In 1985 I had a greenhouse design project through the Louisiana solar design association at LSU. I used an aluminum scissor hinge to open a vent window. It was operated by a wax-filled cylinder that had temperatures etched on the side and you set its range by screwing the cylinder in or out (clockwise or counter). The hinge was passive and worked excellent with about a 5 degree offset. The greenhouse was dismantled by another class and I never got the hinge back. It couldn’t have cost much seeing I was a poor student at the time. Ever ran across these and are they still available?