Compound shaft with flexible disk coupling

Claim 2

A compound shaft comprising: a first stiff shaft; a flexible disk shaft having a flexible disk, a quill shaft, and a tie rod, said quill shaft disposed between and connecting said flexible disk and said tie rod, said flexible disk of said flexible disk shaft interference fit with said first stiff shaft; and a second stiff shaft removably disposed on the tie rod of said flexible disk shaft.

Claim 3

The compound shaft of claim 1 wherein said flexible disk of said flexible disk shaft has soft trunnion spring rate characteristics and stiff radial translation spring rate characteristics normal to the compound shaft axis.

Claim 4

The compound shaft of claim 2 wherein said flexible disk of said flexible disk shaft has a thickness which decreases radially outwardly from the centerline of said flexible disk.

Claim 5

The compound shaft of claim 2 wherein said flexible disk of said flexible disk shaft includes a plurality of spaced holes.

Claim 6

The compound shaft of claim 4 wherein said flexible disk of said flexible disk shaft includes a plurality of spaced spiral slots.

Claim 7

The compound shaft of claim 5 wherein said spaced spiral slots extend radially outwardly at their base.

Claim 8

The compound shaft of claim 5 wherein said spaced spiral slots include an enlarged flared opening at their radially outward end.

Claim 9

The compound shaft of claim 5 wherein said spaced spiral slots extend radially outwardly at their base and include an enlarged flared opening at their radially outward end.

Claim 10

The compound shaft of claim 1 wherein said flexible disk of said flexible disk shaft is generally cup-shaped and interference fits over one end of said first stiff shaft.

Claim 11

The compound shaft of claim 9 wherein said one end of said first stiff shaft has an outer diameter slightly reduced from the outer diameter of the remainder of said first stiff shaft to receive the generally cup-shaped flexible disk of said flexible disk shaft over the slightly reduced outer diameter end of said first stiff shaft.

Claim 12

The compound shaft of claim 1 wherein said compound shaft is for a permanent magnet turbogenerator and said first stiff shaft is a cylindrical sleeve enclosing a permanent magnet of said permanent magnet turbogenerator and said second stiff shaft is a power head shaft of said turbogenerator mounted in compression on said tie bar of said flexible disk shaft.

Claim 13

The compound shaft of claim 11 wherein an inertial ring of increased mass is provided axially near a node of the first flexural critical of said compound shaft.

Claim 14

The compound shaft of claim 12 wherein said inertial ring of increased mass is provided radially outwardly on the back plane of said turbine wheel facing said compressor wheel.

Claim 15

The compound shaft of claim 11 wherein said cylindrical sleeve includes an internal stiffening sleeve inside said end of said cylindrical sleeve operably connected to said flexible disk shaft.

Claim 16

The compound shaft of claim 11 wherein said quill shaft of said flexible disk shaft is tapered from said second stiff shaft to said flexible disk.

Claim 17

The compound shaft of claim 1 wherein said flexible disk of said flexible disk shaft is interference fit into said end of said first stiff shaft.

Claim 18

The compound shaft of claim 16 wherein said flexible disk of said flexible disk shaft is interference fit shallow into said first stiff shaft.

Claim 19

The compound shaft of claim 16 wherein said flexible disk of said flexible disk shaft is interference fit deep into said first stiff shaft.

Claim 20

The compound shaft of claim 16 wherein said flexible disk of said flexible disk shaft has a thickness which decreases radially outwardly from the centerline of said flexible disk.

Claim 21

A compound shaft comprising: a first stiff shaft; a second stiff shaft; and a flexible disk shaft having a generally cup-shaped flexible disk, a tie rod, and a tapered quill shaft connecting said generally cup-shaped flexible disk and said tie rod, said generally cup-shaped flexible disk of said flexible disk shaft interference fit over one end of said first stiff shaft, and said tie rod removably mounting said second stiff shaft.

Claim 22

A compound shaft comprising: a first stiff shaft; a second stiff shaft; and a flexible disk shaft having a generally cup-shaped flexible disk, a tie rod, and a tapered quill shaft connecting said generally cup-shaped flexible disk and said tie rod, said generally cup-shaped flexible disk of said flexible disk shaft interference fit over one end of said first stiff shaft, and said tie rod removably mounting said second stiff shaft.

Claim 23

The compound shaft of claim 20 wherein said first stiff shaft is a cylindrical sleeve having an internal stiffening sleeve inside said one end of said first stiff shaft.

Claim 24

A compound shaft comprising: a first shaft having a hollow sleeve at one end thereof; a second shaft; and a flexible disk shaft having a flexible disk, a tapered quill shaft, and a tie rod, said quill shaft disposed between and connecting said flexible disk and said tie rod, said flexible disk of said flexible disk shaft interference fit into the hollow sleeve end of said first stiff shaft and said tie rod removably mounting said second stiff shaft.

Claim 25

A compound shaft comprising: a first shaft having a hollow sleeve at one end thereof; a second shaft; and a flexible disk shaft having a flexible disk, a tapered quill shaft, and a tie rod, said quill shaft disposed between and connecting said flexible disk and said tie rod, said flexible disk of said flexible disk shaft interference fit into the hollow sleeve end of said first stiff shaft and said tie rod removably mounting said second stiff shaft.

Claim 26

The compound shaft of claim 22 wherein said flexible disk of said flexible disk shaft is interference fit shallow into said sleeve of said first stiff shaft.

Claim 27

The compound shaft of claim 22 wherein said flexible disk of said flexible disk shaft is interference fit deep into said sleeve of said first stiff shaft.

Claim 28

The compound shaft of claim 22 wherein said first stiff shaft is a cylindrical sleeve having an internal stiffening sleeve inside said one end of said first stiff shaft.

Claim 29

A compound shaft for a permanent magnet turbogenerator, said compound shaft comprising: a flexible disk shaft including a generally cup-shaped flexible disk member, a tie rod, and a tapered quill shaft connecting said generally cup-shaped flexible disk member and said tie rod, a flange at the tapered quill shaft end of said tie rod, and a threaded nut at the other end of said tie rod; and said permanent magnet turbogenerator having a permanent magnet shaft including a permanent magnet disposed within a permanent magnet sleeve rotatably supported by a pair of spaced compliant foil hydrodynamic fluid film journal bearings within a permanent magnet stator, and a power head shaft including a compressor wheel, a bearing rotor, and a turbine wheel rotatably supported by a single compliant foil hydrodynamic fluid film journal bearing and a bi-directional compliant foil hydrodynamic fluid film thrust bearing within a compressor and turbine housing, said generally cup-shaped flexible disk member of said flexible disk shaft interference fit over one end of said permanent magnet sleeve and said power head shaft removably disposed on the tie rod of said flexible disk shaft and held in compression between said flexible disk shaft flange and said threaded nut.

Claim 30

A compound shaft for a permanent magnet turbogenerator, said compound shaft comprising: a flexible disk shaft including a generally cup-shaped flexible disk member, a tie rod, and a tapered quill shaft connecting said generally cup-shaped flexible disk member and said tie rod, a flange at the tapered quill shaft end of said tie rod, and a threaded nut at the other end of said tie rod; and said permanent magnet turbogenerator having a permanent magnet shaft including a permanent magnet disposed within a permanent magnet sleeve rotatably supported by a pair of spaced compliant foil hydrodynamic fluid film journal bearings within a permanent magnet stator, and a power head shaft including a compressor wheel, a bearing rotor, and a turbine wheel rotatably supported by a single compliant foil hydrodynamic fluid film journal bearing and a bi-directional compliant foil hydrodynamic fluid film thrust bearing within a compressor and turbine housing, said generally cup-shaped flexible disk member of said flexible disk shaft interference fit over one end of said permanent magnet sleeve and said power head shaft removably disposed on the tie rod of said flexible disk shaft and held in compression between said flexible disk shaft flange and said threaded nut.

Claim 31

The compound shaft of claim 26 wherein said turbine wheel includes an inertial ring of increased mass on the back plane thereof facing said compressor wheel.

Claim 32

The compound shaft of claim 26 wherein said permanent magnet sleeve includes an internal stiffening sleeve inside one end of said permanent magnet sleeve.

Claim 33

A compound shaft for a permanent magnet turbogenerator, said compound shaft comprising: a flexible disk shaft including a flexible disk member, a tie rod, and a tapered quill shaft connecting said flexible disk member and said tie rod, a flange at the tapered quill shaft end of said tie rod, and a threaded nut at the other end of said tie rod; and said permanent magnet turbogenerator including a permanent magnet shaft having a permanent magnet disposed within a permanent magnet sleeve rotatably supported by a pair of spaced compliant foil hydrodynamic fluid film journal bearings within a permanent magnet stator, and a power head shaft having a compressor wheel, a bearing rotor, and a turbine wheel rotatably supported by a single compliant foil hydrodynamic fluid film journal bearing and a bi-directional compliant foil hydrodynamic fluid film thrust bearing within a turbine and compressor housing, said flexible disk member of said flexible disk shaft interference fit into one end of said permanent magnet sleeve and said power head shaft removably disposed on the tie rod of said flexible disk shaft and held in compression between said flexible disk shaft flange and said threaded nut.

Claim 34

A compound shaft for a permanent magnet turbogenerator, said compound shaft comprising: a flexible disk shaft including a flexible disk member, a tie rod, and a tapered quill shaft connecting said flexible disk member and said tie rod, a flange at the tapered quill shaft end of said tie rod, and a threaded nut at the other end of said tie rod; and said permanent magnet turbogenerator including a permanent magnet shaft having a permanent magnet disposed within a permanent magnet sleeve rotatably supported by a pair of spaced compliant foil hydrodynamic fluid film journal bearings within a permanent magnet stator, and a power head shaft having a compressor wheel, a bearing rotor, and a turbine wheel rotatably supported by a single compliant foil hydrodynamic fluid film journal bearing and a bi-directional compliant foil hydrodynamic fluid film thrust bearing within a turbine and compressor housing, said flexible disk member of said flexible disk shaft interference fit into one end of said permanent magnet sleeve and said power head shaft removably disposed on the tie rod of said flexible disk shaft and held in compression between said flexible disk shaft flange and said threaded nut.

Claim 35

The compound shaft of claim 29 wherein said turbine wheel includes inertial ring of increased mass on the back plane thereof facing said compressor wheel.

Claim 36

The compound shaft of claim 29 wherein said permanent magnet sleeve includes an internal stiffening sleeve inside said one end of said permanent magnet sleeve.

Claim 37

The compound shaft of claim 29 wherein said flexible disk member is generally cup-shaped with the open end thereof facing toward said permanent magnet of said permanent magnet sleeve.

Claim 38

The compound shaft of claim 29 wherein said flexible disk member is generally cup-shaped with the open end thereof facing away from said permanent magnet of said permanent magnet sleeve.

Claim 39

A compound shaft for a permanent magnet turbogenerator, said compound shaft comprising: a flexible disk shaft including a generally cup-shaped flexible disk member, a tie rod, and a short tapered quill shaft connecting said generally cup-shaped flexible disk and said tie rod, a flange at the short tapered quill shaft end of said tie rod, and a threaded nut at the other end of said tie rod, said generally cup-shaped flexible disk member having a thickness which decreases radially outwardly from the centerline of said flexible disk member; and said permanent magnet turbogenerator including a permanent magnet shaft having a permanent magnet disposed within a permanent magnet sleeve rotatably supported by a pair of spaced compliant foil hydrodynamic fluid film journal bearings within a permanent magnet stator, and said permanent magnet sleeve including an internal stiffening sleeve inside one end thereof, said permanent magnet turbogenerator also including a power head shaft having a compressor wheel, a bearing rotor, and a turbine wheel rotatably supported by a single compliant foil hydrodynamic fluid film journal bearing and a bi-directional compliant foil hydrodynamic fluid film thrust bearing within a compressor and turbine housing, said generally cup-shaped flexible disk member of said flexible disk shaft interference fit over the end of said permanent magnet sleeve including the internal stiffening sleeve therein and said power head shaft removably disposed on the tie rod of said flexible disk shaft and held in compression between said flexible disk shaft flange and said threaded nut, said turbine wheel including an inertia ring of increased mass on the back plane thereof facing said compressor wheel.

Claim 40

A compound shaft for a permanent magnet turbogenerator, said compound shaft comprising: a flexible disk shaft including a generally cup-shaped flexible disk member, a tie rod, and a short tapered quill shaft connecting said generally cup-shaped flexible disk and said tie rod, a flange at the short tapered quill shaft end of said tie rod, and a threaded nut at the other end of said tie rod, said generally cup-shaped flexible disk member having a thickness which decreases radially outwardly from the centerline of said flexible disk member; and said permanent magnet turbogenerator including a permanent magnet shaft having a permanent magnet disposed within a permanent magnet sleeve rotatably supported by a pair of spaced compliant foil hydrodynamic fluid film journal bearings within a permanent magnet stator, and said permanent magnet sleeve including an internal stiffening sleeve inside one end thereof, said permanent magnet turbogenerator also including a power head shaft having a compressor wheel, a bearing rotor, and a turbine wheel rotatably supported by a single compliant foil hydrodynamic fluid film journal bearing and a bi-directional compliant foil hydrodynamic fluid film thrust bearing within a compressor and turbine housing, said generally cup-shaped flexible disk member of said flexible disk shaft interference fit over the end of said permanent magnet sleeve including the internal stiffening sleeve therein and said power head shaft removably disposed on the tie rod of said flexible disk shaft and held in compression between said flexible disk shaft flange and said threaded nut, said turbine wheel including an inertia ring of increased mass on the back plane thereof facing said compressor wheel.

Claim 41

A compound shaft for a permanent magnet turbogenerator, said compound shaft comprising: a flexible disk shaft including a generally cup-shaped flexible disk member, a tie rod, and a tapered quill shaft connecting said generally cup-shaped flexible disk member and said tie rod, a flange at the tapered quill shaft end of said tie rod, and a threaded nut at the other end of said tie rod; and said permanent magnet turbogenerator having a permanent magnet rotor rotatably supported by a pair of spaced compliant foil hydrodynamic fluid film journal bearings within a permanent magnet stator, said permanent magnet rotor having a permanent magnet disposed within a permanent magnet sleeve with the outer surface of said permanent magnet sleeve serving as both the outer surface of the permanent magnet rotor and as the rotating element supported by said pair of spaced compliant foil hydrodynamic fluid film journal bearings within said permanent magnet stator, said permanent magnet turbogenerator also having a power head shaft including a compressor wheel, a bearing rotor, and a turbine wheel rotatably supported by a single compliant foil hydrodynamic fluid film journal bearing and a bi-directional compliant foil hydrodynamic fluid film thrust bearing within a compressor and turbine housing, said generally cup-shaped flexible disk member of said flexible disk shaft interference fit over one end of said permanent magnet sleeve and said power head shaft removably disposed on the tie rod of said flexible disk shaft and held in compression between said flexible disk shaft flange and said threaded nut.

Claim 42

A compound shaft for a permanent magnet turbogenerator, said compound shaft comprising: a flexible disk shaft including a generally cup-shaped flexible disk member, a tie rod, and a tapered quill shaft connecting said generally cup-shaped flexible disk member and said tie rod, a flange at the tapered quill shaft end of said tie rod, and a threaded nut at the other end of said tie rod; and said permanent magnet turbogenerator having a permanent magnet rotor rotatably supported by a pair of spaced compliant foil hydrodynamic fluid film journal bearings within a permanent magnet stator, said permanent magnet rotor having a permanent magnet disposed within a permanent magnet sleeve with the outer surface of said permanent magnet sleeve serving as both the outer surface of the permanent magnet rotor and as the rotating element supported by said pair of spaced compliant foil hydrodynamic fluid film journal bearings within said permanent magnet stator, said permanent magnet turbogenerator also having a power head shaft including a compressor wheel, a bearing rotor, and a turbine wheel rotatably supported by a single compliant foil hydrodynamic fluid film journal bearing and a bi-directional compliant foil hydrodynamic fluid film thrust bearing within a compressor and turbine housing, said generally cup-shaped flexible disk member of said flexible disk shaft interference fit over one end of said permanent magnet sleeve and said power head shaft removably disposed on the tie rod of said flexible disk shaft and held in compression between said flexible disk shaft flange and said threaded nut.

Claim 43

A compound shaft for a permanent magnet turbogenerator, said compound shaft comprising: a flexible disk shaft having a flexible disk, a tie rod, and a tapered quill shaft connecting said flexible disk and said tie rod; and said permanent magnet turbogenerator having a permanent magnet rotor including a permanent magnet disposed within a permanent magnet sleeve, and a permanent magnet stator housing including a pair of spaced journal bearings to rotatably support said permanent magnet rotor, said permanent magnet turbogenerator also having a power head shaft including a compressor wheel, a bearing rotor, a turbine wheel, and a compressor and turbine housing including a single journal bearing and a bi-directional thrust bearing to rotatably support said compressor wheel, said bearing rotor, and said turbine wheel, said flexible disk of said flexible disk shaft interference fit with one end of said permanent magnet sleeve and said power head shaft removably mounted on the tie rod of said flexible disk shaft.

Claim 44

A compound shaft for a permanent magnet turbogenerator, said compound shaft comprising: a flexible disk shaft having a flexible disk, a tie rod, and a tapered quill shaft connecting said flexible disk and said tie rod; and said permanent magnet turbogenerator having a permanent magnet rotor including a permanent magnet disposed within a permanent magnet sleeve, and a permanent magnet stator housing including a pair of spaced journal bearings to rotatably support said permanent magnet rotor, said permanent magnet turbogenerator also having a power head shaft including a compressor wheel, a bearing rotor, a turbine wheel, and a compressor and turbine housing including a single journal bearing and a bi-directional thrust bearing to rotatably support said compressor wheel, said bearing rotor, and said turbine wheel, said flexible disk of said flexible disk shaft interference fit with one end of said permanent magnet sleeve and said power head shaft removably mounted on the tie rod of said flexible disk shaft.

Claim 45

The compound shaft of claim 36 wherein said journal bearings are compliant foil hydrodynamic fluid film bearings.

Claim 46

The compound shaft of claim 36 wherein said bi-directional thrust bearing is a compliant foil hydrodynamic fluid film bearing.

Claim 47

A compound shaft comprising: a first stiff shaft; a second stiff shaft; and a flexible disk shaft having a generally cup-shaped flexible disk, a tie rod, and a tapered quill shaft disposed between and connecting said generally cup-shaped flexible disk and said tie rod, said generally cup-shaped flexible disk of said flexible disk shaft interference fit with one end of said first stiff shaft, and said tie rod removably mounting said second stiff shaft.

Claim 48

A compound shaft comprising: a first stiff shaft; a second stiff shaft; and a flexible disk shaft having a generally cup-shaped flexible disk, a tie rod, and a tapered quill shaft disposed between and connecting said generally cup-shaped flexible disk and said tie rod, said generally cup-shaped flexible disk of said flexible disk shaft interference fit with one end of said first stiff shaft, and said tie rod removably mounting said second stiff shaft.

Claim 49

The compound shaft of claim 39 wherein said flexible disk of said flexible disk shaft is interference fit into said end of said first stiff shaft.

Claim 50

The compound shaft of claim 40 wherein said flexible disk of said flexible disk shaft is interference fit shallow into said first stiff shaft.

Claim 51

The compound shaft of claim 40 wherein said flexible disk of said flexible disk shaft is interference fit deep into said first stiff shaft.

Claim 52

A compound shaft for a permanent magnet turbogenerator, said compound shaft comprising: a flexible disk shaft having a generally cup-shaped flexible disk, a tie rod, and a tapered quill shaft connecting said generally cup-shaped flexible disk and said tie rod, a flange at the tapered quill shaft end of said tie rod, and a threaded nut at the other end of said tie rod; and said permanent magnet turbogenerator including a permanent magnet rotor having a permanent magnet disposed within a permanent magnet sleeve rotatably supported by a pair of spaced compliant foil hydrodynamic fluid film journal bearings within a permanent magnet stator, said permanent magnet turbogenerator also having a power head shaft including a compressor wheel, a bearing rotor, and a turbine wheel rotatably supported by a single compliant foil hydrodynamic fluid film journal bearing and a bi-directional compliant foil hydrodynamic fluid film thrust bearing within a compressor and turbine housing, said generally cup-shaped flexible disk of said flexible disk shaft interference fit with one end of said permanent magnet sleeve and said power head shaft removably disposed on the tie rod of said flexible disk shaft and held in compression between said flexible disk shaft flange and said threaded nut.

Claim 53

A compound shaft for a permanent magnet turbogenerator, said compound shaft comprising: a flexible disk shaft having a generally cup-shaped flexible disk, a tie rod, and a tapered quill shaft connecting said generally cup-shaped flexible disk and said tie rod, a flange at the tapered quill shaft end of said tie rod, and a threaded nut at the other end of said tie rod; and said permanent magnet turbogenerator including a permanent magnet rotor having a permanent magnet disposed within a permanent magnet sleeve rotatably supported by a pair of spaced compliant foil hydrodynamic fluid film journal bearings within a permanent magnet stator, said permanent magnet turbogenerator also having a power head shaft including a compressor wheel, a bearing rotor, and a turbine wheel rotatably supported by a single compliant foil hydrodynamic fluid film journal bearing and a bi-directional compliant foil hydrodynamic fluid film thrust bearing within a compressor and turbine housing, said generally cup-shaped flexible disk of said flexible disk shaft interference fit with one end of said permanent magnet sleeve and said power head shaft removably disposed on the tie rod of said flexible disk shaft and held in compression between said flexible disk shaft flange and said threaded nut.

Claim 54

The compound shaft of claim 43 wherein said flexible disk of said flexible disk shaft is interference fit into said end of said permanent magnet sleeve.

Claim 55

The compound shaft of claim 44 wherein said flexible disk of said flexible disk shaft is interference fit shallow into said permanent magnet sleeve.

Claim 56

The compound shaft of claim 44 wherein said flexible disk of said flexible disk shaft is interference fit deep into said permanent magnet sleeve.

Claim 57

A compound shaft for a permanent magnet turbogenerator, said compound shaft comprising: a flexible disk shaft having a generally cup-shaped flexible disk, a tie rod, and a tapered quill shaft connecting said generally cup-shaped flexible disk and said tie rod, a flange at the tapered quill shaft end of said tie rod, and a threaded nut at the other end of said tie rod; and said permanent magnet turbogenerator having a permanent magnet stator including a pair of spaced compliant foil hydrodynamic fluid film journal bearings to rotatably support a permanent magnet rotor including a permanent magnet disposed within a permanent magnet sleeve with the outer surface of said permanent magnet sleeve serving as both the outer surface of the permanent magnet rotor and as the rotating element supported by said pair of spaced compliant foil hydrodynamic fluid film journal bearings, said permanent magnet turbogenerator also having a power head shaft including a compressor wheel, a bearing rotor, a turbine wheel, and a compressor and turbine housing including a single compliant foil hydrodynamic fluid film journal bearing and a bi-directional compliant foil hydrodynamic fluid film thrust bearing to rotatably support said compressor wheel, said bearing rotor, and said turbine wheel, said generally cup-shaped flexible disk of said flexible disk shaft interference fit with one end of said permanent magnet sleeve and said power head shaft removably disposed on the tie rod of said flexible disk shaft and held in compression between said flexible disk shaft flange and said threaded nut.

Claim 58

A compound shaft for a permanent magnet turbogenerator, said compound shaft comprising: a flexible disk shaft having a generally cup-shaped flexible disk, a tie rod, and a tapered quill shaft connecting said generally cup-shaped flexible disk and said tie rod, a flange at the tapered quill shaft end of said tie rod, and a threaded nut at the other end of said tie rod; and said permanent magnet turbogenerator having a permanent magnet stator including a pair of spaced compliant foil hydrodynamic fluid film journal bearings to rotatably support a permanent magnet rotor including a permanent magnet disposed within a permanent magnet sleeve with the outer surface of said permanent magnet sleeve serving as both the outer surface of the permanent magnet rotor and as the rotating element supported by said pair of spaced compliant foil hydrodynamic fluid film journal bearings, said permanent magnet turbogenerator also having a power head shaft including a compressor wheel, a bearing rotor, a turbine wheel, and a compressor and turbine housing including a single compliant foil hydrodynamic fluid film journal bearing and a bi-directional compliant foil hydrodynamic fluid film thrust bearing to rotatably support said compressor wheel, said bearing rotor, and said turbine wheel, said generally cup-shaped flexible disk of said flexible disk shaft interference fit with one end of said permanent magnet sleeve and said power head shaft removably disposed on the tie rod of said flexible disk shaft and held in compression between said flexible disk shaft flange and said threaded nut.

Claim 59

The compound shaft of claim 47 wherein said flexible disk of said flexible disk shaft is interference fit into said end of said permanent magnet sleeve.

Claim 60

The compound shaft of claim 48 wherein said flexible disk of said flexible disk shaft is interference fit shallow into said permanent magnet sleeve.

Claim 61

The compound shaft of claim 48 wherein said flexible disk of said flexible disk shaft is interference fit deep into said permanent magnet sleeve.