Gimbal mechanism and gearbox for same

There is disclosed an angle positioning platform for positioning objects around first and second axes and a gearbox for same. The platform comprises a base, an intermediate stage, and an upper stage. The platform may have motors and first and second output gearboxes connected to the motors for driving the platform. The orientation of the stages of the platform permits the platform to be relatively compact in a stowed position and to have high angular rotation from the stowed position to a maximum travel position. The gearboxes may have a mechanism for isolating worm shafts and wormgears from heavy loads when the platform is in the stowed position. Another aspect of the invention is an output gearbox with a wormgear having stops for stopping rotation of a matingly engaged worm. Another aspect of the invention is a gearbox having torsion springs to counter backlash in the gearbox. Such a gearbox has a wormgear and a torsion spring retainer plate, one or both of which have a plurality of holes to permit adjusting the torque of a torsion spring in the gearbox by providing a plurality of positions for the ends of a spring to be placed with respect to one another. A suitable fuel line assembly is disclosed to connect an ion thruster that is mounted in the platform to a fuel tank, the fuel line assembly comprising two bellows tubes and an elbow joint.