A magnetic base for selectively magnetically latching to a ferromagnetic surface includes a magnet holder, a fixed magnet assembly supported within the magnet holder, a movable magnet assembly supported within the magnet holder, and a transmission. The transmission includes an input, an output coupled to the movable magnet assembly for moving the rotatable movable assembly relative to the fixed magnet assembly through a predetermined range of motion, and a plurality of transmission elements positioned between the output and the input. The transmission elements are configured to provide a variable mechanical advantage between the output and the input during at least a portion of the predetermined range of motion.