Abstract: Apparatus and method for gravity-augmented preload of drive wheels in a monorail vehicle travelling along a guide rail with bearing and contact surfaces that are non-parallel with the gravity vector. The vehicle defines a pivot location against the bearing surface and a constraint point on the contact surface for engaging the rail on the bearing and contact surfaces, respectively. The vehicle is mounted so its center of gravity is at a rear longitudinal offset rrl from the pivot location and a vertical offset rvert from the guide rail. A force and moment balance thus created result in a normal load on a drive wheel engaged with the bearing surface at the pivot location, where the load value exceeds a standard normal load generated by the mass of the monorail vehicle alone.

Abstract: Techniques for transferring torque between a first unit, such as a mobile machine or a robot, and a second unit, such as a fixed or stationary machine. The units are arranged such that a drive coupler of the first unit designed for delivering torque about a drive axis can engage the driven coupler, which belongs to the second unit and has a driven axis, along an engagement direction that is nearly perpendicular to the direction of the driven axis. A lateral displacement mechanism of the first unit achieves a first-order coaxial alignment between the drive and driven axes. Additional measures are provided for improving engagement, coupling and reducing the level of axial misalignment. Techniques disclosed are tolerant of imprecise alignment between the drive and driven couplers.