Patent ID: 12208868

DETAILED DESCRIPTION

Referring now to the drawings,FIGS.1A and1Billustrate a control moment gyroscope (CMG)10mounted in a boat5for roll stabilization. Multiple embodiments of the CMG10are described. For convenience, similar reference numbers are used in the following description of the embodiments to indicate similar elements in each of the embodiments.

Referring now toFIGS.2and3, the main functional elements of the CMG10comprise a single-axis gimbal20, an enclosure30mounted to the gimbal20for rotation about a gimbal axis G, a flywheel assembly40mounted by bearings50inside the enclosure, a motor60to rotate the flywheel assembly40, and a torque control system70(FIG.5) to control precession of the flywheel assembly40so that the energy of the flywheel assembly40is transferred to the hull of the boat5to counteract rolling motions. Each of the embodiments further comprises a bearing cooling system100(FIG.4) to cool the flywheel bearings50. Various designs of the bearing cooling system100may be employed.

The gimbal20comprises a support frame22that is configured to be securely mounted in the boat5. Preferably, the gimbal20is mounted along a longitudinal axis L of the boat5with the gimbal axis G extending transverse to the longitudinal axis L. Conventionally, the gimbal20is mounted in the hull of the boat5, but could be mounted at any location. The support frame22of the gimbal20comprises a base24and two spaced-apart supports26. A bearing28is mounted on each support26for rotatably mounting the enclosure30to the supports26. For this purpose, the enclosure30includes two gimbal shafts32projecting from diametrically opposed sides of the enclosure30. The gimbal shafts32are rotatably journaled in the gimbal bearings28to allow the enclosure30and flywheel assembly40to rotate or precess about the gimbal axis G in the fore and aft directions.

The basic elements of enclosure30are the same in the various embodiments described herein but vary in some details depending on the design of the bearing cooling system100. The enclosure30is generally spherical in form and comprises two main housing sections34and two cover plates36. The two main housing sections34join along a plane that typically bisects the spherical enclosure30. The cover plates36join the main housing sections34along respective planes closer to the “poles” of the spherical enclosure30. All joints in the enclosure are sealed to maintain a below-ambient pressure within the enclosure30to reduce aerodynamic drag on the flywheel assembly40. Typical below-ambient pressures should be in the range of 1-40 torr (133-5333 Pa, 0.02-0.77 psi). Although the construction of the enclosure is generally the same in the embodiments herein described, the details of the housing sections34and cover plates36vary as described more fully below depending on the design of the bearing cooling system used.

Referring toFIG.3, the flywheel assembly40comprises a flywheel42and flywheel shaft44that is mounted for rotation inside the enclosure30of the gimbal20so that the axis of rotation F of the flywheel assembly40is perpendicular to the gimbal axis G. Thus, when the boat5is level such that gimbal axis G is horizontal, the axis of rotation F of the flywheel shaft44will be in the vertical direction, typically perpendicular to the deck of the boat. The flywheel42and shaft44may be formed as a unitary piece, or may comprise two separate components. In one exemplary embodiment, the diameter and the flywheel42is approximately 20.5 inches and the flywheel assembly40has a total weight of about 614 lbs. The flywheel assembly40has a moment of inertia of about 32,273 lbm in2. When rotated at a rate of 9000 rpm, the angular momentum of the flywheel assembly40is about 211,225 lbm ft2/s.

The flywheel assembly40is supported by upper and lower bearing assemblies inside the enclosure30. Each bearing assembly comprises a bearing50mounted within a bearing block58. Each bearing50comprises an inner race52that is affixed to and rotates with the flywheel shaft44, an outer race54that is mounted inside the bearing block58, and one or more ball bearings56disposed between the inner and outer races52,54. The bearing blocks58are secured to the interior of the enclosure30. Seals (not shown) are disposed on the top and bottom of the bearings50to contain lubricant in the bearings50.

The motor60rotates the flywheel assembly40at a high rate of speed (e.g., 9000 rpm). The motor60includes a rotor62that connects to the flywheel shaft44and a stator64that this secured to the enclosure30by any suitable mounting system. Although the motor60is shown mounted inside the enclosure30, it is also possible to mount the motor60on the exterior of the enclosure30. In one embodiment, the motor60operates on 230 Volt single phase AC power (or could be three-phase AC power, or AC or DC battery power, such as from a lithium ion battery pack) and is able to accelerate a flywheel assembly with a moment of inertia of about 32,273 lbm in2 from rest to a rotational speed of 9000 rpm preferably in about 30 minutes or less for an average acceleration of about 5 rpm/s, and more preferably in about 20 minutes or less for an average acceleration of about 7.75 rpm/s, and even more preferably in about 10 minutes or less for an average acceleration of about 15 rpm/s (or 1.57 radians/s2).

The torque control system70, shown inFIG.5, controls the rate of precession of the flywheel assembly40about the gimbal axis G. The rolling motion of a boat5caused by wave action can be characterized by a roll angle and roll rate. The rolling motion causes the flywheel42to precess about the gimbal axis G. Sensors74,76measure the roll angle and roll rate respectively, which are fed to a controller72. The controller72generates control signals to control an active braking system or other torque applying device78that controls the rate of precession of the flywheel assembly40. By controlling the rate of precession, the flywheel assembly40generates a torque in opposition to the rolling motion. This torque is transferred through the gimbal20to the boat5to dampen the roll of the boat5. An example of the active braking system78is described in U.S. Patent Application Publication No. 2020/0137308, entitled “Braking System For Gyroscopic Boat Roll Stabilizer”, which is incorporated herein its entirety by reference.

When the flywheel assembly40rotates at high speed, the bearings50and motor60will generate a substantial amount of heat, which could lead to bearing and/or motor failure. Conventional air and liquid cooling techniques are not suitable for bearings50or other heat generating components contained within a vacuum or significantly below ambient pressure environment. Various embodiments of the bearing cooling system100are disclosed herein allow cooling of bearings50and other heat generating components contained within the enclosure without direct contact of the recirculated oil or liquid coolant with the bearings50or other moving heat generating components, which would result in high frictional losses. In general, heat is transferred by solid and/or liquid conduction to a heat sink that is cooled by oil, glycol, or other liquid coolant. Oil or liquid cooling enables more heat to be dissipated compared to air cooling or gaseous convection and conduction. Reliance on gaseous convection and conduction in existing CMGs imposes limitations on the amount of heat that can be dissipated because the interior of the enclosure30is typically maintained at a below ambient pressure. The limited heat transfer capacity in conventional CMGs imposes limitations on the size of the electric motor that is used, which in turn limits the time to engage and use the conventional CMG. Because the electric motor in conventional CMGs is undersized to avoid heat generation, conventional CMGs require significant time to accelerate the flywheel assembly40to a speed that provides the desired counter-torque and roll stabilization. Providing more efficient cooling of the bearings50and/or motor60as herein described enables use of a larger and more powerful motor60and faster acceleration of the flywheel assembly40so that the benefits of using the CMG10can be obtained in significantly shorter time periods.

FIG.6is a schematic diagram of a cooling circuit80for circulating the liquid coolant. A fluid reservoir82contains the liquid coolant which is circulated in a “closed” circuit by a fluid pump84. The fluid reservoir82may include a heat exchanger83to cool the liquid coolant in the fluid reservoir82. After leaving the fluid reservoir82, the liquid coolant passes through the heat exchanger86where it adsorbs and carries away heat generated by the bearings50, as described more fully below. In some embodiments, heat is transferred from the flywheel shaft44to a heat sink and then by solid and liquid conduction to the heat exchanger86. In other embodiments, heat is transferred from the flywheel shaft44to the liquid coolant which is circulated through a cavity46in the flywheel shaft44. Accordingly, the heat transfer to the liquid coolant occurs within the cavity46of the flywheel shaft44so the heat exchanger86is not required. In some embodiments, a scavenging circuit88is provided to collect liquid coolant that may seep into the interior of the enclosure30and return the liquid coolant to the fluid reservoir82.

FIG.4illustrates one embodiment of a bearing cooling system100using a heat sink to dissipate heat generated by the bearings50and/or motor60. While the present discussion of the bearing cooling system100is generally in the context of cooling the upper bearing50, it should be noted that the upper and lower bearings50may be cooled in similar ways, if desired. For the upper bearing50, the upper portion of the flywheel shaft44is secured within bearing50that is, in turn, secured within the enclosure30. Each bearing50includes an outer race54, one or more ball bearings56, and an inner race52that engages the flywheel shaft44and rotates therewith. The flywheel shaft44includes a cavity46at each end thereof. The cavity46in each end of the flywheel shaft44is open at one end and includes a side wall and a bottom wall.

A heat transfer member102that functions as a heat sink is suspended in the cavity46. The heat transfer member102does not directly engage the side or bottom walls of the cavity46. Rather, the outer surface of the heat transfer member102is spaced from the side and bottom walls of the cavity46. In one embodiment, the spacing between the heat transfer member102and the walls of the cavity46is approximately 0.035″-0.095″. Various materials can be used for the heat transfer member102discussed herein. Preferably, copper, aluminum, or alloys thereof are used because of their relatively high thermal conductivity.

A heat transfer medium is contained in the gap between the heat transfer member102and the walls of the cavity46. As one example, the heat transfer medium comprises a low vapor pressure fluid that is suitable for the low pressure environment in the enclosure30. A low vapor pressure fluid is a liquid, such as oil, that has a relatively low boiling point compared to water and is suitable for employment in a vacuum environment. For example, aerospace lubricants, such as perfluoropolyether (PFPE) lubricants, designed for vacuum environments can be used as the heat exchange medium. The low vapor pressure fluid enables transfer of heat from the flywheel shaft44to the heat transfer member102by liquid conduction and liquid convection. A labyrinth seal110extends around the heat transfer member102and effectively seals the cavity46such that the heat transfer medium is maintained within the cavity46. The labyrinth seal110is preferably fixed to the heat transfer member102, which means that the flywheel shaft44rotates around the labyrinth seal110.

As seen inFIG.4, heat transfer member102projects from cavity46, through an opening in a cover plate36forming a part of the enclosure30, and into a heat exchanger86. Seals108located in corresponding grooves in the cover plate36maintain vacuum within the enclosure30. The heat exchanger86is mounted to the exterior surface of the cover plate36. The heat exchanger86comprises a housing106and a heat exchange plate104confined within the housing106. The heat transfer member102is secured by a fastener103to the heat exchange plate104so that the heat transfer member102is effectively suspended in the cavity46formed in the flywheel shaft44. More particularly, the heat exchange plate104includes a recess in the bottom surface thereof that receives the end of the heat transfer member102. The surface contact between the end of the heat transfer member102and the heat exchange plate104facilitates the efficient transfer of heat by solid conduction from the heat transfer member102to the heat exchange plate104.

A liquid coolant, such as a glycol coolant, is circulated through the heat exchanger86to absorb and carry heat away from the heat exchange plate104as shown inFIG.5. The upper surface of the heat exchange plate104can be provided with fluid channels and/or cooling fins to increase surface area of the heat exchange plate104and to facilitate heat transfer from the heat exchange plate104to the liquid coolant.

Heat is generated in the inner and outer races of the bearing assemblies50due to the high side loads generated from the CMG's torque as the enclosure30rotates about the gimbal axis G. The outer race54has a continuous heat conductive path through the enclosure30which permits the heat associated with the outer race54to be conveyed into the atmosphere. The inner race52requires a heat sink path through parts of the enclosure30. In this embodiment, heat from the inner race52of the bearing assembly50is transferred by solid conduction to the flywheel shaft44. The heat is then transferred by liquid conduction from the flywheel shaft44to the heat transfer member102, and by solid conduction through the heat transfer member102to the heat exchange plate104that continuously conveys the heat into surrounding liquid coolant. In some embodiments, the heat exchanger86could employ air or gas cooling rather than liquid cooling.

Alternative approaches to bearing cooling systems100for cooling the bearing assemblies50may be employed, including the use of heat transfer members102that are internally cooled via circulation of cooling fluid internally through the heat transfer member102. The various bearing cooling systems100may be used alone, or in combination with the motor cooling systems (e.g., motor cooling circuit220) described herein. Just by way of example, the CMG10may include the motor cooling system(s) ofFIGS.7-13, and the bearing cooling system(s) described above, or just the bearing cooling system(s) described above, or just the motor cooling system(s) ofFIGS.7-13.

FIGS.7-11show a motor cooling system for cooling the motor60when the motor60is mounted inside the enclosure30. In general, the motor cooling system includes a motor cooling circuit220that includes a closed fluid pathway222. The fluid pathway222extends through a fluid channel224disposed in close proximity to the motor60. Cooling fluid90flows through the fluid pathway222(including through the fluid channel224), and absorbs heat from the motor60and transfers that heat away from the motor60.

As shown inFIG.7, the enclosure30includes a boss200that is integrally formed with enclosure30, and is configured to receive the motor60for mounting the motor60in the enclosure30. The boss200extends inwardly into the interior of the enclosure30, and toward the flywheel42, generally parallel to the flywheel axis F. The boss200includes a chamber202generally aligned with the flywheel axis F, and advantageously peripherally surrounds the flywheel axis F. The chamber202is sized and shaped to receive the motor60. The chamber202is bounded by an inner face204on the boss200which faces the motor60. The stator64of the motor60advantageously abuts the inner face204or is at least very closely spaced therefrom. A plurality of seals210are advantageously abutting the stator64and the inner face204, so that a fluid-tight seal is maintained. One or more retention plates212may be used to secure the motor in the boss200.

The motor cooling circuit220is schematically shown inFIG.8. The motor cooling circuit220includes the fluid pathway222, which in turn includes the fluid channel224. The fluid channel224is jointly defined by the motor60and the enclosure30, meaning for a given section of the fluid channel224, the motor60forms a part of the channel wall for that section, and the enclosure30forms another part of the channel wall of that section that overlaps (along the path of the channel) with the part of the channel wall formed by the motor60. InFIG.8, the fluid channel224is formed at the interface between the stator64and the inner face204of boss200of enclosure30. The inner face204includes one or more grooves206. SeeFIGS.7,9-11. Such groove(s)206are conceptually closed off, to form the fluid channel224, by the outer face of stator64. Note that seals210may be used to trap any cooling fluid90that escapes fluid channel224. Alternatively and/or additionally, the stator64may include one or more grooves206(not shown) on its outer face that face the inner face204of the boss200. Such stator groove(s)206are conceptually closed off, to form the fluid channel224, by the inner face204of the boss200. Note that the groove(s)206may be oriented perpendicular to the flywheel axis F, or may advantageously spiral around the flywheel axis F, such as by being helical or other spiral shape. Alternatively, the groove(s) may wind around the interface of the boss200and the stator64in any suitable fashion, such as in a sinusoidal shape, or a zig-zag shape, whether regular or irregular. Advantageously, the fluid pathway222peripherally surrounds the flywheel axis F, such as by circumnavigating motor. The flow direction in the fluid pathway222may be in any suitable direction, such as clockwise or counter-clockwise, or both as appropriate. When the fluid channel224is spiral (e.g., helical), the cooling fluid advantageously flows through the fluid channel224spirally (e.g., helically) either outward away from the flywheel42, or inward toward flywheel42.

As shown inFIG.8, the motor cooling circuit220optionally also includes a reservoir82for the cooling fluid90flowing through the motor cooling circuit220, and a fluid pump84operative to recirculate the cooling fluid90through motor cooling circuit220. Thus, the fluid pathway222for the cooling fluid90optionally extends through the fluid reservoir82, the fluid channel224, and the fluid pump84. Thus, the pump84is operatively connected to the fluid channel224and configured to recirculate the cooling fluid90through the fluid channel224to remove heat from the motor60. The presence of the motor cooling circuit220in the gyroscopic roll stabilizer10allows the gyroscopic roll stabilizer10to be configured to transfer heat away from the motor60to the cooling fluid90. Note that a heat exchanger, such as heat exchanger83, is operatively connected to closed fluid pathway222and configured to remove heat from the cooling fluid90to ambient after the cooling fluid90has passed through the fluid channel224.

In some respects, the fluid pathway222also includes an inlet port226and an outlet port228, such as on the enclosure30. The inlet port226is operatively disposed between the pump84and the fluid channel224, and operative to allow passage of the cooling fluid90into the enclosure30toward the fluid channel224. The outlet port228is operatively disposed between the fluid channel224and the heat exchanger83, and operative to allow passage of the cooling fluid90out of the enclosure30toward the heat exchanger83.

For theFIG.7arrangement, the heat flow for dissipating heat from the motor60is from the stator64to the cooling fluid90in the fluid channel224, then to external to the CMG10via the heat exchanger83. Note that the heat is transferred by conduction and convection to the cooling fluid90.

In an alternative design shown inFIG.13, the fluid channel224is not jointly defined by the motor60and the enclosure30, but is instead formed in a separate element that is disposed between the stator64and the enclosure30. For example, a separate cooling ring240may surround (e.g., be disposed immediately outside of) the stator64, between the stator64and the enclosure30in a lateral direction as shown inFIG.13. The cooling ring240should be fluid-tight, and may have one or more internal passages that define the fluid channel224. There may be one or more fins244internal to the cooling ring240that form the internal passages. The internal passages may be substantially circular, or may advantageously spiral around the flywheel axis F, such as by following a helical path. The fluid channel224may be connected, via suitable connections and seals, with the inlet port226and outlet port228. Cooling fluid90may circulate through the fluid channel224in the cooling ring240to extract heat from the motor60and move that heat away from the motor60. Care should be taken to properly secure the cooling ring240inside the enclosure30, such as by suitable screws, to avoid possible damage to the rapidly spinning flywheel42. Because use of such a cooling ring240results in the cooling fluid90being separated from the stator64by the wall of the cooling ring240, this approach is believed to be functional, but less efficient than other approaches disclosed herein.

In some aspects, the CMG10includes both the bearing cooling system100and the motor cooling system (e.g., motor cooling circuit220) described herein, and the two systems may optionally use a common reservoir82, pump84, and heat exchanger83so as to share the cooling fluid90.

A method (300) of operating a gyroscopic roll stabilizer10that includes a motor cooling circuit220as discussed above is shown inFIG.12. The method (300) includes maintaining (310) a below ambient pressure within an enclosure30surrounding a flywheel assembly40, with the flywheel assembly40including a flywheel42and a flywheel shaft44. The method also includes spinning (320) the flywheel assembly40about the flywheel axis F via motor60mounted internal to the enclosure30. In addition, the method includes dissipating (340) heat from the motor60by transferring the heat by conduction and convection to a cooling fluid90flowing through a fluid channel224jointly defined by the motor60and the enclosure30. During the dissipating, the cooling fluid90optionally flows through the fluid channel224helically in an outward direction away from the flywheel42. Further, the method includes cooling (360) the cooling fluid90by removing heat from the cooling fluid90external to the portion of the enclosure30maintained at the below-ambient pressure. In addition, the method includes recirculating (370) the cooling fluid90through closed fluid pathway222that includes the fluid channel224. Note that the recirculating (370) optionally includes routing (372) the cooling fluid from the fluid channel224to reservoir82, and pumping (374) the cooling fluid90from the reservoir82to the fluid channel224, and the cooling (360) the cooling fluid90comprises cooling the cooling fluid90via a heat exchanger83disposed external to the enclosure30. Note that the various steps of method may be carried out in any suitable order, including in whole or in part in parallel. For example, at least the maintaining (310), the spinning (320), and the dissipating (340) are advantageously carried out simultaneously.

The bearing cooling systems100and/or motor cooling systems as herein described allow much greater heat dissipation compared to current technology, which enables use of a larger motor60, and advantageously lower operating temperature even with the larger motor The larger motor and lower operating temperature enable rapid spin up and spin down of the flywheel assembly40, and a significantly lower time to engage as discussed further below.

In use, the gimbal20is normally locked during spin up, i.e., while the flywheel assembly is being accelerated, to prevent precession of the flywheel42until a predetermined rotational speed is achieved. The CMG10can be locked to prevent rotation of the enclosure30by the active braking system78. When the CMG10is unlocked, precession of the flywheel42will place side loads on the bearings50. The bearing friction from the side loading of the bearings generates heat. In addition, the bearing friction from the side loading also adds drag, which must be overcome by the motor60in order to continue acceleration of the flywheel's rotation. Thus, the frictional losses of side loading the bearings50have two impacts: generating heat and increasing the load on the motor60.

Conceptually, there are two main sources of heat in the CMG: heat generated by the motor inside the enclosure30and heat generated by bearing friction. A large percentage of the heat budget is needed to dissipate heat from the bearings in order to prevent bearing failure. The remaining portion of the heat budget, after accounting for bearing cooling, determines the size of the motor that can be used inside the enclosure.

One conventional approach to bearing cooling for a CMG maintained in a vacuum environment uses interwoven fins and relies primarily on gaseous conduction between the interwoven fins to dissipate the heat. See, e.g., U.S. Pat. Nos. 7,546,782 and 8,117,930. The reliance on gaseous conduction as the primary mode of heat transfer severely limits the amount of heat that can be dissipated since gaseous conduction is less efficient than liquid or solid conduction. The heat transfer capacity of the interwoven fins is also limited by the surface area of the interwoven fins. Less surface area means less heat transfer capacity. As the enclosure of CMGs shrink in size, there is less space available for the interwoven fins. These factors place severe limits on the heat budget for conventional CMGs, which in turn limits motor size. Thus, conventional CMGs using interwoven fins for heat dissipation are limited in the size of their motor. The limitation on the motor size results in a poor acceleration profile for the flywheel in conventional CMGs, which in turn means a long waiting period before the conventional CMG can be used. Further, if the gimbal20in a conventional CMG is unlocked too early, the frictional losses will prevent the smaller motors used therein from accelerating the flywheel assembly40, or will greatly diminish the acceleration of the flywheel assembly40resulting in a much longer spin up period. In conventional CMGs, the gimbal20is typically locked until the flywheel assembly40reaches 75-80% or more of the nominal operating rotational speed. Conventional CMGs currently on the market may take thirty minutes or longer to reach the minimum operating speed at which the flywheel can be allowed to precess. However, many boat trips, particularly on smaller boats, are thirty minutes or less. This means the waiting period before the time to engage (unlock the flywheel assembly for precessing) is reached is longer than many boat trips for conventional CMGs.

Further, the size of the motor in conventional CMGs places a floor on the minimum operating speed at which the conventional CMG can be engaged (i.e., unlocked). The bearing friction from the side loading of the bearings when the conventional is engaged dramatically decreases the already slow acceleration rate of conventional CMGs. In some cases, the frictional load may be too much for the motor to overcome so that the further acceleration of the flywheel assembly becomes impossible and the normal operating speed cannot be reached.

Another consideration is that the power to the motor is at its maximum when the flywheel is being accelerated, and is reduced when the flywheel reaches its normal operating speed. Thus, more heat is generated by the motor when it is accelerating. The additional heat generated by the motor also limits the time to engage because the additional heat from the motor may exceed the design limits of the bearing cooling system in conventional CMGs.

The bearing cooling systems100and/or motor cooling circuits220as described herein enable more efficient heat transfer, which enables a far greater heat transfer capacity and an increased heat budget. The increased heat budget means that larger and more powerful motors60that generate more heat can be used without causing bearing failure. With a larger and more powerful motor60, the improved CMG10of the present disclosure is able to achieve greater acceleration of the flywheel assembly40and lower time to engage than a conventional CMG. In addition to the higher rates of acceleration, which naturally lead to lower times to engage assuming the same minimum operating speed, a larger motor60enables the flywheel assembly40to be engaged at a lower operating speed (e.g., a lower percentage of nominal operating speed), which further reduces the time to engage, because the larger motor60is able to overcome the additional friction from the loading of the bearings50. In some embodiments, the motor60is configured to enable the CMG10to be unlocked in under twenty minutes, and preferably in under ten minutes and more preferably in under five minutes. By combining higher acceleration with lower operating speeds at the time of engagement, a time to engage can be reduced to a few minutes. For example, a motor60rated at 10,000 to 15,000 watts could potentially achieve a time to engage rates in the order of a few minutes.

As one example, the flywheel assembly40described above with a moment of inertia equal to about 32,273 lbm in2 can be accelerated from rest to 9000 rpm in about 30 minutes or less, which equates to an average acceleration of about 5 rpm/s or more, and preferably in about 20 minutes or less, which equates to an average acceleration of about 7.5 rpm/s or more, and even more preferably in about 10 minutes or less, which equates to an average acceleration of about 15 rpm/s or more. Additionally, the time to engage for the CMG10as herein described is much shorter because the motor60is powerful enough to overcome the frictional losses when the gimbal20is unlocked. For example, in a flywheel assembly40with a moment of inertia equal to about 32,273 lbm in2, the time to engage (assuming 75% of operating speed) is less than about 20 minutes, and more preferably less than about 10 minutes, and even more preferably less than 5 minutes. The rapid spin up and shorter time to engage enables beneficial use of the CMG10even for short trip times, which makes up a majority of boating trips. Thus, the rapid spin-up enables the CMG10to be used on a greater number of boating occasions.

Similarly, the spin down is in the order of minutes rather than hours compared to the current technology. Cooling systems with interleaved fins that rely on gaseous conduction and convection operate at a high temperature (e.g., 400° F.) and dissipate heat relatively slowly. In such systems, if the flywheel is stopped too fast, the heat may cause components to warp, which in turn may cause bearing life to be shortened. The bearing cooling systems100and/or motor cooling circuits220as herein described enables the CMG10to operate at a lower temperature (e.g., 200° F.) and be more efficient at removing heat. Consequently, the spin down time is cut from 3-4 hours to a few minutes (such as five to twenty minutes). This reduced running temperature as well as the rapid cooldown period prevents the well balanced rotating components from warping and thus the spin down time can be reduced. The short spin down time also eliminates the annoying hum and vibration from the spinning flywheel sooner and allows enjoyment of the peace and serenity after returning from a day of boating to begin sooner.

The bearing cooling systems100and/or motor cooling circuits220as herein described enable faster acceleration rates for the flywheel assembly40, which translates to a lower time to engage the CMG10. The lower time to engage in turn will enable beneficial use of the CMG10even on trips of short duration. The bearing cooling systems and/or motor cooling circuits220also enable fast spin down times so that the quiet enjoyment of the boat is not disturbed by the noise emanating from the flywheel assembly40as it winds down.

The present disclosure may, of course, be carried out in other ways than those specifically set forth herein without departing from essential characteristics of the disclosure. The present embodiments are to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

The disclosure of U.S. Provisional Patent Application No. 63/070,494, filed 26 Aug. 2020 and entitled “Gyroscopic Boat Roll Stabilizer with Motor Cooling,” is incorporated herein by reference in its entirety.