OPERATION Product: Document #: Rev:

MANUAL MODEL 21000 GYRO 90078 3

MODEL 21000 GYRO

OPERATION MANUAL
FEBRUARY 2011

Contents:

Section 1 – System Overview

Section 2 – System Operation & M21000 Quick Start Guide

Section 3 – Power Failures, Alarms, and Troubleshooting

Section 4 – Maintenance

Section 5 – Warranty, Limit of Liability, Property Rights

Section 6 – Model 21000 Gyro Specs and Summary

P.O. BOX 809

44731 ST. ANDREWS CHURCH ROAD
CALIFORNIA, MARYLAND, 20619, U.S.A
PHONE: 410-326-1590
FAX: 410-326-1199
E-MAIL: customerservice@seakeeper.com
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MANUAL MODEL 21000 GYRO 90078 3 1 of 10
Section 1: SYSTEM OVERVIEW

1.0 System Overview

The Seakeeper Model 21000 Gyro uses gyroscopic principles to reduce boat roll motions in waves and
wakes independent of boat speed. One Model 21000 Gyro will reduce the roll motions of a boat that
displaces 60 to 100 tons. Boats with higher displacement typically require multiple gyros to provide
good roll reduction. In multiple gyro installations, the gyros operate independently of each other and
therefore this manual only discusses operation of a single unit.

A Model 21000 Gyro consists of a Gyro assembly (including Control Box), Motor Drive Box, 24V Delay‐
Off Timer Box, Serial Communications Boxes (2), and Operator Display and Keypad. Figure 1 illustrates
the interconnection of these components and their interface with the boat.
 SERIAL COMMUNICATIONS SERIAL COMMUNICATIONS DISPLAY & KEYPAD
BREAKOUT BOX 6‐WAY JUNCTION BOX
Section 1: SYSTEM OVERVIEW
MANUAL
OPERATION

SERIAL COMMUNICATIONS LINK GYRO CONTROL

BOX
MOTOR DRIVE
BOX
Product:

WATER / GLYCOL
COOLING LOOP
MODEL 21000 GYRO

CONTROL SIGNALS

24V DELAY‐
OFF TIMER
BOX

FIGURE 1 – MODEL 21000 GYRO STABILIZATION SYSTEM COMPONENTS

90078
Document #:

SHIP’S POWER, 208‐230 VAC, SHIP’S POWER, SEA WATER COOLING OVERBOARD
50/60 Hz, 1Ø 20A 24 VDC, 10A SUPPLY, 4 GPM (15 LPM) DISCHARGE
3
Rev:
Page:
2 of 10
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Technical specifications provided in Section 6 list the power consumption, total weight, and dimensions
of the major components. Gyroscopic principals that apply to boat roll control are discussed on
Seakeeper’s web site at www.seakeeper.com. The Seakeeper web site also contains videos of gyro
operation and videos of several different boats operating in waves with the Gyro on and off. It is
recommended that the reader play these videos prior to reading the remainder of this manual.

The gyro’s gimbal angle and the gyro’s rate of rotation about the gimbal axis (termed precession rate)
play an important role in its operation. These parameters are illustrated in Figure 2. At zero degree
gimbal angle, the gyro is vertical; it can precess a maximum of +/‐ 60 degrees about this position. The
amount of torque that the gyro exerts on a boat’s hull to counter the wave induced roll is directly
proportional to the precession rate. The further the gyro is from vertical (zero degrees) the lower the
anti‐roll torque. The vertical arrows in Figure 2 illustrate the direction of the principal forces that the
gyro exerts on the boat’s hull to damp roll motion.

PRECESSION

FLYWHEEL
AXIS
GIMBAL
AXIS

PRECESSION AFT,
PRECESSION FWD,
POSITIVE GIMBAL
NEGATIVE GIMBAL
ANGLE
ANGLE

ANTI-ROLL TORQUE TO STARBOARD ANTI-ROLL TORQUE TO PORT

FIGURE 2 – GYRO PRECESSION

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Seakeeper gyro precession is actively controlled by an electronic controller and a hydraulic brake
throughout each roll cycle so the gyro supplies the maximum anti‐roll torque and does not make
mechanical contact with hard stops that limit the maximum gimbal angle travel to +/‐ 60o.

There is a large torque about the gimbal axis when the gyro is precessing.
Therefore, the gyro should be housed in a compartment or installed in a cage so
personnel cannot come into contact with the gyro while it is precessing. If it is ever
necessary to touch the gyro while the flywheel is spinning, the Lock button on the
Keypad must be depressed to stop the gyro from precessing. Gyro maintenance
should not be attempted unless the gyro is locked and the flywheel has stopped
spinning.
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1.1 Gyro Assembly

The gyro assembly consists of a flywheel housed in a cast aluminum vacuum‐tight sphere. The flywheel
spins about a vertical axis and is supported by upper and lower pairs of bearings. A DC brushless motor
mounted inside the enclosure spins the flywheel at high speed.

The enclosure is fastened to two gimbal shafts that are supported by gimbal bearings on either side.
These shafts establish an athwartship gimbal axis about which the flywheel and enclosure precess or
rotate up to +/‐ 60 degrees during operation. The gimbal bearings are integral with the gyro frame which
is attached to the hull via four isolation mounts which contain anti‐vibration bushings. In cases of GRP
hull, the isolation mounts are bolted to saddle beams that are bonded to the GRP hull stringers. In the
case of a metal hull, the isolation mounts can be bolted directly to a hull foundation.

An active hydraulic brake mechanism is located on the gyro assembly to regulate the gyro’s precession
motions about the gimbal shaft. It includes four hydraulic cylinders, two per side, and a hydraulic
manifold mounted on the rear brace.

A coolant pump, heat exchanger, surge tank, and thermostatic mixing valve are the main components of
the cooling system. A glycol/water mix is circulated thru a closed loop to the end caps of the spherical
enclosure, hydraulic manifold and Motor Drive Box to remove heat.

ENCLOSURE
ACTIVE
BRAKE
FLYWHEEL
(inside)

GIMBAL
FRAME BEARINGS

GRP HULL
STRUCTURE
SADDLE
BEAMS
ISOLATION MOUNT

FIGURE 3 – GYRO ASSEMBLY

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1.2 Keypad and Display

The Keypad and Display shown below are the user interface to the Model 21000 Gyro and should be
mounted at the primary helm station. They are used to start, operate, monitor and shutdown the Gyro.
Sensors, alarms and shutdowns are provided to allow unattended operation however the gyro is a high‐
speed machine and special attention should be paid to vibration and noise as this could be the first hint
of a mechanical problem.

The Display provides the user with status information such as bearing, motor and drive temperatures,
motor current, vacuum pressure, boat motion and gyro gimbal angle. The Display also provides
information in the event of an alarm or warning. Alarms cause precession to stop (LOCK) and the gyro to
start coasting down (STOP). Warnings have no effect on gyro operations.

FIGURE 4 – KEYPAD FIGURE 5 – DISPLAY

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1.3 Motor Drive Box

The Motor Drive Box contains the electronic components that take 208‐230 VAC at 50/60 Hz from the
boat’s generator or shore power and supply current to the flywheel motor according to commands from
the Gyro Control Box. The glycol/water mix that cools the gyro is also circulated through the two cold
plates on the back of the Motor Drive Box as shown in the photos below.

The Motor Drive Box contains high voltage electronics and the cover should not be
removed while the flywheel is spinning except by an authorized technician. This
high voltage exists even if the flywheel is coasting down and the supply voltage has
been shut off.

FIGURE 6 – MOTOR DRIVE BOX, FRONT FIGURE 7 – MOTOR DRIVE BOX, REAR
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1.4 Gyro Control Box

The Gyro Control Box contains motion sensors and a controller module that monitors and automatically
regulates operation of the gyro.

The motion sensor suite contains rate sensors that measure the angular movements of the vessel and
accelerometers that measure the vertical and lateral boat movement.

The Controller commands the motor speed and regulates the gyro’s precession rate and gimbal angle.
This is accomplished by commands to a high response flow control valve in the brake circuit that
increases or decreases brake pressure.

FIGURE 8 – GYRO MOUNTED CONTROL BOX

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1.5 Brake

The brake mechanism consists of four hydraulic cylinders which are mounted on both sides of the gyro
and attach to crank arms on the gimbal shafts. The hydraulic cylinders are plumbed to a manifold /
valve assembly so when the gyro rotates about the gimbal axis, oil from one side of each cylinder is
pushed through the high response flow control valve into the same side of the other cylinder. The gyro
controller modulates how fast the oil can flow through the control valve thus controlling the precession
rate of the gyro.

The brake hydraulic circuit is a pre‐charged closed loop – there is no pump, motor or reservoir in the
circuit. Accumulators are installed in the circuit so the precharge pressure does not increase as the fluid
temperature rises due to the braking action. Locking solenoids are installed in the circuit to lock the
gyro so it cannot precess if there is a leak in the circuit or there is a mechanical problem with the gyro.

FIGURE 9 – BRAKE
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1.6 Cooling

The cooling circuit is a closed loop that supplies a glycol/water (50% distilled water and 50% glycol) mix
to:

 The gyro sphere end caps to remove heat from the flywheel bearings

 The brake manifold to remove heat from the brake hydraulic circuit

 The Motor Drive Box to remove heat from the drive electronics

The heated fluid then passes through a thermostatic valve before bypassing or flowing through a heat
exchanger that has sea water on the cold side. The circuit also contains a surge tank used to fill the
system and allow the coolant to expand with changes in temperature.

THERMO‐STATIC VALVE SURGE TANK SURGE TANK OVERFLOW PORT

GROUND CIRCULATING
CONNECTION PUMP

SEA WATER SEA WATER HEAT ZINC

OUTLET INLET EXCHANGER ANODE

FIGURE 10 – COOLING SYSTEM COMPONENTS, FIGURE 11 – COOLING SYSTEM COMPONENTS,

STARBOARD SIDE REAR FOUNDATION, STARBOARD SIDE
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Section 2: SYSTEM OPERATION

2.0 Introduction
This section describes operation of the Seakeeper Model 21000 Gyro system.

2.1 Start‐up
Before operating the Gyro, check for system power and alarms.

1) Make sure AC and DC power are available.

!
The DC circuit breaker for the Gyro should remain ON at all times except for service.

2) Turn on the boat’s AC circuit breaker that supplies power to the Motor Drive J‐Box.
 This will also supply DC voltage to the Gyro Control Box unless the DC circuit breaker is Off.
3) Turn on the ON/OFF Switch on the Motor Drive Box. This box is mounted near the Gyro.

Motor Drive Box AC

4) Turn on the boat’s AC or DC circuit breaker that supplies voltage to the sea water pump.

5) At the Gyro Keypad, verify that the LOCK and STOP lights are on.

6) Verify that no alarms are present. Alarms are shown on the RPM Page of the
Gyro Display. (Press the Menu button on the Display to change pages.)
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2.2 Boat Transit Without Stabilization

!
When cruising without Gyro stabilization, run the Gyro at 1000 rpm to lubricate the high‐speed
bearings. The Gyro uses less than 300 watts of AC power in this mode.

1) At the Display, go to the Speed Command page. Set the speed command to 1000 RPM by
pressing the DOWN key.

2) Press RUN.

 The Gyro Control Box will automatically turn on the boat’s pump that supplies seawater
to the Gyro heat exchanger.

 The RUN light will flash until the flywheel reaches 1000 rpm and then the light will be
solid.
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2.3 Stabilization
For stabilization at sea or at anchor:

1) Press RUN.

 The Gyro Control Box will automatically turn on the boat’s pump that supplies seawater
to the Gyro heat exchanger.

 The flywheel increases speed to 4000 rpm for stabilization. It takes approximately 45‐60
minutes for the flywheel to reach 4000 rpm. The RUN light will flash until the flywheel
reaches 3000 rpm. Above 3000 rpm the RUN light is solid indicating that stabilization
can be activated. The LOCK light will be remain lit indicating the Gyro is locked and will
not stabilize the roll motion until SEA is pressed.

!
If it is necessary to shutoff power to the flywheel motor and
slow the flywheel for any reason, press STOP and the RUN light
will go out indicating the command has been accepted. Verify
the SEA light also goes out and the LOCK button illuminates
indicating that precession has stopped. It takes approximately 1‐
1/2 hour for the speed to drop from 4000 rpm to 2500 rpm and
5+ hours for the speed to drop from 4000 rpm to zero rpm.
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2) Press SEA. (To turn on stabilization, the rpm must be above 3000.)

The LOCK light will go off and the SEA light will go on indicating that the Gyro is precessing and
stabilizing the roll motion. Stabilization starts gradually; it takes 5‐10 seconds to reach full
effectiveness.

!
If it is necessary to stop Gyro motion for any reason press the LOCK
button. The SEA light will go off and the LOCK light will go on
indicating that the Gyro is locked. Never attempt to work on the gyro
until the flywheel has stopped spinning. In the event, that the Gyro
system has automatically locked the gyro due to an alarm or failure,
no attempt should be made to bypass the alarm or automatic lock.

In some cases (such as on anchor at night) the sea condition may be very calm and the Gyro is only
required to damp motions from light swell or the wakes from passing boats. In these situations, the
operator can run the Gyro at 3200 rpm to reduce noise and power consumption without significantly
reducing performance.

When the operator first presses the RUN button on the Keypad, the
gyro will start accelerating to full speed (4000 rpm). To reduce the
speed to 3200 rpm, go to the Speed Command page on the Gyro
Display. Press the UP and DOWN keys to set the desired speed.
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Display Operation
The Display has a number of pages for monitoring the Gyro System and changing system settings. The
operator changes pages by pressing the MENU button.

RPM Page

The RPM page displays the gyro speed. The Display will indicate 4.0
KRPM once the Gyro reaches full speed.

The brightness of the Display backlight and Keypad lights can be

adjusted with the UP and DOWN keys.

ANGLE Page

The ANGLE page displays the Gyro angle. Generally, the Gyro should
stay between ± 50 degrees. During boat turns it may slowly go as
high as ± 60 degrees.

BEARING Page

The BEARING page shows the temperature of the bearings. Pressing

the UP key replaces the temperatures with the bearing numbers to
which the temperatures correspond. Bearing numbers 1 and 2 are in
the upper part of the gyro and bearing numbers 3 and 4 are in the
lower. The bearings typically run 20° to 40° C hotter than the
ambient sea water depending on the sea state. The rougher the sea
state, the higher the bearing loads and the temperatures.
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MOTOR Page

The MOTOR page on the Display indicates the temperature and

current of the flywheel motor. The motor typically runs 20° C hotter
than the bearings. Amp readings represent the DC current command
to the flywheel motor, not the AC line current.

Motor current is 25 amps when the motor starts spinning the

flywheel. As speeds increases the motor current decreases so the
Gyro does not draw more than 3 kW of AC power. Once the flywheel
reaches full speed, the current typically drops down to about 4 amps
in Lock. In SEA, the Gyro does not draw more than 3 kW of AC
power.

DRIVE/ENCLOSURE Page

The DRIVE/ENCLOSURE page displays the temperature of the

electronics inside the Motor Drive Box and the pressure inside the
Gyro’s vacuum tight spherical enclosure.

The Drive temperature is typically 15‐20° C hotter than the sea water
during spin‐up and typically 10‐15° C hotter than the sea water in
LOCK and SEA.

The enclosure pressure is typically between 5 and 30 Torr (or mmHg)

at start‐up depending on the ambient temperature. During
operation, the Enclosure pressure slowly rises.
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GYRO/ROLL RATE Page

The GYRO/ROLL RATE page displays the standard deviation of the

gyro angle in degrees, the gyro angle rate in degrees/sec and the boat
roll rate in degrees/sec. The standard deviation is a measure of
movement. For example, as the gyro movement increases the gyro
angle standard deviation increases proportionally.

This information is not required to operate the Gyro, but it is useful in

assessing performance. For example, with the Gyro in LOCK, the
operator can take roll rate readings with the boat in beam seas at
zero speed for 5 minutes and get a quantitative measure of the boat’s
uncontrolled roll motions. If this test is repeated with the Gyro in
SEA, the operator knows how much the Gyro reduced the roll
motions. A test like this should be conducted for at least 5 minutes in
LOCK and 5 minutes in SEA, which correspond to roughly 100 roll
cycles on a typical 15 to 25 ton boat.

RPM Page – Alarms

Alarms and warnings are displayed on the RPM page directly under
the flywheel speed.

Alarms are conditions outside normal operation that require the

Gyro system to shutdown (LOCK and STOP) for safety. RUN and SEA
will not be allowed until all alarm conditions have cleared and the
operator acknowledges the alarms. This is done by pressing any key
on the Keypad.

The switched Alarm Output on receptacle J9 to CABLE 8 is used to

activate suitable visual and audible alarms or to signal the boat’s
central Alarm & Monitoring System.

Warnings are conditions outside normal operation that do not cause

an automatic shutdown and do not trigger alarm outputs on
receptacle J9. The operator should investigate the warning until
resolved. Warnings will be displayed until acknowledged by the
operator. This is done by pressing any key on the Keypad.
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SERVICE Page

The SERVICE Page allows the operator access to pages that may be
required during servicing or troubleshooting. Press UP or DOWN to
select a service page and then press MENU to go to that service page.
To return to the RPM Page, select ‘NEXT’ and press MENU.

HISTORY Page

The HISTORY page displays the last 32 alarms and warnings that have
occurred. They are in chronological order starting with the most
recent. Only one is displayed at a time – press DOWN to view the
entire history. Press MENU to return to the SERVICE page.

An alarm or warning will not be captured in the HISTORY if RUN mode

is not engaged.

BRAKE Page

The BRAKE page is used for servicing the gyro’s hydraulic brake as
discussed in the Maintenance section of this manual. It will display
“Service Brake Not Available” any time that the gyro is spinning. Press
MENU to return to the SERVICE page.
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HOURS Page

The HOURS page displays the number of hours that the gyro motor
has run and the number of hours in SEA. Press MENU to return to
the SERVICE page.

VERSION Page

The VERSION Page displays information about the controller

firmware. Press MENU to return to the SERVICE page.

Note: The version number may not match the one shown in this
picture.
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2.4 Normal Shut‐Down

1) Verify that no alarms are on the Gyro display.

2) Press LOCK. The SEA light will go off and the LOCK light will flash. When the brake is locked, the
LOCK light will be solid.

3) Press STOP. The RUN light will go off out and the STOP light will flash. When the flywheel stops
spinning, the STOP light will be solid.
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4) Turn Off the boat’s AC circuit breaker that supplies voltage to the gyro and turn off the sea
water pump breaker.

!
The boat’s 24 VDC breaker that supplies voltage to the gyro should
remain On at all times except for service.

Turning off the AC breaker triggers a time delay relay that will
automatically turn off DC power in 1.5 hours. This ensures the
glycol pump will remove heat generated by the bearings for the
first 1.5 hours of the 5+ hour flywheel coast down.
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 QUICK M21000 START UP

Power Up
MAKE SURE THE 24V & 230V BREAKERS ARE “ON”, AS WELL AS THE SEA WATER PUMP
BREAKER (DEPENDING ON POWER SYSTEMS CONFIGURATION)

TO START GYRO MOTOR PRESS “RUN”. THE RUN LIGHT WILL FLASH AS THE
FLYWHEEL SPOOLS UP. THE LOCK LIGHT WILL ALSO BE LIT.

Spool Up
WHEN THE FLYWHEEL HAS REACHED 3.0 KRPM, THE RUN LIGHT WILL BE SOLID.
THE LOCK LIGHT WILL STILL BE LIT.

READY TO STABILIZE
AT 3.0 KRPM YOU MAY STABILIZE THE VESSEL. THE RUN LIGHT WILL BE SOLID.
PUSH “SEA”. THE GYRO WILL THEN UNLOCK, PRECESS FORE AND AFT, AND
STABILIZE THE VESSEL. THE UNIT WILL CONTINUE TO SPEED UP TO 4.0 KRPM.

TO STOP STABILIZATION & POWER GYRO OFF

TO STOP GYRO AND SPOOL DOWN, PRESS “LOCK” TO LOCK THE GYRO, AND PRESS
“STOP”. THE STOP LIGHT WILL FLASH UNTIL FLYWHEEL STOPS. THE LOCK LIGHT
WILL BE LIT.

Turn “OFF” the boat’s AC breakers that supply power to the motor drive and seawater
pump. Leave the DC breaker that supplies power to the gyro control box “ON”. Turning off
AC breaker triggers a time delay relay that will automatically shut off 24VDC to gyro control
box in 1.5 hours.

-PLEASE READ FULL OPERATION DETAILS IN OPERATION MANUAL BEFORE USE-

MANUAL CAN BE VIEWED & DOWNLOADED AT WWW.SEAKEEPER.COM

Seakeeper Doc # 90104 Rev 1

 TROUBLE SHOOTING

Most problems occur due to lack of power to the Gyro. There are 2 sources of power:
• 24 Volts DC which powers the controls/electronics in the Gyro Control Box.
• 208-230 Volts AC (+/-10%) which powers the Motor Drive Box.
There is an ON/OFF Switch on the Motor Drive Box that must be ON. This box is mounted near the Gyro.

Motor Drive Box AC

Display and Keypad are blank - Verify the boat’s AC and DC power breakers are ON. You must have the AC
power for the DC power to get to the Gyro Control Box.

Display and Keypad are illuminated - Verify the Motor Drive Box switch is ON.

If you have power to the electronics and motor, depressing “RUN” should begin to spool flywheel up to speed.

COMMON ALARMS & ALERTS

DRIVE FAULT - If power is verified and you experience this alarm, Press RUN to
clear the alarm and restart the motor. If DRIVE FAULT does not clear then:
• Turn OFF Boat’s DC Power to the Gyro, then turn it back ON.
• Turn OFF Boat’s AC Power to the Gyro, then turn it back ON.
• Press RUN button to attempt motor start.
• If Motor Amps remain at 0.0 and DRIVE FAULT occurs in 1 minute, the
Gyro does NOT have power. Check AC power switch on the Gyro Motor
Drive Box and the boat’s AC breaker.
• If Motor Amps increase briefly then return to 0.0 and DRIVE FAULT occurs
in 1 minute, the gyro DOES have power to operate, but has another
problem within the drive. CONTACT SEAKEEPER 610-775-4976.

VACUUM LEAK - The vacuum pressure level will fluctuate due to changes in
temperature and use of the gyro. Monitor the pressure level on the
Drive/Enclosure page. The nominal value is 10 Torr.
• If the TORR level continues to increase with no sign of peaking CONTACT
SEAKEEPER 610-775-4976.

FOR ANY AND ALL TEMPERATURE, BEARING, SENSOR, ACCEL, OR BRAKE PRESSURE ALARMS CONTACT
SEAKEEPER 610-775-4976

PLEASE SEE M21000 MANUAL FOR FULL TROUBLESHOOTING GUIDE AND ALARM LIST OR
DOWNLOAD AT WWW.SEAKEEPER.COM
Seakeeper Doc # 90104 Rev 1
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3.0 Power Failures

There are two sources of power to the Seakeeper Model 21000 Gyro system.

 24 Volts DC powers the Gyro Control Box for all the control electronics.

 208 ‐ 230 Volts AC powers the Motor Drive J‐Box to drive the motor inside the Gyro.

These are supplied on Cables 1 and 2 which are shown on Seakeeper drawing 90068, Cable Block
Diagram.

The Motor Drive Junction Box contains hazardous

voltage and the cover should not be removed while the
flywheel is spinning except by an authorized technician.
This high voltage exists even if the flywheel is coasting
down and the supply voltage has been shut off.

3.1 +24 VDC Failure

The display will be blank and the keypad lights will be off. Gyro flywheel speed will decrease. The brake
is locked (no precession).

 Verify the boat’s circuit breaker supplying +24 VDC has not tripped and the AC breaker is On.

When +24 VDC is restored, the display and the keypad STOP and LOCK lights will be illuminated.

 Press RUN

The Gyro flywheel speed should begin to increase and the RUN light will blink. When Gyro
flywheel speed is above 3000 RPM, stabilization can resume.

 Press SEA

Stabilization will begin and the SEA light will be on.

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230 VAC Failure

If an AC failure longer than thirty seconds occurs, the motor will be disabled and the flywheel speed will
start to decrease. The brake is locked and the gyro will stop moving. A “Drive Fault” alarm will occur.

 Verify the boat’s circuit breaker supplying 230 VAC to the Motor Drive J‐Box has not tripped.

 Verify that the circuit breaker on the Motor Drive J‐Box has not tripped.

Once 230 VAC is restored:

 Press RUN

The Gyro flywheel speed should begin to increase. If the flywheel speed does not increase, look
for an alarm on the RPM page. If no alarm exists, contact customerservice@seakeeper.com.

When Gyro flywheel speed is above 3000 RPM stabilization can resume.

 Press SEA

The SEA light will turn on and stabilization will begin.

3.2 230 VAC Fluctuation, Spike or Momentary Failure

Seakeeper’s specified range for AC input voltage is 208 – 230 VAC. The Gyro can safely operate 10%
outside this range (186 – 252 VAC). If the AC voltage to the Motor Drive J‐Box is outside the protection
range (175 – 264 VAC) or if the AC voltage fails for less than thirty seconds, the Motor Drive J‐Box will
briefly shut down for protection, but will reset itself and continue operating. In this case a “Drive Fault”
alarm will not occur. The operator will not be aware of the power disturbance unless there are 4 power
disturbances in 1 hour. In this case, a FREQUENT DRIVE RESET warning will be issued. If this warning
occurs, Seakeeper recommends that the cause of this large voltage variation be investigated as it could
damage electronic components on the boat.

A brief fluctuation can happen when the generator is unable to regulate its output voltage, particularly
when a large AC load is switched on or off. A momentary AC failure also happens during transition from
shore power to ship’s power.
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3.3 Alarms
The Model 21000 Gyro issues an alarm when it detects a malfunction that could cause damage or erratic
operation.

When an alarm occurs the Gyro switches to Stop and Lock, and an alarm message is shown on the
Display at the RPM page. If the Gyro is connected to the boat’s alarm and monitoring system, it will be
notified when an alarm occurs. If the alarm output is connected to an audible alarm it will sound when
and alarm occurs. The audible alarm is silenced by pressing a key on the Keypad.

The alarm will clear when the reset condition listed on the table below is achieved and the operator
presses a key on the Keypad. The operator can then press RUN and SEA on the Keypad to continue
active roll control. The Gyro will not automatically switch to RUN and SEA.

Display Description Reset condition Troubleshooting

Indication
Bearing 1 Bearing 1 temperature Refer to Seakeeper Drawing 90090 & verify: (1) boat
BEARING 1 temperature above below 50 °C seawater pump is on, (2) seawater supplied to gyro
TEMP 75 °C heat exchanger (3) gyro glycol pump is running, (4) no
HIGH glycol leaks, and (5) knob on thermostatic mixing valve
is full CW.
Bearing 2 Bearing 2 temperature Refer to Seakeeper Drawing 90090 & verify: (1) boat
BEARING 2 temperature above below 50 °C seawater pump is on, (2) seawater supplied to gyro
TEMP 75 °C heat exchanger (3) gyro glycol pump is running, (4) no
HIGH glycol leaks, and (5) knob on thermostatic mixing valve
is full CW.
Bearing 3 Bearing 3 temperature Refer to Seakeeper Drawing 90090 & verify: (1) boat
BEARING 3 temperature above below 50 °C seawater pump is on, (2) seawater supplied to gyro
TEMP 75 °C heat exchanger (3) gyro glycol pump is running, (4) no
HIGH glycol leaks, and (5) knob on thermostatic mixing valve
is full CW.
Bearing 4 Bearing 4 temperature Refer to Seakeeper Drawing 90090 & verify: (1) boat
BEARING 4 temperature above below 50 °C seawater pump is on, (2) seawater supplied to gyro
TEMP 75 °C heat exchanger (3) gyro glycol pump is running, (4) no
HIGH glycol leaks, and (5) knob on thermostatic mixing valve
is full CW.
'Bearing 1 Sensor Bearing 1 temperature Refer to Seakeeper Drawing 90068 Cable Block
FAULTS ON Fault' and 'Bearing 2 sensor working, or Diagram & check connector on Gyro Control Box
BEARINGS Sensor Fault' bearing 2 temperature
1&2 sensor working, or both
sensors working
'Bearing 3 Sensor Bearing 3 temperature Refer to Seakeeper Drawing 90068 Cable Block
FAULTS ON Fault' and 'Bearing 4 sensor working, or Diagram & check connector on Gyro Control Box
BEARINGS Sensor Fault' bearing 4 temperature
3&4 sensor working, or both
sensors working
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MANUAL MODEL 21000 GYRO 90078 3 4 of 8
Section 3: POWER FAILURES, ALARMS, AND TROUBLESHOOTING

Display Description Reset condition Troubleshooting

Indication
Motor temperature Motor temperature Refer to Seakeeper Drawing 90090 & verify: (1) boat
MOTOR
above 100 °C below 75 °C seawater pump is on, (2) seawater supplied to gyro
TEMP
heat exchanger (3) gyro glycol pump is running, (4) no
HIGH
glycol leaks.
Temperature of Temperature of Motor Refer to Seakeeper Drawing 90090 & verify: (1) boat
DRIVE
Motor Drive J‐Box Drive J‐Box electronics seawater pump is on, (2) seawater supplied to gyro
TEMP
electronics above below 45 °C heat exchanger (3) gyro glycol pump is running, (4) no
HIGH
55 °C glycol leaks.
Coolant pump Coolant pump current 1) Determine if the pump is running by sound or
current draw less draw more than 0.25 A. touch.
than 0.25 A 2) If the pump appears to be running but is noisy, then
indicating a bad it is likely that there is air in the glycol loop. Fill and
COOLANT
connection, a bad purge the loop per Section 4.4 of this manual.
PUMP
pump, or a lack of 3) If pump is not running refer to Seakeeper Drawing
FAULT
coolant. 90068 Cable Block Diagram and check J2 connector on
Gyro Control Box and pump connector next to pump.
4) Contact Seakeeper distributor for cooling circuit
parts and service.
One of the four (none) 1) Refer to Seakeeper Drawing 90068 Cable Block
SOLENOID brake solenoid Diagram & check connectors on Brake Solenoid Valves
VALVE 1 valves is not and on Gyro Control Box.
FAULT operating correctly. 2) Contact Seakeeper distributor for brake circuit parts
and service.
Two of the four Brake solenoid current 1) Refer to Seakeeper Drawing 90068 Cable Block
brake solenoid draw less than 0.25 A. Diagram & check connectors on Brake Solenoid Valves
VALVE 1 valves are drawing and on Gyro Control Box.
CURRENT more than 2.5A 2) Contact Seakeeper distributor for brake circuit parts
HIGH indicating a bad and service.
connection or a bad
valve.
One of the four (none) 1) Refer to Seakeeper Drawing 90068 Cable Block
SOLENOID brake solenoid Diagram & check connectors on Brake Solenoid Valves
VALVE 2 valves is not and on Gyro Control Box.
FAULT operating correctly. 2) Contact Seakeeper distributor for brake circuit parts
and service.
Two of the four Brake solenoid current 1) Refer to Seakeeper Drawing 90068 Cable Block
brake solenoid draw less than 0.25 A. Diagram & check connectors on Brake Solenoid Valves
VALVE 2 valves are drawing and on Gyro Control Box.
CURRENT more than 2.5A 2) Contact Seakeeper distributor for brake circuit parts
HIGH indicating a bad and service.
connection or a bad
valve.
Hydraulic pressure Hydraulic pressure in 1) Check all hydraulic components for leaks.
in brake low brake in normal range 2) Refer to Seakeeper Drawing 90068 Cable Block
LOW
Diagram & check connectors on Brake Pressure
BRAKE
Switches and on Gyro Control Box.
PRESSURE
3) Contact Seakeeper distributor for brake circuit parts
and service.
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MANUAL MODEL 21000 GYRO 90078 3 5 of 8
Section 3: POWER FAILURES, ALARMS, AND TROUBLESHOOTING

Display Description Reset condition Troubleshooting

Indication
Fault signal in Motor off for 1 minute 1) Verify boat's AC breaker supplying power to the
DRIVE Motor Drive J‐Box Gyro is on.
FAULT 2) Refer to Seakeeper Drawing 90068 Cable Block
Diagram & check for AC power.
3) Check motor connector on Motor Drive J‐Box
Flywheel not Motor off for 1 minute 1) Verify boat's AC breaker supplying power to the
spinning when RUN Gyro is on.
MOTOR
commanded. 2) Refer to Seakeeper Drawing 90068 Cable Block
FAULT
Diagram & check for AC power.
3) Check connectors on Motor Drive J‐Box.
Gyro angle reading Gyro angle reading 1) Refer to Seakeeper Drawing 90068 Cable Block
more than 64° from within 64° of center Diagram and check sensor connector on Gyro Control
ANGLE center indicating Box.
SENSOR sensor 2) Refer to Seakeeper Drawing 90091 Model 21000
FAULT misalignment, Gyro Assembly and Parts List under Port Side View and
sensor damage, or a confirm sensor is still firmly mounted to Gyro.
bad connection.
Gyro angular rate (none) 1) Refer to Seakeeper Drawing 90091 Model 21000
GYRO more than 150 Gyro Assembly and Parts List under Port Side View and
MOTION degrees per second confirm sensor is still firmly mounted to Gyro.
FAULT 2) Inspect the brake system, including electrical,
mechanical and hydraulic connections.
X RATE X Rate sensor inside Functioning sensor Contact Seakeeper distributor for service
SENSOR Control Box not
FAULT working
Y RATE Y Rate sensor inside Functioning sensor Contact Seakeeper distributor for service
SENSOR Control Box not
FAULT working
Z RATE Z Rate sensor inside Functioning sensor Contact Seakeeper distributor for service
SENSOR Control Box not
FAULT working
X RATE Invalid reading from Valid readings from Contact Seakeeper distributor for service
SENSOR X Rate sensor inside sensors
HIGH Control Box
Y RATE Invalid reading from Valid readings from Contact Seakeeper distributor for service
SENSOR Y Rate sensor inside sensors
HIGH Control Box
Z RATE Invalid reading from Valid readings from Contact Seakeeper distributor for service
SENSOR Z Rate sensor inside sensors
HIGH Control Box
VERTICAL Vertical boat Vertical boat If sea condition is this severe, operator should slow
ACCEL acceleration above accelerations below 2g down and/or alter course to reduce boat motion.
HIGH 2g for 1 min
LATERAL Lateral boat Lateral boat If sea condition is this severe, operator should slow
ACCEL acceleration above accelerations below 1g down and/or alter course to reduce boat motion.
HIGH 1g for 1 minute
DISPLAY Display not Display operational for 1 Refer to Seakeeper Drawing 90068 Cable Block
FAULT communicating with minute Diagram & check Display connector on Serial Comms J‐
Control Box Box.
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MANUAL MODEL 21000 GYRO 90078 3 6 of 8
Section 3: POWER FAILURES, ALARMS, AND TROUBLESHOOTING

Display Description Reset condition Troubleshooting

Indication
KEYPAD Keypad not Display operational for 1 Refer to Seakeeper Drawing 90068 Cable Block
FAULT communicating with minute Diagram & check Keypad connector on Serial Comms
Control Box J‐Box.
INPUT DC power to Control DC power between 17V Verify DC input power is between 17V and 32V;
POWER Box above 32V and 32V excessive load
HIGH
INPUT DC power to Control DC power between 17V Verify DC input power is between 17V and 32V;
POWER Box below 17V and 32V excessive load
LOW
CONTROL DC power to brake DC control power Verify DC input power is between 17V and 32V;
POWER and coolant pump between 17V and 32V excessive load
HIGH above 32V
CONTROL DC power to brake DC control power Verify DC input power is between 17V and 32V;
POWER and coolant pump between 17V and 32V excessive load
HIGH below 17V
DC power from DC power from Control Inspect gyro angle sensor for damage
SENSOR Control Box to Gyro Box to between 4.75 V
POWER Angle Sensor and and 5.25 V.
HIGH Motor Drive J‐Box
above 5.25 V.
DC power from DC power from Control Inspect gyro angle sensor for damage
SENSOR Control Box to Gyro Box to between 4.75 V
POWER Angle Sensor and and 5.25 V.
LOW Motor Drive J‐Box
below 4.75 V.
Three sensors inside All three sensors 1) Refer to Seakeeper Drawing 90068 Cable Block
the gyro are used working or the flywheel Diagram & check connector on Gyro Motor Drive J‐
for speed not spinning. Box.
SPEED
measurement and 2) Contact Seakeeper distributor for service.
SENSOR
motor operation.
FAULT
One inoperable
sensor will cause
this alarm.
Motor speed is over Motor speed below 5.6 1) Check connectors on Motor Drive J‐Box and Gyro
MOTOR
5.6 KRPM. KRPM. Control Box.
OVERSPEED
2) Contact Seakeeper distributor for service.
MOTOR Adjustment to None. Wait for gyro to coast to 0.0 krpm before restarting.
ADJUST motor settings while
FAULT motor running.
Drive runs briefly None. Wait for gyro to coast to 0.0 krpm before restarting.
DRIVE
than stops (3
START
occurrences in 1
FAULT
minute).
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MANUAL MODEL 21000 GYRO 90078 3 7 of 8
Section 3: POWER FAILURES, ALARMS, AND TROUBLESHOOTING

3.4 Warnings
The Model 21000 Gyro issues a warning when it detects a malfunction that is not hazardous (but still
should be corrected). Warning messages are shown on the Display at the RPM page. The warning
message will clear after the reset condition listed on the table below is achieved and the operator
presses a key on the Keypad.

Warnings

Display Description Reset condition Troubleshooting

Indication
BEARING 1 Bad sensor or bad Functioning sensor Refer to Seakeeper Drawing 90068 Cable Block
SENSOR connection Diagram & check connector on Gyro Control Box
FAULT
BEARING 2 Bad sensor or bad Functioning sensor Refer to Seakeeper Drawing 90068 Cable Block
SENSOR connection Diagram & check connector on Gyro Control Box
FAULT
BEARING 3 Bad sensor or bad Functioning sensor Refer to Seakeeper Drawing 90068 Cable Block
SENSOR connection Diagram & check connector on Gyro Control Box
FAULT
BEARING 4 Bad sensor or bad Functioning sensor Refer to Seakeeper Drawing 90068 Cable Block
SENSOR connection Diagram & check connector on Gyro Control Box
FAULT
MOTOR Bad sensor or bad Functioning sensor Refer to Seakeeper Drawing 90068 Cable Block
SENSOR connection Diagram & check connector on Gyro Control Box
FAULT
DRIVE Bad sensor or bad Functioning sensor Refer to Seakeeper Drawing 90068 Cable Block
SENSOR connection Diagram & check connector on Gyro Control Box
FAULT
X ACCEL Bad sensor or bad Functioning sensor Contact Seakeeper distributor for service
SENSOR connection
FAULT
Y ACCEL Bad sensor or bad Functioning sensor Contact Seakeeper distributor for service
SENSOR connection
FAULT
Z ACCEL Bad sensor or bad Functioning sensor Contact Seakeeper distributor for service
SENSOR connection
FAULT
VACUUM Enclosure pressure Enclosure pressure less Contact Seakeeper distributor for service
LEAK more than 35 torr than 30 torr
VACUUM Bad sensor or bad Functioning sensor Refer to Seakeeper Drawing 90068 Cable Block
SENSOR connection Diagram & check connector on Gyro Control Box
FAULT
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MANUAL MODEL 21000 GYRO 90078 3 8 of 8
Section 3: POWER FAILURES, ALARMS, AND TROUBLESHOOTING

Display Description Reset condition Troubleshooting

Indication
The Gyro will operate (none) Verify AC power source is stable.
through AC power
failures less than 30
seconds, e.g. ship to
shore power
FREQUENT
transfers or voltage
DRIVE
dips due to switching
RESET
large generator
loads. Four AC
power disturbances
in one hour produce
this warning.

3.5 Alarm and Warning History

The History page on the Display shows the 32 most recent alarms and warnings. The alarms are in
chronological order starting with the most recent.

1) At the Display, go to SERVICE page. Select HISTORY by pressing DOWN key. Press MENU.

2) View the alarms and warnings in the history by pressing UP and DOWN.
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MANUAL MODEL 21000 GYRO 90078 3 1 of 3
Section 4: MAINTENANCE

4.0 MAINTENANCE
The gyro system is designed to require as little maintenance as possible. However, since the system is
comprised of mechanical and electrical components that operate in a marine environment, some
periodic inspections and maintenance are recommended. Seakeeper recommends an annual inspection
and a 2000 hr service interval to keep the gyro running trouble‐free.

If the gyro is installed in a wet space, efforts should be made to keep gyro free of salt residue from
either condensation or direct exposure to salt spray. If exposed, a regular wipe down with mild soap
and water with a rinse will help limit corrosion and keep the gyro assembly in good cosmetic condition.
Refer to Service Bulletin 90106 for details.

4.1 REFERENCES
 Seakeeper 90025, Service Bulletin, Brake Bleeding
 Seakeeper 90026, Service Bulletin, Gyro Paint Information
 Seakeeper 90083, Service Bulletin, Gimbal Angle Sensor Replacement and Calibration
 Seakeeper 90106, Service Bulletin, Fresh Water Rinse Notice
 Seakeeper 90133, Service Bulletin, Gyro Annual Inspection Instructions
 Seakeeper 90134, Service Bulletin, Gyro 2000 Hour Service Instructions
 Seakeeper 90135, Service Bulletin, Model 21000 Gyro Cable Guide Band Replacement
Instructions

4.2 PRECAUTIONS
 Gyro Hydraulic Hand Pump Kit, Part No. 10384, is required for servicing the brake.
Pressure should NOT be relieved unless this tool is available.

 Never charge the nitrogen charged accumulators with oxygen or shop air!

4.3 PARTS AND SPECIAL TOOLS

Part No. Description Comments
10384 Gyro Hydraulic Hand Pump Kit Required for all brake service tasks.
Contains tools used for changing bushings on all
10449 Brake Bushing Replacement Tool Kit
model gyros.
Model 21000 Gyro Cable Guide Band Contains parts required for 2000 hour cable
10550
Replacement Kit guide band replacement.
Model 21000 Gyro Hydraulic Brake Contains parts required for 2000 hour hydraulic
10607
Parts Kit brake service.
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MANUAL MODEL 21000 GYRO 90078 3 2 of 3
Section 4: MAINTENANCE

4.4 SCHEDULED MAINTENANCE TABLE

 The following pages contain the scheduled maintenance table organized by systems:
Mechanical, Hydraulic, Cooling, and Electrical.

PARTS / SPECIAL
SYSTEM / COMPONENT TASK PER SERVICE BULLETIN 90133 INTERVAL
TOOLS
Inspect unit for severely corroded
Mechanical / Corrosion areas and clean and touch up with Annual
paint. See Service Bulletin 90026.
Inspect cable guide bands around
gimbal shafts. Look for cracks in band
Mechanical / Cable Cable guide band
near mounting holes at both ends of Annual
Guide Bands replacement kit
bands. Replace if damaged. See
Service Bulletin 90135 for instructions.
Mechanical / Isolation Inspect that safety wire is intact and
Annual
Mount Pin Retainer Bolts bolts are not loose.
Check for cracks or chafing. If chafing
found, reposition hose to provide
Hydraulic hand
Hydraulic / Hoses clearance around hose. If chafing is Annual
pump kit
severe, replace hose. Charge system
per Service Bulletin 90025.
With other
Cooling / Zinc Anode Replace zinc anode as needed.
zincs or Annual
Check for cracks or chafing. If
Cooling / Hoses damaged, replace hose. Fill cooling Annual
system and purge air.
Fill with environmentally safe, marine
Cooling / Seawater side anti‐freeze during winter or periods of Winter
in‐operation.
Inspect all connectors for corrosion,
Electrical / Connectors clean as necessary, and treat with Annual
corrosion inhibitor.
Inspect all ground points for corrosion,
Electrical / Grounds clean as necessary, and treat with Annual
corrosion inhibitor.
Electrical / Gimbal Angle Check calibration of sensor. See
Sensor Annual
Service Bulletin 90083 for instructions.
Electrical / Cables Check all cables for cracks or chafing. Annual
Electrical / Power Input Check for seal at cable glands. Annual
Check integrity of motor power cable
Electrical / Motor Power Annual
jacket.
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MANUAL MODEL 21000 GYRO 90078 3 3 of 3
Section 4: MAINTENANCE

SYSTEM / COMPONENT TASK PER SERVICE BULLETIN 90134 INTERVAL PARTS / SPECIAL TOOLS

Replace brake bushings, hydraulic Hydraulic hand pump kit,

accumulators and check valves, and Brake bushing replacement
Mechanical / Hydraulic Brake 2000 hrs
flush hydraulic oil. tool kit, Hydraulic brake parts
kit
Replace cable guide bands. See
Mechanical / Cable Guide Service Bulletin 90135 for Cable guide band
2000 hrs
Bands instructions. replacement kit

Cooling / System Cooling system flush 2000 hrs

Check internal circulator fan inside
Electrical / Motor Drive 2000 hrs
Motor Drive J‐Box.
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MANUAL MODEL 21000 GYRO 90078 3 1 of 2
Section 5: WARRANTY

5.0 WARRANTY, LIMITATION OF LIABILITY, PROPERTY RIGHTS

5.1 WARRANTY

Seakeeper warrants that the Goods sold hereunder are free from defects in material and workmanship
for a period of 24 months or 2000 hours of operation from the date of delivery to the End User or 36
months from the date of manufacture whichever event occurs first. This express warranty is in lieu of
and excludes all other warranties, express or implied, by operation or law or otherwise including THE
WARRANTY OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE (WHETHER KNOWN TO
SEAKEEPER OR NOT), all other such warranties being hereby expressly disclaimed by Seakeeper and
waived by Buyer/User.

Written notice of claimed defects shall have been given to Seakeeper within the Warranty Period, and
within thirty (30) days from the date any such defect is first discovered. The Goods or parts claimed to
be defective must be returned to Seakeeper, accompanied by a Return Material Authorization (RMA)
issued by Seakeeper's facility responsible for supplying Goods, with transportation prepaid by
Buyer/User, with written specifications of the claimed defect.

If a warranty claim is valid, Seakeeper shall pay reasonable one‐way costs of transportation of the
defective Goods from either the original destination or the location where defect occurred, whichever is
closest to Seakeeper's facility.

Under no circumstances shall Seakeeper be liable for removal of Seakeeper's Goods from Buyer's/User’s
equipment or re‐installation into Buyer's/User’s equipment. No person including any agent, distributor,
or representative of Seakeeper is authorized to make any representation or warranty on behalf of
Seakeeper concerning any Goods manufactured by Seakeeper.
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MANUAL MODEL 21000 GYRO 90078 3 2 of 2
Section 5: WARRANTY

5.2 LIMITATION OF LIABILITY

NOTWITHSTANDING ANYTHING TO THE CONTRARY, SEAKEEPER SHALL NOT BE LIABLE FOR ANY SPECIAL,
INCIDENTAL, INDIRECT OR CONSEQUENTIAL DAMAGES INCLUDING BUT NOT LIMITED TO LOST PROFITS
ARISING OUT OF THE PERFORMANCE, DELAYED PERFORMANCE OR BREACH OF PERFORMANCE OF THIS
ORDER REGARDLESS WHETHER SUCH LIABILITY BE CLAIMED IN CONTRACT, EQUITY, TORT OR
OTHERWISE. SEAKEEPER'S OBLIGATION IS LIMITED SOLELY TO REPAIRING OR REPLACING (AT ITS OPTION
AND AS SET FORTH IN SECTION 5), AT ITS APPROVED REPAIR FACILITY, ANY GOODS OR PARTS WHICH
PROVE TO SEAKEEPER'S SATISFACTION TO BE DEFECTIVE AS A RESULT OF DEFECTIVE MATERIALS OR
WORKMANSHIP, IN ACCORDANCE WITH SEAKEEPER'S STATED WARRANTY. IN NO EVENT SHALL
SEAKEEPER'S LIABILITY EXCEED THE TOTAL PURCHASE PRICE SET FORTH IN THIS ORDER.

5.3 PROPERTY RIGHTS

Except where otherwise expressly agreed, all patterns, tools, jigs and fixtures, drawings, designs,
software and other materials and data developed, fabricated by Seakeeper shall be and shall remain
Seakeeper's property. Except as specifically provided for in the order, Buyer shall have no right in any
technical data, Intellectual Property Rights, and computer software associated with the order. Buyer
shall not use or permit the use of the Goods that in any way could result in the disclosure of Seakeeper's
proprietary information.
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MANUAL MODEL 21000 GYRO 90078 3 1 of 3
Section 6: GYRO SPECIFICATIONS

Model 21000 Gyro Specifications & Summary

Rated RPM 4,000 RPM

Angular Momentum at Rated RPM 21,000 N‐M‐S
Anti‐Rolling Torque at Rated RPM 45,000 N‐M
Spool‐up Time to Rated RPM 45 Minutes
Spool‐up Time to Stabilization (70% Rated RPM) 25 Minutes
Spool‐up Power
AC Motor 3000 Watts Maximum
DC Control 240 Watts
Operating Power
AC Motor (sea state dependent) 2500‐3000 Watts
DC Control 240 Watts
AC Input Voltage 208‐230 VAC (±10%), 50/60 Hz, Single Phase
DC Input Voltage 24 VDC @ 10 Amps
Ambient Sea Water Supply to Gyro Heat Exchanger 15 liters/min (4 gal/min)
Maximum Ambient Air Temperature 50 Deg C (122 Deg F)
Weight 1320 Kg (2910 Lbs)
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MANUAL MODEL 21000 GYRO 90078 3 2 of 3
Section 6: GYRO SPECIFICATIONS

Arrangement

The Model 21000 Gyro System consists of the Gyro unit, Motor Drive Box, Gyro Control Box, 24V Delay‐
Off Timer Box, Cooling Loop Components, Keypad, Display, and Cables (for cables not supplied by
Seakeeper, refer to Seakeeper Drawing 90068).

Installation Location

The Gyro is a torque device and does not have to be installed in a specific hull location or on the
centerline. However, the Gyro should not be installed at forward locations in a high speed boat where
the vertical accelerations exceed ±1 G.

Mounting Dimensions

See Seakeeper Drawing 90067 for saddle installation details.

See Seakeeper Drawing 90098 for bolt‐in installation details.

Loads

The installer is responsible for designing the foundation to which the Gyro is attached and for ensuring
that this foundation can safely transfer the concentrated Gyro loads to the adjacent hull structure.
Loads that the Gyro imposes on the foundation are explained in Seakeeper drawings 90067 and 90098.

Cooling

The Gyro bearings, Motor Drive Box, and hydraulic manifold are cooled by a closed glycol cooling loop
that incorporates a sea water heat exchanger. The installer is responsible for providing 15 lpm (4 gpm)
raw water at ambient sea temperature and 8.5 Bar (125 psi) maximum sea water pressure to the heat
exchanger. The ambient air temperature in the compartment in which the Motor Drive Box is mounted
should not exceed 50o C.

Electrical

The installer is responsible for supplying 208‐230 VAC, 50/60 Hz, single phase power on a 20A service to
the Motor Drive Box and 24 VDC @ 10A service to the Gyro Control Box. Separate circuit breakers
should be used for each Motor Drive Box in multiple gyro installations. Similarly, separate circuit
breakers should be used for each Gyro Control Box in multiple gyro installations.
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MANUAL MODEL 21000 GYRO 90078 3 3 of 3
Section 6: GYRO SPECIFICATIONS

Operator Controls

A Keypad and small Display are provided to start, operate, monitor, and shutdown the Gyro.

Performance

Gyro reduction of boat roll is a function of the boat’s displacement, transverse metacentric height (GMT)
and hull damping as well as the operating conditions (speed and heading with respect to waves) and sea
state. The Gyro controller regulates the active hydraulic brake to ensure the Gyro’s anti‐roll torque is
maximized irrespective of hull characteristics or operating conditions. In heavy seas, the Gyro rpm may
droop when the required power exceeds 2000 watts – this is normal and is designed to limit large power
demands at the expense of a small loss of performance.

Alarm and Monitoring

Sensors, alarms and shutdowns are provided to allow unattended operation. Sensors measure flywheel
bearing temperatures, motor and drive temperatures, vacuum pressure, gimbal angle, brake pressure,
and ship motion. The Gyro controller sends sensor values and alarm information to the display and also
locks the brake and shuts down the motor drive in the event of an alarm condition. Gyro operating
history during faults or alarms is recorded in the controller’s memory for subsequent recall if service is
needed.

Safety

The brake automatically locks the Gyro so it cannot generate excessive anti‐rolling torque loads in the
event of a system fault or alarm, loss of electrical power or loss of brake pressure. The brake can be
locked from the Keypad or by shutting off power locally at the Motor Drive Box.