Gyroscopic boat roll stabilizer
A gyroscopic roll stabilizer comprises a gimbal having a support frame and enclosure configured to maintain a below-ambient pressure, a flywheel assembly including a flywheel and flywheel shaft, one or more bearings for rotatably mounting the flywheel inside the enclosure, a motor for rotating the flywheel, and bearing cooling system for cooling the bearings supporting the flywheel. For smaller units, the bearing cooling system is effective to enable a flywheel with a moment of inertia less than 11.7 kg.m 2 (40000 lbm in 2 ) to be accelerated at a rate of 5 rpm/s or greater. For larger units, the bearing cooling system is effective to enable a flywheel with a moment of inertia greater than 11.7 kg.m 2 (40000 lbm in 2 ) to be accelerated at a rate of 2.5 rpm/s or greater.
1. A gyroscopic roll stabilizer for a boat, said gyroscopic stabilizer comprising:
an enclosure mounted to a gimbal for rotation about a gimbal axis and configured to maintain a below-ambient pressure;
a flywheel assembly including a flywheel and flywheel shaft, said flywheel assembly having a moment of inertia greater than 11.7 kg·m 2 (40,000 lbm·in 2 ); the flywheel assembly configured to precess relative to the gimbal axis, when unlocked, in response to roll of the boat;
one or more bearings for rotatably mounting the flywheel assembly inside the enclosure;
a motor for rotating the flywheel assembly, said motor configured to accelerate the flywheel assembly at an acceleration rate of at least 2.5 rpm/s; and
a bearing cooling system effective to cool the one or more bearings at the acceleration rate;
wherein the gyroscopic roll stabilizer is configured to lock the flywheel assembly during the acceleration of the flywheel assembly at the acceleration rate of at least 2.5 rpm/s, and then unlock the flywheel assembly to allow precession of the flywheel assembly to dampen roll of the boat via the precession of the flywheel assembly.
2. A method of operating a controlled moment gyroscope configured for roll stabilization of a boat, said method comprising:
maintaining a below ambient pressure within a vacuum enclosure surrounding a flywheel assembly, the flywheel assembly including a flywheel shaft;
accelerating the flywheel assembly at an acceleration rate of at least 5 rpm/s to an operating speed of at least 9000 rpm;
locking, during the accelerating, the flywheel assembly against precession;
before the flywheel assembly reaches a speed of at least 75% of its operating speed, unlocking the flywheel assembly to allow precession of the flywheel assembly and dampening roll of the boat via the precession of the flywheel assembly; and
dissipating heat from bearings supporting the flywheel shaft by transferring heat by conduction through the flywheel shaft to the exterior of the enclosure.
3. The method of claim 2 , wherein a time, from the start of the accelerating until the unlocking of the flywheel assembly to allow precession, is less than 20 minutes.
4. The method of claim 3 , wherein the time, from the start of the accelerating until the unlocking of the flywheel assembly to allow precession, is less than 10 minutes.
5. The method of claim 3 , wherein the time, from the start of the accelerating until the unlocking of the flywheel assembly to allow precession, is less than 5 minutes.
6. The method of claim 2 wherein dissipating heat from the bearings supporting the flywheel assembly comprises:
transferring heat by conduction through a liquid medium to a stationary heat transfer member; and
transferring heat by solid conduction through the stationary heat transfer member to the exterior of the enclosure.
7. A method of cooling bearings supporting a flywheel assembly in a controlled moment gyroscope configured for roll stabilization of a boat, said method comprising:
maintaining a below ambient pressure within a vacuum enclosure surrounding flywheel assembly, the flywheel assembly including a flywheel shaft and having a moment of inertia of at least 11.7 kg·m 2 (40,000 lbm·in 2 );
applying power to the flywheel assembly to accelerate the flywheel assembly at an acceleration rate of at least 2.5 rpm/s;
locking, during the accelerating, the flywheel assembly against precession;
after the locking, unlocking the flywheel assembly to allow precession of the flywheel assembly and dampening roll of the boat via the precession of the flywheel assembly; and
dissipating heat from the bearings supporting the flywheel assembly by transferring heat from the flywheel shaft to a heat transfer material disposed in a cavity in the flywheel shaft.
8. The method of claim 7 , wherein a time, from the start of the accelerating until the unlocking of the flywheel assembly to allow precession, is less than 30 minutes.
9. The method of claim 7 , wherein a time, from the start of the accelerating until the unlocking of the flywheel assembly to allow precession, is less than 20 minutes.
10. The method of claim 7 , wherein a time, from the start of the accelerating until the unlocking of the flywheel assembly to allow precession, is less than 10 minutes.