gyro and compass

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to be

rerromagneuc materials, for example, elements Iron, Cobalt and Nickel, have a

neighbouring-atoms tend to have axes of their molecular

magnets aligned same direction. A g ro up o f a lig ne d mo lecu les is termed a

"domain". Each d om ain is only a " fr ac ti on o f a m i ll ime tr e across so in a samp le

the domains may be random ly orientated or they may be aligned some extent. That is,

th e m aterial m ay b e u nm ag netised , o r it may h av e some m ag netism in du ced it .

HARD AhTI SOFT IRON

" ''h en ferroma gn etic m ate rial is p lace d in an ex tern al field some o f'th e d om ain s b ecom e

a ligned ""i th th e e xte rn al fie ld . Ifth e field in creases m ore d om ain s b ecome alig ned u ntilfinally all of the doma in s a re ful ly l ined up with th e ex tern al field an d th e m aterial b ecomes

saturated w ith m agnetism . T he manner in which this induction occurs and the le vel o f

field necessary for saturation lead to the idea of H ard iron and S oft iron, The sketch on

the next page illustrates the f oll ow ing t erms.

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FLUX. ..,DENSITY

o;;1'\'!"""".,(H) out allco ncen trated at some

distance pole . F lux: d en sity o r Induc tion

is the am ount' of flux passing through an area

one square m etre at right angles to the flux.

The units are W b/m2 and the sym bol is B.

lNDUCTION

PERMEABILITY This is sim ply a ratio of flux density produced to inducing

field strength. It m easures how easily flux is created in th e

material or m edium . It can be thought of as the slope of the

hys te re sis loop.

The symbol fo r p ermeab ility is J . t an d u nits are n ot u su ally co nsid ered .

E ven m aterials w hich are norm ally considered non m agnetic can support m inute am ounts

ie they are very slightly permeable. a rule permeability of vacuum or "The

to be the to are

\

:::; x

or

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aor

are

are

are

are is in a

2

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3: Like Poles End On

5: t!1'I!!k~ Side Side

3

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4

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. 1 1 ) ; ; ,$

'! I

~ '"

')

ff""'I""",4

*) ' 'f

. ' 1

~ 4>f'1

'I \ «1

L. J

\'j~

,i

8: Molecular domain

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6

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can

1

as

10: The Elements

t~~

he.

7

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are

across

a

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is

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a

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13: P Force

14: Q Force .

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15: R Force

12

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on

p

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/'

E

on

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16: Directive Force

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17.

17: Deviation due to soft iron effect

16

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18:

17

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'1 8

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GHylBAL

CAP & P!VOT

BOWL

STAND

8UCKET

IvlA.,GNETIC

19:

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it

ora

is

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20:

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close to the horizon,

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Deviation

o o o e

0100

020"

030"

0400

050"

0600

070"

0800

0900

1000

1100

120"

5 " '1M

1 E

2° E

4" E

5° E

7" E

50 E

1300

1400

50°

1600

1 "10°

i80°

1° VV

1" E

2°W

3aW

SoW

SoW

4°W

2°W

200"

2100

2200

230"

24000"

2" E

1W.5 00

2600 2 ,0 V ' .l

1 ' -' E

280" 3" E

3° E90'~300"

2° E

340· 1" E

1° E

0"

3500

3600

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Gyrocompass Revision )

Across

~6. Result of

~10.

",11. Force

12.

~'·13

around vertical axis

horizontal motion of

(2 words)

of ft on r andom latitude

in which re to

.,.,14. Path of

Down

,..1

~2.

·,·3.

,.'4.1 : : :

.,~. " ... .) '"

listie sys tem

very large moment of inert

of one of the earth (2 words)

under influence of control pzece ss

of gyro' 8 •

···9.

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Gyrocompass Revision (2)

Across

Reduct; of

ir .~

(2 'ida

error

Off-set ion to

" 14.

in wh.icn

is suspended

A-frame

rotor casing in

east/west direction (2

words)

Damping error (2

Down

"""~ MearlS

- 9~.

~"10.

az

of

se

tial tiea

1

f1.() \~

central arm of E-

tr ans former

of ccnt act s s

s mo+.or

1 . ~ Force of tilt: in

16.

vertical

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T I,lS can b e exoram ec as fo llow s:

the

combin ed v ec to r v, and therefore A w ill not

pass the horizontal of the rotor in P, but

in A'. At that same moment, B is at

the bottom of the rotor and

reasonmg, will p as s t he ho riz on ta l

etc. the in which the

~ t. can

8 .

pass the horizontal of therotor rotates around the

vertical axis and the rotor is said

to p recess in th e h orizo ntal

"r,Y".,."nu to the double-arrows.

When the

the distance between A'

and B' will decrease will

between A' and B' w m increase

increases ,...hile 'V i stays the

and the will

increase.

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=

momentum

T

H =

a

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s N

it name:

to be to use

to

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E

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meridian

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can now

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a

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Attached to the rotor filled with a mercury because of its

to the south ofthe horizontal east-west axis. North-south

at their bases. The are also connectedat their upper ends to allow of air pressure in the of the pots. The whole is

about the east-west axis and the centre of mass of the ballistic system must coincide with that of the rotor

when the rotor is horizontal.

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IS

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P c 1 0 Ih e w elS l

~

F (not vsrtica!)

P c Line

b y

meridian

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meridian

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errors

error:

error.

error:

(per

Az is

cos

error:

courses

on courses

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error:

cos B

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A =-vcos

rad

courses

coursesAls

A=

cos

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=

=f

= f.15

lat

error:

IS same as

error

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c an c au se errors

error.

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shipsails this direction

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a

Schematic gyrocompass

2. Phantom 3. A-FnlmelVertk:a!

6, Soft-iron armature; 7. f.:,-;;;l1aneOHorizontal

1 . 2 . Azimuth gear; 3. Azimuth motor; 14. Control

i6.

F>W

15.

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vertical

im::!ucedcurrent coil Ii

v'-&u.n;~current

vertical

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to

as

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to

transmitter receiver motor

compass

. .. -

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NEW IN

IS

on

3. A to steer the course at

to auto the ship should be on the course

overswing.

IS

at'".,,; ,1'

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course

(

course error,

Settings are

Again,

slow

will depend upon weather, size of

best guide, rememoen

ships considerably. too much rudder

and overshooting the new course, too little rudder results in slow alterations

and possible course errors.

loaded or etc,

on

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or Ii on

course to s te er .

a set

courses to

on

to o n (

to autopilot to warn the or out

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E

(bl In circumstances as above, it bewatch to have without delay

at times to

l e i

versaCDlaIIQf'l-r,VElI from automatic to manual

made by or

The manualautomatic pilot, and

t'caution.

HJ1~"·nLL use of~""4~~U demands

Automatic Pilots,

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R

R R

E

,\'I

o on

R

to R

is set out in the

for Automatic Pilots,

to

STANDARDS FOR

2.

2.1

a n y

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Res.

is ino

3.

amount,

Id a n

in

o r c ou rse

3.4 signalling facilities should near

4.

4,' a n d

automatic adjustments are incorporated

provided with adequate controls

and the performance.

in stallation , th e au to -use to

ld not

Id

5 .