just starting wrote:I'm currently building a layout 6' x 22' that will be open in the center. I noticed some layouts have what is called a drop hinge bridge. How are these made. I'm concerned about track alignment.
Think of a drop hinge bridge as a miniature door that swings in a vertical, rather than horizontal, plane. On the hinge side, the hinges hold that end of the bridge in horizontal and vertical alignment. On the latch side, there has to be something to perform the alignment-locking function. Probably the simplest would be a wedge shape on the bridge, entering a V-shaped space on the abutment, the whole locked into position by a big, solid barrel bolt.
Actually, there are about as many different ways of arranging that latch as there are modelers who have built drop bridges.
One suggestion I would make is to move the hinges back from the edge, so the dropped bridge would go under the abutment. That would protect the bridge tracks and other details from casual contact with passing trouser legs. This could be done by using those long-armed barn door hinges instead of short/squared off residential in-jamb door hinges (although one of the latter, with a removeable pin, could easily be modified to perform the latching/alignment function at the open end.
No matter how the mechanicals are arranged, the electricals must be set up to kill the approach tracks, or the entire railroad, any time the bridge is not in operating position.
Chuck (modeling Central Japan in September, 1964)