An upright active-sitting seat provides a connection of a seating leg to a base through an articulating joint that allows the user to move a seat front to back and side to side, allowing a more active sitting that encourages blood circulation. The chair includes a seat supported by a post that is connected to a mount via a ball joint rod by a transverse rod that is routed through the ball joint rod end. By way of a coil spring that engages with the mount and the post, the post is spring biased to a home position relative to the mount. When using the chair, a person may move the seat from the home position to a comfortable seating position. When the person stands from the chair after using it, the chair returns to its spring biased home position.

The present invention provides a retractable wheel system for snowmobile skis. The retractable wheel system of the present invention may be installed on a snowmobile ski without affecting its structural integrity by installing the system on the reinforced portion of the snowmobile ski. When a user circulates in a path with little or no snow, the retractable wheel system is positioned in the extended configuration by the user and the system will automatically return to the retracted configuration when the user returns in a snowy zone. This is realized by using a pre-tensioned spring that will reposition the wheel in the retracted configuration. The spring transmits a rotational movement to the member on which the wheel is fixed.

A ball stud system that provides a ball stud that will not loosen easily under the application of repetitive side loading on the ball portion of the stud. The ball stud is secured to the vehicle steering knuckle arm using the combination of a tapered nut and tapered washer. The tapered nut includes slots and the pin of the ball stud an aperture. A cotter pin may be placed through the slots and aperture in order to further prevent rotation of the nut.

The present invention provides a retractable wheel system for snowmobile skis. The retractable wheel system of the present invention may be installed on a snowmobile ski without affecting its structural integrity by installing the system on the reinforced portion of the snowmobile ski. When a user circulates in a path with little or no snow, the retractable wheel system is positioned in the extended configuration by the user and the system will automatically return to the retracted configuration when the user returns in a snowy zone. This is realized by using a pre-tensioned spring that will reposition the wheel in the retracted configuration. The spring transmits a rotational movement to the member on which the wheel is fixed.

An upright active-sitting seat provides a connection of a seating leg to a base through an articulating joint that allows the user to move a seat front to back and side to side, allowing a more active sitting that encourages blood circulation. The chair includes a seat supported by a post that is connected to a mount via a ball joint rod by a transverse rod that is routed through the ball joint rod end. By way of a coil spring that engages with the mount and the post, the post is spring biased to a home position relative to the mount. When using the chair, a person may move the seat from the home position to a comfortable seating position. When the person stands from the chair after using it, the chair returns to its spring biased home position.

The present invention provides a retractable wheel system for snowmobile skis. The retractable wheel system of the present invention may be installed on a snowmobile ski without affecting its structural integrity by installing the system on the reinforced portion of the snowmobile ski. When a user circulates in a path with little or no snow, the retractable wheel system is positioned in the extended configuration by the user and the system will automatically return to the retracted configuration when the user returns in a snowy zone. This is realized by using a pre-tensioned spring that will reposition the wheel in the retracted configuration. The spring transmits a rotational movement to the member on which the wheel is fixed.

An adjustable resistance hinge system for a joint connecting at least a first articulating member and a second articulating member, the hinge system comprising a central element defining a hinge axis. The central element comprises a first and a second elongate arm, each elongate arm extending away from the hinge axis, and a first and a second keeping element hinging on the hinge axis are attached to the first and the second articulating members, respectively. A first and a second biasing device are also engageable with the first and the second elongate arms, respectively. The first and the second elongate arms extend into the first and the second articulating members, respectively, and the first and the second biasing devices engage the central element to resist relative motion of the first and the second articulating members about the hinge axis. The adjustable resistance hinge system allows two joined members to be adjusted to replicate desired physiology, limits, and resistance.