Abstract: A coupling includes a driving disk connected to a driving shaft and rotatable about a driving axis. An engagement face of the driving disk includes a predetermined number of at least three driving teeth that are distributed azimuthally on the engagement face of the driving disk along a circle concentric to the driving axis. A driven disk connected to a driven shaft and rotatable about a driven axis has an engagement face including the predetermined number of driven teeth azimuthally distributed along a circle concentric to the driven axis. At least one of the driving shaft and the driven shaft possesses translational freedom or angular freedom of motion with respect to the other so that when the driving teeth of the driving disk engage the driven teeth, the driving axis and the driven axis are self-aligned.

Abstract: A vehicle extraction device includes a track for insertion between a wheel of the vehicle and soft ground below the wheel. A ground-penetration head is connected to a leading end of the traction track. The ground-penetration head includes a plate for placement on an outer perimeter surface of the wheel and a fastening mechanism for attaching the plate to the wheel. Attaching the ground-penetration head to the wheel with the leading end facing an intended direction of rotation of the wheel and rotation of the wheel in the intended direction may insert the ground-penetration head and the track between the outer perimeter surface and the soft ground.

Abstract: A portable removable apparatus for powering a bicycle driven by a chain is disclosed. The apparatus includes a portable and removable drive unit for propelling the bicycle. The drive unit includes an electric motor and a shaft rotatable by the motor, with a sprocket coaxially affixed to the shaft and adapted to engage to a portion of the chain. The apparatus also includes a bracket adapted to be fixed to a frame of the bicycle and to be in bearing contact with the shaft for supporting the shaft. The apparatus further includes at least one additional support for supporting the drive unit on the bicycle frame so that lateral torque on the drive unit when engaged with the chain and operating is substantially eliminated. Another embodiment is disclosed in which the drive unit includes a flexible belt looped around a drive pulley connected to the motor and an idler pulley.

Abstract: A portable removable apparatus for powering a bicycle driven by a chain is disclosed. The apparatus includes a portable and removable drive unit for propelling the bicycle. The drive unit includes an electric motor and a shaft rotatable by the motor, with a sprocket coaxially affixed to the shaft and adapted to engage to a portion of the chain. The apparatus also includes a bracket adapted to be fixed to a frame of the bicycle and to be in bearing contact with the shaft for supporting the shaft. The apparatus further includes at least one additional support for supporting the drive unit on the bicycle frame so that lateral torque on the drive unit when engaged with the chain and operating is substantially eliminated. Another embodiment is disclosed in which the drive unit includes a flexible belt looped around a drive pulley connected to the motor and an idler pulley.