Page:Final Report - The Columbia River Interstate Bridge.pdf/31

 returned to position through means of small counter-balances. The rail connections at the ends of the movable span are simple scarfed joints so that the span lifts away from the fixed rails and returns to them without any movable devices. The machinery is designed with great care and nicely. Gears and pinions which operate together are set in cast steel frames so that they could be adjusted and built complete in the shops; the adjustment of parts of the machinery in the field being reduced

THE COLUMBIA RIVER BRIDGE.

to a minimum. All of the gears are cast steel with cut teeth. There is duplicate motor equipment with either motor of sufficient size to operate the bridge.

At the ends of the fixed spans adjacent to the movable span there are provided roadway gates of substantial design to make an effective barrier across the roadway, and these are connected to derailing switches in the street car tracks so that when the gate is closed across the roadway, the derail is thrown. These