Monday, April 18, 2011
Well folks, they say a picture is worth a thousand words, so here are a couple thousand worth. Shown above is how a three-wheeled PRT vehicle could be tipped forward to create a ramp, and how the swing-arm can be detached to allow the vehicle to travel away from the track. The second picture illustrates how the swing-arm can be used to tilt the vehicle back to give it a more even aerodynamic profile. In this embodiment I assume that the vehicle will not be roadworthy, and that it would have very limited range and speed on battery power. The steering would be accomplished by having a pivoting back wheel and independently controlled front wheels. The rear wheel would extend downward for boarding, and retract for high-speed use, as shown.
In this design windows were minimized to avoid the high air conditioning requirements of a vehicle with lots of glass. Anything short of completely automated driving, however, requires high visibility for the driver, even if the vehicle only goes 10 mph and is controlled by a joystick, so some configurations might need more glass than what I have shown. I envision the ground-driving capability to be primarily for parking lot use, for either ferrying people to their cars or from the PRT station to the front door of a store or other destination. In this capacity it would go one way empty, on autopilot. Allowing passenger control risks taking a vehicle to where it could get stuck or get into traffic, so perhaps the manual-drive option should be limited to privately owned vehicles. Such personal vehicles, in addition to the extra glass and AC requirements, could also have extended range, greater speed, more ground clearance and better suspension. The bogie would only accept a limited amount of weight, however, so such modifications would be at the expense of payload capacity. After all, if we want to have cheap, extendable track we need to draw the line on weight somewhere. In the example above the extra hardware (two motorized drive wheels with rudimentary suspension, rear pivoting wheel with a screwjack for tilting the vehicle forward and a small battery pack) adds an estimated max weight of (perhaps) 100 lbs.