Large 3 foot diameter outrunner wheel Motors are chosen because they have the highest air gap velocity to rim or drive speed ratio with the least component or spinning magnet stresses. The coils remain stationary as does the axle shaft through which electric pure line voltage DC is conducted as well as fluid cooling For the combined variable coil tappe and pole gap coils and directly on each coil the separated IGBT commutation. If single coil units fail the motor keeps going at a slight loss in power.
The commutation frequency at 650 MPH is a little over 800,000 Hz and 1,000,000 Hz using between 80 to 100 coils and magnets. To have the ability to throttle down with high efficiency you can cut out coils in whole or backing off variably the number of shorted turns in each coil like a variable transformer or mechanically increasing the pole gaps as you would have to expand the stationary inrunner coil diameter to compensate for armature expansion at high speed and power levels to close down the air gap. This requires a lot of precision and PRT like systems redundancy to keep from locking up a positive traction geared tread wheel.
Decades ago the idea of retracting a single failed motor occurred using the remaining motors to find an emergency stopping siding for repairs. In all good PRT systems all the traffic that follows a failed vehicle starts coming to a stop at the same instant closing up spacing to reduce regenerative power conductor over load. Emergency radiative dynamic heat dissipation on each vehicle was also considered Over 30 years ago. This might consist of a in air tungsten and quartz resistive bar that operates at the edge of the lower guidewheel aero shell sections. Failure like in aircraft turbines can be catastrophic.
The wheel motors are large in diameter to reduce the bearing RPM at possibly a thin 5 inches wide. These motors are connected together in continuos strings or chains inside gap free smooth aerodynamic I beam shaped shells. These form a flexible row out runner wheel motor using opposed pairs of thin disc guide wheels, one below the guideway beam that resists all the vehicle body side forces from cornering or curving and cross wind pressure, one pair of smaller light weight guidewheels supports the top side of the running gear. These top and bottom guide wheel set take care of all side thrust, guidance and roll motion with the traction wheel motors carrying all gravity and thrust loads.
All the bearings have only radial pressure on them with no twist or significant induced end thrust or twisting to resist. This makes them lighter, stronger and cheaper to manufacture and maintain.
Components form a running gear unit of about 600 KW per wheel at full regenerative throttle at 650 MPH For intermittent service of about 30 seconds which is a full load brought to a stop from the governed top speed. Five of these motors might form a typical all purpose vehicle At about 3,000 KWs at top speed. The excess power out of these about 150 pound each motor units is need for regenerative emergency stopping keeping deceleration heat away from the vehicle. Friction brakes are an impossible heavy item with zero slip wheels and motors that are more powerful than any ever jet fighter plane. A low speed rim rubbing friction brake to hold on a steep grade can never be designed for in motion braking. In long trains one motor per vehicle need create only about 50 KW of thrust to carry a single vehicles share of the frontal drag and average skin drag At 650 MPH. As many as eight of these motors might form the longest 24 foot long interior length vehicles.
Special off setting running gear is needed for carrying spans and other longer items. These running gear that locks ridgidly in alignment control as speed increases to just below the speed of sound. This releases or unlocks as speed is reduced down to lower speeds where the guideway rounds 30 foot radius curves for urban grid access down narrow streets in access networks.
The geared traction rims might be steel but more likely carbon fiber windings retaining tungsten contact troughs that the vehicle runs on like the teeth curved or barrel roots or bases of the teeth of a starter motor flywheel gear to use a common example. As the speed increases the wheels expand from centripetal force and air resistance heating changing the gear pitch slightly to the running rail that may be cool or hot depending on the weather slso differing in pitch. The wheels will settle to make contact at different places on the barrel rail teeth tops depending on thrust and expansion differentials. This will cause micro slipping that increases rolling friction slightly but adds little to the unlubricated but realatively lightly loaded tungsten surfaces. How to make these systems and the cross over steering system are very difficult problems that have thousands of possible answers and finessed design possibilities. Maglev becomes the de facto easier solution we’ll above this operating speed.
The twin rim gears are are on opposite sides of the motor one on each side of the slot riding on the gear rails. A set of small spur gears form a limited slip differential to share the thrust propulsion and braking loads between them. A magnetic lock up might be best to prevent more than slight angle adjustment between them. This prevents spinngcif one should lose traction. At switches the outside radius gear will dienguagecon one side of the point and rebguagexon the other. The point might be resultant and have sharer barrels to make engagement easier as the rim gears need sharp points also.
The suspension would likely be a on board set of small compressor oleo strut cooling fluid adjusted active height control to reduce the vehicles height in restricted space areas yet have a variable foot or so of centered floating travel for rough or misaligned spans.
From the first this suspension has been viewed as a double variably resistive to active side movement swing arm to allow self banking and false center swing or side off set. This creates some very difficult challenges that will require predictive aerodynamic control as well. To reduce the air friction of dynamic control surfaces and their snaging things during access descents they must be both bidirectional swing away and retractable. The vehicles must be able to operate bidirectionally which adds the problem of aerodynamic balanced flutter. By extending the fins to the rear in unentrained or singly operating vehicles flutter Should not be a problem.
Vehicle electronic cooperative train position coupling friction pressure to magnetic coupling allows PRT route selection out from a high speed train. A means of several different varieties is needed to center coupled vehicles to smith out the gaps and edges. The closest example of this high speed separation turbulence at a switch out of a train is large bombs leaving a small bomb bay at very high speeds. By extending the deflated streamlined ends before separation and closing the gap left by the diverging vehicle as it moves to the side a wedge effect might assist in the passive switch turn out without the expected buffeting. All of these features can be programmed into the syncronus motor controls with non slip gear teeth wheels to provide machine tool exacting results.
A Pair of cable tensioned actuators might simsltainiously tension springs to pre arch the pivot points between the wheel segments and at the same time bring a gaped clearance set of neodymium magnets close to the side of the passive switch slot the vehicle or train chooses. Span encoding indicates the arch in each direction and the straight direction arch on outside curve turn outs. This transfers the curve path forces to the guidewheels on either side of the turnout frog or gap through which the vehicles steer themselves.
In trains on a straight section only the first vehicle might need to make the active straight or right or left directional choice. On curves every vehicle will be required to be a active attractor. To balance out it’s centripetal force only through the curved turn out slot gap movement. Wheel twin rim gears are on the same motor or wheel. They cannot drop into the slot as one rim gear will always be supported on the inside curve.
This is running gear basics. Tucking all of the parts into minimum drag places between the wheels and having the whole outside shell be laced with cooling tubes for heat rejection of the all purpose motor cooling and lubrication supply is as complicated as modern car and aircraft constructions.
Keeping cooling reserves for emergency stopping will require slowing more gradually for hot desert locations. Allowing fluids to boil off providing some evaporative surface cooling will be needed. Past this point aero drag brakes are required to take up any remaining unment stopping power or the use of abailative linear friction brakes with explosive one time actuation for extreme emergency stops. Linear guying to prevent guideway collapse is required on higher speed full length entrained lines.