A propulsion device for a bicycle can include a mounting assembly for releasably coupling the propulsion device to the bicycle, a motor, a power source selectively providing power to the motor, a gear assembly, and two frictional drive components coupled to the gear assembly. The two frictional drive components can be movable between an engaged configuration and a disengaged configuration. In the engaged configuration, the two frictional drive components are frictionally engaged with a side of a wheel of the bicycle such that the wheel is arranged between the two frictional drive components. In the disengaged configuration the two frictional drive components are disengaged from the wheel. The motor can drive the gear assembly: (i) to move the two frictional drive components into the engaged configuration, and (ii) to rotate at least one of the two frictional drive components to rotate the wheel of the bicycle.

A propulsion device for a bicycle can include a mounting assembly for releasably coupling the propulsion device to the bicycle, a motor, a power source selectively providing power to the motor, a gear assembly, and two frictional drive components coupled to the gear assembly. The two frictional drive components can be movable between an engaged configuration and a disengaged configuration. In the engaged configuration, the two frictional drive components are frictionally engaged with a side of a wheel of the bicycle such that the wheel is arranged between the two frictional drive components. In the disengaged configuration the two frictional drive components are disengaged from the wheel. The motor can drive the gear assembly: (i) to move the two frictional drive components into the engaged configuration, and (ii) to rotate at least one of the two frictional drive components to rotate the wheel of the bicycle.

Embodiments of a friction drive system include a battery, a drive motor, a control unit, and a speed wheel. When the friction drive system is mounted on a wheeled vehicle, the speed wheel provides an accurate measurement of the vehicle speed by maintaining contact with a tire of the vehicle. An automatic traction control system, which may be part of the control unit, compares the speed of the speed wheel with the speed of the drive motor to determine whether slippage is occurring. If slippage is detected, then embodiments of an automatic traction control system automatically increase an amount of normal force between a contact surface on the drive motor and the tire, by advancing a position of the drive motor relative to a fixed mounting point. If no slippage is detected, then embodiments of an automatic traction control system automatically reduce the amount of normal force, by retracting a position of the drive relative to a fixed mounting point. In embodiments of a friction drive system, the relative position of the drive motor may be controlled by powering a worm gear motor attached to a worm gear in response to commands from the control unit.

Embodiments of a friction drive system include a battery, a drive motor, a control unit, and a speed wheel. When the friction drive system is mounted on a wheeled vehicle, the speed wheel provides an accurate measurement of the vehicle speed by maintaining contact with a tire of the vehicle. An automatic traction control system, which may be part of the control unit, compares the speed of the speed wheel with the speed of the drive motor to determine whether slippage is occurring. If slippage is detected, then embodiments of an automatic traction control system automatically increase an amount of normal force between a contact surface on the drive motor and the tire, by advancing a position of the drive motor relative to a fixed mounting point. If no slippage is detected, then embodiments of an automatic traction control system automatically reduce the amount of normal force, by retracting a position of the drive r elative to a fixed mounting point. In embodiments of a friction drive system, the relative position of the drive motor may be controlled by powering a worm gear motor attached to a worm gear in response to commands from the control unit.

A propulsion device for a bicycle can include a mounting assembly for releasably coupling the propulsion device to the bicycle, a motor, a power source selectively providing power to the motor, a gear assembly, and two frictional drive components coupled to the gear assembly. The two frictional drive components can be movable between an engaged configuration and a disengaged configuration. In the engaged configuration, the two frictional drive components are frictionally engaged with a side of a wheel of the bicycle such that the wheel is arranged between the two frictional drive components. In the disengaged configuration the two frictional drive components are disengaged from the wheel. The motor can drive the gear assembly: (i) to move the two frictional drive components into the engaged configuration, and (ii) to rotate at least one of the two frictional drive components to rotate the wheel of the bicycle.

The power assisting device includes driver with a rotary axis, a main gear, a first transmission rod, a first bevel gear, a second bevel gear, a first rotating rod, a third bevel gear, and a first driving wheel. The main gear is driven by the driver to rotate about the rotary axis. The first transmission rod extends along a direction perpendicular to the rotary axis. The first bevel gear and the second bevel gear are separately sleeved on the transmission rod. The first bevel gear is engaged with the main gear. The first rotating rod extends along a direction parallel to the rotary axis. The third bevel gear is sleeved on the first rotating rod and is engaged with the second bevel gear. The first driving wheel is coupled to the first rotating rod for assisting a wheel of a vehicle to move forward.

The power assisting device includes driver with a rotary axis, a main gear, a first transmission rod, a first bevel gear, a second bevel gear, a first rotating rod, a third bevel gear, and a first driving wheel. The main gear is driven by the driver to rotate about the rotary axis. The first transmission rod extends along a direction perpendicular to the rotary axis. The first bevel gear and the second bevel gear are separately sleeved on the transmission rod. The first bevel gear is engaged with the main gear. The first rotating rod extends along a direction parallel to the rotary axis. The third bevel gear is sleeved on the first rotating rod and is engaged with the second bevel gear. The first driving wheel is coupled to the first rotating rod for assisting a wheel of a vehicle to move forward.