An apparatus (132, 134) comprising: a linkage, comprising a link (252, 291, 292) coupled between a proximal bracket and a distal bracket, the proximal bracket coupled to a support structure (101, 192, 136) at a first end, the linkage being adapted to support a load applied to a second end of the linkage opposite the first end; a balancing mechanism coupled to the linkage around a pivotal joint, the balancing mechanism including a compression spring, a cable, and three pulleys (502, 503,504) with center points of the three pulleys (502, 503, 504) forming corners of an adjustable triangle having one side which changes in length when the link (252, 291, 292) and the linkage moves, with a first of the three pulleys coupled to a shaft at the pivotal joint, wherein the cable wraps over the three pulleys (502, 503, 504) and has a first end coupled to the compression spring to counter balance the load applied to the second end of the linkage; wherein the link (252, 291, 292) houses the compression spring and is coupled to the three pulleys (502, 503, 504) and a second end of the cable; wherein as the linkage vertically adjusts the position of the load with a varying moment arm length, the balancing mechanism varies a cable path length to modify the compression of the compression spring and the tension in the cable to adjust a counter balance force applied to the linkage; and wherein a linear distance between the other two (502, 503) of the three pulleys that are not the first of the three pulleys varies to modify the cable path length in response to changes in positions of the linkage to adjust the counter balance force. a linkage, comprising a link (252, 291, 292) coupled between a proximal bracket and a distal bracket, the proximal bracket coupled to a support structure (101, 192, 136) at a first end, the linkage being adapted to support a load applied to a second end of the linkage opposite the first end; a balancing mechanism coupled to the linkage around a pivotal joint, the balancing mechanism including a compression spring, a cable, and three pulleys (502, 503,504) with center points of the three pulleys (502, 503, 504) forming corners of an adjustable triangle having one side which changes in length when the link (252, 291, 292) and the linkage moves, with a first of the three pulleys coupled to a shaft at the pivotal joint, wherein the cable wraps over the three pulleys (502, 503, 504) and has a first end coupled to the compression spring to counter balance the load applied to the second end of the linkage; wherein the link (252, 291, 292) houses the compression spring and is coupled to the three pulleys (502, 503, 504) and a second end of the cable; wherein as the linkage vertically adjusts the position of the load with a varying moment arm length, the balancing mechanism varies a cable path length to modify the compression of the compression spring and the tension in the cable to adjust a counter balance force applied to the linkage; and wherein a linear distance between the other two (502, 503) of the three pulleys that are not the first of the three pulleys varies to modify the cable path length in response to changes in positions of the linkage to adjust the counter balance force.