Since xrad has shown interest and responded to this project, I will carry on.
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The bridge span has both longitudinal and lateral bumper rollers to keep the span from getting hooked up somewhere in its travel.
Made my own version by using microswitch actuator arms, which can be bought separately.
Added vessel traffic control lights to span hut balcony railings. Fed its wires into the hut area.
There are boxed-in areas on the balconies. Boxes (A) and (B), on actual bridge, contain the drive gearing and winch drum system for raising and lowering the span. The winch motor is in the centre of the hut. It has a differential and two axles (like in a car) which are attached to the the winches (A) and (B). Other bowes contain a back-up generator, and maintainance equipment.