A system for converting a force applied in one direction to a rotational force comprising: a pressure part for receiving an operative force in a first direction; a motive force transfer mechanism comprising two arms joined at a pivot point and moveable relative to each other in a scissors fashion between at least two states including an uncompressed state and a compressed state, the motive force transfer mechanism being operatively coupled to the pressure part, for moving the two arms from the uncompressed state to the compressed state upon a suitable force in the first direction being received by the pressure part; a bias member that provides a bias force on at least one of the two arms, for biasing the two arms toward the uncompressed state, a spin restricting mechanism with at least two parts, a first part and a second part that are arranged to be coupled and rotate together around a shared axis in a first rotary direction, but rotate independently around the shared axis in a second rotary direction opposite to the first rotary direction; and a linkage structure for operatively linking at least one of the two arms to the first part of the spin restricting mechanism, to communicate movement of at least one of the arms from the uncompressed state to the compressed state into rotational motion of the first part of the spin restricting mechanism in a first rotary direction; characterized in that the pressure part is operatively coupled to the motive force transfer mechanism at the pivot point and moveable relative to the motive force transfer mechanism in a tilting fashion between at least two states including a forward tilt state and a backward tilt state; wherein the pressure part is operatively coupled to the motive force transfer mechanism at the same pivot point as the two arms and; wherein at least one of the two arms of the motive force transfer mechanism has an end provided with a series of teeth for operatively engaging the linkage structure and a further end attached to a wheel. a pressure part for receiving an operative force in a first direction; a motive force transfer mechanism comprising two arms joined at a pivot point and moveable relative to each other in a scissors fashion between at least two states including an uncompressed state and a compressed state, the motive force transfer mechanism being operatively coupled to the pressure part, for moving the two arms from the uncompressed state to the compressed state upon a suitable force in the first direction being received by the pressure part; a bias member that provides a bias force on at least one of the two arms, for biasing the two arms toward the uncompressed state, a spin restricting mechanism with at least two parts, a first part and a second part that are arranged to be coupled and rotate together around a shared axis in a first rotary direction, but rotate independently around the shared axis in a second rotary direction opposite to the first rotary direction; and a linkage structure for operatively linking at least one of the two arms to the first part of the spin restricting mechanism, to communicate movement of at least one of the arms from the uncompressed state to the compressed state into rotational motion of the first part of the spin restricting mechanism in a first rotary direction; characterized in that the pressure part is operatively coupled to the motive force transfer mechanism at the pivot point and moveable relative to the motive force transfer mechanism in a tilting fashion between at least two states including a forward tilt state and a backward tilt state; wherein the pressure part is operatively coupled to the motive force transfer mechanism at the same pivot point as the two arms and; wherein at least one of the two arms of the motive force transfer mechanism has an end provided with a series of teeth for operatively engaging the linkage structure and a further end attached to a wheel.