The University of Texas System

Board of Regents

John H Gully

William F Weldon

W Alan Walls

Elvin Estes

Steve M Manifold

Mark A Pichot

Michael L Spann

Raymond C Zowarka

Dennis Roger Peterson

Jim L Upshaw

Mike L Spann

Damon A Weeks

Kurth P Bousman

William A Walls

The maximum safe operating speed or flywheels and shafts made of low tensile strength material is often determined by the speed at which radial tensile stress exceeds a radial tensile stress limit for the material. Circumferentially wound fiber composite material, for example, has a relatively low tensile strength along the radial direction perpendicular to the fibers. To increase the maximum safe operating speed, it is therefore desirable to form a fiber composite flywheel or shaft with radial compressive prestress. Such a prestressed flywheel or shaft has an outer annulus and an inner cylinder disposed in the outer annulus, and an annular layer of solidified bonding agent within an annular region between the outer annulus and the inner cylinder, wherein the outer annulus and the inner cylinder include substantial radial prestress induced by the bonding agent. The rim portion of a flywheel, for example, is formed from an outer ring (the annulus) and an inner ring (the cylinder, which is hollow in this case). Large, thick flywheels preferably have multiple cylindrical sections joined by such layers of bonding agent, and a plurality of the cylindrical sections each including an outer layer of relatively stiff fiber-composite material, and an inner layer of relatively compliant fiber-composite material within an integral matrix material.

Reinforced composite flywheels and shafts

The maximum safe operating speed of flywheels and shafts made of low tensile strength material is often determined by the speed at which radial tensile stress exceeds a radial tensile stress limit for the material. Circumferentially wound fiber composite material, for example, has a relatively low tensile strength along the radial direction perpendicular to the fibers. To increase the maximum safe operating speed, it is therefore desirable to form a fiber composite flywheel or shaft with radial compressive prestress. Such a prestressed flywheel or shaft is made by placing a cylinder within a fiber composite annulus, injecting a bonding agent under pressure into the interface between the annulus and the cylinder, and maintaining the bonding agent under pressure while the bonding agent solidifies. Preferably, the cylinder and annulus are aligned in a concentric relationship during solidification by a chamber into which the cylinder and annulus are placed. The rim portion of a flywheel, for example, is formed from an outer ring (the annulus) and an inner ring (the cylinder, which is hollow in this case). The chamber is defined by a pair of plates which abut opposite faces of the rings, and by two concentric cylinders which limit the radial movement of the rings as the rings expand or contract, respectively, in response to the pressure of the bonding agent. The bonding agent is preferably a mixture of epoxy resin and chopped fiber or other randomly oriented epoxy reinforcing material.

Methods for making reinforced composite flywheels and shafts

A railgun operates at high pressure (up to 350 MPa) without structural damage and is readily disassembled for inspection, maintenance and component testing. A rail assembly is pressed into a hoop-wound epoxy fiberglass containment tube and clamped within a steel compression frame. The geometry of the rail assembly permits rail movement without insulator intrusion and achieves bore sealing during rail movement at maximum pressure. The rail assembly also has replaceable insulator inserts which are isolated from rail re-bound shock. Fused quartz insulator inserts provide the best results. A flash tube is provided at the gun muzzle to suppress precursor discharge and commutate precursor current back to the armature. To realize increased velocity without sacrificing in-bore projectile stability, a cut-corner projectile is used having a L/D ratio as small as 0.65 which reduces the mass by about 11%.

High performance electromagnetic railgun launcher

A homopolar generator (HPG) having the stator and an inner brush mechanism housed within the machine support structure utilizes a rotor separated into halves electrically insulated from each other, so as to fit around the stator and brush mechanism. A shaft is mounted in the support structure to carry the rotor. A first rotor half is thermally shrunk-fit onto the shaft, and the second rotor half is hydraulically expansion fit thereon. To hydraulically fit the second rotor on the shaft, a shaft is provided having a downward taper from its midpoint toward one end. The shaft also has a circumferential groove and a port therethrough from the end of the taper for communicating high pressure oil from an external pump to the shaft-rotor interface. High-pressure seals on each side of the groove prevent leakage. The application of high-pressure oil expands the bore in the rotor half and shrinks the shaft diameter. A hydraulic ram then pushes the rotor half onto the tapered shaft, whereupon the pressure is released and the rotor half bore contracts against the shaft.

Method of constructing a rotor assembly for homopolar generator

A homoplanar generator (HPG) having the stator and an inner brush mechanism housed within the machine support structure utilizes a rotor separated into halves electrically insulated from each other, so as to fit around the stator and brush mechanism. A shaft is mounted in the support structure to carry the rotor. A first rotor half is thermally shrunk-fit onto the shaft, and the second rotor half is hydraulically expansion fit thereon. To hydraulically fit the second rotor on the shaft, a shaft is provided having a downward taper from its midpoint toward one end. The shaft also has a circumferential groove and a port therethrough from the end of the taper, for communicating high pressure oil from an external pump to the shaft-rotor interface. High-pressure seals on each side of the groove prevent leakage. The application of high-pressure oil expands the bore in the rotor half and shrinks the shaft diameter. A hydraulic ram then pushes the rotor half onto the tapered shaft, whereupon the pressure is released and the rotor half bore contracts against the shaft.

Rotor assembly for homopolar generator

A homopolar generator includes a stator producing a magnetic field and a rotor which rotates in the stator magnetic field to generate electrical discharge current. The current is available from a slip ring surface defined on the rotor, and a plurality of brush mechanisms are provided to collect and transfer the discharge current from the rotor slip ring. Each brush mechanism includes a brush pad for contacting the rotor slip ring. The brush pad is attached to one end of a laminated trailing arm brush strap. A brush actuator forces the brush pad into contact with the rotor slip ring against the yieldable brush lifting force of the brush strap. To compensate for the reaction between adjacent brush straps due to the magnetic fields set up by the discharge current being transferred by each, a conductor strap is electrically connected to the end of the brush strap opposite the attached brush. The conductor strap receives current from the brush strap and directs it oppositely to the direction of the current in the brush strap.

Brush mechanism for a homopolar generator

A high-energy, high-current homopolar generator pulsed power supply system that is compact and field portable. The power supply system includes a hompolar generator (HPG), an auxiliary supply and drive system, both mounted on a skid frame, and a control system coupled to the HPG and drive system. The homopolar generator has a split rotor with insulation between the halves and a recess in the periphery. A stator ring and field coil, for producing a magnetic field through which the rotor halves make two simultaneous voltage-generating passes, are disposed within the recess in the rotor. Air-actuated brush mechanisms inside and outside the recess contact surfaces of the rotor and collect discharge current. The auxiliary supply and drive system includes a motoring system comprising hydraulic motors for driving the HPG to speed, a bearing lubrication system, a generator for energizing the field coil, and a brush actuator air supply system, all of which are driven by a prime mover. The control system comprises a logic controller for executing a prescribed sequence of steps including turning on the prime mover, initiating motoring of the HPG, energizing the field coil, and initiating the discharge of electrical current.

Homopolar generator power supply system

A homopolar generator having a rotor with a slip ring surface utilizes an inflatable diaphragm to force the current-collecting brushes into contact with the rotor slip ring. The diaphragm is molded around a metal core. An opening in the metal core directs pressurized gas into a diaphragm cavity to expand the diaphragm against the back of the brush.

Growing community of inventors

Austin, TX, United States of America

John H Gully