forces result ina torque which is absorbed inthe bearings.Ina windmill these forces are small, however, owing to the light construction of the fan. Inorder to obtainmaximumgyroscopic effects a rotor should be comparatively heavy, with as muchof its weight concentrated atthe rimas practicable, and it should spinwith considerable velocity. Gyroscopic inertia depends uponangularvelocity, weight and radius at which the weight is concentrated. Maximumeffect is obtained therefore from amass, with its principalweight concentrated near the rim, rotating at high speed.

5a

REASON FOR PRECESSION

16. The reason for precessionmay be explained quitesimply ifwe consider the mass ofthe rotor to beconcentrated in separate particles such as A, B, C, and DinFigure 6a. Figure 6a is a section through the center oftherotor,just as though you sliced it inhalfwith a knife, threwthe upper halfaway and lay the bottomhalfon the paper.We will assume that the wheel is spinning with considerablevelocity in the direction ofthe arrow R at the top, and wewill select that instant in the cycle when the particles are inthe positions shown inFigure 6a. Ifwe can show what willhappento four particles equally spaced as are A, B, C, andD, we can show what happens to the entire rotor, since all



other particles within it act in the same manner.

SOUTH F0LE

FIGURE 7aA gyro with its spinning axis set inthe East-Westpositionat the equator appears to turn about its

horizontal axis once each twenty-four hours.

17. Inorder to make the explanation clearer we will simulate the movements ofthe rotor by correspondingmotions ofthe booklet itself and as a first step inthis directionwe will lay the booklet flat uponthe table.

18. Now let us assume that a force F is applied against the rotor just as though we pressed down against thepaper with a pencilat this point as though we tipped the top of the booklet down, the bottomup. Thiswould tend to rotate the wheel about the axis X-X'. Sir Isaac Newtonsaid, ineffect, that allmatter ispigheaded and stubborn that it will continue to move ina straight line unless disturbed, and ifdisturbed, it willoffer resistance to the disturbing force. Let us see what happens to particle A. This particle was movingto theright before we started pushingdown at F.Now, however, it tends to move to the right and down into thepaper a combination of the motiondue to the wheel's rotation and the motiondue to our applied force F.Likewise particle C, which was movingto the left, now tends to move to the left and up out ofthe paper.

19. As a result ofthese motions the wheel actually turns about the axis YY' which is at right angles to the axisabout which the force F was applied. Its motion is the same as though we tipped the right hand side of thebooklet down, the left up. This is precession.

20. The reader will probably ask, "What happens to B and D?" Since B and D lie inthe axis about which theforce F is applied, they are unaffected by that force. Like A and C, however, they are pigheaded and want tohave their ownway.

21.Because ofthe wheel's rotation, B moves toward the bottomofthe page, Dtoward the top. But the wheelis now turning about axis YY' because of its precession. Therefore B tends to move toward the bottomofthepage and down into the paper, D tends to move

toward the top ofthe page and up out of the paper. Ina perfectly balanced gyro operating without friction, thesum ofthese motions would exactly offset the force F, so that no motion could take place about axis XX'.Thus the only motionwhich could result from the application ofa force as at F would be precessionalrotationabout an axis at right angles to the axis about which the force is applied. Inother words, the wheel moves in

6a



the direction ofthe least resistance to any force which tends to disturb its plane ofrotation -and the point ofleast resistance is always 90 degrees away inthe direction of the wheel's rotation.

VERTICALAXISi

4

p

FIGURE 8aA gyro with its spinning axis set horizontal

at the Pole appears to turn about itsvertical axis once each

twenty-four hours.

OPERATING PRINCIPLES OF THE GYROCOMPASS

22. Inthe Gyro-Compass the characteristics ofthegyroscope, "inertia" and "precession", which we have justexplained, are combined with two constant, naturalphenomena the earth's rotationand the force ofgravity,with the result that the instrument aligns itselfwith thegeographic meridianand provides a constant true northindicationregardless ofthe rolling, pitching, and yawing ofthe vessel.

APPARENT ROTATION

23. Let us consider the gyro to be mounted at the equatorwith its axle east and west. We will observe its behaviorfrom a point inspace beyond the Southpole as shown inFigure 7a. To avoid contusionwe will dispense with thesupporting rings in this and subsequent illustrations, and showonly the wheel and axle ofthe gyro, as these are the partswith which we are concerned chiefly.

24. The earth turns inthe direction ofthe arrow, or clockwise, with an angular velocity ofone revolutionevery24 hours, carrying the gyro around with it; but the gyro, because of its inertia, maintains its originalplane ofrotation inregard to space just as it did when its base was tilted as shown inFigure 3a. With respect to theearth, however, the gyro rotates about its horizontalaxis with an equal velocity (one revolution in24 hours)but inthe opposite direction to the rotationofthe earth. After three hours the end ofthe axle which waspointing east apparently is elevated at an angle of45 degrees; after six hours, 90 degrees; after twelve hours,180 degrees; and so on, until, at the end of24 hours, it is back where it started.

25. Similarly, ifwe consider the gyro to be placed either at the Northor the Southpole at the theoretical axisofrotationofthe earth, with the axis of the gyro horizontal as shown inFigure 8a, the gyro will appear torotate, but this time about its vertical rather than its horizontal axis.

7a

26. At points betweenthe poles and the equator thegyro appears to turnpartly about the horizontalaxisand partly about the vertical, because it is affected by


Cj|ftr5 IkjUT**1


both the horizontal component and the verticalcomponent ofthe earth's rotation. See Figure 9a. Thehorizontal component of the earth's rotationcauses thenorthend ofthe axle to rise. The vertical componentcauses it to turn to the east.

FIGURE 9aA gyro with its spinning axle set horizontalat any pointaway from the equator maintains its plane ofrotation

inspace and apparently moves about both itshorizontaland vertical axis.

FIGURE 10aTo make the gyro seek the Northa mercury tube isadded, its effect being applied about the horizontal

axis.

27. The reader willperceive that the differencebetweengyroscopic inertia and apparent rotation issimply one ofpoint of view. As tar as space isconcerned the gyro remains fixed. Incomparison withthe earth, however, the gyro actually rotates asdescribed above. It is this rotationwhich makes itpossible to apply the force ofgravity so as to convertthe gyroscope into a Northseeking gyro-compass.

28. The first step inthis direction is to cause the gyroto precess toward the meridian. Figure 10 showsdiagrammatically a gyro to which has beenadded apair ofcontainers with interconnecting tube; theassembly is partially filled with mercury and is attachedto the gyro frame insuch a way that it will tilt with thegyro when the gyro tilts or rotates about its horizontalaxis. With the gyro at the equator and horizontalasshown at A inFigure 11a, the mercury is distributedequally in the tube and its weight exerts an equaldownward pressure oneach end ofthe axle.Therefore, inthis position, the mercury has no effectuponthe gyro. As the end ofthe axle which is pointingeast (the right-hand end) slowly rises, some of themercury, under the influence ofgravity, is transferredto the lower end ofthe axle, as shownby the arrow atthe left inBofFigure 1la. Inthis positiona force isbeingexerted about the horizontalaxis; the effect ofthe mercury beingthe same as though we were topushdown onthe west end (the left-hand end) ofthegyro axle. The result is that the gyro precesses about

8a



CAftTH 5

FIGURE 11aEffect ofthe mercury ballistic when applied about the horizontalaxis.

the vertical axis as shown by the small arrows at the top inC and D, the axle turning slowly counterclockwise.As the end ofthe gyro which at first was pointing east (whichwe shallnow refer to as the northend) precessestoward the meridian, it continues to rise under the influence ofthe earth's rotation. After the gyro axle hasprecessed so that it is parallelto the meridian, the excess mercury at the south end causes its precessiontocontinue, and the end ofthe gyro axle which was at first pointingwest (whichwe shallnow refer to as the southend) is earned to the east ofthe meridian. This south end now commences to rise and the mercury startsflowing back to the north end, precessionbeinggradually diminished untilthe axle is again horizontaland themercury evenly distributed. At this point precessionofthe north end toward the west ceases. The south endcontinues to rise, however, because it is still east of the meridian, and at length the mercury inthe north side ofthe tube overbalances that inthe south side. Precession, therefore, is reversed, and the north end returnstoward the meridian, declining more and more as the south end continues to rise. This oscillationofthe gyroabout the meridianmay be clearly understood by referringto Figure 12a which shows the movements ofthegyro axle projected onto a vertical plane. The ellipse inFigure 12a is the result ofa displacement ofthe gyroaxle ofonly a few degrees fromthe meridian. Ifthe gyro axle were pointing east and west at the beginning ofthe cycle, as shown inFigure 11a,precessionwould take place through 180 degrees ineach direction, and atone extreme the northend ofthe gyro axle would point east, at the other, west. Inany case the gyro nevercomes to rest, as there is no force tending to restore its axle to a horizontalpositionuntil after it has passed themeridian.

29. The ratio ofthe movement about the horizontalaxis (caused by "apparent rotation") to the precessionalmovement about the vertical axis (caused by the flow ofmercury) determines the shape ofthe ellipse. Ifthefree surface ofthe mercury inthe

9a

containers is increased so that more mercury canbetransferred, the rate ofprecessionwill increase andtherefore the ellipse will be flatter. Ifthe mercury effectis decreased, the rate ofprecessionwill diminish to a



point where the ellipse would, theoretically, be almostcircular.

FIGURE 12aDiagramshowing the movement ofa mercury-

controlled gyro wheel when set with its axle pointingeast ofnorth.

30. Inthe precedingparagraphs we have explainedthe behavior ofa gyro under the simplest fonnofmercury control, the mercury beingattached directlyto the ring, frame or casing which supports the gyro.With such an arrangement the mercury can act onlyabout the horizontalaxis, and therefore the gyro willprecess only about the vertical axis. An additionalpressure is required about the vertical axis inorder togenerate precession about the horizontalaxis whichwill counteract the naturaltendency ofthe gyro axle totilt. The manner inwhich this is accomplished will beshown in the following paragraphs.

3 1. Itwill be necessary first, however, to explain thebasic elements ofan actual gyro-compass. As showninFigure 13a the rotor is contained ina case (1) andthe case is supported onhorizontalbearings inavertical ring (2). The rotor-case and the vertical ringare free to turn about the vertical suspension axis (3).Although the gyro-compass, as shown inFigure 13a,necessarily differs in its details ofconstruction from themodelgyros shown insome ofthe previousillustrations, it has the same angular freedom about itsspinning, horizontal, and vertical axes, and exhibitsexactly the same characteristics.

32. Figure 13a shows the addition ofan outer frame(4) called the phantom, which is drivenby an electricalfollow-up system so that it follows every movement ofthe gyro about the vertical axis. By supporting themercury tube or ballistic (5) inbearings inthe phantomringwe can obtain a controlling action about thevertical axis ofthe gyro so as to arrest its oscillationsand cause it to align itselfwith the meridian.

FIGURE 13aElements ofthe Gyro-Compass Inorder to obtain amore symmetrical construction, the mercury ballistic

consists oftwo sets ofcontainers and tubes, instead ofthe single pair ofcontainers shown inpreceding

illustrations.

10a

33. This is accomplished by connecting the mercury ballistic to the gyro case at a point (6) slightly to theeast of the vertical centerline . With this arrangement the major effect ofthe mercury still acts about thehorizontal axis and causes the gyro to precess toward the meridian as before; but there is now an additionaleffect about the vertical axis which causes the gyro to precess about the horizontalaxis, introducing a tilt ofthegyro counter to the natural tilt resulting from "apparent rotation". Therefore the end ofthe axle will follow aspiralpathas shown inthe polar diagram, Figure 14a. The reductionofthe oscillation which is produced by the



action ofthe mercury ballistic about the vertical axis is called "Damping". Si careful consideration ofthe actionofthe mercury ballistic will make it apparent that the only positionofrest which the gyro can find at theequator will be with its axle horizontaland inthe meridian. Inother words, we have obtained a true, meridian-seeking Gyro-Compass.

34. A number ofother factors must be considered,however, before we can obtain a gyro-compass whichwill flinction accurately and reliably, at various latitudeson a rolling, pitchingvessel moving over the earth'ssurface at considerable speed.

FIGURE 14aAction of the gyro axis when the mercury ballistic isconnected to its casing through an eccentric pivot.

35. We have seen that the action ofthe mercury ballistic about boththe horizontaland vertical axes is madepossible by the use ofthe phantomelement. Tlfis element serves another important purpose; it provides ameans ofsuspending the gyro so that it is practically free fromfriction about its vertical axis. The gyro issupported fromthe top ofthe phantomby steelwires and the phantomis kept inexact alignment with the gyroby means ofan electrical follow-up system. The compass card is a part ofthe phantomelement, the whole ofwhich is supported onballbearings fromthe main supporting frame or "spider". Thus, with the exception of theeccentric connection betweenthe mercury ballistic and the gyro case and the upper and lower guide bearings,which are practically frictionless, there is no physicalcontact which can result inany friction betweenthesensitive gyro element and the compass card or other externalparts.

36. Ifthe compass were to be used on shore, it would be feasible to control the gyro simply by suspending aweight fromthe phantom, like a pendulum, and connecting the weight to the eccentric pivot on the bottomofthe rotor case. This would be impracticalonboard ship, however, where a compass is subjected to rollingmovements inan inter-cardinalplane (northeast to southwest, or northwest to southeast). Inter-cardinal rollingcauses a compass to swing in its gimbals, with the result that the pendulumwould be subjected to accelerationforces which would cause a continuous torque about the vertical axis ofthe compass.

11a

37. One way ofavoiding this effect would be to stabilize the compass gyroscopically and so prevent it fromswinging. Inthe Sperry compass, however, the complication ofstabilizing gyros is avoided by the use ofthemercury ballistic, which controls the gyro as we have already explained. The mercury ballistic is non-pendulous: its weight is distributed equally above and below the gyro axle so that it is neither top-heavy norbottom-heavy. Therefore, no acceleration forces are generated and no torque about the vertical axis of thecompass is introduced by the swinging ofthe compass inits gimbals.

38. Under slow rates of inclination such as thoseproduced by the earth's rotation, the action ofthemercury ballistic is equivalent to that ofan ordinarypendulum, but opposite indirection. Under rapid rates


DAMPINGFACTOR


ofmovement, however, the small bore ofthe mercurytubes prevents the mercury from surging back andforth and introducing errors inthe compass.

FIGURE 15aGyro-Compass damping curve as charted by a courserecorder operated fromthe master compass. A shows

settling characteristics when compass is set 30degrees away from the meridian. B shows undamped

oscillations.Chart is read frombottomup.

39. The extent ofthe damping action is governed bythe displacement ofthe mercury ballistic connectinglink from the centerline. Commercial compasses aregiven a damping factor of66%, i.e., the eccentricity ofthe connecting link is such that each swing ofthe gyroaxle from the meridian is one-third ofthe precedingswing, the amplitude being reduced by 66% at eachoscillation. Ifthe compass is started 30 degrees east ofthe meridian, the first swing will carry the compass to10 degrees west, the return swing to 3-1/3 degreeseast, then 1-1/9 degrees west, and so on, until itcomes to rest. Figure 15a shows graphically thedamping characteristics ofthe gyro-compass.

PERIOD OF OSCILLATION

40. The naturalperiod ofthe compass, i.e., the time it takes to perform a complete oscillation (fromA to B inFigure 14a) is 85 minutes. The period ofoscillation is governed by two factors:

(1) The angular momentumofthe gyro (the product ofweight, speed and square ofradius ofgyration) and(2) The torque about the horizontalaxis supplied by the action ofthe mercury ballistic. (This, inturn, is governed by the free surface of the mercury inthe containers and the distance of thecontainers from the horizontalaxis.)

12a

41. Ifthe weight or the speed ofthe gyro is increased, the period ofoscillation will be longer. Ifthe free surfaceofthe mercury is increased, the period ofoscillationwill be shorter.

42. As is explained under the heading Ship's Speed and Course the effect of the ship's speed and course whensuperimposed on the earth's speed and direction of travel is such as to cause the compass to settle on a newapparent meridianwhich is not coincident with the true meridian. The compass must have an 85 minute periodso that during any given change inspeed and course the compass will be oriented to its new apparent meridianduring the length oftime required to change to the new speed and course.

COMPENSATINGWEIGHTS

43.Unsymmetricaldistribution ofweight is another potential source ofdisturbance, when the compass is



swinging, which must be neutralized. When the unsymmetrical weight shown in Figure 16a is swung in the planeA-B, centrifugal stresses act upon it insuch a way as to cause allof its particles to place themselves as lar aspossible fromthe axis ofswing. This causes a tendency to turn, as indicated by the arrows. The same effectmay be observed when a watch is swung back and forth on its chain through a small arc. Inthe gyro-compassthis effect is avoided by the use ofcompensating weights which permit ofa symmetrical distribution ofweightabout the vertical axis.

44. The foregoing explanation applies particularly to acompass at the equator and ina vessel which is notunder way. At points other than the equator and onboard ships which are moving over the surface oftheearth, certain factors are introduced which wouldresult inerrors ifthey were not compensated orcorrected inthe design ofthe compass.

LATITUDE CORRECTION

45. The latitude correction is necessary because oftheeccentric connection employed to damp theoscillations ofthe compass. The correction is made bymeans ofa latitude adjustment scale, no specialknowledge ofthe problembeingrequired in order tomake the correction. A complete explanation ofthereasons for the latitude error, however, will bewelcomed by the student because it involves a generaldiscussion ofcompass behavior and will give thestudent an opportunity to find out some ofthe whysand wherefores that might otherwise escape attention.

46. At the equator, where only the horizontalcomponent ofthe earth's rotationaffects the gyro, the axle of thecompass is horizontaland parallelto the earth's axis. At the equator, therefore, as soon as the compass hassettled onthe meridian, the ballistic will he at rest and the compass may be considered as a true gyroscope.

13a

47. Ifwe move the compass to a point to the northor south ofthe equator, however, it will be affected by thevertical as well as the horizontalcomponent ofthe earth's rotation. At a point northofthe equator, for instance,the north

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