TM 5-6675-316-14
(2) On one side, the parallel rod passes through precision bearings fixed to
the carriage stepping assembly. On the other side, two ball bearings rest on the
upper and lower surfaces of the second parallel rod, preventing any rotational
movement of the carriage stepping assembly as it is driven by the helix screw.
(3) The helix screw is rotated by the variator stepping motor, the motor being
mounted horizontally in a casting approximately midway along the optical plane. The
motor shaft is coupled to the helix screw by a taper pin.
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